Full 3D Viscous Numerical Simulation Of The Aerodynamic Performance Of Centrifugal Impeller Mechanism

Centrifugal impeller mechanism are used in many industrial applications, for example as air compressors. The designer of centrifugal impellers needs knowledge of the flow phenomena inside the impeller passages. Using computational fluid dynamics(CFD), it is possible to examine the flow field inside the impeller and to reduce the number of expensive measurements. Numerical flow simulations can also provide information which is difficult to obtain experimentally. An example is the prediction of the flow separation areas inside the flow channel. In present dissertation, a high performance scheme is employed to simulate the complicated flow field inside centrifugal impeller passages. The work includes several principal points as follow.A hybrid grid generation technique which couples the method of solving partial differential equations with the geometric method is applied to generate high quality structured grid for CFD calculation. Based on former work, a finite difference viscous code that uses a high convergence, high accuracy, high resolution LU-SGS-GE implicit scheme and an improved fourth(fifth)-order high resolution MUSCL TVD scheme to integrate the full 3D Navier-Stokes equations and the low-Reynolds number two-equation turbulence model is extended to simulate the flow field inside centrifugal impeller mechanism.Numerical simulation of 3D flow field in VKI transonic cascade is presented to verify the algorithm's ability of simulating transonic flow, the result confirms it's applicability . Detailed numerical simulation of Krain impeller at design operating condition is made, the computed results, such as circumferentially averaged shroud static pressure distribution, meridional velocity and relative flow angel et al., show good agreement with experimental data. The secondary flow mechanism has been further understood. The full conditions numerical simulations of the NASA Low-Speed Centrifugal Compressor(LSCC) are carried out. The impeller's full conditionscharacteristic curve of mass flow rate vs total pressure ratio is given. The flow features in impeller passages at quasi-design and low mass flow rate conditions are discussed.Numerical platform for solving centrifugal impeller mechanism has been constructed by this dissertation's research. The platform provides a solid basis for the centrifugal mechanism design and the further research of the complicated flow in centrifugal mechanism.