Using a Car's Spaceframe to Store & Regulate Compressed Air Prior to Combustion

I remember a story about one of the good-ole-boy NASCAR racers who used his tube frame to hold extra gas.

They finally figured out how he could go so far on a single "tank" of gas.

Thanks for the feedback

Just as well I don't mind looking stupid, eh? Still, if you don't ask you don't get.

Another way to look at the underlying idea: Imagine an air-car with a range extender (piston-engine driven pump) to add, er... range. As was said, "An internal combustion engine is nothing more than an air pump" - so the key principle of the idea I had (never mind where the energy is stored) is 'make a part-hybrid, but store the averaged 'work' of the power-plant before combustion. Less room & pressure is needed (for air) if it is yet to be expanded (by the bang!) but just as much work will be extracted (on average) in the end.

Another way to do it would be to have a turbo-generator that charges extra battery capacity. Then have a intelligently controlled electric supercharger.

Both ways have similarities to a parallel hybrid (eg. Prius) - in as much as the 'battery' (and e-motor) stage needn't be as large as a series electric hybrid to deliver the peak torque and power. I.e. they work side-by-side. The 'store' in this idea also works sort of side-by-side, by maxing out the 'air pump' engine's expansion work at key moments.

.... right, back to the looney ward for me!....

If I can make some important clarifications in response to your questions:
Driving the compressor(s) would be an exhaust turbine (just like a normal turbo, but driving a compressor with 4-5 times the pressure & a fifth the flow).
I never envisaged the engine drawing air at 10 bar - more like a max of 2 bar. I picked a big pressure because I was aware that not alot of space would be available, even if the car was built solely with air storage in mind. It was always my intention to have a device to mix natural airflow with the higher pressure (and colder, if appropriate) stored air - mixed by means of a equalizer.

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Re moment-to-moment drag on the engine: A variable geometry turbine(s) should ensure all but the very lowest revs would give some pumping work, without choking the exhaust. Once stored the (for arguments sake, say) 25cu.ft of air at (a more realistic) 6 bar would be available for mixing (not running it alone) with incoming air (boosting and cooling it) to suit the power needs dynamically.

Regenerative braking could be utilised to top up the air storage as well.

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Re: storage - a thin, double skinned, composite-ribbed steel, segmented floor and boot (trunk) area would greatly increase the air 'space' whilst being of almost no danger at the pressures suggested.

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Valentin Technologies Ingo

This example chassis has an air storage 'backbone' that can hold a lot of air (at much higher) pressures than I suggest. NB, this isn't what I'm going for - I just wanted to show a comparison.

This would require a huge of volume of air at very high pressure if you are using the air for energy recovery. Check out MDI, they make compressed air vehicles. You can get an idea of the pressure and amount of air storage you need even for a small amount of boost.

A better idea to eliminate turbo lag would be to drive the turbo with an air motor. Kind of like attaching an impact air gun to the shaft of the turbo. You would have to couple it with a gear drive so you can target the correct driven RPM range to get the turbo going. I assume you would recharge the reservoir with compressed air generated from a regenerative breaking system?

You could also use some compressed air to help run the fuel injectors atomizing the spray with compressed air. That may be dangerous though...

I recommend you go to the university and take a few classes that apparently you have not heard of before.

For everyday use the idea has no merit at all. If you could do the calculations involved you would realize that.

Unless you and the OP can find some way to rewrite the laws of physics this just won't work.

Do some simple math. Pick an engine, any engine of known displacement. Now, if you agree that air volume coming out of the exhaust is equivalent to air volume going in the intake, do the math. Each engine revolution will produce an exhaust stream equal to the displacement of the engine. The numbers get really big, really fast. This is what is required to drive current turbochargers.

Try it.

lynlynch says: "air volume coming out of the exhaust is equivalent to air volume going in the intake"

Air/gaseous mass is more or less that of the intake air (plus that added in by the now combusted fuel). The volume is, most definitely very much greater - due, of course, to being a damn site hotter (at the exhaust manifold).

It is well known that over 25% of fuel's combustion energy is disappearing every stroke as a rush of hot, fast-moving gas out of the cylinder every time the exhaust valve opens. I'm not pulling energy out of thin here - if even a fraction of this quarter is recoverable (yes, as already done with the ubiquitous turbocharger) into compressive work (or electrical work or whatever) this has the potential to be used not simply to pump more horses out of a small block (with of course plenty of added fuel), but to gain more average-cycle-efficiency through more effectively cooled (on average) charge.

"The volume is, most definitely very much greater - due, of course, to being a damn site hotter (at the exhaust manifold)."

