GATE AG 2016 • Q45 NAT • 2 Marks

Section 3: Farm Power

Farm Power

Subtopic: Thermodynamic principles of I.C. engines

Question Statement:

The intake pressure of a diesel engine is 1 bar and pressure at the end of the compression is 34 bar. The adiabatic exponent is 1.3 and the expansion ratio is 7. The diesel cycle efficiency in percentage is ______

Official Answer Key:

48 to 50

Step-by-Step Solution & Explanation

Compression ratio from the isentropic compression: P2/P1 = r_c^γ, so r_c = (34/1)^(1/1.3) = 15.07. Given the overall expansion ratio (V1/V3) = 7, the cut-off ratio ρ = r_c/7 = 15.07/7 = 2.153. Diesel-cycle efficiency: η = 1 − (1/γ)×[(ρ^γ − 1)/(r_c^(γ−1)×(ρ−1))] = 1 − (1/1.3)×[(2.153^1.3 − 1)/(15.07^0.3×(2.153−1))] = 49.4%, within the accepted band 48–50.

Practice This in Real CBT Exam Interface

Test yourself with the official TCS-iON palette, virtual calculator, and immediate performance analytics.

Launch CBT Mock Test