Investigations On Off-Design Performance Computation And Predicting Methods Of Inlet Flow Distortion For Fan/Compressor

During the past decades, great progress of engineering techniques has been made for the gas turbine engines. The fan/compressor is a key component of aero-engines, thus its performance parameters are being improved continually, and also design methods. Among techniques, methods for off-design performance computation and for predicting and analyzing influences of the inlet flow distortion as hotspots for researchers are important tools in the fan/compressor aerodynamic design.At the beginning, this thesis reviews the development of aero-engines and the contents of several advanced research plans of the western countries. Based on analysis of the fan/compressor off-design performance computation and some predicting methods of the inlet flow distortion, the main research contents and achievements are expatiated in detail.The main research works are itemized below:Firstly, on the basis of the classical off-design performance computing method, element cascade method, according to aerodynamic characteristic of the modern advanced fan/compressor, a computing method of off-design performance and surge boundary of the multi-stage axial fan/compressor is established, and validated by related experimental data.Secondly, based on the above computation for the uniform inlet flow, a quasi-3D computational model and an integrated analytic system for analyzing the influences on the performance and stability of the fan/compressor in the condition of the distorted inlet flow are built up. The existing results testify that they are flexible, reliable and adaptable, could be used to resolve the engineering problems.Thirdly, enlightened by the theory and composition of the body force model, a 3D unsteady computational method is developed for predicting the influences on the fan/compressor performance and stability when the non-uniform inlet flow. Based on unsteady Euler equations, element cascade method and unsteady actuator method, a 3D unsteady integrated analytic system is set up for the multi-stage axial fan/compressor. Compared with the test results of a high speed and low speed fan/compressor, it is proved that the method is solved quickly and effectively, and can reflect the 3D effect of the inlet flow distortion. Thus the method has the important theoretical value and engineering application foreground. Fourthly, the experimental tests have been carried out in the low speed two-stage axial compressor in test rig with an inlet flow distortion screen in NUAA. The distorted total pressure characteristics and its effects on off-design performance, stability and the stall inception of the test compressor have been investigated emphatically. In addition, it is validated by test results that the distorted total pressure characteristics with the inlet flow distortion screen, measured at AIP by the 6×6 measurement method, have to be corrected for a given correcting method. Finally, some correction curves are given.The main highlights of the thesis consist of the following items:(1) The computing method of the off-design performance and surge boundary for the modern advanced multi-stage axial fan/compressor is developed. By introducing the Reynolds number relation, it can evaluate its influence on the fan/compressor performance and stability.(2) On the basis of the off-design performance computation for the uniform inlet flow, the quasi-3D computational model and the analytic system for analyzing the influences of the inlet flow distortion on the multi-stage fan/compressor performance and stability are built up.(3) The 3D unsteady computing method and the 3D analytic system for computing the multi-stage axial fan/compressor off-design performance, surge boundary and predicting the influence of inlet flow distortion are established.(4) By means of introducing the concept of the critical distortion angle, the Koch's maximum pressure rise potential is used for confirming the surge boundary effectively and validated by the existing data on the different inlet flow condition.(5) The subsystem for calculating the multi-stage axial fan/compressor off-design performance, surge boundary and predicting the influences of the inlet flow distortion consists of the computing method of the off-design performance and surge boundary for the uniform inlet flow, the quasi-3D and the 3D computational method for analyzing the influences of the inlet flow distortion, and can be brought into the fan/compressor aerodynamic design system and developed as an important design tool.