Study On The Effect Of Blade Opening On Cavitation Flow In Centrifugal Pump

The process that the low pressure area in hydraulic machinery evolves into steam cavitation is called cavitation,which will lead to the disorder of internal flow field.With the further development of cavitation,the cavitation will spread from the blade head area to the blade tail area.Cavitation will not only reduce the hydraulic efficiency of hydraulic machinery,affect the normal operation of the unit,but also affect the service life of hydraulic machinery.Taking a centrifugal pump as the research object,this paper presents a method to suppress the cavitation of the centrifugal pump by setting a perforation at the blade head.By combining computational hydrodynamics with theoretical analysis,the external characteristics of centrifugal pump,internal flow field and the volume variation of primary cavitation were studied under design conditions and variable conditions.Ten perforation schemes and models were established by changing the perforation area and perforation combination shape,and the effect of different perforation schemes on the cavitation suppression of centrifugal pump was discussed.Three optimal perforation combinations are obtained,which can inhibit the cavitation of centrifugal pump obviously.Using three groups of optimal perforation combination parameters,unsteady numerical calculation of centrifugal pump was carried out to analyze the variation of unsteady flow field and pressure pulsation.The main research contents and innovative achievements of this paper are as follows:(1)The cavitation generation mechanism and the research progress of cavitation and cavitation erosion are introduced,and the methods of suppressing cavitation in hydraulic machinery are summarized.The determination method of cavitation initiation and several main forms of cavitation are summarized to lay a theoretical foundation for subsequent work.(2)Taking NACA0012 airfoil as the research object,the change of velocity field and pressure field of the airfoil before and after the perforation is analyzed.Under a certain perforation area,the anti-cavitation performance of the perforated airfoil is improved.(3)Nine schemes of different blade perforation arrangement and different perforation area are proposed,which are the single circular hole model with the perforation area of 1/4πmm~2,9/4πmm~2,25/4πmm~2,square combined hole model and plum flower combined hole model respectively.The influences of different combination schemes on the external characteristics of centrifugal pump were studied under the designed flow rate,and three perforation schemes which could improve the anti-cavitation ability of centrifugal pump were obtained,and the internal mechanism was analyzed.(4)At the initial stage of cavitation in the centrifugal pump,the influences of various perforated combinations on the external characteristics and cavitation performance of the centrifugal pump under varying working conditions were analyzed,and the optimal operating range of the centrifugal pump under different perforated combinations was obtained.(5)Under the initial cavitation condition,the variation of pressure pulsation amplitude at each monitoring point of the original model and the perforation model was compared and analyzed,and the variation rule of pressure pulsation in different perforation combination schemes was obtained.