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Steam Compression

Posted by kyleborg 
Steam Compression
June 29, 2020 10:22PM
Maybe a thermodynamic guy can answer this question:

10 lbs of liquid water occupies 0.0045 m3 of space.

Boiling that water (superheating it) would make it expand and occupy 7.65 m3 of space.

Since the steam is now a gas, could it not be compressed (mechanically) to make it occupy a lot less space for transport or storage? It expanded 1700X from water, couldn't it be re-compressed say 1500X back to "almost water but not quite" ?
Re: Steam Compression
June 30, 2020 02:08PM
There's no point to do such a thing. Compressing it back to nearly the density of water means that we have to add an enormous amount of energy in compression --- the pressure and temperature will skyrocket incredibly. It would be easier to raise water to the equivalent pressure with a pump and then simply add heat to make steam.

The second problem is that you need to consult steam tables. At 0 psig and 72 degrees F, water has a density of 62.2858 lbs/cu-ft. At 1000 psig and 1000 F, we are looking at a density of 1.22225 lbs/cu-ft. My tables can't even reach steam conditions that equal anything even vaguely close to 60 lbs/cu-ft. It's highly unlikely you could make a practical compressor and storage tank for the kinds of temperatures and pressures involved.


Re: Steam Compression
June 30, 2020 03:31PM
Thanks Ken.

I find it most absurd that we can start with room temperature/pressure water .... turn it into steam with a small campfire..... and then require ENORMOUS energy to turn that steam back into water.

But then turning steam into water is a steam engine's job lol
Re: Steam Compression
June 30, 2020 07:31PM
Water to steam, add energy. Steam to water, release of energy. Returning spent steam water back into steam again, replace the spent energy. Simple as that. We use reverse braking with our Stanley steamers. With that, atmospheric air is being compressed for braking with heat resulting. Unless the engine is occasionally burped at the steam chest, and lubricated with a bump of the throttle, damage with result from the too high of heat energy in the engine. The non fueled energy comes from the braking action from the down hill compression braking. Reported by Ole Vickery: In the high Sierras one year with his 1914 Stanley, Ole Vickery about ran out of water at the crest of the mountain. As Ole had used up his water supply and only had a half boiler of water left. Ole turned off his main fuel and pilot light fuel and used reverse braking to charge his boiler with hot compressed air to heat his remaining water and keep his boiler pressure up. About half way down the mountain, 20 miles, he soon found a little town for water and he had just enough boiler pressure built up that he was able to drive around the town for about a half a mile in search of a water supply. Anyway, by the time that he found a water supply, he said that his boiler was about dry. The hot compressed air and hot boiler water combination save his day.
Re: Steam Compression
July 01, 2020 04:45PM
SSsssteamer Wrote:
We use reverse braking with our
> Stanley steamers. With that, atmospheric air is
> being compressed for braking with heat resulting.

Thanks for your input,
I have never heard of "reverse braking" sounds pretty interesting. I know about "regenerative braking" for battery cars, but for a STEAM CAR? What????? I would love to learn more about how it is used. I don't actually own a steam car myself, just doing research.

Re: Steam Compression
July 02, 2020 10:55AM
Reverse braking in a steam car is really just the compressing of atmospheric air by the steam engine. Heat is generated in the process, but compressing the air is not really very effective in raising boiler temperatures. As stated above, the boiler pressure can be raised from being flat zero PSI to about 250 pounds, which won't get you very far down the road on compressed air. Ole Vickery added a whole new slant to his travels when he stuffed the compressed air into his partially filled boiler of boiling water. I used reverse braking on the Continental Divide at Estes Park, Colorado, and judging about how the oil was burning out of my engine, I would guess that I was compressing air at about 400+ degrees F. My oil is good to 600 degrees F. The hot compressed air being made was plenty hot enough to make water boil. I eventually had to stop on the decent to let my 1914 Stanley's engine cool off.

Re: Steam Compression
July 02, 2020 04:21PM
SSsssteamer Wrote:
> Reverse braking in a steam car is really just the
> compressing of atmospheric air by the steam
> engine.

So you shut off the steam and let the engine become a pump. since well, you don't have a choice because the engine is directly connected to the axle. And then you send the hot air somewhere to do something. That's

Does the engine's cutoff ratio have anything to do with the resulting air compression? Seems a 30% cutoff ratio would mean a 3:1 air compression, and a 10% cutoff ratio would mean a 10:1 compression. Kinda makes me want to run the steam at 30% for maximum power, and then switch the engine to 10% for maximum recovery. I'm just thinking out loud.

Thanks for your info, it really helps.

Re: Steam Compression
July 02, 2020 09:03PM
During reverse braking, the steam engine's hot air is vented to the exhaust by occasionally letting up on the reverse pedal. No hook-up is used here because you are steadily holding down on the reverse pedal for reverse braking. Reverse braking works best for speeds under 25 MPH. Over 25 mph, it becomes rough on the engine because of the higher engine speeds decreases the efficiency of the slide valves. I have used reversed braking at 40 mph, but it is unwise to do it. Also, do not vent the steam chest of its air pressure through the steam chest valve because you will be blowing out all of you valve/cylinder lubrication to the ground. Instead, momentarily let up on the reverse pedal to dump the compressed air. While traveling and using reverse braking, occasionally bump the throttle open for a shot of fresh cylinder lubrication.
Re: Steam Compression
July 03, 2020 01:38AM
Very interesting, thanks for sharing. That will make quite a difference to the research I'm doing.
Love the blue Stanley! Almost all the ones I see are red for some reason lol

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