Question

What is compression ratio of an Otto cycle? How does it affect the thermal efficiency of the cycle?

Answer 1

`r= (V_1)/(V_2)`

`\eta =1-(1)/(r^(\gamma-1))`

Step-by-step explanation:

Compression ratio:

Compression ratio is the ratio of volume in the cylinder.Generally it is denoted by r.

The compression ratio for Otto cycle is about 8 to 12.But the compression ratio of diesel engine is about 14 to 25.

So from the Otto cycle compression ratio can be define as

`r= (V_1)/(V_2)`

As we know that efficiency defines as the ratio of work out to the heat input.In the Otto cycle the efficiency is given as in terms of compression ratio r as

`\eta =1-(1)/(r^(\gamma-1))`

Where γ is the heat capacity ratio.