|Renewable Energy Discussion on various alternative energy, renewable energy, & free energy technologies. Also any discussion about the environment, global warming, and other related topics are welcome here.|
Oh man I drive myself crazy sometimes, great simple idea like this and I am not near my workshop for a week!
So I was amusing myself doing some simple calculations...
Energy $ IN by water company = Who gives a **** ?
Energy $ IN by YOU = 0
Energy OUT is positive!
So the more efficient you make your device, the more energy you get for free $ paid for by the water company, who would be happy to compensate you for the damage they have done lacing your water supply with fluoride poison, and they will also be happy to absorb the rapidly rising cost of electricity bills as their buddies in the electricity monopolies stiff everyone for more $...
hahaha what a good day!
"It's hard to know what is going to work best for my particular design because nobody has built it before, once I have the parts though a little trial and error should give me the 5 HP I am looking for, If I cannot achieve that then 2 1/2 HP would also be good because that should give me 15V and I then have a 12V system. My goal in all this is to charge a battery, once I have achieved that, I will look at improving the efficiency of the system."
You will easily obtain these results if you build a more modern hearth and plate setup than the most basic of basic designs: The FEMA. 5 as a minimum, and up from there.
Let me share some quoted conversation a while back with Matt from Vulcan:
Just a quick update... New even simpler design...
We have the sink science turbine which uses the potential energy you have already paid for in your water bill, and turn it into kinetic energy by leaving the tap on 24/7:
SinkScience #01 -Tesla CD Turbine: Fun Science Learning Tool - YouTube
Then we have the DIY alternator that is magnetically coupled to the turbine:
Radial Air core alternator
DIY PMG Generators cheap and easy to make whit in a day!
I am going to aim for the 30 - 50 Watts version and see if the turbine can run it.
Then we can use the electrode boiler idea in the Peter Davey thread and wire the output from the alternator directly to it. As the stator coils and the boiler are stationary no problem! I am going to go with the Joe Cell kinda design because I have the pipes already and have tested the concept.
Peter Daysh Davey Water Heater Query
The beauty of this is that those folks wanting to experiment with resonance via altering the AC frequency can now do so by throttling the tap and are not stuck at 110 or 220 Hz.
The way this is all linking together is very spooky!
30 - 50 Watts is not a lot but seeing as it is energy available that is just sitting there doing nothing right now, seems a waste not to play with it. It is enough for simple electrolysis in a small dry cell, and it is enough to heat water if you wait long enough, maybe not boil it though unless heavily insulated.
Anyway I will leave that with you all, I need some sleep!
Last edited by evolvingape : 02-20-2012 at 04:28 AM.
Whatever you build you have to feed.
Woodgas is a really great (And very OLD) Tech. Providing 3x heat for same volume wood compared to a standard wood burning heating application.
But, when we start talking running engines, it becomes a bit more difficult to match the engine fuel demand to the Gas producer without making tar gas.
The BIG problem is feeding the producer the correct shaped fuel for its design.
If your running a saw mill, after a much welding work is done. You can run the mill on woodgas in short order. Using chunks of wood.
Wood chippers make shredded wood that should be sifted and then still has a bridging problem. If producer is shaken to much the chips pack in tighter and restricts the flow of gasses. Not enough and it bridges.
Pellets seem good in small systems <20hp? They don't like the wet environment of most hopper designs, And must be burnt up at the end of a run. Or they turn to oatmeal and then sometimes re-harden.
Here is some of the effort put into making fuel processing equipment.
Wood Chunker - YouTube +some good advice
wayne keith wood chunker - YouTube
as can be seen there is an energy input. human or otherwise.
ALL OF THE ABOVE PROBLEMS CAN BE OVERCOME in the design of the producer. If, you can get the wood.
Running the v8 engine truck on woodgas is about pound a mile +- if stationary, 1lb per minuet. Think about that long and hard before investing $ into this. A 12 hour run is 720 minuet/pounds. Thats lots of chunks...
For the guy that wants to add HHO to Woodgas I remind you that wood gas is 20-30% hydrogen already. Those bubbles wont make much difference.
However using the exhaust heat and urea to make ammonia bubbles WILL make a difference on small engines. Nitrogen Hydrogen Booster- WFC - YouTube and may help with the engine clogging tar problem.
I wish anyone that is in a position where wood is abundant in chunks to JUMP on this as it DOES work!
Anyone that wants to purchase a wood-chips heating system.
Here is a guy in Canada that's making them. Contact info is at the bottom of Downdraft Gasification (Gasifier, Woodgas, Gengas, Producer Gas ) the building of a unit.
I have other posts on this subject, here on another older thread.
"For the guy that wants to add HHO to Woodgas I remind you that wood gas is 20-30% hydrogen already. Those bubbles wont make much difference."
On my home built (crude) setup - quite the contrary. While you are correct - what you didn't mention, is, the gas is also about 50% nitrogen, and therein lies the problem: NOX. In my crude tests, emissions, were drastically improved; but we shall see when using a better system.
The Universe is a Potential Difference Engine...
The sink science turbine is really exciting and I have been working on developing the concept for a long time. It took that long for all the variables to be reduced to a simple system and that only happened a few days ago, when I told everyone. I also needed the sonic boiler info and energy creator's thread on PMA's, that gave me the missing knowledge I needed to finish the concept, and judging by the silence people either like it, or hate it!
Anyway, it has larger implications than anyone yet realises...
Remember the PLASMICS thread ? Well there I am talking about using the sea as a simple sea siphon. The thing about the sea is that it has a natural 1 bar of atmospheric pressure pushing down on it, and in addition for every ten meters below the surface you go the pressure increases by 1 bar... so... at a depth of ten meters you have 2 bar of pressure, and at 20 metres you have 3 bar etc...
So the simple formula is (depth in metres / 10 ) + 1 = actual pressure in bar
CalcTool: Pressure at depth calculator
The thing about the sea is that it is so huge, with such a large volume, that the mass flow rate for a siphon is for all intents and purposes, infinite. If you put 2 pipes side by side they will have identical pressure and identical mass flow rate. The pressure will always be constant, ie 2 bar for a pipe 10 metres below the surface, but the mass flow rate is a user defined variable. What this means is you can control the amount of water by controlling the bore size of the pipe, so if you double the bore size you double the mass flow rate at that pressure (approximately), you can also add another pipe with an identical bore which will be more efficient with less pressure drop than a larger bore pipe. This is not how it works in your tap, because the next door neighbour turns their tap on and you share the flow that is available, if there is not enough then the pressure drops to compensate and you both get less water (and you start banging on the wall and shouting at them for stealing your energy!).
So what I am saying is that you can for all intents and purposes tap as much energy as you want from the sea, at a constant pressure, just by increasing the mass flow rate of the fluid. Imagine two of these sink science turbines, side by side on the same tap performing as if only one was connected. Now imagine 10 of them, now 100, now 1000, you get the point ? Of course the sea level will drop, but not very noticeably we are probably talking millimetres a year at most and all the time extracting useable, exponentially expandable power. The water will get returned through natural processes anyway, more on that in a minute
The secret to this system is what you do with the water when you have siphoned it out of the sea, and run it through your turbine ? Here's the answer...
Sahara Desert - The Sahara Desert in Africa
Lowest Land Points Below Sea Level Map | Depression Elevations
“An important feature of the Sahara in Egypt is the Qattara Depression. This desert area is 436 ft (133 m) below sea level at its lowest point. There are several other depressions in the Sahara. “
So we can see that the lowest point of the depression is at 130m below sea level, and a siphon tube from a depth of 130m in the sea, going up and over land at sea level, and then dropping to the bottom of this depression will give us a pressure of 14 bar (196 psi) at a virtually infinite mass flow rate! This could easily run a large turbine acting as a power plant generator and produce substantial power.
There will be a limit to what you can siphon out of the sea, and that limit will be set by how you get rid of the water. The electrode boilers being 100% efficient can boil the water off with the power generated by the turbines, which will involve losses but will empty your tank for more water, this will also create a cloud seeding technology comprising of only natural water vapor. However there is also natural evaporation which is governed by temperature and surface area, the enthalpy of evaporation, so a very large area flat plate with a few mm of water on it, painted black will evaporate the water off by the power of the sun, leaving behind all the impurities, minerals, heavy metals, salt etc, all the valuable stuff!
Abundances of the elements (data page) - Wikipedia, the free encyclopedia
<Gold from the Sea
Can Gold be Extracted from Seawater?
A simple sea siphon running in a closed loop (ie from the sea into the depression tank, and from the tank back to the sea will circulate the sea water at the cost of the sea pressure one way, and a relatively small pumping cost the other way). To siphon the depression tank water back into the sea the water level must be slightly higher than sea level. The easiest way to do this will be to use the same principle as those wave machines in the swimming pools, create a tsunami! Easy to do, just run massive HHO generators, detonate a big charge of primary explosive, a shaped pressure wave will generate a tsunami with a maximum amplitude above sea level. A correctly designed tank will transfer huge volumes of water into another tank that was already at sea level, and the tank will siphon back into the sea. Be a fun job to have!
If the sea water is below saturation point in it's salt levels, it will pick up the dried salt deposits on its way and transport that salt back to the sea. The sea salt saturation level now becomes a controlled variable. If the sea water is already heavily saturated run it through a pre evaporation chamber, and remove the excess salt and sell it into the world's economy.
A vacuum will need to be applied to the sea siphon and this can be easily done by using a prime mover and driving the turbine (backwards in effect) and it becomes a pump. Once the siphon is self powering, you turn the motor off and run the turbine from the fluid pressure and the motor now acts as the generator! Easy!
So do you see what I am saying ? We can run massive turbines like the power stations do now, but we can do it virtually for free, for ever, and we can purify the sea, and we can turn the sahara desert green, and we can grow food, and provide drinking water and power to the people. This can be implemented all over the world...
You could also get inventive, and use those deep sea oil drilling rigs to drill a bore into rock, which will fill with fluid (water) and be pressurised by the weight of the entire ocean above it. So as an example you can drill a hole 6,000 ft into solid rock, drop a siphon to the bottom, and the water at the bottom will be at 3,000 psi... quite an improvement on our 196 psi natural pressure!
