“HEAVER”

The “Serious as a Heart Attack Valvular Equalizer”.

 

It started with a pain in my chest that motivated me to go ahead and finish a little sketch I’d started in case I should die with nothing finished.

Two pistons were shown inside a tank between two check valves, rushing toward each other and almost touching, smashing air into the tank, and all powered by the air in the tank.  A nice idea but since I didn’t have a heart attack, there has been time to simplify the concept and make it easier to build.  The design isn’t finished but I wanted to get it online now, just in case…

 

The sketch above shows the whole tank.  More detail is shown below.

My idea, like most of my ideas, is a compressor that uses a constant pressure reserve—a tank pre-charged with compressed air—to compress more air by mixing with it, instead of using a conventional compressor to beat atmosphere into a tank against the tank’s resistance.  Instead of fighting what’s already in the tank, the idea is to get that tank pressure on the other side of the compression effort.

To me the concept pictured here, named “Heaver” after what was probably a bad case of heartburn, is too simple to fail, if built well.  The design is not finished but the basic ideas are all shown here.

A pair of check valves in a series in the tank’s inlet pipe move in relation to each other.  Only one of them has to move.  They almost touch so that as the movable one moves away from the stationary one, it tries to create one of those “vacuums” that nature abhors so much.  The result is that atmosphere enters the EQUALIZER which is the space between the check valves.  It does this basically under its own power, atmospheric pressure, although it takes work to move the piston/check valve out of the way to let it happen, because tank pressure is on the other side of the moving check valve (really a piston with check valves in it.)

There can be no leakage back into the equalizer from the tank environment, so I show several seals on the long piston.  O-rings might work, I’ve used them in something like this, and for the big intake pipe maybe self-lubricating filament-wound plastic tubing should be used.  It’s called Black Amalgon and is made for pneumatic cylinders.  O-ring “glands” or annular grooves are easy to design, just follow the instructions in the manufacturer’s catalog, or your machinist might be able to design them if you already have the o-rings.  The flat check valve member on the left is designed to eliminate clearance or pockets of unswept volume where compressed air will hide after discharge into the tank, reducing volumetric efficiency.  Some clearance is shown in the channels leading to the ball members of the check valves on the right.  These are just simple sketches.  Ball check valves have some disadvantages, mainly they leak if you ever take them apart since the ball gets grooved and won’t go back together exactly how they came apart.  Poppet check valves don’t have this problem.

When the piston reaches the end of the inlet pipe on the right, the equalizer is full of atmosphere.  The atmosphere is provided by a piston compressor (not shown) which should in the end not have to work any harder than a supercharger, but will add positive filling to the system and if at times the experimental system inside the tank fails to do what it’s supposed to do—very likely during initial tests—the piston compressor will take over for a few seconds.  For this reason you should test the system at no more than 100-120 psi at first, then if it works it should do well up to 140-160 psi according to Bob Neal’s experience.

Now because of the work of the DRIVER, the piston (moving check valve) changes directions and starts back to the left.  This is where its function resembles a heart.  The air doesn’t just go right through it into the tank, until pressure in the equalizer is the same as the pressure in the tank.  Then because the driver is motivated ultimately by high pressure air from outside the tank, the piston is able to keep moving the last few centimeters and the atmosphere goes through it right into the tank.  It almost touches the stationary check valve, then turns around and starts filling the equalizer with atmosphere again.

The driver is a special cylinder mounted to the inside of the tank (mounting not shown).  It is a single-acting cylinder, with only the left side powered.  Its power source is high pressure air from the storage tanks, maybe up to 1200 psi if you want it to run fast, though it should function slowly at much lower pressures, maybe 300-500 psi.  The faster it runs, the more air will be brought in.  Again, good seals made of high-temperature resistant materials, inside a self-lubricated cylinder, are probably needed.  Otherwise you have to lubricate it somehow and I don’t know what to suggest except that you can’t mix oil and compressors if you aren’t a compressor engineer who knows what he’s doing, unless you’re trying to re-invent the “Diesel engine”.  Boom.

If you build this, I was not the one who suggested you start out with over 1000 psi.  Remember I said to test it at the lowest possible pressure, and what you do with high pressure air is your problem.  Safety is your problem.  Don’t get yourself hurt.  Use safety valves (not shown), good seals (o-rings, not gaskets), and don’t assume that this document contains all the information you need about safety.  The usual disclaimer, blah blah blah.

A SPOOL VALVE is the modern version of what once caused pistons to go back and forth in steam engines.  I used to buy the WABCO type D valve from Rexroth since it has clockable ports (air can come in from any direction since the valve housing is in segments that can each be rotated in a different direction).  A three-way valve is needed to control a single-acting cylinder.  A cylinder port in the center is connected in turn to first a supply port on one end, then the exhaust port on the other end, by a spool-shaped solid cylinder reciprocating inside the housing.  The center position is closed.  The valve can be operated in a variety of ways (see below) but the basic idea is routine.  I’ve built some air engines this way and it’s not hard.

