Bob O'Neil Air Engine

[AlanA]

Thanks for the very interesting discussion.
I found the patents of Charles E. Tripler very easy (google patent search).
There are various patents from Tripler. Two are from 1900:
- US 652.058, Liquefier for atmospheric air
- US 652.304, Liquid-Air generator.
I also found a very remarkable detail about Tripler. In 1901 it seems that he has invented a car that was propulsed by liquefied air. But I have not found further details about it (

But could it be really efficient to liquefy air? I think there must be a lot of energy to get this kind of air. Tripler compressed the air with 2500 pound.

[Tom Booth]

I also found a very remarkable detail about Tripler. In 1901 it seems that he has invented a car that was propulsed by liquefied air. But I have not found further details about it (

But could it be really efficient to liquefy air? I think there must be a lot of energy to get this kind of air. Tripler compressed the air with 2500 pound.

There are a lot of articles from the NY Times Newspaper available on Google about Tripler and his Liquid Air Company. I haven't read all of them but what I've gathered so far he had plans of manufacturing all kinds of engines to run on Liquid air.

I don't think there is any doubt that he was making huge quantities and shipping it all over the country.

He claimed, according to that article, to be able to use liquid air to run his compressors to make more liquid air. That he got 10 gallons of liquid air out of his liquifier for every 3 gallons he used to run the machine.

I think that this was possible because his plant was located on a river into which a lot of heat could be dumped for free. He compressed the air which got it hot then cooled it with river water then let it expand so it got extremely cold then used the very cold air that resulted to pre-cool more compressed air so that the temperature kept dropping. The point to be noted is that he was getting the cold river water for free. It would not be possible to do this with an engine running in a car for example as you can't travel around in your car with a river.

It looks like there was a lot of controversy. Several US senators joined the company. Then accusations of fraud. Scientists were writing articles denouncing his claims, then some scandal involving the disappearance of investors money.

The company was apparently going strong shipping barrels of liquid air all over the continent in 1900 - 1901. By 1902 the company collapsed in bankruptcy. There was apparently some kind of official inquiry into the collapse. What the conclusion, if any, I haven't found out. He died just a few years later in 1905.

[Tom Booth]

I'm not really sure if this makes sense or not or if it is even possible or effective but I had another idea about the possible purpose of the "throttling valve" that would not necessitate actual liquefaction of the air but would still be useful.

Perhaps the purpose of expanding the air in the cylinder for cooling (if that was in fact the purpose) was not so much to cool the air itself or liquify it, as I think in such a process, very little air would actually be drawn in, but to pre-cool the cylinder itself.

The same cylinders are used for expansion/cooling and compression.

Perhaps the idea was to fist expand some air by  "throttling" or the "Joule - Thompson Effect" in the cylinder to chill the cylinder walls and piston before introducing the actual air to be compressed into the same cylinder.

I think this could explain just about everything. Why the same cylinder does double duty. Why the piston is unusually thin (as pistons go), so the cold produced on one side (top) would also chill the other side (bottom). Why the different types of valves are used instead of all regular check valves.

Why expand and cool such a small amount of air in the cylinder and then just expel it adding a strain on the engine to no apparent purpose: It serves the purpose of pre-chilling the cylinder before doing the actual compression of a much larger volume of air in the same cylinder.

As long as the air was substantially colder than ambient. (The air already in the tank would be warming up to ambient) I think the idea that the "equalizer" served as a kind of "Thermal Pump" would still be valid.

Very cold dense air enters the equalizer through the first check valve. Once between the two valves in the equalizer it begins to warm up and build up pressure forcing itself through the second check valve and into the tank at higher pressure.

So the compression would be a two stage process. First cooling by Joule-Thompson expansion or throttling to cool the piston and cylinder. Second, introducing air into the same cylinder for compression after the cylinder has already been pre-cooled by stage 1.

The small amount of air used for expansion and cooling, once it has done its job of pre-cooling the cylinder, is then largely incidental and is just expelled into the pipes along with the rest of the compressed air.

I'm intentionally neglecting the cooling due to the water circulating around the compression cylinders to avoid confusions, but this would provide an initially cool environment more or less insulating the cylinders from the surrounding ambient heat to help make the cooling by expansion most effective.

[Tom Booth]

OK, I'm wondering if anyone here is good at calculating or figuring out mathematically the whole "ideal gas law" Pv=nrt thing, because I'm not, but I know there are formulas for figuring this sort of thing out.

The air being drawn in by the engine through the valve is initially plain old fresh air at ambient temperature and atmospheric pressure.

There are three possible cooling effects going on.

The valve, depending on how strong the spring is, restricts the amount of air that can be admitted in a given time.

Say the cylinder holds 1 liter (normally by volume). But less than 1 liter of air gets through the valve. Say 1/2 liter or "normal" atmospheric air at 60 degrees F.

So the 1/2 liter is mechanically expanded to twice its volume.

At the same time the air is entering an environment that is, lets say 20 degrees cooler than ambient (the cylinders are water cooled) So there is an inital drop in temperature due to heat being drawn off into the water jacket. At the same time the 1/2 liter of air that gets past the valve is expanded to twice its initial volume.

There is also Joule Thompson "Throttling" as an additional source of cooling but by itself, without a change in volume and environmental temperature is, I think, rather negligible.

Lets just say X amount of gas at 60 degrees Fahrenheit is mechanically expanded in a cylinder to twice the volume.

In other words. If the valve were fully open then 1 full liter of gas would be drawn in by the piston. But the valve is held closed by a strong spring (apparently) so only 1/2 that much air gets into the cylinder but it is mechanically forced to expand to the full 1 liter that the cylinder can hold. It is as=if any amount of air was expanded to twice its volume. (could actually be 1 and 1/2 its volume or twice or three times its volume depending on how tightly closed the valve is.)

This by itself should be fairly easy to calculate with the standard "Ideal Gas Law" formulas. Right ?

So anyway, I've been doing some figuring using some of the Online Calculators available just plugging in values such as might be suggested by the above ramblings - but I am coming up with temperatures that are like hundreds of degrees below zero. I'm wondering if this is realistic or if I'm just not using the calculator right.

Maybe someone knowledgeable in this area can help.

I think most of the relevant values are known or could be approximated.

How much air the cylinders could normally hold, average ambient temperature, etc. This should basically plug right in to standard formulas like pv=nrt.

We could get a rough idea how much cooling might be possible by mechanical expansion alone by 1 stroke of the piston and go from there.

So far it's looking to me like the temperature drop due to mechanical expansion alone could be quite extreme but I'm no expert.

[Motorcoach1]

Tom; I have a copy of Audels E&M guide2 book, printed in 1921. Look up Uni-flow engines by Johann Stumpf of Berlin Germany. There are charts of working pressures , althoe these are steam related-  this engine was used as a compressed air unit in mineing operations.