The key here will be to excavate a deep crater, use a tunnel drilling machine to bore horizontally, and when you have laid a pressure pipe structure breach the wall and let the sea in. Then connect up your high pressure siphon. The pressure differential between sea level, the depth of the bore hole, and the depth of the power plant will allow you to exploit a much higher pressure than using natural depressions in the Earth.
Bit Tooth Energy: Oil well pressures - what brings out the oil
Pretty exciting stuff eh ?
Last edited by evolvingape : 02-18-2012 at 08:42 AM.
Everyone is well on the way to understanding the water tap turbine generator and some people will have it on the prototype bench by now... so... here is a little extra add on project for you!
Lord Kelvins thunderstorm - YouTube
The water that is being exhausted out from your turbine is currently going right down the drain and carrying it's potential energy with it. Instead of wasting it let's use it!
The turbine exhaust fluid is used to fill the top reservoir of the Kelvin's Thunderstorm device, which then drips out under gravity and generates a charge imbalance which produces a 15,000 Volt spark across a gap. This is interesting because that is exactly what we need for a spark plug... so those people that are choosing to use the electrical output from the generator (AC rectified to DC) and pumping that energy into a HHO Cell, can now use that HHO to charge a chamber and detonate it cyclicly with a high voltage spark.
All of the above are system component requirements for the basis of a combustion engine that produces water and heat as it's exhaust product. Now it is just a case of scale. Remember you are doing all this with only your standard 1 – 2 bar tap pressure and a modest flow rate of water.
The other thing you should remember is that the turbine speeds you are generating are very low for a turbine (your probably running way less than 1000 RPM under full load), so you need to know about torque and how that effects a turbine generator system.
See page 7 Reply # 95
Alternate Fuel for Diesel and Gasoline Engines - 100% off the Bowser
What I am talking about here in this post is torque moment, a few key excerpts are as follows:
Torque - Wikipedia, the free encyclopedia
“The magnitude of torque depends on three quantities: the force applied, the length of the lever arm connecting the axis to the point of force application, and the angle between the force vector and the lever arm. “
“The length of the lever arm is particularly important; choosing this length appropriately lies behind the operation of levers, pulleys, gears, and most other simple machines involving a mechanical advantage.”
“A force applied at a right angle to a lever multiplied by its distance from the lever's fulcrum (the length of the lever arm) is its torque. A force of three newtons applied two metres from the fulcrum, for example, exerts the same torque as a force of one newton applied six metres from the fulcrum.”
There are three selective quotes from that Wikipedia page I linked to above. So we can see that the length of the lever arm is particularly important. This is why Tesla went so big with his discs, he was trying to maximise the turning moment (and also the time component), or torque.
We know the problems we have with large discs tearing themselves apart due to the speed differential which the discs radii are turning at, and because centrifugal force applies a tensile force that also wants to tear the material apart. So it is being pulled apart in different planes and so must be very strong to withstand this.
This was the reason I went to this design, the support frame is just that, a support frame. Each part of it can be designed to absorb the forces it will be undergoing. It can also be made super light out of modern materials.
I was also able to get rid of the turbine housing using this design, because they give me a headache, as housings always do. Boundary layer turbine housings are annoying anyway because you lose pressure due to the inability to seal a static to a rotating without applying a drag force through friction.
So, basically this design allows a fantastic potential power to weight ratio, because we can go so light on the support structure and increase the power by extending the lever. It is going to be limited by how large a diameter you can go and still support the impulse force without critical failure.
The reason the above is important ? Remember Tesla's 60” Turbine ?
The water tap turbine operates primarily on low pressure / high mass flow rate ratio, which is perfectly suited to a large slow spinning turbine such as the one we are involved with here. So you can improve the performance of your turbine by building a high quality unit on single row sealed bearings (highest RPM capability) and increasing the size of the rotor diameter drastically, which will mean a larger torque moment about the generator shaft and produce more Watts out for the same RPM, because you can use a generator design with more resistance.
Now you have a miniature fuel processing plant, powered by low water pressure, that produces HHO and also creates it's ignition source spark... only question is what are you going to do then ?
Linear piston engine and crankshaft ? (need ceramic seals)
Rotary Engine of some sort ? (no seals, more efficient)
That's enough for tonight,
Last edited by evolvingape : 02-18-2012 at 08:35 AM.
Here are some pretty cool and recent videos I just found on youtube that should demonstrate the relevance of turbines in a woodgas thread:
New Steam Turbine 150psi 15krpm 1kW.wmv - YouTube
I love this guys video's he is pretty clued up, although I can see a lot of areas where he can improve his efficiency drastically, beyond what he has already mentioned in his comments. One of the most important is superheating the steam before injection into the turbine. The steam needs to be as close to 100% dry as possible because it is then fully expanded, when the turbine is run on saturated steam it is only partially expanded, with a corresponding high volume loss and therefore pressure loss. Ideally the steam will be coming out of the turbine exhaust still superheated and then just begin to drop into saturated temperature range as it enters the heat exchanger, through an expansion nozzle on the exhaust outlet, with a corresponding drop in fluid volume which will apply a nice partial vacuum to the turbine exhaust, improving efficiency by reducing back pressure. If it is still saturated while it is in the turbine it condenses and pools in the bottom of the housing slowing the rotor down via friction drag, as some of you know. If you look closely on some of the videos you can see it pouring out of the bottom of the housing when he shuts the system down.
Remember that with a system like this the overall efficiency is not just conversion to shaft horsepower, it is about the efficiency of the input energy to the output energy, and most of that energy is still present and recoverable in the saturated steam in the form of heat (75% energy recovery is common and achievable in steam turbine power generation systems). The rest of this guys videos are great as well for those of you looking to go fully off grid for all your needs powered by woodgas!
This next video is interesting as it shows a 24” Tesla turbine stack, minus the housing:
24" Boundary Layer Tesla Turbine - YouTube
I am including this link below from an old article because it is quite good in an exploratory potential sense and at the bottom has a chart of “expected ways to improve performance” and suggested directions of research into improving the efficiency of these machines. Those of you who have read my work will know that I have attempted to address a lot of the ideas raised here with my designs, and quite a few more besides. Ken Riely's site has a report on the Winglet's design which improved efficiency of RPM by 30% over the original Tesla patent design without load. It is important to remember that this technology sat idle with practically no interest, research or innovation at all for around 100 years! Now compare this to the $ trillions ? spent on developing ICE's over the same time period which are still at best only 20% efficient and polluting. The counter argument is normally that ICE's produce more torque which you want for car applications etc, however I counter that turbines are designed for electrical power generation and electric motors are very high torque also. There is lot's of potential here, my hybrid turbine engine designs are primarily impulse and reaction rotors with boundary layer effects secondary for example:
and my hybrid RotoMax designs:
RotoMax Rotary Engine... Tesla - Wankel - Mason HHO Hybrid
and here is something to get you all thinking, I was not going to say anything about this yet, but I changed my mind about 5 minutes ago...
Soda Can Crusher - Cool Science Experiment - YouTube
How to Crush a 55 Gallon Drum - Cool Science Demo - YouTube
How does this principle observed in the two can crushing videos above relate to the principles of operation of my RotoMax design ? That should get you thinking
Have a nice day all, I am now off to get some much needed sleep, starting to feel like a zombie!
I am going to split this up into two posts as there is a lot to cover. I have copied over the most important paragraphs from these pages:
Potential and Kinetic Energy
Whenever we say that we are producing energy, what we really mean is that we are transforming energy from one form to another that is more usable. For example, water at the top of a waterfall has more gravitational potential energy than when is at the bottom of the waterfall, because the water at the top is further from the centre of the Earth than at the bottom. So, if the water is allowed to fall from the top to the bottom, (that is, the Earth's gravitational force does work on the water moving it), then the energy stored as potential energy at the top becomes transformed into the kinetic energy of this water and we can use it to do work. This is the principle behind the production of hydroelectric power.
Potential energy, therefore, is the energy associated with different positions in the force field. The water at the top of a waterfall has higher gravitational potential energy than at the bottom because of the different positions in the gravitational field. Consider two points (A and B) in the Earth's gravitational field (g) where B is h meters higher than A. Then a mass (m) has a potential energy mgh higher than its potential energy at A. At a point 2h above A, the mass has a potential energy of 2mgh. So height is a measure of the potential energy.
Thus, an analogy with water and gravitational potential energy gives us a way to represent energy levels showing the potential energy state of a system in terms of horizontal lines. Thus we could say that the 100 m point above the lowest level in a waterfall has 980 Joules gravitational potential energy per kg of water above the lowest point.
m * g * h = E (Energy)
1 kg * 9.8 m/sec2 * 98 m = 980 J
These formulas also demonstrate that potential energy is a representation of the position of a system in a field of force. The 1 kg of water in our example has higher potential energy when it is further away from the center of force (center of the Earth). At point A, the water is more "bound" (to the Earth) than at point C. We will use this idea later to draw the analogous levels to represent chemical potential energy.
[From this we can see that water in free fall will be accelerated by gravity and will convert it's potential gravitational energy into kinetic energy which can be used to generate power. The potential difference of the system arises from the height differential in a gravitational field which is called the “head”]
Renewable Energy, Hydroelectric Power
Moving water is a powerful entity responsible for lighting entire cities, even countries. Thousands of years ago the Greeks used water wheels, which picked up water in buckets around a wheel. The water's weight caused the wheel to turn, converting kinetic energy into mechanical energy for grinding grain and pumping water. In the 1800s the water wheel was often used to power machines such as timber-cutting saws in European and American factories. More importantly, people realized that the force of water falling from a height would turn a turbine connected to a generator to produce electricity. Niagara Falls , a natural waterfall, powered the first hydroelectric plant in 1879.
Man-made waterfalls dams were constructed throughout the 1900s in order to maximize this source of energy. Aside from a plant for electricity production, a hydropower facility consists of a water reservoir enclosed by a dam whose gates can open or close depending on how much water is needed to produce a particular amount of electricity. Once electricity is produced it is transported along huge transmission lines to an electric utility company.
