compressed air car

[mechanic6]

has anyone seen an article on compressed air cars?
i think this might be an interesting backyard project.
i looked at building an electric car but the price for batteries is just nuts.

any thoughts?

 

[thruthefence]

http://hybridautoinfo.com/air-powered/compressed-air-cars-to-hit-the-indian-roads-in-2008/

 

[MikeHalloran]

Notice the date on the, ahem, forward- looking, article, and the shiploads of compressed air cars that aren't arriving.



Mike Halloran
Pembroke Pines, FL, USA

 

[franzh]

A company in France tried to market a model, and at least one university in the US has played around with one too. Several colleges have played around with liquid nitrogen:

http://www.mtse.unt.edu/CooLN2Car.html

http://www.washington.edu/alumni/columns/dec97/car1.html

Franz


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[GregLocock]

If you were ever thinking of spending serious money on one, buy a book on thermodynamics first. The main promoter of these things has been announcing their imminent manufacture on a regular basis since 2000, with no sign of them appearing to date.

The main problem is that releasing the air from the high pressure tank cools it down.

This tends to freeze the engine up.

The overall efficiency is also poor for various obvious reasons.

That being said, compressed air storage is viable in some applications, particularly where a large reservoir of warm water is available to unfreeze things, or where range is relatively unimportant.





Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[BrianPetersen]

Should work well in a warm climate to provide A/C without any additional hardware ... just route the engine "exhaust" into the cabin ...

 

[thruthefence]

And Greg, you started an interesting thread in "Engineering History"

http://www.eng-tips.com/viewthread.cfm?qid=208284&page=4

 

[turbocohen]

Aside from building the Monster Fire Truck that runs on CNG, our local votech built a small dragster powered by the air motor from a 3/4" impact gun mounted to a neon with an automatic and a 25 gallon tank at 200psi. The hole shot was amazing. In its former life it was a little red gasoline hybrid. I think it caught on fire while recharging and that was the end of the road.

 

[JSteve2]

I remember this was going to be all the rage when I was in engineering school in the 80s (not to date myself). I see from the link above (cool thread) that the idea has been around far longer.

 

[turbocohen]

Correction to the above.. the cng tank was filled to 3600psi with air and regulated to 200psi using a heated cng regulator. Another typo, the car was a cng hybrid from the 1996 hybrid electric challenge sponsored by sae, chrysler and others such as my former employer. To control speed they manifolded the cng injectors we provided.. damn surprised they lasted this long.

 

[turbocohen]

http://www.engineer.ucla.edu/stories/2003/hybrid.htm

 

[dcasto]

If you read some of the reports, you can pick out the freezing issue is being addressed by adding a diesel burning heater, so much for that high efficiency,

if you let 3000 psi air down to atmospheric pressure, the exit temp would be about -215, sure hope you dried that air, so, multi-stage expanders are used with huge heaters between each stage.

 

[kjfmecheng]

CNG and compressed hydrogen vehicles already have a source of compressed gas on board. Wouldn't it make sense that they could use some sort of turbine to capture the energy when reducing the pressure of the fuel on the way to the engine or fuel cell, rather than "wasting" it in a pressure regulator? This wouldn't be the primary power source, but it could supplement the power of the IC engine or fuel cell to improve efficiency. Has anyone ever heard of this being done?

 

[Lou Scannon]

kjfemecheng, homework assignment: work out how much energy there is to be recovered and a rough installed cost of the the turbine, transmission & control to deliver the net recovered energy to the drivetrain and report back.

 

[GregLocock]

Bear in mind that your little turbine could be operating in mixed phase gas/liquid, at sub zero temperatures.



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Nemesis4]

To get back to Mechanic6's original question - if this is just for an interesting project, maybe he should work on a steam/hot water (very hot water) storage system. This is in the sense of the old "fireless" steam locomotives. These locos could usually work a full shift on the one charge of steam/hot water, this is probably a better endurance than any compressed air storage system.

 

[thundair]

I would think you could use a V6 and LPG inject the two center cylinders fire them and use that exhaust to heat the other four intakes FWIW

What would the torque curve look like? Hmmmmmmm

I don't know anything but the people that do.

 

[dcasto]

A car that gets 30 miles/gallon on propane (that would be 40 mpg on gasoline)travelling at 60 miles/hr consumes .0333 gallons/minute. If a let down turbine were installed, it would generate 10 watts at a 70% Isentropic efficency.

 

[GregLocock]

Grins, well thanks for that.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.