The first time I asked Bill Truitt how his air car could keep its own tanks full, he said, “Because there are three separate systems.” The air compressor, the electric generating system, and I think the other one was the plurality of hydraulic air pumps, or the tanks. I didn’t get the point at the time; he wasn’t giving me an answer in terms of the laws of physics that I was referring to. He was giving me practical advice, based on his own experience.
Now that I have experience in trying to devise methods of designing with and around the laws of thermodynamics in order to do something that most people think is impossible, I can tell you that it isn’t easy. What’s easy is to become temporarily deluded, not because of senility (yet) nor insanity (I hope), but because there is always an element of wanting to believe in a good thing, and this causes selective blindness. That’s like wishful thinking but more sophisticated. I hope.
I thought up the equalization engine in 1988 and have been fighting with it, off and on ever since, to try and get it to yield a simple practical manifestation. Some arrangement of hardware that can be expected to actually work. It has always been my ideal to try and work with strictly pneumatic processes, for a variety of reasons. Mainly because transforming to electric or anything but air has losses, so if it can all be done with air, it should be. But Bill Truitt wasn’t afraid of working with electricity; he seemed to think it was necessary.
Many times I have sat down to put the equalization engine in hardware, on paper, and ended up with extravagant processes, pistons in tanks, compressors in tanks, etc. It’s all OK, I don’t mind. But my job isn’t to design something that neither I nor anyone else is going to understand without an hour or two of studying drawings and spreadsheets. As an advocate of compressed air it’s my job to get the point across in a few moments, because that’s all the time you’re going to get from qualified technical people who have all, without very many exceptions, been trained to consider compressed air a finished science and a loser of energy.
So here’s the problem with the piston that operates the delivery stroke of the equalized air into the tank. This problem keeps cropping up and I keep forgetting it, then as happened today it suddenly re-enters the atmosphere of my imagination, a place that is crowded with enthusiasm generated by work equations that work. With an overunity COP from a seemingly robust spreadsheet, I had once again forgotten about PISTON BALANCING FORCES.
The work needed to get the equalized air back into the tank is tiny. The piston needed to do it is big! Why the seeming paradox? The problem is caused by assumptions, naturally. The assumption that pressure is energy. It isn’t; a little energy is used, but that doesn’t mean a little piston will do it. The assumption that the piston idea has to work because it should work because I want it to work. Not. The assumption that whatever size the piston is, then the energy it handles is all supposed to be useful. Not that either.
What really happens in the design as previously depicted, with the piston outside the tank pushing the equalized air mass out of the equalizer into the tank, is nothing. Unless the piston is bigger than the equalizer in area, or uses a higher pressure from some other source, it won’t move. The tank air pushing the piston will cause it to shift slightly, until the pressure is the same in tank and piston, and then it will stop, and not budge. There are many times more energy available in the piston, or would be if we could get air into it, than what is needed to push 197 psi air from the equalizer into the 200 psi tank. That’s actually part of the problem. Since the piston has to be bigger than the equalizer in area in order for it to move, and a lot bigger if you want it to move fast, the amount of air being “used” (but not expended) has to be put back into the tank. It can be done, but not simply. A genius could figure out how to do it simply, but then there’s me standing between the genius and the result.
Using a high pressure air source is another bugaboo I want to avoid. It also could be made to work, and Bill Truitt was doing it too. But here’s my goal: make it seeable in three seconds of some engineer’s precious time, or some fundraiser’s precious time. That’s how much time they are going to give to it. The experimental stuff comes later, when someone has funded the Subgenius Compressed Air Research Facility (SCARF). That someone won’t stop to study the plans, with my limited or nonexistent powers of persuasion, unless I give it to them simply.
The complication of the piston that needs to be big to do a job that is small and then makes us design around not wanting to throw away a big piston-full of air. It’s probably the sort of design problem that got Bill Truitt to name his car an Electro-Pneumatic Air Car. Because that’s what the electric component can do. Forget the piston with its moving parts, its air eating ways, and worst of all, its tendency to balance against the tank pressure. Ideals like “all air” are for that research institute I just mentioned. As I lecture to my eager audience all the time, trying to combine all your best ideas into one actual machine spells doom for your first several tests, and most tests don’t make it past the first several tests because of financial constraints, time constraints, family obligations, lack of patience, lack of knowledge or skill, etc. Brilliance is for people who already have money, time, a supportive family, lots of patience, and a solid technical background. For the rest of us, we wanna-be inventors, the place to start is with the simplest possible way that your most important concept can be proven, and never mind the bells, whistles, and movie rights.
