| Due to the compact structure and small volume of the high-speed centrifugal pump,cavitation is easily generated in the centrifugal pump when running at high speed,and the cavitation flow will greatly affect its performance.The inducer is an important pressurizing component in the high-speed centrifugal pump.It is necessary to conduct a comprehensive and in-depth study of the internal flow of the inducer after cavitation to improve the cavitation performance of the high-speed centrifugal pump.Based on a certain type of front varying pitch inducer of high-speed centrifugal pump as the research object,based on the RNG k-ε turbulence model and Zwart-Gerber-Belamri cavitation model,the numerical analysis of the high-speed centrifugal pump was carried out.The influence of the gap drainage of the inducer blades on the development of cavitation in high-speed centrifugal pumps under design conditions and variable speed conditions is studied.The main research contents and conclusions are as follows:1.Flow characteristics in the gap of inducer section under non-cavitation condition.Five groups of high-speed centrifugal pump design schemes with the slot coefficient k of inducer blade being 0(prototype),6.7%,13.3%,20% and 26.7% were selected to study the influence of slot on the velocity,pressure and turbulent kinetic energy distribution of inducer section under non-cavitation condition.The results show that the gap structure is arranged near the inlet edge of the inducer blade to form an energy exchange channel between the pressure surface and the suction surface of the blade.The high pressure fluid is introduced into the suction surface from the pressure surface to improve the pressure in the low pressure area of the suction surface,and weaken the impact of the leakage flow at the tip of the inducer blade on the wall of the pipe.The vortex near the suction surface of the blade inlet is reduced,and the flow state of the fluid in this area is improved.2.Effect of inducer blade gap drainage on cavitation performance of high-speed centrifugal pump.The cavitation characteristic curve,cavitation development and static pressure distribution in inducer and impeller passages of high-speed centrifugal pump under five groups of gap schemes were studied.The results show that in the initial cavitation stage,with the increase of the gap coefficient k,the cavitation in the rim region of the suction surface of the inducer inlet blade moves to the tail of the gap.When the effective cavitation margin decreases,the gap structure induces the change of pressure in the runner,resulting in the change of cavitation distribution in the runner.Reasonable selection of gap coefficient can improve the cavitation performance of high-speed centrifugal pump.In this study,when the gap coefficient k=13.3%,the gap inhibits and reduces the generation of cavitation,making the cavitation performance of the high-speed centrifugal pump optimal.3.The influence of gap drainage of inducer blade on cavitation performance of high-speed centrifugal pump under variable speed conditions.The cavitation performance of the high-speed centrifugal pump and the original model pump with the best blade gap coefficient k=13.3% under three groups of different rotational speeds was studied.The results show that when the initial cavitation occurs in the high-speed centrifugal pump,with the increase of the rotational speed,the inhibitory effect of the gap drainage structure of the inducer blade on the cavitation distribution at the flange of the blade inlet suction surface is more significant.In the critical cavitation stage,the improvement effect of the pressure in the middle and rear sections of the gap structure inducer is more significant than that of the prototype only at the rotational speeds of 18000r/min and 31590r/min.The development law of cavitation in the high-speed centrifugal pump with gap drainage and prototype inducer is generally consistent,but the degree is different. |
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