AN ANALYSIS METHOD FOR MULTISTAGE TRANSONIC TURBINES WITH COOLANT MASS-FLOW ADDITION

The subject of this paper is a numerical method for the calculation of the transonic flow field of multistage turbines, taking high coolant pow into account. To reduce the processing time, a throughflow method based on the principels of Wu is used for the hub-to-tip calculation. The pow field is obtained by an iterative solution between a three-dim ensional inviscid hyperbolic time-dependent algorithm with an implicit finite volume method for the blade-to-blade calculations using C-mesh es and a single representative meridional S-2m-streamsurface. Along th e S-2m-plane with respect to nonorthogonal curvilinear coordinates, th e stream function equation governing fluid pow is established. The coo ling air inflow inside the blade passage forbids the assumption of a c onstant mass flow along the main stream direction. To consider the cha nge of the aerodynamic and thermodynamic behavior, a cooling air model was developed and implemented in the algorithm, which allows the mixi ng of radially arbitrarily distributed cooling air in the trailing edg e section of each blade row. The viscous effects and the influence of cooling air mixing are considered by the use of selected loss correlat ions for profile, tip leakage, secondary pow and mixing losses in the S-2m-plane in terms of entropy. The method is applied to the four-stag e high-temperature gas turbine Siemens KWU V84.3. The numerical result s obtained are in good agreement with the experimental data.