Definition of "polytropic" []

• Of any change in the thermodynamic properties of a gas in which its specific heat remains constant (adjective)

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• "Actual values for the polytropic exponent of air and air/fuel mixtures range from n = 1.30 .. .1.36."
• "Beyond about 5 stages or a 4: 1 design pressure ratio, polytropic at their design conditions."