In the case of the last two steps, the part the piston was supposed to do, once you get rid of the moving parts which won’t get out of the way, you eliminate the problem. The energy that air uses is heat. Compressing air isn’t the only way to heat it. Try heating it directly with electricity. No moving parts to get in the way. Proven technology. Electric resistance heating will solve both problems, the two final steps:
1. Getting the equalized air—the two joined air masses—out of the equalizer into the tank by adding a few psi to the equalized result.
2. Getting ALL the equalized air out of the equalizer so that the next filling of atmosphere to go into the equalizer will be a whole equalizer full of air. Volumetric efficiency should be close to 100% or it will have a trickle-down effect of negatively influencing everything else that is supposed to happen.
Electric resistance heating is a 100% efficient way of wasting electricity on purpose, thus 100% inefficient but perfectly effective at what it is supposed to do. All the electricity turns into heat; resistance is friction. Unlike the piston it replaces, enough is enough. There’s no piston balancing forces problem forcing you to use more than you want, and it all happens right in the equalizer where it should. No extra valves. No moving parts. After the equalization has taken place inside the equalizer, heat the air and away it goes into the tank.
In order to get ALL the air out of the equalizer, the discharge check valve would need a strong spring so that pressure has to build up way past tank pressure before the valve can open. Better yet, have the valve operated by a mechanical method instead of a spring, so its time of opening and closing can both be controlled and varied experimentally. If the valve just opens a little, air will remain in the equalizer and it will never empty. The air has to empty all at once, en masse, as a unit, a burst. Then the equalizer will be fairly empty and will accept a full charge of new air. This is the Kadenacy effect. The tailpipe on the equalizer can be sized and shaped to tune this effect, just like a two-stroke motorcycle engine.
A check valve on the equalizer discharge is probably not suitable. It presents a substantial blockage and because of the spring, it will want to close as soon as the equalizer is partially relieved of its air. It can’t make experimentation easy, when you have to take the tank apart to change the spring. The valve that opens the discharge part of the equalizer has to be adjustable from outside of the tank so that many experiments can be done in a few hours. Otherwise it won’t get done. Design it this way from the start. The port has to be big. The valve has to open fast and get out of the way, not present a constriction or blockage. Scavenging—complete emptying of the equalizer—is dependent on how fast the valve opens, the pressure differential between the inside of the equalizer and the tank, and the size and shape of the tailpipe. With the valve open, it should be open wide at the back, like a pulsejet.
I have actually seen this principle work with water, in a toy steam boat that used a coil of aluminum tubing heated by a candle to create a periodic outward bursting that drove the boat forward and left behind a suction in the tube that drew in a fresh water supply. Air is harder since it’s compressible, so the valve is needed to make the air build up enough pressure to give it a blasting outward effect when the valve suddenly opens. There is plenty of information on the Kadenacy effect in my book The Piston Made of Air.
The same thing works with water, even through a check valve in a pump that drives water uphill with heat only. Between two check valves heat is applied. It is an acoustic principle so tapping the pipe with a screwdriver might be necessary to get it started. Details are available from Roy Phillips of ABCO. A key word you can search is Fluidyne. The Metal Box Company in Calcutta, India had a large pump operating this way at one time. One of my books contains a chapter about the Fluidyne pump which was a little more complicated but worked on the same principle.
Before you start putting electricity into an air tank I hope you know what you’re doing or hire someone to do it for you. I am not going to say one word about how to assure you don’t electrocute yourself, because it is your responsibility to do it right so no one gets hurt. Conduits, sealing problems, controls, etc. Moisture may be a problem, or it might be helpful since steam is more expansive than air.
The spreadsheet will show how much electricity is required to drive the pressure in the equalizer up to tank pressure, then how to drive it up to a pressure that will be able to induce more air in through the Kadenacy effect. I don’t know the math for the Kadenacy effect, and I’m guessing on electricity since I have never done calculations with it.
Here’s the link for the new spreadsheet:
(not done yet)
Luther
Subscribe to:
Post Comments (Atom)
0 comments:
Post a Comment