Modelling the Transient Behaviour of Jet Engines
Dieter Peitsch · Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery · 2000
Understanding the behaviour of turbomachinery components has rapidly improved during the last years. The focus has been set mainly on unsteady component characteristics such as compressor stall and combustion chamber flameout. However, modelling the whole engine during transient operation is still a major workpackage during the development process of modern jet engines. The aim of transient modelling of jet engines is the prediction of the normal engine behaviour during changes of the powersetting, but also to prove engine safeness in abnormal operation, e.g. caused by failures of the control system. Various approaches are used depending on the application purpose. For the most accurate prediction, complex synthesis programs model each component separately and iterate to match the components against each other. For customer use as well as for evaluation whether the real control software in the Electronic Engine Controller operates satisfactorily, more simple programs are derived from this, which include the engine characteristics in a more general way. This gives a very robust tool for simulation of simple transient manoeuvres as well as e.g. flameout or starting predictions. The paper will present the variety of approaches for modelling transient engine behaviour and will discuss the limitations of these. It will also include a description, how the control system of modern jet engines, the FADEC, is set up in these environments. This modelling is needed, if a realistic approach towards reliability of in service operation shall be performed. Synthesis results are given from the development process. The use of advanced modelling of the control system with dedicated tools to improve the capabilities of the whole system is highlighted. An example for this is included with regard to the scheduling of the handling bleed valve of the booster compressor. Finally, the paper will give an outlook on the future planning of the synthesis of transient engine operation within Rolls-Royce Deutschland GmbH (RRD).