Experiment Test And Optimization Design Of Slope-type Casing Treatment

Casing treatments are widely used in compressors,those with trench-like shape are proven to be able to improve compressor efficiency but usually reduce stall margin as a cost.A novel casing treatment designated as slope-type casing treatment is proposed and investigated in this paper in order to find the method of improving both compressor efficiency and stall margin.First,an experiment of slope-type casing treatment was carried out on Shanghai Jiao Tong University low-speed axial flow compressor rig.Then numerical method was applied on rear stage of a high-pressure compressor with three different casing treatments including trench,step tip gap and slope-type casing treatment.The three different casing treatments were compared and the effect of their geometry parameters on compressor performance as well as flow field was studied.At last,parameterization and optimization method,based on numerical simulation and agent model,was designed and applied on the slope-type casing treatment.The configuration improving both compressor efficiency and stall margin was found;the performance and flow field of optimum cases were investigated in detail.The results showed that there exist slope-type casing treatments which are capable to improve both design efficiency and stall margin on both low-speed axial compressor and rear stage of high-pressure compressor.Compared with trench and step tip gap,slope-type casing treatment effectively eliminated the recirculation zone in the head of trench and stepped tip gap,which was one of the sources of efficiency loss in the compressor.The result of orthogonal experimental design illustrated that the effect of slope depth was the most important in the four parameters investigated.Four typical slope-type casing treatments were achieved by multi-objectives optimization design.A recirculation zone was observed at the rotor tip in each case.The position of the recirculation zone was decided by axial position of slope-type casing treatments' peak point while the size of that was related to the tip clearance.Geometrical configuration of slope-type casing treatment was able to influence the whole spanwise distribution at the outlet of rotor.