Abstract: To improve the adverse effect of a semi spiral suction chamber on a double suction centrifugal pump,the effect of baffle length on the flow and cavitation inside the semi spiral suction chamber is investigated.Three types of baffle length are used to compare the hydraulic performance of the semi spiral suction chamber and analyze the impact of the baffle on the performance of the semi spiral suction chamber double suction pump.With the computational flow field software ANSYS CFX,the SST turbulence model and the cavitation model based on the Rayleigh Plesset equation are used to numerically simulate the steady-state three-dimensional turbulent full channel flow in the semi helical suction chamber of a double suction centrifugal pump.The distribution of velocity and pressure changes in the semi spiral suction chamber is calculated,and further research is conducted on the flow pattern before entering the impeller.The calculation results show that at a flow rate of 0.8～1.2 Q,the closer the end of the baffle is to the center of the impeller,while an efficiency change is maintained less than 0.36%,the head gradually increases,with an amplitude of 1.2%～1.6%.At the same time,the flow pattern at the tongue of the non cutting semi spiral suction chamber is improved.After exploring the different effective cavitation margins and their development in the initial stage of cavitation under cavitation,it is found that baffles can lead to an earlier initial stage of cavitation,but the development of cavitation is relatively slow.When the head decreases by 3%,the corresponding critical cavitation margin decreases by 0.3 m.Therefore,increasing the baffle can improve cavitation performance and increase the head while maintaining efficiency,providing assistance for the design of a semi spiral suction chamber.