Turbomachinery Loss Analysis: The Relationship Between Mechanical Work Potential and Entropy Analyses

Physics-based loss analysis methods have been developed to interpret the detailed three-dimensional and time-dependent predictions of turbomachinery CFD simulations. This paper contrasts two analysis methods for assessing loss: entropy loss analysis (Zhao & Sandberg, GT2019-90126) and mechanical work potential analysis (Miller, GT2013-95488). The two individual analyses are applied to high-fidelity simulation data for linear high-pressure compressor and high-pressure turbine cascades. The results show each analysis captures the loss generating processes in different ways, corresponding to different terms in their equations. The key loss generation processes are shown to be turbulent and mean viscous dissipation in the mechanical work potential analysis, and mean viscous dissipation and turbulence production in the entropy loss analysis. A relationship between the two approaches is derived rigorously, providing a means to convert between the results of the two approaches, enabling designers to assess individual stage performance using the entropy-based analysis and multiple stages in terms of mechanical work potential, by using the same reference pressure.