"By the 1940s, the best sites for large dams had been developed." But like most other renewable sources of energy, hydropower could not compete with inexpensive fossil fuels at the time. "It wasn't until the price of oil skyrocketed in the 1970s that people became interested in hydropower again." Today one-fifth of global electricity is generated by falling water.
There are several favorable features of hydropower. Anywhere rain falls, there will be rivers. If a particular section of river has the right terrain to form a reservoir, it may be suitable for dam construction. No fossil fuels are required to produce the electricity, and the earth's hydrologic cycle naturally replenishes the "fuel" supply. Therefore no pollution is released into the atmosphere and no waste that requires special containment is produced. Since "water is a naturally recurring domestic product and is not subject to the whims of foreign suppliers," there is no worry of unstable prices, transportation issues, production strikes, or other national security issues.
Hydropower is very convenient because it can respond quickly to fluctuations in demand. A dam's gates can be opened or closed on command, depending on daily use or gradual economic growth in the community. The production of hydroelectricity is often slowed in the nighttime when people use less energy. When a facility is functioning, no water is wasted or released in an altered state; it simply returns unharmed to continue the hydrologic cycle. The reservoir of water resulting from dam construction, which is essentially stored energy, can support fisheries and preserves, and provide various forms of water-based recreation for locals and tourists. Land owned by the hydroelectric company is often open to the public for hiking, hunting, and skiing. Therefore, "hydropower reservoirs contribute to local economies. A study of one medium-sized hydropower project in Wisconsin showed that the recreational value to residents and visitors exceeded $6.5 million annually." Not to mention the economic stimulation provided by employment.
Hydroelectric power is also very efficient and inexpensive. "Modern hydro turbines can convert as much as 90% of the available energy into electricity. The best fossil fuel plants are only about 50% efficient. In the US , hydropower is produced for an average of 0.7 cents per kilowatt-hour (kWh). This is about one-third the cost of using fossil fuel or nuclear and one-sixth the cost of using natural gas," as long as the costs for removing the dam and the silt it traps are not included. Efficiency could be further increased by refurbishing hydroelectric equipment. An improvement of only 1% would supply electricity to an additional 300,000 households.
Hydropower has become "the leading source of renewable energy. It provides more than 97% of all electricity generated by renewable sources worldwide. Other sources including solar, geothermal, wind, and biomass account for less than 3% of renewable electricity production." In the US , 81% of the electricity produced by renewable sources comes from hydropower. "Worldwide, about 20% of all electricity is generated by hydropower." Some regions depend on it more than others. For example, 75% of the electricity produced in New Zealand and over 99% of the electricity produced in Norway come from hydropower.
The use of hydropower "prevents the burning of 22 billion gallons of oil or 120 million tons of coal each year." In other words, "the carbon emissions avoided by the nation's hydroelectric industry are the equivalent of an additional 67 million passenger cars on the road 50 percent more than there are currently." The advantages of hydropower are therefore convincing, but there are some serious drawbacks that are causing people to reconsider its overall benefit.
Since the most feasible sites for dams are in hilly or mountainous areas, the faults that often created the topography pose a great danger to the dams and therefore the land below them for thousands of years after they have become useless for generating power. In fact, dam failures do occur regularly due to these terrain conditions, and the effects are devastating.
The majority of this post is self explanatory. The key point I want everyone to realise is that the ocean is the world's biggest dam, it is so huge and contains so much water that it will continue to supply water under natural atmospheric, and gravitational pressure at a virtually infinite mass flow rate. So if we were to adopt the siphon principle, we could reduce or eliminate siltation inlet problems, harness potential gravitational energy in freefall, and possibly convert that high mass flow rate into higher pressure for direct injection into a turbine by using the de laval nozzle principle on a very large scale.
Some background information. However if we are going to apply these principles on a small scale at home we have to look at how we can do that:
Pico hydro is a term used for hydroelectric power generation of under 5kW. It is useful in small, remote communities that require only a small amount of electricity - for example, to power one or two fluorescent light bulbs and a TV or radio in 50 or so homes. Even smaller turbines of 200-300W may power a single home in a developing country with a drop of only 1 meter. Pico-hydro setups typically are run-of-stream, meaning that dams are not used, but rather pipes divert some of the flow, drop this down a gradient, and through the turbine before being exhausted back to the stream.
Like other hydroelectric and renewable source power generation, pollution and consumption of fossil fuels is reduced (there is still typically an environmental cost to the manufacture of the generator and distribution methods)
This is particularly useful for what we are exploring with sink science! There is also the possibility of using small streams that run through your property to do the same thing, especially if there is a height difference between the top and bottom of the streams, a head.
Now let's examine the most efficient way to extract this water flow energy:
The Pelton wheel is an impulse turbine which is among the most efficient types of water turbines. It was invented by Lester Allan Pelton in the 1870s. The Pelton wheel extracts energy from the impulse (momentum) of moving water, as opposed to its weight like traditional overshot water wheel. Although many variations of impulse turbines existed prior to Pelton's design, they were less efficient than Pelton's design; the water leaving these wheels typically still had high speed, and carried away much of the energy. Pelton's paddle geometry was designed so that when the rim runs at ½ the speed of the water jet, the water leaves the wheel with very little speed, extracting almost all of its energy, and allowing for a very efficient turbine.
The Pelton Turbine is going to be a much better option for extracting the energy in the water flow efficiently and is not too demanding a project. At this point we will have a turbine spinning at approximately 200 RPM, so we either need to design our PMA to generate most efficiently at a low speed, or we need to convert torque into higher RPM. This can be achieved using a pulley and belt system which will step up the RPM by a factor of 10 to give us an alternator RPM of 2000 in this example.
The previously stated goal of running the alternator and generating between 30 – 50 Watts no longer seems so improbable. Your results will vary depending on the design of your system, efficiencies of components, and the water pressure and flow rate available for you to use. If you can generate electricity in the 100+ Watt range then things will get really interesting!
A quick summary so far...
Water flow available to you for free is efficiently converted into rotary moment, this rotary moment is then used to generate electricity via a PMA. This electricity is then converted to HHO in a small dry cell. The water that has been used in these energy conversion processes has had most of it's kinetic energy stripped from it and now resides in a reservoir, where it only has potential energy.
Via controlled release from this potential energy reservoir in small, rapid droplets, the potential energy is converted to kinetic energy by gravity and the thin water stream falls through a Kelvin generator and generates a cyclic pulse of high voltage DC electricity. The Kelvin generator is a separate system from the Turbine generator and so it's properties can be considered separately in relation to the source energy.
The output flow rate from the potential energy reservoir required for operation of the Kelvin generator is not equal to the input flow rate or pressure of the inlet tap, it is considerably less, therefore a potential difference has been created, in order to balance these two factors it will be necessary to increase the flow rate from the potential energy reservoir. In practice this will mean multiple Kelvin generators being installed until the flow rate from the potential energy reservoir = the water tap inlet flow rate. Keep adding Kelvin generators until the potential energy reservoir at the turbine exhaust maintains a steady water level, then the system is balanced.
We have already discussed how a system like this can produce HHO and an ignition source, but now you have to decide what your going to do with all those extra high voltage DC spikes being generated by the additional Kelvin generators. Maybe a good way to experiment with HV DC low Current electrolysis ? Can you store the energy efficiently in a capacitor and transform it to a lower voltage higher current output for electrolysis by using a transformer ?
The transformer may be considered as a simple two-wheel 'gearbox' for electrical voltage and current. The primary winding is analogous to the input shaft and the secondary winding to the output shaft. In this comparison, current is equivalent to shaft speed, voltage to shaft torque. In a gearbox, mechanical power (speed multiplied by torque) is constant (neglecting losses) and is equivalent to electrical power (voltage multiplied by current) which is also constant.
The gear ratio is equivalent to the transformer step-up or step-down ratio. A step-up transformer acts analogously to a reduction gear (in which mechanical power is transferred from a small, rapidly rotating gear to a large, slowly rotating gear): it trades current (speed) for voltage (torque), by transferring power from a primary coil to a secondary coil having more turns. A step-down transformer acts analogously to a multiplier gear (in which mechanical power is transferred from a large gear to a small gear): it trades voltage (torque) for current (speed), by transferring power from a primary coil to a secondary coil having fewer turns.
[Above is the principle of converting RPM and Torque already discussed above, in a different context with the common denominator of energy types all being viewed as fluids.] The many electrical geniuses that lurk on these forums would be most helpful if they could design and demonstrate a practical way to transform the approximate 15kV from a Kelvin generator into useful power for HHO production, or other applications... Please ?
So, quite a lot to take in, lot's of avenues to explore. My personal goal is to develop a HHO processing plant that is powered by water pressure from the tap and then use that HHO to run a small scale engine, of some type. The principles learned with these little models will help develop the technology to be deployed on a larger scale with a water supply source available that has more potential energy to tap.
Another avenue that I am contemplating exploring is using the small scale HHO produced and detonating it inside a cylinder chamber, transferring that energy to a piston which will compress air, generating heat that will then be transferred to water... here is what I am talking about:
Weekend Project: Fire Piston - YouTube
So my thinking is, Produce HHO from your tap, detonate it with a Kelvin generator spark, the expansion from the gases drives the piston, which rapidly heats the air in the tube (compressible gas) and transfers all that pressure and heat to a small volume of water in the bottom of the chamber, which vaporises the water instantly into steam, and as steam expands up to 1600 times it's liquid volume, it drives the piston back up with huge force... ooh and look at all these model piston engines with a crankshaft and everything...
Just Engines Model Fuel Info
Have to overcome the oil requirement issue, maybe inject it with the water charge, maybe use emulsified oil and water which Mr Goose kindly added to my information library, have to machine a new head gasket incorporating the fire tube and HHO chamber, but overall considering the gearbox and crankshaft are already there, and the engines are very cheap really, and some of them generate 4HP + it might be a nice little way of exploring this project. Imagine if you could run a 4HP micro motor from your tap ?
Steam Engines | Cotswold Heritage | Model Engineering Casting Kits
Does this make me an ICE guy now, or a steam guy, or a turbine guy... ?
