Numerical Research On The 3-D Complex Viscous Flow In Radial Turbo-machinery

In recent years, the study of coupling numerical computations between impeller and volute has become one of the major research areas in radial turbo-machinery aerodynamics. In comparison with axial turbo-machinery, the internal flow in radial turbo-machinery is more complex. Furthermore, more problems concerning the 3-D flow structure in radial turbo-machinery are yet to be solved. In this dissertation, the research work is focused on the investigation into the three dimensional viscous flow in a diagonal fan impeller coupled with volute to be used in cooling system by means of CFD after the practical choice of turbulence model. These studies mainly consist of the following aspects:The 3-D viscous N-S governing equations as well as its temporal and spatial discretizations used in NUMECA are given. Then, the formation of B-L algebraic turbulence model and standard k-e turbulence model are introduced. In order to accelerate the convergence, residual smoothing local time stepping and multi-grid techniques were employed. Furthermore, the validation of the numerical simulation with the two types turbulence models by means of the NASA Low Speed Centrifugal Compressor is studied. The numerical precisions and convergence abilities are compared with the algebraic B-L and standard k-e turbulence models on the basis of detailed comparisons with available experimental data. Additionally, the secondary flow structure within LSCC impeller in order to get further insight into the secondary flow in radial turbo-machinery.The computation coupled total diagonal impellers with volute and detailed investigation into its internal flow field have been taken on the basis of a cooling complex installation as an illustration. The principal flow pattern has been discovered. The author also concluded that this computation is obvious superior to the traditionalsingle-impeller computation method. The results reveal that secondary flow within the impeller tip gap and the vortex induced by the interaction are the main cause of low efficiency, which forms a solid basis for its further optimization research.