Studv On Cavitation Flow And Pressure Pulsation In High-speed Centrifugal Pump With Inducer

Centrifugal pumps are the key power equipment of fluid delivery systems and are widely used in civil and military fields such as petrochemicals,agriculture and ships.The safe and stable operation of pumps is an important guarantee for the normal operation of the fluid delivery system.Cavitation is one of the important factors,which affects the stable operation of centrifugal pumps.Centrifugal pumps running under cavitation condition for a long time will cause erosion and damage to the surface materials of impellers and other fluid passage components,lower the hydraulic performance and reduce pump life.At the same time,the pressure pulsation generated by the pump during operation will cause the impeller blades to bear alternating loads,causing the blades to vibrate,which will affect the stability of fluid flow in the centrifugal pump.Therefore,the research on centrifugal pump cavitation and its pressure pulsation is of great significance.The main research contents and conclusions of this article are as follows:(1)The full flow field model of the centrifugal pump with jetting device is modeled based on the three-dimensional modeling software UG8.5.The ICEM15.0 software is used to mesh the full flow field of the pump.Based on the computational fluid dynamics software CFX18.0,the unsteady cavitation flow in the centrifugal pump was numerically simulated,and the numerical results were compared with the experimental results to verify the reliability of the numerical simulation method.(2)Through the external characteristics and cavitation performance test of the pre-inducer centrifugal pump,it is found that as the increase of the flow rate the head of the pump gradually reduces,the efficiency gradually increases and the critical NPSHa gradually reduces.When the cavitation of the device drops below the critical NPSHa,the head of the centrifugal pump drops rapidly.(3)In the case of cavitation,the unsteady value calculation of t pre-inducer centrifugal pump was carried out for the three flow points of 0.6Qd,1.0Qd/and 1.2Qd,and the pressure distribution of the inducer and the impeller under the same NPSHa were analyzed.And pressure distribution and bubble volume fraction distribution of the inducer and impeller under different NPSHa were analysized.It was found that the bubbles initially generated at the leading edge of the inducer vane,and it gradually develops towards the passages of the inducer blade and the impeller as the NPSHa decreases.(4)For three flow conditions of 0.6Qd,1.0Qd and 1.2Qd,the pressure pulsation of monitoring points in the induce passages were analyzed.It was found that at the beginning of cavitation,the main frequency of the pressure pulsation at the monitoring points of the induce passages was 1.8 times of the axis frequency;with the development of cavitation,the main frequency of the pressure pulsation changed to 6 Hz;at the critical cavitation,the amplitude of the main frequency of the pressure pulsation reached the maximum value;at severe cavitation condition,the main frequency of pressure pulsations suddenly decreases.(5)For three flow conditions of 0.6Qd,1.0Qd and 1.2Qd,the pressure pulsations of the impeller passages and the volute were analyzed.It is found that the change law is similar.From the beginning of cavitation to the critical cavitation,the main frequency of the pressure pulsation is 8 times of the axis frequency,and the RMS value of the monitoring point and the pressure pulsation intensity Cpsd have little change.When at the critical cavitation condition,the main frequency changed to 6Hz,and the main frequency peak is significantly larger than the previous main frequency peak under NPSHa.At severe cavitation condition,the RMS and pressure pulsation intensity Cpsd of the volute monitoring point increase.