Compressed-air kinetic energy recovery system?

All that has to do with the power train, gearbox, clutch, fuels and lubricants, etc. Generally the mechanical side of Formula One.
g-force_addict
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Compressed-air kinetic energy recovery system?

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Would it be feasible and legal to use some kind of kinetic recovery system when engine braking compresses air within the cylinders, stores compressed air in a tank to use it as some means of supercharging in the next straight?

Maybe they could be required to start the race with the compressed air tanks empty?

jhietter
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Re: Compressed-air kinetic energy recovery system?

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Interesting idea. I have long though about pre compressing the air for the engine and holding it in a storage tank so that it is available from standstill. I asked my auto shop teacher about this and one of the biggest issues he mentioned is the weight of a container that can hold compressed air and the weight of the equipment to compress it. This may not be a problem, how do I calculate what volume of air would be needed for a cylinder to fire? This would help me determine how much air can be pre Compressed and stored conveniently.

Lycoming
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Re: Compressed-air kinetic energy recovery system?

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You could store braking energy this way, it's been done before. But in those cases it was used to drive a pneumatic motor as opposed to supercharging a combustion engine. I suspect that they would be opposed to doing that due to engine wear, and batteries/flywheels/supercaps are probably better methods of storing energy anyways.

riff_raff
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Re: Compressed-air kinetic energy recovery system?

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Using air compression/expansion is not a very efficient way to capture and reuse energy on a race car. The typical process is not very efficient compared to other established methods such as flywheels or battery/electric. Using the engine cylinders for performing the compression/expansion work would make the valve system quite complex. The KERS cycle pressures would also be limited to what the engine could tolerate.
"Q: How do you make a small fortune in racing?
A: Start with a large one!"

mzivtins
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Re: Compressed-air kinetic energy recovery system?

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Surely you would lose a measurable amount of engine braking by sapping off the compressed air? Seeing as it is the pumping losses and compression cycles that give us engine braking? I'm not sure how you would transfer compressed air without using the compression itself to deliver the medium?

Tommy Cookers
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sounds like a job (in part) for a pressure wave rotor device ?
(the Comprex supercharger is one such)

riff_raff
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Re: Compressed-air kinetic energy recovery system?

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mzivtins wrote:Surely you would lose a measurable amount of engine braking by sapping off the compressed air? Seeing as it is the pumping losses and compression cycles that give us engine braking? I'm not sure how you would transfer compressed air without using the compression itself to deliver the medium?
mzivtins- Using engine braking does not necessarily imply that the process needs to be inefficient. In fact, a pneumatic KERS would want to have high cycle efficiency by definition, right?

One major drawback with using the engine for compressing air in a KERS system is that the engine would only be able to compress air to about 300 psi or less. This would require a compressed air storage system designed for very high volume at low pressures. Given such low pressures, the pressure vessel would need to be quite large to accumulate any significant amount of energy.

Maybe someone can do a quick calculation to determine just how large the pressure accumulator would need to be to store the amount of energy permitted by current F1 regs at a max pressure of around 300 psig.
"Q: How do you make a small fortune in racing?
A: Start with a large one!"

bigpat
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Re: Compressed-air kinetic energy recovery system?

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Audi developed a compressed air KERS system in 2012 for Le Mans, but it was banned when the ACO got wind of it. Audi Motorsport director Dr Ullrich expressed disappointment, as he felt that with refinement, it would find its way onto road cars within only a few years...

Lycoming
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bigpat wrote:Audi developed a compressed air KERS system in 2012 for Le Mans, but it was banned when the ACO got wind of it. Audi Motorsport director Dr Ullrich expressed disappointment, as he felt that with refinement, it would find its way onto road cars within only a few years...
But what's the point? electric hybrids, which regenerate energy under braking then use it in the motor to drive the wheels (which is exactly what KERS does) have been on the road for years. And pneumatics are not efficient... compressed air has low energy density when used as a means of energy storage and pneumatic systems have large transmission losses, hence why Boeing went all electric on the 787.

So, again, what's the point?

timbo
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The energy density of air (presuming isothermal storage as adiabatic is IMO impractical on F1 car) is proportional to ln(p2/p1), where p2 and p1 is pressures before and after compression. The problem with that is that for a double pressure you only get (e1+0.69)/e1 better density. You can store 460kJ per 1 cubic meter of ambient air isothermally compressed air at room temperature at 100 bar, 530 kJ at 200bar and 600 at at 400 bar. The mass of container needed to store compressed air would not increase linearly, though.

bigpat
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Compressed-air kinetic energy recovery system?

