A Quasi-One Dimensiona Model for Axial Turbines

An axial turbine model is presented that is intended to predict its aerodynamic performance based only on the turbine geometry and thermodynamic environment. The model is an extension of an existing quasi-1D compressor representation. The simulation tool is able to compute the flow through a whole multistage turbine, with detail at the blade row level. It relies upon a quasi-one dimensional Euler system of equations, expressed here in curvilinear coordinates, and resulting from the application of mass, momentum and energy conservation principles in finite-volume formalism. The source terms expressing the interactions between the flow, the blades and the flowpath are determined using the velocity triangles for each blade row, at mid-span. The solver performs an elaborate implicit time-marching resolution of the equations.
The enthalpy loss coefficients as well as the blade outlet flow angles are evaluated through open
literature correlations. An efficient representation of the Craig-Cox loss coefficients and the Ainley-Mathieson outlet flow angle correlation brings the necessary empirical information for the velocity triangle computations. The computer code was validated against a high pressure turbine test case featuring multiple cooling flows. The results show the good capabilities of the turbine model using only standard correlations. The computed efficiency also shows the need to model the cooling losses. The low speed, low expansion rate results may finally indicate that the code accuracy would benefit from a correlation parametric identification such as the one led in the
compressor case.