Here is some interesting Pelton turbine information:
smartdrive pelton wheel 1 - YouTube
Pelton water turbine generator powering saw - YouTube
Pelton Turbine Learning Module - http://octavesim.com - YouTube
Turbina Pelton, Pelton Turbine, Pelton Wheel - YouTube
Pelton turbine hydro.wmv - YouTube
Last edited by evolvingape : 02-19-2012 at 03:27 AM.
Let's bring all this information round full circle and see how it can assist those people heavily invested or otherwise interested in gasifier systems for off grid power generation...
Here we have a commercial Pelton Turbine, very well made, but expensive, so I will be making my own.
PowerSpout - Water goes in, Power comes out
and a very useful calculator:
So, this is great if I live on a mountain or have the Amazon flowing past my back garden but what do I do if I cannot use the mains water pressure because it is metered and will cost me a fortune, and have no source of water with a pressure head I can access ?
The Pulsometer steam pump is a pistonless pump which was patented in 1872 by American Charles Henry Hall. In 1875 a British Engineer bought the patent rights of the Pulsometer and it was introduced to the market soon thereafter. The invention was inspired by the Savery steam pump invented by Thomas Savery. Around the turn of the century, it was a popular and efficient pump for quarry pumping.
This extremely simple pump was made of cast iron, and had no pistons, rods, cylinders, cranks, or flywheels. It operated by the direct action of steam on water. The mechanism consisted of two chambers. As the steam condensed in one chamber, it acted as a suction pump, while in the other chamber, steam was introduced under pressure and so it acted as a force pump. At the end of every stroke, a ball valve consisting of a small rubber ball moved slightly, causing the two chambers to swap functions from suction-pump to force-pump and vice versa. The result was that the water was first suction pumped and then force pumped.
The pump ran automatically without attendance. It was praised for its "extreme simplicity of construction, operation, compact form, high efficiency, economy, durability, and adaptability". Later designs were improved upon to enhance efficiency and to make the machine more accessible for inspection and repairs, thus reducing maintenance costs.
So you can run your gasifier, create steam pressure in a boiler, use this pressure in an automatic pump to create a pressure head in your water supply, use the higher pressure head to drive a Pelton turbine which drives your generator, and then recirculate the water back to the reservoir for another cycle.
No expensive engines or turbines involved, and very useful power output without the need for a natural pressure head. This system will also operate in a suitable boiler over an open fire, or preferably hot ashes, but will be less efficient than a gasifier design and require more fuel, but does allow you to get going on the other parts of the system and add the gasifier last.
As always the steam boiler is the most dangerous part of the system so pay this the most attention!
The Pulsometer Steam Pump is a virtually forgotten technology from what I can gather and there is very little information available on it, but I did manage to find a few pictures:
Pulsometer Engineering Co
You don't need thousands of psi output from it, but something like 100 psi at a high mass flow rate would be extremely useful in this application.
Last edited by evolvingape : 02-21-2012 at 03:08 PM.
This is my favourite picture:
“The illustration shows a Pulsometer attached to a Vertical Boiler on Wheels, forming a very handy arrangement for many purposes. The Pulsometer can readily be detached from the boiler, and slung down a shaft, well, or used for other work, at some distance away.”
Now imagine the same device in the illustration, built using modern technology, with a gasifier powering the boiler, and a Pelton turbine on the pump outlet. It will be portable so that it can be used anywhere there is a ground lake, it can be built into a vehicle with an onboard reservoir just like a fire truck, or it can sit in your back garden and use a reservoir of water, that you dug out and then filled just like a pond. The only requirement will be fuel... woodchips!
Not an undesirable system to my mind... you guys still with me ?
I almost forgot, here is the output figures they give for different models:
Model 1 - 600 Gallons per Hour
Model 2 - 2000 Gallons per Hour
Model 3 - 3800 Gallons per Hour
Model 4 - 5000 Gallons per Hour
Model 5 - 9000 Gallons per Hour
Model 6 - 13200 Gallons per Hour
Model 7 - 17000 Gallons per Hour
Model 8 - 28000 Gallons per Hour
Model 9 - 35000 Gallons per Hour
Model 10 - 52000 Gallons per Hour
Model 11 - 65000 Gallons per Hour
The pumps are priced between £10 and £200 so I guess that is incentive enough for me to get working on that time machine!
I wonder what the "GREL" arrangement means ? 40 - 50% saving on steam sure sounds interesting... hmmm ? Should be in the patent
Last edited by evolvingape : 02-19-2012 at 05:11 AM.
Ok... I have been in the dog house for a week now and it is time to stop working and take a break... so... here is the last little bit you need:
Heating Water With HHO Hydroxy Hydrogen Part 1 of 2 from HHOG Labs - YouTube
Heating Water With HHO Hydroxy Hydrogen Part 2 of 2 from HHOG Labs - YouTube
So, no need for steam injectors, no need to vent the boiler to atmosphere to refill... just heat it in a way that the waste product is water and refills your boiler... close the loop
That's it, that's all the information you need, so go forth and be happy and free!
Pulsometer Theory of Operation Part 1
562 Forms of the Steam Engine
Halls pulsometer is a peculiar pumping engine without cylinder or piston, which may be regarded as a modern representative of the engine of Savery. The sectional view fig 261, shows it's principal parts. There are two chambers, A, A', narrowing towards the top, where the steam pipe B enters. A ball valve C allows steam to pass into one of the chambers and closes the other. Steam entering (say) the right hand chamber forces water out of it past the clack valve V into a delivery passage D, which is connected with an air vessel. When the water level in A sinks so far that steam begins to blow through the delivery passage, the water and steam are disturbed and so brought into intimate contact, the steam in A is condensed and a partial vacuum is formed. This causes the ball valve C to rock over and close the top of A, while water rises from the suction pipe E to fill that chamber. At the same time steam begins to enter the other chamber A', discharging water from it, and the same series of actions is repeated in either chamber alternately.
While the water is being driven out there is comparatively little condensation of steam, partly because the shape of the vessel does not promote the formation of eddies, and partly because there is a cushion of air between the steam and the water. Near the top of each chamber is a small air valve opening inwards, which allows a little air to enter each time a vacuum is formed. When any steam is condensed, the air mixed with it remains on the cold surface and forms a non conducting layer. Further, when the surface of the water has become hot the heat travels very slowly downwards so long as the surface remains undisturbed. The pulsometer of course cannot claim high efficiency as a thermodynamic engine, but it's suitability for situations where other steam pumps cannot be used, and the extreme simplicity of it's working parts, make it valuable in certain cases. Trials of it's performance have shown that under favourable conditions a pulsometer may use no more than 150lb of steam per effective horse power hour. This consumption, large as it is when judged by the standard of an efficient large engine using steam expansively, does not compare very unfavourably with that of small non rotative steam pumps.
1 Proc. Inst. Mech. Eng. 1893, p456
The Steam-Engine and Other Heat-Engines - Google Books
This is google books, when they realise people want to read this they will try and make you pay for it, so I have typed it out. Ignore the references to letters designating parts of the system, as the diagram is not there, but that does not matter because I will provide a better one in a few minutes.
This has valuable insights into the theory of operation of the Pulsometer, which when combined with Part 2 about to follow tells you everything you need to know to replicate the design.
Pulsometer Theory of Operation Part 2
This section is from the book "Cassell's Cyclopaedia Of Mechanics", by Paul N. Hasluck. Also available from Amazon: Cassell's Cyclopaedia Of Mechanics.
The illustration shows a sectional elevation of a pulsometer, which is an appliance for raising water by the alternate pressure and condensation of steam.
To describe the parts, K is a pipe from a boiler containing steam under pressure. The gunmetal spherical valve is free to move and to alternately cover the necks I and J. The latter form the upper parts of the chambers A A, into which water passes through the valves E E from the suction pipe F. G G are doors for access to the valves E E for repairs or other attention.
Near the bottom ends of A A are side outlets, as shown by the dotted circles, covered by the valves V P, also shown by dotted lines, opening into a chamber with which are connected the air vessel K (should be B) and the outlet branch D, to which the delivery pipe is attached. The action is as follows.
The pump is first charged with water through plugholes provided for the purpose, and then steam is turned on at K. This presses on the water on the right hand chamber A (which is not covered by the spherical valve), and forces it, as shown by the arrows, through the right-hand valve F and up the delivery pipe.
The steam in the right-hand chamber A then condenses, and causes the spherical valve to roll over and cover the neck J, and also creates a vacuum, which is again filled with water through the right-hand valve E from the suction pipe C. When the valve has rolled over J, the steam passes through the open neck I and presses on the water in the left-hand chamber A, forcing it through the dotted left-hand valve F into the delivery chamber.
When the left-hand chamber A is nearly empty, the valve is again pulled back by the condensation of the steam in the chamber, which again fills with water during the time the other chamber is being emptied, and these actions continue as long as steam under efficient pressure is supplied.
As water will not rise in a vacuum beyond a certain height, a pulsometer should not be fixed more than about loft. or 20 ft. above the water to be raised, although theoretically the limit is a little more than 30 ft. The pump can be slung on chain s in a well or sump, so that there is very little trouble in fixing it, or lowering it when necessary for keeping within a working distance of the water.
The height to which a pulsometer will raise water depends on the pressure of steam in the boiler, which is used in conjunction with the apparatus.
Read more: The Pulsometer
The central chamber that was causing everyone a headache operates as a pneumatic buffer to prevent water hammer, as in a hydraulic system. The two non return valves that allow air into the chambers (not shown on any diagrams) now make perfect sense as to the function, because of the insulating and compressible layer they form between the steam and the water, preventing instant condensation on contact and allowing the Pulsometer to function as both a vacuum and compression pump.
With modern technology and improved design this device will become much more efficient, it reportedly produces 50 metres of head at high mass flow rates, and as we all know mass flow rate can be converted into higher pressure by use of a de laval nozzle.
The system I have described in this thread is perfect for small scale home power generation, and if at some point in the future a heat source becomes available that does not require high levels of fuel it can simply replace the gasifier.