With atmospheric intake ready to start, the driver piston is somewhere near the left head of its cylinder but it’s not critical that it be extremely close.  The spool valve shifts to “intake” at this point and high pressure air from another tank enters the driver cylinder to the left of the piston.  It would slam the piston all the way to the right (assuming up to 1200 psi is being supplied) and probably smash the head of the cylinder if not for the fact that its supply will be cut off before it has travelled halfway through its stroke, say for example a 25% cutoff.  This is done by shifting the spool valve to its middle position where the “lands” of the spool block all the intake and exhaust ports.  Now the high pressure air already in the cylinder will expand and no more will enter till the next power stroke. 

Also slowing the driver piston’s motion to the right is the AIR SPRING formed on the other side of the piston by partially blocking the air from its in-tank environment.  Since the right side of the piston is in communication around the piston rod with tank air, the air spring has a built-in back pressure of at least that of the tank pressure but it builds from there because the hole around the rod is small.  Usually, single-acting cylinders are returned by metal springs but I like air springs because they are made of air, so they don’t wear out or break.  In fact they are so strong they can break what they’re in, which is why there has to be clearance around the rod or the air spring would stop the power cylinder in its stroke.

Instead, the air spring stores most of the work done by expanding high pressure air as the expanding air pushes the pistons in both driver and equalizer to the right.  It doesn’t take much work, but the tank pressure has to be overcome.  All this work is stored either in making way for atmosphere to enter under its own pressure or storing tension in the air spring, except for the air that escapes the air spring to keep its pressure from climbing above what is required for the return trip.  The escaping pressure vents to the tank where it also is not wasted.

Assuming that a medium high pressure has been generated in the air spring balanced by the same pressure remaining in the partially-expanded high pressure intake, the driver piston will be told to turn around when the spool valve is told by whatever mechanism is used to operate it to shift into exhaust mode.  The air that has expanded to somewhat over tank pressure will now leave in a hurry and the air spring will have no problem pushing the driver back to beginning position, but the main point is that it is compounding its force with the force of the tank air to compress incoming atmosphere by equalization inside the tank.

It is upon freely exhausting into the tank that the driver is called upon to start pushing against the atmosphere that has just been enticed into entering the equalizer.  Now the real work starts, right?  Wrong.  There isn’t much work to do, necessarily, in compressing air.  You can make a real chore out of it as conventional compressors do, or you can make a neat trick out of it.  The discharge end of the intake pipe in the center of the tank now admits tank pressure to push the moving check valve to the left until the tank pressure and the equalizer pressure have equalized.  If that’s all that was going on, the atmosphere and tank would now be at the same pressure but the atmosphere wouldn’t be able to come in.  But really what’s been happening is that the effort of the tank air lazily moving along behind the moving check valve has had added to it the effort of the air spring.  They push together from the start of the stroke, so instead of reaching that equalization point (tank pressure) and stopping, the two pistons push together from the start, with more than enough power to make all the atmosphere enter the tank. 

Both pistons have reached the leftmost end of their stroke, ready for another sip of high pressure.  

Why do I say there is little work to be done?  Compressors work hard and this compressor is no exception.  But most of the hard work of compressing air—the compression part of it—is done in this system by tank air rushing into the discharge end of the intake pipe as the moving check valve moves to the left.  It is the same as mixing high and low pressure air, but with a partition between them until tank pressure is reached and the partition, like the wall of your heart, keeps moving until the fluid on the low pressure side is pushed through the partition into the pressurized environment.

The mechanical pushing in both directions urges the process onward by ensuring that the two side duties of a compressor get done—intake and delivery—while the real work of changing the air’s volume, squeezing it into a smaller space so it will be able to expand later, is done by mixing through a moving partition.  That big job of compression is done by tank pressure with a little jolt from the high pressure air to get it over the last hump.

Why so much pressure?  It will probably work at 300 or 500 psi for the driver, but maybe too slowly.  For its size, this machine has to compress a lot of air or it’s just a novelty.  So it has to be kept simple, safe, and stout, in case 1000 psi or more is required to get enough piston speed out of it.  Air car inventor Bill Truitt’s “secret leakproof valve that worked like a heart” apparently needed 1000 psi for city driving but 1200 for driving in the hills.

The other parts of this design that are incomplete, aside from all the dimensions and not knowing what pressures will be needed, are the air spring and the spool valve operation system.

The air spring will blow the cylinder head right off if there is no way out for some of the air.  You only need to return a piston and raise the pressure of the atmosphere a few notches, not shoot piston rods at the moon.  But I don’t yet know how to calculate flow of air through orifices of different sizes and shapes at different pressures and going into different pressure environments.  So I don’t know how the air spring will work till you (yes you) build it and test it.  The alternative is to have a big clearance around the driver rod and use a metal return spring till it breaks.  But an experimental model of the air spring can be built with a large threaded hole around the rod, into which various size orifices can be screwed or otherwise attached, starting big and going smaller till the required return spring pressure is attained that gets the pistons all the way to the start of the intake stroke but not at too high a speed.

