Effect Of Impeller Inlet Geometry On Cavitation Performance Of Centrifugal Pumps Based On Radial Basis Function

Along with the development of the science and technology,the theory and the application of fluid mechanics,computational fluid dynamics,fluid mechanical testing technology has also got ahead.So the research of centrifugal pump internal flowing has rapid development.Currently,the higher requirement about safe,stable operation of centrifugal pump has been proposed,when the application of centrifugal pump is wider than before.But the development of centrifugal pump has always been restricted by the cavitation which is a complicated phenomenon of hydraulic machinery.Not only has the stable operation of centrifugal pump been affected,but also the flow components have been destroyed seriously.There are many factors that can affect the occurrence of cavitation internal the centrifugal pump.In the paper,the blade leading edge of centrifugal pump has been used as the research object.The theoretical analysis and numerical calculation has been combined to research and analyze the effects of the shape and position of blade leading edge on the centrifugal pump cavitation performance.The main works and achievements are as follows:1.The shape of blade leading edge of centrifugal pump has been changed.And the conical blade leading edge has a better cavitation performance than others.That blade accords with the streamline law at the inlet and can improve the inflow state of fluid near the entrance of blade and reduce the impact from blade leading edge to fluid.2.The the meridian section curves of impeller are kept unchanged.The blade leading edges owing different forward-sweep and backward-sweep angle are obtained through changing the position of blade leading edge near shroud and hub on the meridian section plane.Different cavitation performance carves of blade samples are obtained through numerical calculation.And the distribution of cavitation bubbles in centrifugal pump is analyzed.The position of blade leading edge on the shroud has a great effect on cavitation performance of centrifugal pump,and the position of blade leading edge on the hub has a slight effect on cavitation performance.3.The blade load distributions of blade samples are analyzed.When the blade leading edge extends towards the entrance along the shroud,the cavitation performance is improved greatly.Comparing to the original blade,the blade load distribution of that sample at the entrance is lower,and pressure is lower on the pressure side and higher on the suction side.When the pressure at the centrifugal pump entrance reduces,the suction side pressure of that blade sample is hardly reduced under the vapour pressure of that fluid at that temperature.So the cavitation bubbles appear hardly on the suction side near entrance.That makes the cavitation performance of centrifugal preferably.The forward sweep blade along the hub makes a small amount of fluid entering the impeller is forced by the blade in the direction from the hub to the shroud.And the blade inlet pressure at the hub is higher than the prototype pump because of the fluid impact force.These two factors makes the bubbles which produce at the blade inlet near the shroud cannot transfer to the blade inlet near the hub.So the blockage of blade passage can be avoided.Therefore,the dropping speed of head of this kind of pump is slower than the prototype pump when the cavitation already exists in the centrifugal pump.4.The pressure pulsation in volute of different blade samples is analyzed.At the same NPSHa,the distribution area of bubbles in the impeller is small which has a good cavitation performance.That has a slight effect on the internal flow area.But the blade samples which has a bad cavitation performance.The cavitation bubbles area in the impeller leads to the chaos at internal flow area,and generates many of vortexes.That affects the degree of pressure pulsation in volute directly.5.A relatively accurate response model based on the radial basis function(RBF)has been established to predict the effect of the shape of blade leading edge on the cavitation performance of centrifugal pumps.The sweep angle along the shroud and the hub are taken as the design variable,and the required cavitation margin NPSHr of centrifugal pump is taken as the response value.The response model is built using the radial basis function method.And a relatively accurate response consequence is obtained.