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pentazoid

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## Homework Statement

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.

## Homework Equations

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

## 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.

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