Question Bank • QB_PARAMETRIC_FP_CYC_015MSQ • 2 Marks
Section 3: Farm Power
Thermodynamic Air Cycles: Otto, Diesel & Dual
Subtopic: Comparison of cycles for given compression ratio
Question Statement:
When comparing the theoretical air-standard efficiencies of Otto, Diesel, and Dual cycles, which of the following statements is/are TRUE? (Variation QB_PARAMETRIC_FP_CYC_015)
Options:
(A) For the same compression ratio and heat input, $\eta_{\text{Otto}} > \eta_{\text{Dual}} > \eta_{\text{Diesel}}$
(B) For the same maximum peak cylinder pressure and temperature, $\eta_{\text{Diesel}} > \eta_{\text{Dual}} > \eta_{\text{Otto}}$
(C) In an Otto cycle, heat addition occurs strictly at constant volume
(D) In a Diesel cycle, heat addition occurs strictly at constant pressure
Answer Key:
A, B, C, D
Step-by-Step Solution & Explanation
1. For the same compression ratio $r$, constant volume heat addition brings maximum temperature earlier, so Otto is highest. (A is true)
2. When constrained by peak pressure and temperature (the real metallurgical limit), Diesel expands further and has highest efficiency. (B is true)
3. Otto cycle features isochoric heat addition. (C is true)
4. Diesel cycle features isobaric heat addition. (D is true)
All statements A, B, C, D are correct.