Numerical Predicting Methods Of Compressor Stability Boundary

OFF-design point performance calculation and stability boundary prediction have been an important part of the design of axial compressors,and the design method needs to be improved to meet the requirements of advanced aircraft engine.This paper include three parts: Firstly,the improvement of Off-design performance calculation method based on cascade element method.Secondly,the applyment and verification of maximum static pressure method in surge-margin prediction.Thirdly,analyze and summarize the stability boundary of multi-stage axial compressor simulated by NUMECA FINE/Turbo.On the basis of previous work,the calculation method of off-design performance was improved,including following parts: 1.As the use of forward-swept wings and more and more compact compressor structure,the radial equilibrium equation was modified to make the program suitable for the situation in which the integral lines are not parallel to the radial lines.2.According to the effect of span-wise mixing on multistage compressors,a model was considered to evaluate the mixing effect.3.the flow loss model used in the program was refined,the end wall effect,passage vortex and clearance effect was taken into consideration,and corresponding loss model was discussed to evaluate the effect on flow structure within the compressor.A four-stage low-speed compressor was simulated with this program to verify the accuracy of the model.The results were compared to the experimental data and it shows that the calculations are more consistent with the experiment results if secondary flow loss models were took into consideration.The off-design performance calculation was combined with maximum static pressure rise method to form a complete off-design performance calculation method.A four stage low-speed compressor and RB-199 five-stage compressor was simulated to verify the accuracy of off-design performance and stability boundary prediction method.According to the experimental data,the calculation shows the method was with certain accuracy in stability prediction,and the influence of relevant parameters on the results is consistent with the understading of compressor stability.The stability boundary of four stage low-speed compressor was simulated with commercial CFD software NUMECA Fine/turbo.In this paper,systematically analyzed the effect of different meshing means(including different percentage of mid-flow cells,number of points in thround gap,number of grid points),different turbulence models and different scheme on calculation results.It suggested that the factors in consideration all influence the accuracy of simulation results.