I have highlighted in bold what I believe is an error in the description, the air vessel is denoted B on the diagram, K is the steam injection pipe.
Last edited by evolvingape : 02-21-2012 at 06:22 AM.
The Turgo turbine is an impulse water turbine designed for medium head applications. Operational Turgo Turbines achieve efficiencies of about 87%. In factory and lab tests Turgo Turbines perform with efficiencies of up to 90%.
Developed in 1919 by Gilkes as a modification of the Pelton wheel, the Turgo has some advantages over Francis and Pelton designs for certain applications.
First, the runner is less expensive to make than a Pelton wheel. Second, it doesn't need an airtight housing like the Francis. Third, it has higher specific speed and can handle a greater flow than the same diameter Pelton wheel, leading to reduced generator and installation cost.
Turgos operate in a head range where the Francis and Pelton overlap. While many large Turgo installations exist, they are also popular for small hydro where low cost is very important. Like all turbines with nozzles, blockage by debris must be prevented for effective operation.
Theory of operation
The Turgo turbine is an impulse type turbine; water does not change pressure as it moves through the turbine blades. The water's potential energy is converted to kinetic energy with a nozzle. The high speed water jet is then directed on the turbine blades which deflect and reverse the flow. The resulting impulse spins the turbine runner, imparting energy to the turbine shaft. Water exits with very little energy. Turgo runners may have an efficiency of over 90%.
A Turgo runner looks like a Pelton runner split in half. For the same power, the Turgo runner is one half the diameter of the Pelton runner, and so twice the specific speed. The Turgo can handle a greater water flow than the Pelton because exiting water doesn't interfere with adjacent buckets.
The specific speed of Turgo runners is between the Francis and Pelton. Single or multiple nozzles can be used. Increasing the number of jets increases the specific speed of the runner by the square root of the number of jets (four jets yield twice the specific speed of one jet on the same turbine ).
Renewable Components - Manufacturers of MiniWind Downwind Domestic Turbines
These Turgo Cups are moulded in very durable Polycarbonate plastic, and are easily replaceable if they become worn or damaged.* Their design allows the user to create a wide range of wheel diameters, but we can supply a moulded plastic turgo disc of 260mm diameter (giving a jet PCD of 330mm) to match the performance of our 2200W PMG range of generators.
The design of our turgo discs gives a very robust mounting of the cups, allowing the completed turgo wheel to be used with up to 4 jets of 30mm diameter, giving powers from a few hundred watts to over 2200W.* The flexibility of this design allows the user to match the turgo turbine's performance to the available water head and flow rate.* Each plastic turgo disc takes 24 turgo cups.
Turgo turbines are generally more suited to lower head, higher flow rate applications than the pelton turbines, and typically your site will require a minimum head height of 10-15m to be effective.
Custom Turgo Turbines - better than a pelton.
3 Phase Brushless generators for MicroHydro
EcoInnovation - Pelton Spoons and Fixings
The Turgo Turbine, quite an interesting device. Let's see what we can learn from the available information...
The efficiency is good with operational turbines producing up to 87%, and controlled lab tests under optimum conditions producing 90%, and very similar to the Pelton Turbine. When you factor in the added simplicity of the spoon design, and the suitability of the Turgo to lower head (pressure) and higher mass flow rate (larger volume of water), this is the design that ticks more boxes.
“Increasing the number of jets increases the specific speed of the runner by the square root of the number of jets ( four jets yield twice the specific speed of one jet on the same turbine )”. This shows us that adding more jets is not necessarily a good idea, with diminishing returns, so a 2 jet per rotor design will stabilise and produce more torque per rotor at a slower speed, and we can compensate by adding more rotors and the extra jets can power them more efficiently, with a cost in specific speed of the drive shaft.
Minimum head height for effective operation of a Turgo is 10 – 15m, 10m of head = 1 Bar, 1 Bar = 14 psi, So a Turgo will need between 14 and 21 psi minimum to operate, which is well within the range of tap water, and you can increase the mass flow by turning on a second tap. The water company will sense a loss of pressure, and boost the pressure to your ring main to compensate, after a few weeks they will figure they have a leak and send someone to check it out, who will promptly go away scratching his head finding no leak anywhere!
260mm diameter is a large wheel according to this information, with a jet PCD (Pitch Centre Diameter) of 330mm. Ok, so now we know that, let's look at how we could build one of these as cheap as possible...
Turgo Turbine Part 2
SM20 Bolt on Hub, Disc Diameter 270mm, Bush size 2012, £33.66 (1 off)
SM Bolt on Hubs
2012 Taper Bush, Bore Size 25mm, £6.26 (1 off)
2012 Taper Bushes
Flanged Bearing Unit 4 Bolt Cast 25mm, £9.77 ea, (2 off @ £19.54)
Flanged Bearing Unit 4 Bolt Cast 25mm
25mm Axle with pocket keyway and circlip groove £30.95 (1 off)
KART CADET AXLE 25MM X 1020MM LONG - BRAND NEW - | eBay
Alternatively get a custom shaft from the horses mouth:
Kart Components - Axles - Copper Axles - Hollow Pocket Key Axles
Box of 24 Red Soap Dishes Individually Wrapped | eBay
So what we have above is an economical way to build a heavy duty Turgo turbine. I have opted for the hub because it will last a very long time and is the right size, The taper lock bush is very secure on its own and should not slip but can be enhanced for torque transmission to shaft with a key. The bearings are 4 bolt flange mount so you fit them facing each other on opposite sides of the housing, you have to use two because it will hold the shaft rigid, a single bearing will float as they are self aligning.
The rotor is going to be heavy compared to a plastic injection molded one, but the mass will function as a flywheel, and it's a small price to pay considering the robustness and cost of the design.
The shaft, being a common part in the Kart industry will be easy to replace and is a bargain at the price, if you are going for the single rotor horizontal Turgo design you will only need to use 200mm of the shaft or thereabouts, which has a keyway and a circlip groove (to stop the shaft dropping through the bearing should the grub screw fail).
The spoons are the hard part, I have just bought a box of the soap dishes, I plan to use them as a master. Cut some rectangular stainless box section to size for strength and attachment via double bolt to holes drilled in the hub, and then cast polyurethane fast cast (with suitable fillers for strength and waterproofing) around them to form the finished spoons. I will be using the soap dishes as masters to give me close to the correct shape. The added bonus is that once I am happy with the performance and design I can make a pattern and then cast 24 in one go, producing a complete set in about 30 minutes, which will be handy if your friends like your turbine and want to buy one
I myself will be deviating slightly from what I have described here due to my circumstances. I will be mounting multiple Turgo rotors vertically with a bearing and hub each end. This is to keep water out of the bearing, which would be at the bottom in a multiple horizontal rotor system. If your just going for a single horizontal rotor there is no problem suspending the rotor from two opposing bearings above.
I will be using stainless steel discs bolted between my end hubs to mount the spoons on. This is because I have them already cut as they are from the cancelled HELT project of a couple of years ago. Finally I have found a use for them!
I will probably be using 3 Turgo rotors because I have a plain 300mm shaft in 25mm diameter already, and 3 is all I think I can fit on it. If you go with the Kart axle you will have a 1 meter shaft which would probably easily handle 10 rotors.
Once the rotor is constructed, degreased, and loctited permanently in place I will be coating it in either spray paint, clear varnish or some type of waterproof epoxy to prevent it rusting. Seems a sensible option.
Later on when Gasifier powered Steam boilers, powering a Pulsomenter, come on line the additional rotors will be how to use all that mass flow.
I will be using a DC500 PMA because once again I already have it left over from the HELT, the issue here is that water turbines typically operate at between 200 – 300 RPM, so in order to achieve charging voltage I am going to have to construct a gearbox, which will be pulleys and belts, to step up my RPM from 200 – 300 range to 2000 – 3000 RPM range. This is a ratio of 10:1.
It would be most useful if we had a DIY PMA design along the lines of windmill's using many coils, this would mean that we could produce the same power without having to use a gearbox. There is quite an interest in custom PMA's for wind turbines so lot's of information out there about it.
One thing to mention is that gasifiers are particularly interesting because they produce two outputs, the heat from the combustion chamber can be used to run a boiler by sleeving a double wall, the same principle the kelly kettle works on, and the combustible gases produced can also be burnt through a nozzle as with traditional boiler technology to run a second boiler. This will allow you to run two Pulsometers, which will provide much more mass flow from just a single closed loop water reservoir, and the resultant water can be injected into separate rotors on the same shaft, in effect doubling your power generation from the gasifier.
One thing I want to point out is that the suggestion of burning a HHO torch to refill the boiler should be considered carefully. It remains to be established if the isostatic pressure inside the boiler will extinguish the flame, if it does so then the pressure will attempt to move up the HHO feed line and into your bubbler. A non return valve may be effective in this scenario, but much testing needed SAFELY before this becomes viable. The idea is not to heat the boiler purely with HHO, but to burn HHO at a rate that replaces the steam being used. Steam injectors will remain the most efficient way of filling your boiler for now, but this is also about developing new technologies and techniques.
And finally some links:
Steam powered Generator
Otherpower.com: Steam Powered Generator - YouTube
1/2" / 12.7mm STAINLESS STEEL SQUARE TUBE / BOX -750mm | eBay
Mold Making - Mass Casting Complex Parts (w/ parting line) - YouTube
RTV Silicone Rubber
Polyurethane Fast Cast Resin
3m Glass Bubbles : Microspheres
Glass Fibre Reinforcements : Composite Materials
Bearings | Oil Seals | Rotary Shaft Seals | Metric | R23 Double Lip | R21 Single Lip |
About the heating of the water with HHO, i would suggest using a preferably tungsten plate to aim your flame at and the water above.
Why? note: It's my opinion, no scientific claim
In my experience i came to the conclusion the temperature of HHO flame differs with the subject touched by the flame.
I know it sounds strange, but you can almost touch a hho flame with your skin (don't try!) but when you aim the flame at a solid material it gets much hotter.
So heating a tungsten, or more simple steel or pottery from the outside makes it more hot as with direct heating the water with the flame inside.
