Effect Of Shunt Vane On Flow Field Characteristics Of Centrifugal Pump With Low Specific Speed

The centrifugal pump with low specific speed has complex flow characteristics in operation because of it has narrow impeller channel.In the long-term engineering practice,scholars found that changing the blade structure in the channel and replacing the part of the long blade with the shunt short blade can improve the flow situation of the internal flow field,and the proper bias of the short blade will make the improvement effect better.Therefore,the study and analysis of its flow characteristics at different bias angles and its influence on steady and unsteady flow of impeller can help us to understand clearly the characteristics of internal flow excitation of fluid,It also provides a good foundation for guiding the hydraulic design of centrifugal pump with low specific speed.At the same time,combined with a certain signal analysis method,the pressure fluctuation caused by vibration can be analyzed,and a more suitable bias angle of the shunt short blade can be found,It can also provide an important reference for the low noise design of the pump.In this paper,the single stage impeller of a low specific speed centrifugal pump is taken as the research object.First of all,six different bias angles are designed,After three-dimensional modeling and simulation pretreatment,the constant simulation and unsteady simulation are carried out respectively,and finally combined with the analysis of signal analysis method,the following conclusions can be obtained.(1)Through the results of steady simulation,it can be seen that the velocity and pressure distribution of each interface is more uniform with the addition of shunt blades to a certain extent.However,with the increase of the bias angle,cavitation occurs in the blade channel,and the effect of the blade bias towards the working face and the back of the blade is different.The deviation to the blade face increases the overall velocity of the impeller more obviously,but the improvement of the fluid outflow and the separation of the boundary layer is not ideal,and the generation of vortices is aggravated.(2)From the unsteady simulation results,it can be seen that different bias schemes also reflect the flow characteristics inside the impeller.With the change of time,the change of flow field mainly concentrates on the front end of the shunt short blade,and the region of variation is between the blade passage near the tongue and the upper edge of the section.The trend of variation is the diffusion and movement of different flow bands along the bias direction with the increase of bias angle.(3)From the time-domain and frequency-domain diagrams obtained from the pulsation analysis data,it can be seen that the number of wave peaks of pressure fluctuation with time is the same as the number of blades.Different bias angles can change the characteristics of time-frequency domain.The variation of pressure in the time domain of each cross-section under counterclockwise bias is mainly reflected in the wave valley.In the case of fluctuations,there was no significant improvement,and there was no significant change in the frequency components.In the case of clockwise bias,the pressure fluctuation of each cross section in the time domain is obviously improved,and the fluctuation amplitude of each frequency component is decreased.The most significant improvement was achieved at a clockwise bias angle of 5°for shunt short blades.