22 solved GATE ME questions on Turbomachinery, drawn from 10 exam years and grouped by year. Every question shows the official answer and a step-by-step solution.
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Identify the machine type (impulse or reaction), draw inlet and outlet velocity triangles, and apply the Euler turbomachinery equation to find energy transfer. These selected foundations cover basic turbine and pump analysis. They are not a complete syllabus; detailed cascade analysis, compressor maps, and cavitation need separate study.
Our study notes and original examples support the PYQs below; they are not official exam questions or a replacement for the current syllabus.
At each rotor stage, the absolute velocity C, blade velocity U, and relative velocity W form a triangle: C = U + W (vector). Resolve into axial (C_a) and tangential (C_w) components. Axial velocity is often assumed constant through the stage. The change in whirl (tangential) velocity drives energy transfer.
Check yourself: Are the inlet and outlet triangles consistent with the blade angles and axial velocity?
Specific work = U₁C_w1 - U₂C_w2 for a turbine (work output). For an axial machine where U₁ = U₂ = U, specific work = U(C_w1 - C_w2). Power = mass flow rate x specific work. This equation applies to both turbines and compressors; the sign of (C_w1 - C_w2) determines whether energy is extracted or added.
Check yourself: Have you used consistent sign conventions for whirl velocities?
Degree of reaction R = static enthalpy drop in rotor / total stage enthalpy drop. For an impulse turbine, R = 0: all pressure drop occurs in the nozzle, and relative velocity magnitude is constant across the rotor (ideally). For 50% reaction, the velocity triangles are symmetric. Reaction turbines have pressure drop in both stator and rotor.
Check yourself: Does R = 0 truly apply, or does some pressure drop occur in the rotor?
A centrifugal pump adds energy to fluid: head H = U₂C_w2/(g) for zero inlet whirl. Specific speed N_s = N√Q/H^(3/4) (with consistent units) classifies pump type: low N_s indicates radial, high N_s indicates axial. Pump performance curves plot head vs. flow rate; the operating point is the intersection with the system curve.
Check yourself: Are the units of N, Q, and H consistent in the specific speed formula?
Axial compressors add energy to increase pressure. The pressure ratio per stage is limited by blade stalling. Polytropic efficiency accounts for the progressive temperature rise across multiple stages. For centrifugal compressors, the slip factor reduces the ideal whirl velocity at the impeller exit.
Check yourself: Have you accounted for slip when computing the actual whirl velocity?
Original teaching example · not a PYQ
Original example: an axial-flow impulse turbine stage has blade speed U = 200 m/s. Steam enters the rotor with absolute velocity C₁ = 500 m/s at angle α₁ = 20° to the plane of rotation (nozzle angle). Assume axial exit with no whirl (C_w2 = 0) and steady flow. Find the specific work output.
Specific work output ≈ 94.0 kJ/kg.
A centrifugal pump impeller has outer diameter 0.3 m and rotates at 1500 rpm. Water enters the impeller radially (no inlet whirl). The tangential component of absolute velocity at exit is 10 m/s. Assume g = 9.81 m/s². Find the theoretical head developed.
H ≈ 24.0 m.
U₂ = πDN/60 = π x 0.3 x 1500/60 = 23.56 m/s. With zero inlet whirl, Euler head H = U₂C_w2/g = 23.56 x 10/9.81 ≈ 24.0 m.
Supplemental reading, not an official GATE reading list or an endorsement of these notes.
Free supplemental video lectures on velocity triangles, Euler's equation, turbines, pumps, and compressors aligned with the GATE ME syllabus.
This page shows 22 recent questions from the released archive, newest first. For older questions and complete papers, browse all GATE ME papers. Questions can carry more than one subject tag; counts are not marks weightage.
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