See this: Water power - YouTube
Last edited by Cherryman : 02-21-2012 at 07:47 AM.
Yes there are quite a few options I have been considering for a while now.
Have a look at these links:
Plasma Flame Theory
Plasma Gas Flow Conversion Calculator for Metco 7MC
Plasma spray processing - Appropedia: The sustainability wiki
One viable option I have been thinking about pursuing is placing an air venturi on the low pressure HHO line from the bubbler. As we can see from the ionisation energies chart Nitrogen has a high energy content per volume, and as the air around us is 78% Nitrogen with about 21% Oxygen it seems a very sensible option, considering it is abundant and free.
The other gases Argon and Helium provide more heat output, but you need to supply them so probably not the most efficient option in terms of infrastructure.
If we look at it from the perspective of using the Hydrogen as a secondary supplemental gas, and for example split the HHO line into two output torches, with the primary gas in both lines being Nitrogen, then we may substantially increase the energy created for the same amount of HHO generation cost.
I have also been considering using an absorber to store the heat, same principle as putting a hot rock into a fire and then dropping it into a bucket of water to boil the water. The only problem I have here is finding a material that will not melt from the plasma flame. HHO flames cut through just about everything and many years ago I tried it on everything I could find, everything melted. One possibility might be some kind of ceramic ?
Interesting stuff anyway, HHO heating, even secondary as a gasifier does now will become much more efficient when we start using Nitrogen plasma as the main gas, because it is free!
Just a quick note - There would be two ways of doing this:
The first would be as I have already suggested, adding a venturi to the low pressure HHO line, which would suck in a little air, but not that much as it is reliant on the HHO gas pressure passing over the venturi to draw the air in under vacuum, but still worth trying because of it's simplicity. Then compare the results to straight HHO heating and the difference is the efficiency increase.
The second way would be to run a pressurised air line via a Tesla turbine pump, and use the venturi to suck in small amounts of HHO constantly. The Tesla pump can be run from the Turgo turbine shaft with very little cost because the air is such a thin fluid it would not load it very heavily, and we are only looking for low feed pressures, and the infrastructure to drive the pump is already there. The amount of HHO required to generate a flame could then be determined by altering the pump speed. (probably best to run the Tesla pump off a variable motor for testing purposes, and when the correct speed is known hard wire that ratio from the main turbine shaft.
Multiple venturis at different points on the air line would allow plenty of time for the gases to mix before reaching the torch tip. Then it's just a case of seeing what ratios you can get to reliably stay lit and testing the resultant heat output.
Make sure you only conduct these experiments in an open container, do not go sealing it, don't want any explosions now do we
Last edited by evolvingape : 02-21-2012 at 09:36 AM.
Time for a summary of the system so far...
We have a gasifier burning a hydrocarbon fuel such as woodchips, turning potential energy into heat energy. This is our prime mover of the system and the heat generated is used to power a boiler filled with water.
The boiler creates steam pressure because the heat energy applied to the water causes a phase change from liquid into steam, which is used to power a Pulsometer steam pump.
The Pulsometer creates water pressure and high mass flow rates, via opposite cycles of expansive compression and partial vacuum implosion, the implosion caused by the rapid condensation of steam into liquid water. These cycles are used to power a Turgo turbine, optimised for low pressure and high mass flow rates.
The turbine is driven by water jets and rotates about a shaft, this rotary moment turns a permanent magnet generator that creates an electrical potential. This electrical energy is our output from the system.
The water that is exhausted from the turbine enters a reservoir. This water has been stripped of it's kinetic energy in order to turn the turbine and now has only potential energy because it is within a gravitational field.
This static water potential is then gravity fed to our individual Kelvin generator reservoirs, which are powered by the gravitational field to drip water and induce an electrostatic potential difference of 15,000 kV approximately.
The electrical output from the PMA is used to power a DC parallel series dry cell bank resistor. The HHO produced is pumped under it's own low pressure to our nozzle ring, which is submersed within an open water tank which surrounds our boiler in a secondary sleeve.
The nozzle ring consists of two sleeved tubes. The inner tube carries low pressure HHO, Hydrogen and Oxygen in a stoichiometric ratio. The outer ring carries low pressure air, 78% Nitrogen, 21% Oxygen, 1% Argon, + trace gas elements.
The two pipes carry opposite electrical potentials at the tips. This potential difference is supplied by a capacitor bank, which is in turn charged by the electrostatic potential difference of the Kelvin generators. A control circuit will sense the charge status of each individual capacitor storing energy from the Kelvin generators, and trigger capacitive discharge as appropriate in a timed pulse cycle.
The high voltage capacitive discharge will cause dielectric breakdown of the air and electrostatic discharge will result, creating a conductive path and the generation of a rapid increase in the number of free electrons and ions in the air. The spark will also cause the Hydrogen and Oxygen, supplied separately to the same location to detonate.
A high temperature plasma will result, rapidly heating the localised area, and transferring that heat energy to water that the plasma detonation is submersed in.
This water will then heat the steam boiler. Should the resultant energy released by the plasma detonations equal the energy being supplied by the gasifier, the gasifier can be turned off by closing the air intake, and the process will become self sustaining, at unity.
This system exploits the many different possibilities that exist for energy conversion, phase changes of matter, pressure, velocity, mass flow, and in general it is based on potential difference, the fundamental principle that drives our universe.
One particularly elegant example of this principle is the choice of the Turgo turbine as the optimum because it requires low pressure but high mass flow rate. The Kelvin generators require gravitational pressure and low mass flow rate, so the potential difference between the high mass flow rate of the turbine exhaust and the low mass flow rate demand of the Kelvin generators can be fully exploited by multiplying the Kelvin generators until balance is achieved. The pressure required by the Kelvin generators is supplied by the gravitational field, which converts potential energy into kinetic energy.
As the main water reservoir supplying the Pulsometer must be replenished from time to time, smart circuitry with float sensors will trigger a release from the Kelvin generator exhaust reservoirs and the water will gravity flow back to the main reservoir, where the opposite charges will neutralise, and the cycle continues.
This entire process rests on one simple question... Will the plasma be able to match the gasifier for heat output ? If the answer is yes then unity at minimum is achieved. If the answer is no then the gasifiers will continue to supply heat to make up the difference.
It sure is going to be fun finding out though... isn't it ?
HHO High Voltage Plasma Torch Detonation Heating
Let's have some fun!
HHO flame / ionized spark gap 2 - YouTube
plasma flame - YouTube
Plasma Electrolysis with tap water - YouTube
Pretty cool stuff eh!
Twin HHO and compressed air feeds to the same nozzle, with a 15,000 kV DC spark will create an ionised plasma and will also detonate Hydrogen. This Plasma Detonation Torch being submerged under water will transfer it's energy as heat and shock waves and the water will boil.
The positive gas supply pressure will create a protective shield to prevent water extuingishing the flame as demonstrated by hhoglabs very nicely!
The high voltage capacitor discharge event required to generate both plasma and ignition conditions is supplied by the gravitational field at zero cost to you.
The prime mover to stimulate a reaction in the gas composition is free as long as the water, which the gravitational field requires to work on, has a potential difference head. This is supplied continuously by the turbine, which being at a higher level relative to the centre of the Earth, will create a natural head.
The cost in moving water against gravity to balance the system, and to rotate the turbine to create the gas, is provided by the Pulsometer which is powered by steam. The generation of steam requires heat and so the input energy is now the same form as the output energy. This allows potential for a closed loop system.
The cost of producing the gas for the torch is in HHO generation and air compression (possible venturi option for the air, if there is sufficient HHO pressure to cause a vacuum, a HHO pump would be useful).
You build the infrastructure of the system in such a way that all of the necessary energy change conversions required to generate the raw materials for the reaction, are provided for, and the prime mover is a single source, heat.
The catalyst for the fluid phase change reaction is primarily gravitational, with conversion from potential to kinetic energy. The resultant effects on a water droplet, creating a static electrical field, that creates an electrical discharge event, that creates a plasma event, are all free to you.
This is how you can use gravity as a catalyst to create a plasma reaction, if the environment is right.
Fun isn't it, and you have a large selection of components, processes and systems to choose from... what can you make ?
Last edited by evolvingape : 02-22-2012 at 08:16 AM.
To give you an idea of the sort of things you can design with all these concepts here are some examples:
Take this principle:
Plasma Electrolysis with tap water - YouTube
Use it in this device:
Generate an energetic fluid impulse and fire it into this device:
RotoMax Rotary Engine... Tesla - Wankel - Mason HHO Hybrid
And this principle observed here:
Soda Can Crusher - Cool Science Experiment - YouTube
will happen... won't it ?
Cavitation is the formation and then immediate implosion of cavities in a liquid*– i.e. small liquid-free zones ("bubbles")*– that are the consequence of forces acting upon the liquid. It usually occurs when a liquid is subjected to rapid changes of pressure that cause the formation of cavities where the pressure is relatively low.
Cavitation is a significant cause of wear in some engineering contexts. When entering high pressure areas, cavitation bubbles that implode on a metal surface cause cyclic stress. This results in surface fatigue of the metal causing a type of wear also called "cavitation". The most common examples of this kind of wear are pump impellers and bends when a sudden change in the direction of liquid occurs. Cavitation is usually divided into two classes of behaviour: inertial (or transient) cavitation and non-inertial cavitation.
Inertial cavitation is the process where a void or bubble in a liquid rapidly collapses, producing a shock wave. Inertial cavitation occurs in nature in the strikes of mantis shrimps and pistol shrimps, as well as in the vascular tissues of plants. In man-made objects, it can occur in control valves, pumps, propellers and impellers.
Non inertial cavitation is the process in which a bubble in a fluid is forced to oscillate in size or shape due to some form of energy input, such as an acoustic field. Such cavitation is often employed in ultrasonic cleaning baths and can also be observed in pumps, propellers, etc.
Since the shock waves formed by cavitation are strong enough to significantly damage moving parts, cavitation is usually an undesirable phenomenon. It is specifically avoided in the design of machines such as turbines or propellers, and eliminating cavitation is a major field in the study of fluid dynamics.
