Question

The work done per unit mass in a centrifugal compressor mainly depends on

• A. Change in axial velocity
• B. Change in whirl velocity
• C. Diffuser vane angle
• D. Eye diameter only

Hint:

Euler's equation for compressors is \[ \boxed{ W=u(V_{w2}-V_{w1}), } \] showing that the work input depends on the change in whirl velocity.

Answer 1

The Correct Option is B

Step 1: Recall Euler's compressor equation. The work done per unit mass is \[ \boxed{ W=u\left(V_{w2}-V_{w1}\right), } \] where
• \(u\) = impeller speed,
• \(V_{w1}\) = inlet whirl velocity,
• \(V_{w2}\) = outlet whirl velocity.

Step 2: Interpret the equation. The work transfer depends directly on the change in the whirl (tangential) component of velocity. Hence, \[ \boxed{ \text{Work done} \propto \left(V_{w2}-V_{w1}\right). } \] Therefore, \[ \boxed{\text{Change in whirl velocity}} \] is the correct answer. Thus, \[ \boxed{(B)} \] is the correct answer.