Sure, for a few seconds, maybe. If we throw reduced density due to heat into the mix, the amount of work done in either case would be close.

You will agree that no "new" air comes about as a result of combustion, right?

"You will agree that no "new" air comes about as a result of combustion, right?"

- Of course.

"If we throw reduced density due to heat into the mix, the amount of work done in either case would be close."

- Sorry? The amount of work done where? The amount of work available at the exhaust valve is about a quarter of total. A turbo (running an ideal accumulator) might recover, what, 15% of this?

If you are going to keep pushing this the provide something other than a general feeling that things should be better.

Something, anything to support your case.

We realize that is impossible but you don't seem to though you do seem to be mixing topics.

As others have pointed out you have a massive misunder standing of the problems involved.

I would not work.

You would need Huge storage cylinders.

How would you recoup or generate air from braking ?

may i suggest you learn how the existing systems work first them try to improve on them in a pratical and cost effective way.

it has to be easy to build, and cheap to run for it to be of any use

http://cr4.globalspec.com/search/sitesearch?do=show&sort=textmatchrank&srch=air%20powered%20vehicles&order=asc

I can, now, see the figures are huge in terms of air volume into even a smallish engine. I had definitely underestimated the capacity, even at 10 bar storage down to 1.5bar inducted. I would still like to test the theory that 'some is better than none'...

I'm off to look at the figures myself to avoid an ear-bashing...

In your reflections, it is worth considering that turbocharging in petrol engines has no beneficial effect on fuel efficiency, when theory is put into practice. The 2004 BMW 330i and Volvo S60 are illustrative of the classic trade-off -- a smaller turbo (2.3l) vs a larger NA engine (3.0l) , in precisely the same market segment and with very similar performance. The BMW EPA figures are 18 city, 27 hwy, 21 combined. The Volvo figures: 18 city, 27 hwy, 21 combined.

The theory is that a smaller engine can be used in the interests of light weight, (and only for that reason can improve fuel efficiency) but this does not hold up particularly well in practice, because the internal components need to be equally heavy given equal HP output (and, if anything, there tends to be a need for even heavier duty components in turbo engines, because very high torques (and thus high cylinder pressures) can be produced at low engine speeds, where destructive detonation can be particularly likely. Then there is the extra weight of additional exhaust plumbing, the turbine itself, additional intake plumbing, etc. Volvo curb weight: 3410. BMW 3340. Quarter mile times: BMW 14.7. Volvo 15.5

When manufacturers "pull out the stops" for fuel efficiency in petrol engines, they do not go for turbos, but instead for Atkinson cycle (asymmetrical compression and expansion).

Also worth considering: the Volvo engine in this test was characterized as a great engine in need of a better chassis, and the "killer engine of the group". The old complaints of turbo lag, etc rarely come up in discussion of modern turbos. What problem is crying out to be solved?

Also worth considering: although you claim the elimination of waste gates (why?), you will have to add a more sophisticated intake pressure regulator. The old (pre electronic) turbos had the simplicity advantage that as the engine demanded more airflow, the turbo produced more airflow naturally. Circumventing that basic feature will require additional regulation controls, the attendant flow restrictions and efficiency losses, new technology to generate these high pressures (an off-the-shelf turbo does not operate at 150 psi output), etc.

Also worth reflecting upon: What is the key problem that your complicated and expensive scheme, requiring revamping of not just engine controls but chassis structure, is intended to solve? That is unclear in your original post. If regen is your main goal, compressed air is near the bottom of the heap in terms of energy storage efficiency. Batteries are near the top, and have the advantage that they are already in use for the purpose, the control architecture is well-understood and relative simple, and there is a successful history of implementation in production cars. If turbo lag is the issue you are concerned with, then read the tests of modern turbo engines. You will find few people saying "This engine would be OK if it just didn't have so much lag."

Perhaps you are intending your system for diesels, for which specific fuel consumption has the potential for being better with a turbo than without?

Smart car (800cc) at 3,000rpm - Air consumed 72,000l/hr - 20l/sec.

Floor pan, boot, etc ~ 300 litres of air space. Air at 6 bar. -equiv to 1800 L.

So, enough air for a 1.5minutes, yes? NB. this is running 100% stored air with no turbo-recuperation.

Next question: how much more energetic is the air leaving the engine than entering it? Enough to run contiuously at 20% mixing with fresh air, for example?

This seems to satisfy your complaint about turbo lag.

This negates the need for bulky storage frames.

And, no. You only have 6 bar for a little while. Depends how you use it and what the critical pressure of the system is. Sooner or later, you have to trade volume for pressure.

My Mom's calling me, I can't play any more.