Calculations on the compressed air to an engine cycle

bernardd · by **bernardd** » 04/05/10, 22:20

Following discussions on the car of the future, I found the energy to do some calculations on the subject, in order to clean up a clear vision of the compressed air cycle, particularly in terms of energy.

It will be the objective of this thread to present this vision and consolidate it with the arguments that everyone can bring to it.

Beforehand, I would like to clarify that thermodynamics is a highly delicate area of physics: intuition is sometimes faulty.

And as always, it's the demonstration that counts, not the one who presents it :-) I recently heard that it is this property that brought demo-cracy ...

bernardd · by **bernardd** » 04/05/10, 22:24

Before going into the technique, read a little what is said of the few companies specializing in compressed air.

If compressed air was as energy consuming as some people claim, could they maintain such a good position, for a very long time ...?

Christophe · by **Christophe** » 04/05/10, 22:39

No need to redo calculations that some have already done:

https://www.econologie.com/telechargeme ... nes-paris/

https://www.econologie.com/telechargeme ... nes-paris/

Debate:

new-transport / calculations-on-the-air-engine-of-mdi-of-the-figures-finally-t6407.html

Otherwise, I don't really see the relationship between Air Liquide (whose activity is to sell compressed gases but mainly for chemicals) and the compressed air cycle for propulsion :?:

bernardd · by **bernardd** » 04/05/10, 23:09

Christophe wrote:Otherwise, I don't really see the relationship between Air Liquide (whose activity is to sell compressed gases but mainly for chemicals) and the compressed air cycle for propulsion

Well to get compressed air, you have 2 methods:

- the shadock method: pumping;

- the Air Liquide method, but also Linde, Praxair, ...: reflect :-)

And if you don't see the difference, it may be that information is missing in the existing presentations : Cry:

Christophe · by **Christophe** » 04/05/10, 23:21

Sorry it's still not coming ...

Explain to us in a few words the methods Air Liquide, Linde, Praxair ...

And if this can possibly improve the overall balance, it will not change the fact that compressed air is a bad energy vector ... just like hydrogen!

Now I stay open, give us details of your calculations ...

Alain G · by **Alain G** » 05/05/10, 04:23

Bernard

When you compress the air you create heat which is lost in energy!

How will you keep this heat to heat this air to recover this lost energy and restore the performance of this air which comes out cold when you use it ???

The air has efficiency at low pressure and the more the pressure increases the more there is loss!

bernardd · by **bernardd** » 06/05/10, 00:24

Alain G wrote:When you compress the air you create heat which is lost in energy!

Indeed, mechanical compression by reduction in volume increases the temperature.

But it will only become a waste of energy if the final temperature is higher than the ambient temperature.

And that is the problem with all internal combustion engines: a large part of the energy goes out as heat instead of going out in motion. Because in an internal combustion engine, you lose both compression and decompression ...

This is one of the great advantages of a pure decompression engine, like the compressed air engine: it ATTRACTS thermal energy instead of diffusing it.

But I will come back to it in the next episode

To return to compression, it all depends on what temperature we start ...

Alain G wrote:How will you keep this heat to heat this air to recover this lost energy and restore the performance of this air which comes out cold when you use it ???

As with everything: just use the laws of physics.

The paths of thermodynamics are sometimes surprising : Twisted:

Alain G wrote:The air has efficiency at low pressure and the more the pressure increases the more there is loss!

You give me a good pole!

I wanted to start by clarifying that the words yield et efficiency have different meanings in physics.

Efficiency, it is the ratio between an input quantity and an output quantity of a studied system. This quantity is often an energy, but one can choose according to the objective of the study.

Often there is a difference between a efficiency calculated by one theoretical model or another, with respect toefficiency that we can measure on a real system.

This difference is characterized by a yield, which is the relationship between a efficiency theoretical and a efficiency measured.

Contrary to popular belief, the yield is not a quantification of the quality of implementation of a real system, but rather an estimate, subject to measurement precision, of the representativeness of a theoretical model used and of its capacity to predict the behavior of a system real.

For example, if the machining precision of a part affects theefficiency energy of an engine, then a model that we want precise must take into account the quality of the machining in its parameters and its equations.

I know, it's not the common usage of the word yield. But i can't help it : roll:

Alain G · by **Alain G** » 06/05/10, 03:53

bernardd · by **bernardd** » 06/05/10, 10:16

Alain G wrote:: Shock:

aerialcastor · by **aerialcastor** » 06/05/10, 10:27

I think AlainG means that your message is incomprehensible.

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Calculations on the compressed air to an engine cycle