Numerical Study Of Flow Field In Transonic Centrifugal Impeller With Splitter Blades

The proposal of sustainable development enhances the application of the centrifugal compressors with high efficiency and stable operating range. As key component, the aerodynamic performance of the impellers will decide the efficiency of centrifugal compressors. For the transonic centrifugal compressors, flow loss gradually focuses on tip clearance, boundary layer and shock wave. The exit flow field and aerodynamic performance affected by tip clearance flow, secondary flow, boundary layer flow, shock wave and interaction of them are more complex. In order to clarify the effect of tip clearance vortex and shock wave on the transonic centrifugal impeller with splitter blades, the numerical method is used to analyze the performance parameters varying with working conditions and tip clearances. The basic formulae are applied to assess and evaluate the shock wave in flow channel.A typical transonic centrifugal impeller with splitter blades is numerically simulated and analyzed. The results indicate that the aerodynamic performance decreases due to the tip clearance. With the increasing of the flow rate and tip clearance, pressure jump at the suction surface of main blade moves to downstream of the flow passage, while the pressure fluctuation at the pressure surface increases. The greater mass flow rate, the stronger blade loading fluctuation. The shock wave begins at the leading edge of main blade. A low energy area occurs at the downstream of the passage and develops along the main blade pressure surface with the increasing of the mass flow rate. The tip leakage is affected by both the shock wave and the blade loading.To access and evaluate the shock wave in transonic centrifugal impeller with splitter blades, the basic formulae are applied to analyze the flow information. It is found that there exits shock wave at the leading edges of main and splitter blades and in the passage between main blade suction surface and the splitter blade pressure surface. The shock wave intensity is strongest at the leading edge of splitter blade. Respect to shroud impeller, the shock surface in the unshroud impeller is discontinues at the leading edge of splitter blade at high flow rate, and moves to downstream at design flow rate. It is worth note that the decrease of the mass flow rate would make the shock surface in unshroud impeller move to upstream at same tip clearance value.The study of the flow characteristic of the transonic centrifugal impeller with splitter blades can provide help for the three-dimensional complex design and the application of transonic centrifugal impellers.