Study On Tip Clearance Flow And Circumferential Groove Casing Treatment Of The Oblique Flow Pump

Urban flooding is frequent and poses a serious threat to the safety of citizens.Therefore,emergency drainage devices with high flow and high head play a key role in controlling floods.Oblique flow pump is the core of emergency drainage device,also known as guide lobe mixed flow pump,because its flow structure and performance parameters between axial flow pump and centrifugal pump,so it has the advantages of both,but also compensate for the shortcomings of both,is a more ideal effect of the pump.Oblique flow pump has the advantages of large flow,high efficiency,strong anticavitation ability and wide operating range.However,there are unstable phenomena such as stall,leaf top leakage flow and secondary flow in the operation process,which seriously affects the stability of pump operation and makes the pump performance degrade.Therefore,it is necessary to apply the cassette treatment method used for the pressurized air machine to expand the stability to the inclined flow pump,so that the inclined flow pump can operate more safely,efficiently and stably.In this paper,the accuracy of the calculation results of a large flow diagonal pump model at design speed is checked against the test results.Theoretical basis is laid for the treatment of the cassette.Then the circumferential slot magazine treatment is carried out on the basis of the solid wall magazine pump to investigate the mechanism of expanding stability of the magazine treatment and the principle of the influence of the treatment slot on the expansion stability results under different conditions.It was found that the solid-wall cassette slant flow pump had a larger working range and better overall performance at higher speeds when calculated for variable speed conditions.In the calculation of solid-wall cassette pumps with different lobe top clearances,the pumps with smaller clearances have a wider working range and better overall performance,while the "hump" phenomenon appears in advance for large clearances.Based on the previous analysis of the solid wall magazine performance and flow field,in order to suppress the leaf top leakage flow and thus improve the performance and operational stability of the pump,the pump calculation model at the design gap(1mm)is selected in this paper to first conduct a study on the magazine treatment at different locations with different numbers of circumferential slots.Thus,it is found that the leading edge position of the blade is the best processing position,and the processing effect of three slots is better than that of a single slot.At the same time,on the basis of the best processing position,the circumferential groove magazine processing is carried out for solid-walled magazine pumps with different vane top clearance,comparing the magnitude of expansion stability improvement under each clearance compared with the solid-walled magazine,and seeking the best clearance for magazine processing,and obtaining the design clearance as the best processing clearance,followed by the large clearance and the worst small clearance.Finally,a parametric numerical simulation study of the circumferential groove under the design gap was conducted,and it was found that the groove width has a greater influence on the expansion stability of the circumferential groove,while the groove depth and groove spacing have a smaller influence on it.This paper provides some reference for the study of inclined flow pump magazine treatment.