Accounting for losses and definitions of efficiency in turbomachinery stages

Abstract

A method of accounting for losses and defining efficiencies in the blade rows of adiabatic turbomachinery stages is described. This is based on the concept of specific dissipation work which is the integral of the product of local temperature and entropy change due to the losses (∫ T ds). This formulation allows various entropy-based efficiencies and loss coefficients to be derived with equations that are exact for all types of fluid (liquids, ideal gases, and real gases). The expressions for the polytropic and isothermal efficiency, as well as for the Markov blade row loss coefficient, resulting from this can be directly visualized in a Mollier chart (h-s diagram) as the ratio of entropy and enthalpy changes between two real states and a single virtual state.