Comparison of Thermodynamic Loss Models Suitable for Gas Turbine Propulsion

The description of Several e gures of merit for estimation of loss in work potential based on the second law of thermodynamicsandevaluationoftheirrelativemeritsforpropulsionsystemanalysisanddesignaretheobjectives. Thelosse guresofmeritexamined areexergy,gashorsepower,and thrustwork potential.Dee nitionsandsimplie ed expressions for evaluating each are presented and related via contours on a Temperature-Entropy diagram, and a working comparison is provided by way of a pedagogical example using the J-79 turbojet engine. It is shown that thrust work potential is a special case of gas horsepower, which is in turn a special case of exergy. Based on these results, a general taxonomy is suggested to classify the various work potential e gures of merit. The results of this analysis are then used to draw inferences as to what applications each work potential e gure of merit is best suited, the general conclusion being that they are complimentary, with each e gure of merit being well suited to a particular application. Finally, a general work exclusion principal is suggested as a guide to which of the various loss e gures of merit is most appropriate for a given application.

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