Question

The rating of a diesel engine, with increase in air inlet temperature, will

• A. increase linearly
• B. decrease linearly
• C. increase parabolically
• D. decrease parabolically

Answer 1

The correct option is B decrease linearly

For a diesel engine, compression ratio, ${\rho }_c=\frac{V_1}{V_2}$

Fuel cut-off ratio,$r_c=\frac{V_3}{V_2}=\frac{T_3}{T_2}$

Efficiency $\eta =1-\frac{1}{\gamma {{\rho }_c}^{\gamma -1}}\left[\frac{{r^{\gamma }}_c-1}{r_c-1}\right]=1-\frac{A}{{{\rho }_c}^{\gamma -1}}$

where $A=\frac{{r^{\gamma }}_c-1}{\gamma (r_c-1)}$

Also, $\eta =1-\frac{T_1[\frac{T_4}{T_3}-1]}{\gamma T_2[\frac{T_3}{T_2}-1]}$

Thus with the increase in air inlet temperature,efficiency decreases linearly and so rating decreases linearly.