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

Vt > Vo
Vi = 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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