Question

Stage efficiency of a single-stage axial compressor is defined as

• A. Ratio of actual work input to isentropic enthalpy rise
• B. Ratio of isentropic enthalpy rise to actual work input
• C. Ratio of rotor speed to stator speed
• D. Ratio of inlet temperature to exit temperature

Hint:

For an axial compressor, \[ \boxed{ \eta_s = \frac{\Delta h_{\text{isentropic}}} {\Delta h_{\text{actual}}}. } \] Higher stage efficiency means less actual work is required for the same pressure rise.

Answer 1

The Correct Option is B

Step 1: Recall the definition of stage efficiency. The stage efficiency of an axial compressor is \[ \boxed{ \eta_s = \frac{\text{Isentropic enthalpy rise}} {\text{Actual work input}}. } \]

Step 2: Interpret the expression. Since the actual work input is always greater than the ideal (isentropic) work, \[ \boxed{ \eta_s<1. } \] Hence, \[ \boxed{\text{Ratio of isentropic enthalpy rise to actual work input}} \] is the correct answer. Thus, \[ \boxed{(B)} \] is the correct answer.