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GATE 2016 ME (ME3) – Question 29

Thermal Engineering Applications · Turbomachinery: turbines, compressors, pumps · 1 mark · Numerical answer

The blade and fluid velocities for an axial turbine are as shown in the figure. The magnitude of absolute velocity at entry is 300 m/s at an angle of 65° to the axial direction, while the magnitude of the absolute velocity at exit is 150 m/s. The exit velocity vector has a component in the downward direction. Given that the axial (horizontal) velocity is the same at entry and exit, the specific work (in kJ/kg) is__________

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Correct answer: 50 to 54

Explanation

The axial component is V_a=300cos65°=126.785m/s. Inlet whirl is300sin65°=271.892m/s; the150m/s outlet velocity has opposite whirl −√(150²−V_a²)=−80.159m/s. Euler work is U(V_w1−V_w2)=150×352.051=**52.807kJ/kg**. The negative outlet whirl must be retained.