Numerical Investigations For The Three-dimensional Flow Field And Aerodynamic Performance Of Transonic Multi-stage Compressors

As a core component of aeroengine, aerodynamic performance of compressors isthe critical factor in engine efficiency, thrust and operability. With the rapiddevelopment of high performance computers (HPC), computational fluid dynamics(CFD) method has been widely used in the turbomachine’s design and analysis. Somekey aerodynamic parameters like efficiency and pressure ratio can be preciselypredicted by CFD. The flow in compressors is very complex, with inherently unsteadyflow field, and transitional and turbulent flow fields with complicated secondary flowsand leakage effects. In addition, modern large turbojet and turbofan engines usually usemulti-stage axial compressors. Unsteady interactions between adjacent rows of rotatingand stationary blades make it difficult for CFD to simulate. In this paper, an in-housethree-dimensional unstructured-grid flow solver based on a mixing plane method wasused to simulate the flow field of the compressors. Pitchwise averaging was used at therotor/stator interface to pass the information, making the unsteady problem to become a“qusi-steady” problem. Thus the computational gird needs only one flow passage,which greatly reduced the amount of the calculation. The overall performance maps andspanwise profiles of several aerodynamic parameters were obtained from the calculation,and the results were compared to the experiment data. The results presented here are ingood agreement with the experiment data, indicating the applicability and reliability ofthe software.In the introduction, the background and importance of turbomachinery CFD werepresented. And some fundamental theories of compressors were described here. Themain research of this thesis is given at the end.Chapter2is focused on numerical methods, the theoretical basis of the full text.The governing equations, numerical schemes, boundary conditions, multigrid method,turbulent models and so on were detailed described here. And the chapter givesemphasis to the inlet and outlet boundary condition, rotor/stator interface treatment.Chapter3presents the tests cases for a single rotor. Two different transoniccompressor rotors were simulated. The performance maps including pressure ratio,temperature ratio and adiabatic efficiency were obtained through the calculation. Theresults were compared to experiment data and agree very well. Meanwhile, somecomplicated flow phenomena like “secondary flows”,“leakage flows” were also studiedin this section.Chapter4discusses the test cases for multi blade rows. Compared to the cases inchapter3, there added rotor/stator interface treatment using mixing plane method. A single stage compressor and a1.5stage compressor were separately simulated. Thoughthe quantities at the interface are not locally continued, but the entire mass, momentum,energy is conserved. Similarly, some aerodynamic parameters were obtained andmatches well with experiment data and commercial software’s results.The last chapter is the summary of all the content from this dissertation. Someshortages of the research were also listed. Finally is the expectation for the future work.