At the eye tip of a centrifugal impeller, blade velocity is 200 m/s while the uniform axial velocity at the inlet is 150 m/s. If the sonic velocity is 300 m/s, then the inlet Mach number of the flow will be
- A. 0.75
- B. 0.66
- C. 0.90
- D. 0.83
Answer: D. 0.83
Explanation: Absolute velocity $V = \sqrt{200^2 + 150^2} = 250$ m/s. Mach number $M = V/c = 250/300 = 0.83$.