Minimization of the Local Rates of Entropy Production in the Design of Air-Cooled Gas Turbine Blades

Abstract

The paper presents the results of a numerical configuration study made on a two dimensional model of an internally cooled gas turbine vane. The analysis applies to a two-dimensional cascade at medium Reynolds number, subsonic Mach number, and steady state. The full Navier-Stokes equations of motion for turbulent viscous flow, together with the appropriate energy equation, are solved via a standard finite-element code with a k-ε closure, to obtain complete velocity and temperature fields. These fields are then used to compute the entropy generation rates corresponding to the viscous (sv ) and thermal (st ) dissipation. The thermo-fluid dynamic efficiency of difference versions of the same base configuration is assessed comparing the global (or integral) entropy generation rate in the passage. The procedure is general, can be extended to different configurations and different operational conditions, and provides the designer with a rational and effective tool to assess the actual losses in the fixed and rotating turbomachinery cascades.