GATE 2020 AE – Question 23

Propulsion · Turbomachinery: Centrifugal compressors and axial turbines · 1 mark · Multiple choice

For a rotating centrifugal-compressor impeller operating with its exit closed, the exit/inlet stagnation-pressure ratio is

0
1
Greater than 1
0.5

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Show answer and explanation

Correct answer: (C) Greater than 1

Explanation

A rotating impeller can sustain a pressure rise even at shutoff. Although throughflow is zero, rotation produces a radial pressure gradient and the exit pressure exceeds the inlet pressure. Thus the ratio is greater than one, C. Zero mass-flow rate does not mean a stationary pressure ratio of unity.

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