# Homework Help: Frustrated with Adiabatic compression problem

1. Sep 26, 2014

### sfgoat

1. The problem statement, all variables and given/known data
In a diesel engine air is adiabatically compressed to autoignition temperature (287oC) of diesel. Given
C/nR=2.78 for air, and the room temperature is 27oC, what is the compression
ratio where diesel vapor is added for ignition.

2. Relevant equations

PV=nRT
PV=NkT
C=(dU/dT)

3. The attempt at a solution

I'm just frustrated with this review problem and think I may be over thinking it but I am not given an initial pressure or volume and so I am not sure where to even start with this problem. Could someone please give me a push in the right direction.

2. Sep 26, 2014

### SteamKing

Staff Emeritus
Well, most diesel engines take their combustion air from the atmosphere, so what is the pressure there?

If you want a volume to work with, assume one: a liter, a cubic meter, whatever you feel comfortable with.

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