(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

In a diesel engine, atmospheric air is quickly compressed to about 1/20 of its original volume. Estimate the temperature of the air after compression , and explain why a Diesel engine does not require spark plugs.

2. Relevant equations

f/2*ln(T_f/T_i)=-ln(V_f/V_i)

3. The attempt at a solution

I will assume the temperature inside a diesel engine is room temperature or 300 K.

f=5 since air is a diatomic gas.

T_i=300 K

T_f=?

V_i=V_i

V_f=.05*V_i

2.5*ln(T_f/(300K)=-ln(.05)

ln(T_f/300 K)=3/2.5

In(T_f/300)=1.2

T_f/300=exp(1.2)

T_f=300*exp(1.2)

since this is an adiabatic compression , no heat escapes. I guess spark plugs are not required because they produced heat and heat production isn't required to compress air inside a diesel engine. OR . The compression must be so high that heat is produced and the engine ignites by itself that there is no need for spark plugs.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Adiabatic compression in a diesel engine

**Physics Forums | Science Articles, Homework Help, Discussion**