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Compression ratio x compression pressure
4

Compression ratio x compression pressure

Compression ratio x compression pressure

(OP)
What is the reason why with a compression ratio of 1:8,5 you should get between 11 and 13 bar of compression pressure? You shouldn't only multiply compression ratio times the atmospheric pressure?

Thank you.

RE: Compression ratio x compression pressure

...because the temperature rises during compression, further increasing pressure.  Look up "polytropic compression" on the internet if you want more.

RE: Compression ratio x compression pressure

(OP)
Thank you, I'll do that!

RE: Compression ratio x compression pressure

I use a polytropic exponent of between 1.3 ~ 1.35 when I begin to model an engine.  However, to more accurately model the actual process, one would require a continuosly changing exponent as the thermal energy, volume, molecular species, and surface area (heat transfer in or out of the cylinder) change.

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