Hydrodynamic cavitation describes the process of vaporisation, bubble generation and bubble implosion which occurs in a flowing liquid as a result of a decrease and subsequent increase in pressure. Cavitation will only occur if the pressure declines to some point below the saturated vapour pressure of the liquid. In pipe systems, cavitation typically occurs either as the result of an increase in the kinetic energy (through an area constriction) or an increase in the pipe elevation.
Hydrodynamic cavitation can be produced by passing a liquid through a constricted channel at a specific velocity or by mechanical rotation through a liquid. In the case of the constricted channel and based on the specific (or unique) geometry of the system, the combination of pressure and kinetic energy can be created when the hydrodynamic cavitation cavern downstream of the local constriction generating high energy cavitation bubbles.
The process of bubble generation, subsequent growth and collapse of the cavitation bubbles results in very high energy densities, resulting in very high temperatures and pressures at the surface of the bubbles for a very short time. The overall liquid medium environment, therefore, remains at ambient conditions. When uncontrolled, cavitation is damaging; however, by controlling the flow of the cavitation the power is harnessed and non-destructive. Controlled cavitation can be used to enhance chemical reactions or propagate certain unexpected reactions because free radicals are generated in the process due to disassociation of vapours trapped in the cavitating bubbles.
Orifices and venturi are reported to be widely used for generating cavitation. A venturi, because of its smooth converging and diverging sections, has an inherent advantage, over the orifice, that it can generate a higher velocity at the throat for a given pressure drop across it. On the other hand, an orifice has an advantage that it can accommodate more number of holes (larger perimeter of holes) in a given cross sectional area of the pipe.
Hydrodynamic cavitation can improve industrial processes. For instance, cavitated corn slurry show higher yields in ethanol production compared to uncavitated corn slurry in dry milling facilities.
This is also used in the mineralization of bio-refractory compounds which otherwise would need extremely high temperature and pressure conditions since free radicals are generated in the process due to the dissociation of vapours trapped in the cavitating bubbles, which results in either the intensification of the chemical reaction or may even result in the propagation of certain reactions not possible under otherwise ambient conditions.
Pumps and propellers
Major places where cavitation occurs are in pumps, on propellers, or at restrictions in a flowing liquid.
As an impeller's (in a pump) or propeller's (as in the case of a ship or submarine) blades move through a fluid, low-pressure areas are formed as the fluid accelerates around and moves past the blades. The faster the blades move, the lower the pressure around it can become. As it reaches vapour pressure, the fluid vaporizes and forms small bubbles of gas. This is cavitation. [B]When the bubbles collapse later, they typically cause very strong local shock waves in the fluid, which may be audible and may even damage the blades[/b].
Cavitation in pumps may occur in two different forms:
Suction cavitation occurs when the pump suction is under a low-pressure/high-vacuum condition where the liquid turns into a vapour at the eye of the pump impeller. This vapour is carried over to the discharge side of the pump, where it no longer sees vacuum and is compressed back into a liquid by the discharge pressure.
This imploding action occurs violently and attacks the face of the impeller. An impeller that has been operating under a suction cavitation condition can have large chunks of material removed from its face or very small bits of material removed, causing the impeller to look spongelike. Both cases will cause premature failure of the pump, often due to bearing failure. Suction cavitation is often identified by a sound like gravel or marbles in the pump casing.
In automotive applications, a clogged filter in a hydraulic system (power steering, power brakes) can cause suction cavitation making a noise that rises and falls in synch with engine RPM. It is fairly often a high pitched whine, like set of nylon gears not quite meshing correctly.
Discharge cavitation occurs when the pump discharge pressure is extremely high, normally occurring in a pump that is running at less than 10% of its best efficiency point. The high discharge pressure causes the majority of the fluid to circulate inside the pump instead of being allowed to flow out the discharge.
As the liquid flows around the impeller, it must pass through the small clearance between the impeller and the pump housing at extremely high velocity. This velocity causes a vacuum to develop at the housing wall (similar to what occurs in a venturi), which turns the liquid into a vapor.
A pump that has been operating under these conditions shows premature wear of the impeller vane tips and the pump housing. In addition, due to the high pressure conditions, premature failure of the pump's mechanical seal and bearings can be expected. Under extreme conditions, this can break the impeller shaft.
Innovative Hydrodynamic Cavitation Technologies from Arisdyne
Hydrodynamic Cavitation can occur in any turbulent fluid. The turbulence produces an area of greatly reduced fluid pressure. The fluid vaporizes due to the low pressure, forming a cavity. At the edges of the cavity, small amounts of vapor break off. These form smaller cavities 100 nm to 3 mm in diameter. The smaller cavities implode under the high pressure surrounding them. This process of formation and collapse is called cavitation.
Cavitation is an enormously powerful process. Conditions in the collapsing cavity can reach 5000°C and 1000 atmospheres. The implosion takes place during the cavitation process in milliseconds, releasing tremendous energy in the form of shockwaves. The power of these waves generated by the cavitation process disrupts anything in their path. Whether the waves are destructive or productive depends on Arisdyne's process control.
How does hydrodynamic cavitation differ from ultrasonic cavitation?
Ultrasonic cavitation is dependent on a source of vibrations. This makes them difficult or impossible to scale up and often creates "hot spots" in the dispersion/emulsion. There is no upper or lower flow rate limitations to a CFC™ system, and all fluids flow continuously through the cavitation zone.
Won’t CFC™ cause my equipment to wear more quickly?
Uncontrolled cavitation is a very destructive force. The CFC™ system uses controlled cavitation. Optimal process conditions also protect your equipment from impingement. In fact, CFC™ systems last longer than those with moving parts.
What if one of my reactants is a particulate?
CFC™ works equally well on solid and liquid reactants. Solids are fractured into smaller pieces (100 nm to 3 mm in diameter). Smaller particles mean a better dispersion and greater surface.
Much research has been done on preventing cavitation. Its uncontrolled form causes damage to turbulent-flow systems. But Arisdyne Systems’ patented hydrodynamic cavitation technology harnesses it’s power.
CFC™ (Controlled Flow Cavitation™) controls the location, size, density, and intensity of cavity implosions. The system is calibrated to produce optimum process conditions. Shockwaves resulting from the implosions impact the surrounding process fluid. Tiny droplets or particles result producing high-quality emulsions and dispersions.
Innovative Hydrodynamic Cavitation Technologies from Arisdyne
And a video cool... hmmm... those shapes look familiar... where have I seen them before ? what do they do ?
A de Laval nozzle (or convergent-divergent nozzle, CD nozzle or con-di nozzle) is a tube that is pinched in the middle, making a carefully balanced, asymmetric hourglass-shape. It is used to accelerate a hot, pressurized gas passing through it to a supersonic speed, and upon expansion, to shape the exhaust flow so that the heat energy propelling the flow is maximally converted into directed kinetic energy.
Because of this, the nozzle is widely used in some types of steam turbines, and is an essential part of the modern rocket engine. It also sees use in supersonic jet engines.
Similar flow properties have been applied to jet streams within astrophysics.
Nozzles can be (top to bottom):
If under or overexpanded then loss of efficiency occurs. Grossly overexpanded nozzles have improved efficiency, but the exhaust jet is unstable.
A jet is an efflux of fluid that is projected into a surrounding medium, usually from some kind of a nozzle, aperture or orifice. Jets can travel long distances without dissipating. In the Earth's atmosphere there exist jet streams that travel thousands of miles.
Jet fluid has higher momentum compared to the surrounding fluid medium.In the case where the surrounding medium is assumed to be made up of the same fluid as the jet and this fluid has a viscosity then the surrounding fluid near the jet is assumed to be carried along with the jet by a process called entrainment.
Some animals, notably cephalopods use a jet to propel themselves in water. Similarly, a jet engine as it name suggests, emits a jet used to propel rockets, aircraft, jetboats, and submarines.
A supercritical fluid is any substance at a temperature and pressure above its critical point, where distinct liquid and gas phases do not exist. It can effuse through solids like a gas, and dissolve materials like a liquid. In addition, close to the critical point, small changes in pressure or temperature result in large changes in density, allowing many properties of a supercritical fluid to be "fine-tuned".
Supercritical fluids are suitable as a substitute for organic solvents in a range of industrial and laboratory processes. Carbon dioxide and water are the most commonly used supercritical fluids, being used for decaffeination and power generation, respectively.
Water Steam - Critical Point
When water and steam reach the level of absolute pressure 3206.2 psia (221.2 bar) and a corresponding saturation temperature 705.40oF (374.15oC), the vapor and liquid are indistinguishable.
This level is called the Critical Point.
At the critical point there is no change of state when pressure is increased or if heat is added. At the critical point the water and steam can't be distinguished, and there is no point referring to water or steam.
For states above the critical point the steam is supercritical. Supercritical is not the same as superheated - which is saturated steam at lower pressures and temperatures heated above the saturation temperature.
The supercritical water reactor (SCWR) is a Generation IV reactor concept that uses supercritical water (referring to the critical point of water, not the critical mass of the nuclear fuel) as the working fluid. SCWRs resemble light water reactors (LWRs) but operating at higher pressure and temperature, with a direct once-through cycle like a boiling water reactor (BWR), and the water always in a single, fluid state like the pressurized water reactor (PWR). The BWR, PWR and the supercritical boiler are all proven technologies[clarification needed]. The SCWR is a promising advanced nuclear system because of its high thermal efficiency (~45% vs. ~33% for current LWRs) and simpler design, and is being investigated by 32 organizations in 13 countries.
The PRotoMax on the other hand is a Generation I reactor that operates via controlled plasma ionisation and hydrogen detonation events in an environment with sub and supersonic fluids, jet's and mediums, while undergoing controlled expansion and implosion phenomena in an environment that is experiencing standing shock waves due to controlled cavitation of the jet stream.
The PRotoMax and related technologies are currently the focus of a small but talented community of open source energy researchers spread across the globe. The PRotoMax technology's are not, and never will be, subjected to patent restrictions by the inventor.
Water achieves supercritical point at 374oC, 647.096 K and 217.7 atm, 22060 kPa.
