Question Bank • QB_EXP_FP_CYC_041 MCQ • 1 Mark

Section 3: Farm Power

Sources of Power

Subtopic: Thermodynamic cycles of IC engines

Question Statement:

On the P-v indicator diagram of the Diesel cycle, as the cut-off ratio approaches unity ($r_c \to 1$), the Diesel cycle converges in thermal efficiency to that of the:

Options:

  • (A) Otto cycle operating at the same compression ratio
  • (B) Carnot cycle operating between same temperatures
  • (C) Brayton cycle operating at same pressure ratio
  • (D) Stirling cycle with ideal regeneration

Answer Key:

A

Step-by-Step Solution & Explanation

As $r_c \to 1$, $\lim_{r_c \to 1} \frac{r_c^\gamma - 1}{\gamma(r_c - 1)} = 1$, so $\eta_{\text{Diesel}} \to 1 - \frac{1}{r^{\gamma - 1}}$, which is the air-standard Otto cycle efficiency.
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