Compressors, Gas Turbines and Jet Engines
If V, U and Vr represent the absolute velocity of fluid, velocity of blade, and relative velocity of fluid, and suffix ‘I’ and ‘o’ stand for entry and exit conditions, then in a rotary machine whose degree of reaction is unity

Vi = Vo
Vt > Vo
U < Vo
V = Uo

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Compressors, Gas Turbines and Jet Engines
For a two stage reciprocating compressor, compression from p₁ to p₃ is with perfect intercooling and no pressure losses. If compression in both the cylinders follows the same polytropic process and the atmospheric pressure is pa, then the intermediate pressure p₂ is given by

p₂ = p₁. p₃
p₂ = (p₁ + p₃)/2
p₂ = Pa p₃/p₁
P₂ = Pa × p₃/p₁

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Compressors, Gas Turbines and Jet Engines
The specific output per kg mass flow rate of a gas turbine (having fixed efficiencies of compressor and turbine and fixed higher and lower temperature) with increase in pressure ratio will

Decrease continuously
Increase first at fast rate and then slow
Increase first at slow rate and then fast
First increase, reach maximum and then decrease

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