| The high-speed centrifugal pump has a very broad application prospect under the current background of high speed and light weight of hydraulic machinery.Meanwhile,the cavitation phenomenon of inducer at high speed is still an important research target worth paying attention to.As an axial-flow fluid machine,the cavitation of the inducer is mainly due to the leakage flow generated by the pressure difference between the suction surface and the pressure surface of the blade,and the complex vortex system structures such as tip clearance leakage vortex and tip separation vortex are generated under the joint action of centrifugal force and inertia force.Vortices in different directions are intertwined to jointly cause cavitation phenomenon.In this paper,a certain type of high-speed centrifugal pump is taken as the research object,and the influence of different flow stabilizer devices on the cavitation performance of the high-speed inducer is explored by adding the guide gate,stabilizer and annular groove.The main work content and research results are as follows:1.Influence of inlet diversion grid on cavitation performance of highspeed inducer.The cavitation performance of centrifugal pump was improved by adding a diversion grid in front of the inlet of the inducer to suppress the rotating vortex.The results show that the critical cavitation number decreases and the cavitation performance is improved in the centrifugal pump with elliptic diversion grid.After the addition of the diversion grid,the rotation strength of the inlet section of the inducer is obviously weakened,and the head of the centrifugal pump is obviously improved,among which the elliptic diversion grid scheme is increased by 3%compared with the original scheme.By restraining the circumferential rotation of the main flow in the inlet section and enhancing the absorption energy of the inducer,the diversion grid can improve the power capacity of the inducer,thus improving the hydraulic characteristics and cavitation characteristics.2.Influence of length-diameter ratio of flow stabilizer device on cavitation performance of high-speed inducer.By separating tip clearance backflow from the main flow,the stabilizer minimizes the influence of backflow on the main flow and transfers the adverse effects of tip clearance leakage vorticity near the inlet of the inducer to the upstream,so as to stabilize the flow regime at the inlet of the inducer and enhance its anticavitation performance.A large length-diameter ratio has a weak guiding effect on tip clearance reflux.Tip clearance reflux vortex develops in the gap between the stabilizer and the inlet wall,and only a small amount of reflux is guided upstream,resulting in cavitation accumulation at the inlet of the inducer.When the length-diameter ratio is 1.08 and 1.05,most tip clearance leakage flows are guided to the upstream of the stabilizer.Due to the small gap between the stabilizer and the wall,the reflux flow rate is larger and vortex is generated at the inlet of the stabilizer.Combined with the flow field structure and cavitation volume distribution,it is concluded that the slenderness ratio of 1.05 has an advantage in restraining the cavitation of the inducer.3.Influence of annular groove geometry on cavitation performance of high-speed inducer.Based on the optimum position and size of annular grooves,the influence of three annular grooves with different geometric shapes on the cavitation performance of inducer was investigated.It is found that the distribution of turbulent kinetic energy on the blade of the inducer is more uniform with the addition of annular groove,and the pressure in the inducer channel is obviously increased.The critical cavitation allowance of the centrifugal pump can be reduced more by single curvature groove.The horizontal pressure increase rate of the rectangular groove scheme is not as good as that of single curvature groove and double curvature groove scheme.The influence of tip clearance reflux on upstream mainstream decreases after energy consumption in annular groove.The circumferential vortices are inhibited by the circumferential vortices because of the smooth transition of the circumferential vortices in the single curvature grooves,while the rectangular and double curvature grooves can weaken the development and influence of the upstream asymmetric vortices in the induced rotation channel because of their stronger absorption capacity of the wall vortices. |