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No doubt Audi would have done the same calculations.....
As we are unaware as to how the system actually worked, it may be hard to comment on it's downsides.
As we know in top end Motorsport, nothing is unnecessarily added to a car, unless it brings a warranted gain. The fact that Audi was committed to putting it on an already extremely refined package, tells you that it must have worked well.....

xpensive
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Re: Compressed-air kinetic energy recovery system?

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g-force_addict wrote:Would it be feasible and legal to use some kind of kinetic recovery system when engine braking compresses air within the cylinders, stores compressed air in a tank to use it as some means of supercharging in the next straight?

Maybe they could be required to start the race with the compressed air tanks empty?
If you search for Guy Negre on the web, you'll find a whole heap of his ideas, I believe he has a pneumatic car on sale in France?
"I spent most of my money on wine and women...I wasted the rest"

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Ciro Pabón
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Re: Compressed-air kinetic energy recovery system?

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Just a "technical" comment to riff raff (hi, mate!), as I'm "on duty" with Korean GP and Steven's out of town and Principessa birthday is Saturday. Five seconds to finish qualy, so I have just the time to write one of my "short" posts.

(IMPORTANT SIDE NOTE: you can send her gifts to me, I'll be happy to store them for her. She likes books on tyre friction and circuit design, as you all know. DISCLAIMER: any mistakes in the news are made by Kiril, not by me):

Energy density of compressed air can be almost doubled IF air is heated before compression.

That's easy to do in an F1 car (and provides you refrigeration, so double whammy).

The expanded air (if not heated) would give you problems with freezing the KERS engine, because of adiabatic decompression. No one in his right mind would design a compressed air engine without it, or the pipes would clog.

A beautiful example of a compressed air engine is the Brotherhood one (oh, I'm sure you remember the Brotherhood brothers, bros), because those guys knew well what happens when air is compressed: it heats. The same, but in reverse, happens when it decompress: it gets cold as hell.

I guess the cyclists in the forum have burnt once or twice while pumping air in their bicycle tyres...

Brotherhood engine: stick it in a new F1 car and you have a KERS without adiabatic problems. It can give you 4500 psi with one hand tied behind its back
Image

This magnificent KERS prototype also runs on steam, so it will give you an advantage for F1 2020 season, when, as we all know, engines will have one cylinder (a.k.a as "V1 engine"), which will make them more efficient than the old and noisy V6 of the 2010's, and they will use carbon monoxide fuel or solar heated steam only (to alleviate global warming, of course, although carbon monoxide engines are tricky to design: you have to burn all the fuel before using it).

For example, you can read about the Tresher nuclear submarine tragedy and ponder how important is to design things that doesn't kill you by "adiabatic messing":

Image

Pressure for compressed commercial air cars is around 300 bar, riff...

(... and, yes, you can design and build a regular, commercial car without spending one hundred million euros in building a prototype to race at Le Mans: that's the usual procedure, btw).

That's the pressure used in torpedo propulsion for decades, if not centuries (that's what the Brotherhood engine was used for: the first torpedo built by Whitehead, propelled by compressed air, reached the then impressive distance of 180 meters, almost twice the length of a modern submarine).

Whitehead ponders why his (battered) test torpedo did not move further (he heated the air afterwards). Notice his look: it seems he works for McLaren, the poor guy...
Image

So, you might want to redo your calculations, young man, taking in account the real pressure and the adiabatic thingamagij. You get a C+ for effort, anyway. :wink:
Last edited by Ciro Pabón on 05 Oct 2013, 08:03, edited 1 time in total.
Ciro

xpensive
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Re: Compressed-air kinetic energy recovery system?

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riff_raff wrote: ...
One major drawback with using the engine for compressing air in a KERS system is that the engine would only be able to compress air to about 300 psi or less.
...
Where did you get that idea, 300 psi is just 20 bar, while MDI uses 300 bar with a tank tested for 450.

Fills up in a few minutes btw. http://www.mdi.lu/english/index.php
"I spent most of my money on wine and women...I wasted the rest"

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Ciro Pabón
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Re: Compressed-air kinetic energy recovery system?

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That's what I said, Professor X.
Ciro