Frustrated with Adiabatic compression problem

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SUMMARY

The discussion centers on solving a problem related to adiabatic compression in diesel engines, specifically determining the compression ratio required for diesel vapor ignition at an autoignition temperature of 287°C. The participants reference the ideal gas law (PV=nRT) and specific heat capacities (C/nR=2.78 for air). A key point made is that initial pressure can be assumed as atmospheric pressure, allowing for simplification in calculations. The suggestion to assume a volume, such as one liter or a cubic meter, aids in progressing through the problem.

PREREQUISITES
  • Understanding of the ideal gas law (PV=nRT)
  • Familiarity with adiabatic processes in thermodynamics
  • Knowledge of specific heat capacities and their significance (C/nR)
  • Basic principles of diesel engine operation and combustion
NEXT STEPS
  • Research the principles of adiabatic processes in thermodynamics
  • Learn about the ideal gas law and its applications in engineering
  • Study the combustion process in diesel engines, focusing on ignition temperatures
  • Explore methods for calculating compression ratios in internal combustion engines
USEFUL FOR

Students studying thermodynamics, automotive engineers, and anyone interested in the principles of diesel engine operation and adiabatic processes.

sfgoat
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Homework Statement


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.

Homework Equations



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

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.
 
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sfgoat said:
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.

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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