Investigations On Predicting Method Of Influence Of Inlet Flow Distortion On The Stability Of Variable Cycle Engine

The influence of inlet flow distortion on the stability of aeroengine is a key problem throughout the whole process of engine development.With the birth and employment of the modern high-performance variable cycle engine,the adverse effect of inlet flow distortion on its stability becomes more and more prominent.Therefore,it is of great theoretical and practical value for the development of variable cycle engine to carry out the prediction research on the aerodynamic stability.In this paper,the double bypass variable cycle engine with core driven fan stage is used as the research object.The influences of inlet distortions(such as pressure distortion,temperature distortion)on the aerodynamic stability and the operation of influences of the pre-variable area bypass injector are studied.The main contents and results are as follows:(1)The influence of the stability factors and the assessment of the stability margin in the different development stages of the engine are analyzed.The stability index allocation of the variable cycle engine and the allocation principle of the stability margin index of the compression components are given.The stability margin of the compression components of the variable cycle engine was evaluated quantitatively by using the software of engine stability comprehensive evaluation.(2)According to the research object of this paper,an analytical model which describes the influence of inlet pressure and temperature distortion on the stability of variable cycle engine is established.The influence of inlet pressure and temperature distortion on the aerodynamic stability and performance of the variable cycle engine under different working modes(single and double mode)is calculated by GasTurb-Dis calculation program.The results show that the distortion in the runner of the variable cycle engine is attenuated,and the attenuation is the greatest after the compression components,and the core drive fan stage is more sensitive to the inlet distortion.In addition,the calculation gives rises to the movement of the operating point of the various types of aberration variable cycle engine,the corresponding critical distortion index and sensitivity coefficient.(3)The effect of the VABI1 on the stability of the variable cycle engine is studied.The CFD calculation software and GasTurb-Dis program were used to simulate the different opening and adjustment scheme of VABI1.The results show that,as the increasing of the CDFS duct loss,the anti-distortion ability of variable cycle engine are reduced.The stability of the variable cycle engine can be affected by the opening area of the VABI1.In a certain range,the longer the axial length,the smaller the pitch angle,the stronger of the anti-distortion is.Through this method,stability could be greatly improved.