These temperature and pressure limits are heavily exceeded in a cavitation event. An event which is itself on it's way somewhere because it is occurring in a fluid that possesses inertial momentum and angular velocity, while undergoing rapid positive and negative acceleration, and experiencing extremes of pressure and vacuum, expansion and implosion events.
What is going to happen to the water, the fluid medium of immersion ?
And the good thing about the Plasma RotoMax is... the housing is the rotor...
Last edited by evolvingape : 02-22-2012 at 01:44 PM.
Compare the PRotoMax Plasma Repulsor Linear Firing Valve with the Plasma Detonation Spray Process.
See the identical function of water cooled barrels and Nitrogen purge cycle in both devices ?
There are additional processes occurring due to hydrogen detonation waves and the ionisation of air.
What processes will occur with a staggered timed injection of high pressure low temperature water jets, hot ionised plasma supersonic jet streams, and ambient temperature high pressure air jets, into the rotor ?
Which fluids are compressible and which are non-compressible ? Do these properties change with temperature ?
Map the expansion and compression phases for each fluid, including velocity, pressure and temperature variables, through time.
What is happening ?
Last edited by evolvingape : 02-22-2012 at 02:24 PM.
In thermodynamics and fluid mechanics, compressibility is a measure of the relative volume change of a fluid or solid as a response to a pressure (or mean stress) change.
Compressibility is an important factor in aerodynamics. At low speeds, the compressibility of air is not significant in relation to aircraft design, but as the airflow nears and exceeds the speed of sound, a host of new aerodynamic effects become important in the design of aircraft. These effects, often several of them at a time, made it very difficult for World War II era aircraft to reach speeds much beyond 800 km/h (500 mph).
Some of the minor effects include changes to the airflow that lead to problems in control. For instance, the P-38 Lightning with its thick high-lift wing had a particular problem in high-speed dives that led to a nose-down condition. Pilots would enter dives, and then find that they could no longer control the plane, which continued to nose over until it crashed. The problem was remedied by adding a "dive flap" beneath the wing which altered the center of pressure distribution so that the wing would not lose its lift.
A similar problem affected some models of the Supermarine Spitfire. At high speeds the ailerons could apply more torque than the Spitfire's thin wings could handle, and the entire wing would twist in the opposite direction. This meant that the plane would roll in the direction opposite to that which the pilot intended, and led to a number of accidents. Earlier models weren't fast enough for this to be a problem, and so it wasn't noticed until later model Spitfires like the Mk.IX started to appear. This was mitigated by adding considerable torsional rigidity to the wings, and was wholly cured when the Mk.XIV was introduced.
The Messerschmitt Bf 109 and Mitsubishi Zero had the exact opposite problem in which the controls became ineffective. At higher speeds the pilot simply couldn't move the controls because there was too much airflow over the control surfaces. The planes would become difficult to maneuver, and at high enough speeds aircraft without this problem could out-turn them.
These problems were eventually solved as jet aircraft reached transonic and supersonic speeds. German scientists in WWII experimented with swept wings. Their research was applied on the MiG-15 and F-86 Sabre and bombers such as the B-47 Stratojet used swept wings which delay the onset of shock waves and reduce drag. The all-flying tailplane which are common on supersonic planes also help maintain control near the speed of sound.
Finally, another common problem that fits into this category is flutter. At some speeds the airflow over the control surfaces will become turbulent, and the controls will start to flutter. If the speed of the fluttering is close to a harmonic of the control's movement, the resonance could break the control off completely. This was a serious problem on the Zero. When problems with poor control at high speed were first encountered, they were addressed by designing a new style of control surface with more power. However this introduced a new resonant mode, and a number of planes were lost before this was discovered.
All of these effects are often mentioned in conjunction with the term "compressibility", but in a manner of speaking, they are incorrectly used. From a strictly aerodynamic point of view, the term should refer only to those side-effects arising as a result of the changes in airflow from an incompressible fluid (similar in effect to water) to a compressible fluid (acting as a gas) as the speed of sound is approached. There are two effects in particular, wave drag and critical mach.
Wave drag is a sudden rise in drag on the aircraft, caused by air building up in front of it. At lower speeds this air has time to "get out of the way", guided by the air in front of it that is in contact with the aircraft. But at the speed of sound this can no longer happen, and the air which was previously following the streamline around the aircraft now hits it directly. The amount of power needed to overcome this effect is considerable. The critical mach is the speed at which some of the air passing over the aircraft's wing becomes supersonic.
At the speed of sound the way that lift is generated changes dramatically, from being dominated by Bernoulli's principle to forces generated by shock waves. Since the air on the top of the wing is traveling faster than on the bottom, due to Bernoulli effect, at speeds close to the speed of sound the air on the top of the wing will be accelerated to supersonic. When this happens the distribution of lift changes dramatically, typically causing a powerful nose-down trim. Since the aircraft normally approached these speeds only in a dive, pilots would report the aircraft attempting to nose over into the ground.
Dissociation absorbs a great deal of energy in a reversible process. This greatly reduces the thermodynamic temperature of hypersonic gas decelerated near an aerospace vehicle. In transition regions, where this pressure dependent dissociation is incomplete, both the differential, constant pressure heat capacity and beta (the volume/pressure differential ratio) will greatly increase. The latter has a pronounced effect on vehicle aerodynamics including stability.
Water is an incompressible fluid. ( Liquid Phase )
Water Vapor is a compressible fluid. ( Gas Phase )
A supercritical fluid is any substance at a temperature and pressure above its critical point, where distinct liquid and gas phases do not exist.
A phase transition is the transformation of a thermodynamic system from one phase or state of matter to another.
A phase of a thermodynamic system and the states of matter have uniform physical properties.
During a phase transition of a given medium certain properties of the medium change, often discontinuously, as a result of some external condition, such as temperature, pressure, and others. For example, a liquid may become gas upon heating to the boiling point, resulting in an abrupt change in volume. The measurement of the external conditions at which the transformation occurs is termed the phase transition point.
Phase transitions are common occurrences observed in nature and many engineering techniques exploit certain types of phase transition.
The term is most commonly used to describe transitions between solid, liquid and gaseous states of matter, in rare cases including plasma.
In any system containing liquid and gaseous phases, there exists a special combination of pressure and temperature, known as the critical point, at which the transition between liquid and gas becomes a second-order transition.
Near the critical point, the fluid is sufficiently hot and compressed that the distinction between the liquid and gaseous phases is almost non-existent. This is associated with the phenomenon of critical opalescence, a milky appearance of the liquid due to density fluctuations at all possible wavelengths (including those of visible light).
Critical exponents and universality classes
Continuous phase transitions are easier to study than first-order transitions due to the absence of latent heat, and they have been discovered to have many interesting properties. The phenomena associated with continuous phase transitions are called critical phenomena, due to their association with critical points.
It turns out that continuous phase transitions can be characterized by parameters known as critical exponents. The most important one is perhaps the exponent describing the divergence of the thermal correlation length by approaching the transition. For instance, let us examine the behavior of the heat capacity near such a transition. We vary the temperature T of the system while keeping all the other thermodynamic variables fixed, and find that the transition occurs at some critical temperature Tc. When T is near Tc, the heat capacity C typically has a power law behaviour.
A similar behaviour, but with the exponent ν instead of α, applies for the correlation length.
The exponent ν is positive. This is different with α. Its actual value depends on the type of phase transition we are considering.
For -1 < α < 0, the heat capacity has a "kink" at the transition temperature. This is the behavior of liquid helium at the lambda transition from a normal state to the superfluid state, for which experiments have found α = -0.013±0.003. At least one experiment was performed in the zero-gravity conditions of an orbiting satellite to minimize pressure differences in the sample. This experimental value of α agrees with theoretical predictions based on variational perturbation theory.
For 0 < α < 1, the heat capacity diverges at the transition temperature (though, since α < 1, the enthalpy stays finite). An example of such behavior is the 3-dimensional ferromagnetic phase transition. In the three-dimensional Ising model for uniaxial magnets, detailed theoretical studies have yielded the exponent α ∼ +0.110.
Some model systems do not obey a power-law behavior. For example, mean field theory predicts a finite discontinuity of the heat capacity at the transition temperature, and the two-dimensional Ising model has a logarithmic divergence. However, these systems are limiting cases and an exception to the rule.
Real phase transitions exhibit power-law behavior.
Several other critical exponents - β, γ, δ, ν, and η - are defined, examining the power law behavior of a measurable physical quantity near the phase transition. Exponents are related by scaling relations such as β = γ / (δ − 1), ν = γ / (2 − η). It can be shown that there are only two independent exponents, e.g. ν and η.
It is a remarkable fact that phase transitions arising in different systems often possess the same set of critical exponents. This phenomenon is known as universality. For example, the critical exponents at the liquid-gas critical point have been found to be independent of the chemical composition of the fluid. More amazingly, but understandable from above, they are an exact match for the critical exponents of the ferromagnetic phase transition in uniaxial magnets.
Such systems are said to be in the same universality class. Universality is a prediction of the renormalization group theory of phase transitions, which states that the thermodynamic properties of a system near a phase transition depend only on a small number of features, such as dimensionality and symmetry, and are insensitive to the underlying microscopic properties of the system. Again, the divergency of the correlation length is the essential point.
Critical slowing down and other phenomena
There are also other critical phenoma; e.g., besides static functions there is also critical dynamics. As a consequence, at a phase transition one may observe critical slowing down or speeding up. The large static universality classes of a continuous phase transition split into smaller dynamic universality classes. In addition to the critical exponents, there are also universal relations for certain static or dynamic functions of the magnetic fields and temperature differences from the critical value.
Another phenomenon which shows phase transitions and critical exponents is percolation. The simplest example is perhaps percolation in a two dimensional square lattice. Sites are randomly occupied with probability p. For small values of p the occupied sites form only small clusters. At a certain threshold pc a giant cluster is formed and we have a second order phase transition. The behaviour of P∞ near pc is, P∞~(p-pc)β, where β is a critical exponent.
Last edited by evolvingape : 02-22-2012 at 03:41 PM.