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Author Topic: Why not use a IC engine with a pre-compressed air tank?  (Read 5062 times)

Offline peppercorn

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Such a vehicle could operate in three modes:

1. Short journeys on a compressed air-driven motor alone (with ambient heat exchanger to warm expanded air).

2. Medium range on IC engine taking compressed air from from tank. Partially expanded air would be chilled -giving increased Carnot efficiency and being under pressure - better power-to-weight.  Ambient air cooling of engine block would suffice for simplified cooling system.

3. Air reservoir empty - runs (at slightly reduced peak power) in normal IC configuration. Lean-burn operation only to keep cool.


Further: For mode 2, hot exhaust gas could be mixed with a separate stream of cooled ambient air drawn from heat exchanger (as used in mode 1). This would condense out the water vapour and reaction acids, before being fed into the compressed air motor for hybrid operation.


Catalytic converter may have trouble getting to temp. -Although lower inlet temps may prevent NOx's forming... ?


 

Offline daveshorts

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Why not use a IC engine with a pre-compressed air tank?
« Reply #1 on: 24/09/2008 16:57:58 »
Would probably have some advantages, there are definitely people looking into  high pressure air as a way of storing energy, although very high pressure air tanks are very, very very scary things, as if they go bang they release all their energy mechanically and very quickly.
 

Offline peppercorn

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Why not use a IC engine with a pre-compressed air tank?
« Reply #2 on: 24/09/2008 17:16:55 »
there are definitely people looking into high pressure air as a way of storing energy

Yes, I read there's (at least) one manufacturer out in India & with surprisingly usable range & speeds. Clearly Gasoline has much higher energy densities than C-Air (& the simplest fuel container), but potentially a far greater percentage of said energy can be delivered to the wheels.

I just think: we already have plugin hybrid vehicles in the form of petrol-electric. Why not petrol-air? Mainly because one produces waste heat & the other needs additional heat.
« Last Edit: 24/09/2008 17:20:18 by peppercorn »
 

Offline peppercorn

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Why not use a IC engine with a pre-compressed air tank?
« Reply #3 on: 24/09/2008 17:19:42 »
It should be possible to make crash proof containers from GRP or carbon composites.
 

Offline lightarrow

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Why not use a IC engine with a pre-compressed air tank?
« Reply #4 on: 25/09/2008 16:41:14 »
I just think: we already have plugin hybrid vehicles in the form of petrol-electric. Why not petrol-air? Mainly because one produces waste heat & the other needs additional heat.
Apart from the safety problems, a compressed air tank storages less energy with the same volume and mass; furthermore, electric energy now is quite available, while high pressure compressed air is not, yet. Anyway it could be an idea. I have to inform you that I already had it more than 30 years ago, however...

Another idea is to store energy and at the same time use as engine in a car, a couple of fast rotating  flywheels.
« Last Edit: 25/09/2008 16:44:26 by lightarrow »
 

Offline Pumblechook

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Why not use a IC engine with a pre-compressed air tank?
« Reply #5 on: 25/09/2008 23:18:45 »
It is very inefficient. 
 

Offline peppercorn

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Why not use a IC engine with a pre-compressed air tank?
« Reply #6 on: 26/09/2008 14:38:57 »
I have to inform you that I already had it more than 30 years ago, however...

Oh, I'm sure it's not an original thought! However, parallel hybrid cars were suggested many moons ago also. The big difference is the advances in control technologies: computerisation & electromechanical -now make them practical.

Another idea is to store energy and at the same time use as engine in a car, a couple of fast rotating  flywheels.

My gut instinct is flywheels add too much mass to all but the largest vehicle. Plus they don't 'absorb' waste heat.
 

Offline peppercorn

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Why not use a IC engine with a pre-compressed air tank?
« Reply #7 on: 26/09/2008 14:40:34 »
It is very inefficient. 

SO ENLIGHTEN ME!!
Perhaps you could substantiate that statement...
 

Offline lightarrow

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Why not use a IC engine with a pre-compressed air tank?
« Reply #8 on: 26/09/2008 16:15:02 »
Another idea is to store energy and at the same time use as engine in a car, a couple of fast rotating  flywheels.
My gut instinct is flywheels add too much mass to all but the largest vehicle.
That's correct. Wih the present technology we are not able to make a flywheel with "normal" dimensions rotate so fast to store enough kinetic energy, unless we give it a large mass.

Quote
Plus they don't 'absorb' waste heat.
I haven't understood this. What do you mean?
 

Offline peppercorn

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Why not use a IC engine with a pre-compressed air tank?
« Reply #9 on: 26/09/2008 16:29:00 »
Quote
Quote
Plus they don't 'absorb' waste heat.
I haven't understood this. What do you mean?

Ooops, I meant do absorb heat....

I was pointing out earlier in the thread that one 'issue' with compressed-air vehicles is the need for the air to be reheated to gain the best energy return (as an expanding gas will always cool). Hence decompressing air can utilise heat from another 'engine' that would otherwise be wasted.
« Last Edit: 26/09/2008 16:30:39 by peppercorn »
 

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Why not use a IC engine with a pre-compressed air tank?
« Reply #9 on: 26/09/2008 16:29:00 »

 

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