An Alternative Compressor Modeling Method within Gas Turbine Performance Simulations

The precise prediction of compressor operation within gas turbine performance simulation is key to an accurate performance simulation model. This paper describes the modeling of multistage axial-flow compressors in gas turbine performance simulations. An alternative modeling technique to the conventional characteristic based approach is presented. The purpose is an improved prediction of the compressor’s overall performance as well as of its interstage pressures and temperatures when changing its geometry by bleed extraction or displacement of the variable stator vanes. Usually, within performance programs the compressor is modeled using a characteristic which describes the relation of its non-dimensional thermodynamic parameters in order to predict the off-design behavior. The performance effect caused by changes in variable geometry has so far been modeled differently within performance programs. Therefore, this paper starts with an overview about the various modeling methods within performance simulations. As an alternative method the coupling of a compressor meanline calculation with an aero engine performance simulation as a substitute to the compressor map is presented. The required changes to the performance program as the compressor module, the adjacent components including the secondary air system and the matching scheme are described in detail. When running the coupled system, the compressor overall and stage-wise off-design behavior is predicted by the meanline program whereby the performance program defines the actual working point by taking the operation of the surrounding components into account. The successful operation of the whole simulation package has been demonstrated. The resulting working lines for a certain stage are shown. Furthermore the ability of forecasting the performance effect of geometry changes is presented. Finally an outlook on the range of applications is given which could benefit from employing the presented method.