The 3-way spool valve can be operated very simply with a cam.  The illustration will teach you what little I know about designing cams, but it’s worked for me.  I made cams with a saber saw, a hacksaw and ½” thick plastic which I bolted to an old sprocket or a hub off a sheave, that could be fixed to a shaft.  A wood rasp and a big file got the final product to actually work.  (Hint: if the total valve travel is exactly ¾”, don’t try to shift it a full ¾” or you’ll jam the cam between the cam follower and the valve if there is a little bit of imprecision.)

But while this is the simplest way to operate a spool valve, it is inconvenient in this case because if you want rotary motion you’ll have to devise some, with a little crankshaft or a rack-and-pinion arrangement, or something.  It’s a nuisance, once you have a linear motor, to make rotary motion when you don’t really need it.  I also thought of sending a rod out the tank head and mounting a cam outside with a little air motor running off tank air and pushing the rod in and out ¾” to operate the valve.  (Don’t let a rod like that turn into a bolt through your head.  I speak from experience, as in “near death experience.)  But a cam-operator is the easiest way if you don’t want to learn the right way to do it, which is with pilot operated valves.

A pilot is a little air piston that will be cued by some signal to open and close the valve somehow.  I’m vague on it because I’ve never done it.  Research continues.  I’ve seen them work well in player pianos, which are suction-powered computers from the early 20^th century that played automatic pianos.  Little leather pouches and precisely-sized bleed holes were signalled by a hole in a paper roll what note to play when and how long to play it.  So I know this system can be reliable if done well, because the player piano could play the piano better than a live person, in terms of doing what it was told.  The problem is to design the pilot system or get it designed.  The problem is not lack of information but too technical for this simple application.  The spool valve and air cylinder system is found throughout industrial environments and does so much complicated signal-motivated jerking around that the easy job we want to do with it is below the dignity of technical writers to describe simply.  If you find a simple description of how to replace the cam pictured above with an air pilot, please send it on to me, and if you personally know how to design such air-logic circuits, you will be my new best friend till we get this design finalized.

When you build this machine and it doesn’t work the first time, it is not because you failed and need to quit.  It is because you got to the starting line successfully and have now created some real work for yourself.  It may be a little tricky on a few points, but I’ve been working on this for a long time and the system pictured here is infinitely simpler that any other way I’ve dreamed up, and it seems to me like it “has to work”.  Please send your comments.

 

THE BOTTOM LINE

The “heart attack valvular equalizer” or HEAVER for short has a higher COP than the equalization engine because there is no mixing so the equalizing tank air doesn’t leave the tank and doesn’t have to be compressed back into the tank.  It is more efficient because the only work done by a standard external compressor working against tank pressure is a dribble of high pressure air representing only the amount of energy needed to allow the atmosphere itself into the tank once it’s already compressed to 99% of tank pressure…

…vs. the equalization engine in which the volume of atmosphere intake times the compression ratio of the tank has to be raised in pressure by the same amount in addition to raising the pressure of the atmosphere itself that much.

The HEAVER process is non-dissipative once two tanks exist at different pressures: the drive tank has “tank pressure” (maybe 140-180 psi) and the storage and compression tank has high pressure air, maybe 2000 psi used at 500-1200 psi.  The pressure stored (by external compressors) in the two tanks before starting constitutes a constant pressure reserve that contains enough energy to compress many times more air than is needed—for a few seconds or minutes—by pressure equalization without further mechanical compression, and the added heat of the atmosphere thus brought in contributes the outside energy to make up for all the losses and the external work done such as running a car or a generator or a pump.  So the constant pressure reserve, instead of being used up in a few minutes, is constantly replenished by fresh air. 

Here is the non-dissipative process comprising the reasons why this machine will have a high overunity COP:

• high pressure air forces two check valves apart inside a cylinder inside a drive tank against

  • the resistance of an air spring in a driver cylinder end which stores some of the pressure used

  • the tank air resisting the motion of the check valve/piston into the tank.  The tank air resisting this motion also stores the pressure thus used.

• As pressure of the high pressure air goes down, its volume goes up, but pressure has not gone down yet even to tank pressure and none of the air has left the tank.

• Most of the high pressure air exhausts into the tank at large, and now increases tank pressure by mixing with it.

• The larger piston in the intake pipe, when forced away from the upstream check valve, creates a suction space immediately occupied by atmosphere under its own power assisted by a supercharger or single-stage piston compressor, replacing any pressure lost anywhere by more volume and fresh heat energy.

• When the larger piston is pushed back toward the intake check valve by tank pressure, the atmosphere trapped between the two check valves is raised to tank pressure by equalization with no losses and the extra push from the high pressure air spring in the end of the driver cylinder is added to it and transmitted through the same rod so the big pistons close all the way (almost touching each other), pushing the atmosphere into the tank.

• The result is more air made available than the little bit of high pressure air used, so the low pressure compressor supplying atmosphere and the high pressure compressor can be run in effect for free with extra air available for any purpose.

• The source of energy is the ambient heat of atmosphere caught in a pile-up of existing pressures that raises the pressure of the atmosphere the little bit necessary to get it into an expandable condition.

The COP is very high.  The spreadsheet with preliminary calculations is available from HEAVER spreadsheet Feb 16 2009.

 

HEAVER

THE “SERIOUS AS A HEART ATTACK VALVULAR EQUALIZER”