SSC JE Mechanical Engineering 2014 Set 1 Paper

Diesel Engines operate under Diesel Cycle. In Diesel cycle, compression ratio is $\left(\mathit{r}\right)=\frac{{\mathit{V}}_2}{{\mathit{V}}_1}$ ;
and Cut-off ratio is $\left(\mathit{\rho }\right)=\frac{{\mathit{V}}_3}{{\mathit{V}}_2};$
and Expansion Ratio will be $\frac{{\mathit{V}}_4}{{\mathit{V}}_3}$.
The thermodynamic process 3-4 is constant volume process and thus, V${}_1$ will be equal to V${}_1$ .
Thus, ER will be $\frac{{\mathit{V}}_1}{{\mathit{V}}_3}\mathrm{or}\left(\frac{\mathit{r}}{\mathit{\rho }}\right)$
$=\left(\frac{{\mathit{V}}_2}{{\mathit{V}}_1}\right)\times \left(\frac{{\mathit{V}}_3}{{\mathit{V}}_2}\right).$
So, ER $=\frac{\mathit{r}}{\mathit{\rho }}=\frac{21}{2}$
= 12.5 ; and $\frac{1}{1}=1$ ; ER = 12.5 : 1.