Multi-Stage Compressor Model for Transient Performance Simulations

This paper describes the development of a multi-stage compressor model for transient performance calculations. The aim of the model is to simulate the interaction of the compressor stages with each other and the rest of the engine components during transient engine maneuvers. Especially rematching effects caused by transient heat flows and tip clearance changes are of interest, since they have a major impact on the stability of the compressor. In the first section of the paper the stage stacking ability is implemented in the performance tool. Therefore the compressor is split into several stages each of which is represented by a single compressor module. The specifics of this approach are discussed and the validity of the multi-stage model is shown by a comparison with results calculated with a conventional compressor model. Then the model is extended to simulate transient heat flows and tip clearance changes in each compressor stage. This is achieved by a state space approach which allows the calculation of the thermo-mechanical effects based on a set of previously identified matrices. The thermal calculation modules are linked to the performance model, and the quality of the combined simulation is shown by a comparison of results for two transient maneuvers with reference data. Finally the stage working line excursions of an acceleration are compared with those of a hot reslam demonstrating the advantage of the combined multistage performance model.