Research On Fault Characteristics Of Marine Centrifugal Pump Based On CFD

With the rapid development of the global economy and shipping industry,the safety of ships during operation is gradually being valued.The normal operation of marine equipment,especially centrifugal pumps,is a key factor affecting the safety of ships.This paper analyzes and researches the operating characteristics under three common faults of marine centrifugal pumps,and provides a reference for fault monitoring and diagnosis of centrifugal pumps.The main work of this paper are as follows:In the beginning,the operating characteristics of the centrifugal pump under partial flow failure are analyzed.It is found that the design of the centrifugal pump under the design conditions has uniform flow field characteristic distribution,and the pressure pulsation changes periodically.The frequency of the pressure pulsation is Frequency doubling,the radial force of the impeller is small and distributed around the origin,at this time the efficiency of the centrifugal pump reaches the maximum.When deviating from the design conditions,the flow field distribution in the pump becomes no longer uniform,the pressure difference and the speed difference on both sides of the cutting tongue increase correspondingly,the pressure pulsation becomes significantly larger,and the cutting tongue will also appear strong under small flow conditions Low frequency pulsation.The radial force of the impeller is obviously enlarged under the partial flow failure and the distribution deviates from the origin.Then,the centrifugal pump blade breakage failure model was established,and its operating characteristics were analyzed.It was found that the blade breakage failure mainly caused the performance parameters of the centrifugal pump to decrease,the uneven distribution of pressure and velocity in the adjacent flow path of the damaged blade and the pressure and velocity in the volute reduce.In the state of blade breakage,the pressure pulsation still shows periodic changes,but each monitoring point fluctuates only five times in a cycle.The pressure fluctuations at the broken blade and its adjacent blades are more severe,while the pressure fluctuations of the blades far away from the broken blade have basically no effect.Various points of low-frequency pulsation appeared at various points.For the volute,cutting tongue and centrifugal pump outlet,the main frequency of pressure pulsation shifts to the low frequency.The radial force of the impeller has increased,and the radial force is no longer periodic.Finally,based on the multiphase flow theory,the cavitation fault of the centrifugal pump under standard conditions is numerically simulated.It is found that when the effective cavitation margin is greater than the critical cavitation margin,the head of the centrifugal pump will remain stable and the pressure distribution of the impeller flow field Uniform,the low pressure area and cavitation distribution range are small,and the main frequency of pressure pulsation at the monitoring point in the pump is.When the effective cavitation surplus is equal to the critical cavitation surplus,the cavitation in the pump will cause a small decrease in the head,and the range of the low-pressure area of the impeller flow field and the distribution of cavitation expand toward the outlet of the impeller.When the effective cavitation surplus is less than the critical cavitation surplus,the degree of cavitation in the pump deteriorates rapidly,causing the performance of the centrifugal pump to decrease greatly,the low pressure area and cavitation distribution in the pump expand to the entire blade,and strong Low-frequency pressure pulsation,the main frequency of the pressure pulsation at the outlet shifts to low frequency,and the main frequency amplitude at the tongue cutting has a large increase.In the three cavitation states,the radial force of the impeller is periodically fluctuating.The cavitation failure will cause the radial force of the impeller to increase slightly and deviate from the origin.It will also increase the amplitude of the main frequency of the radial force frequency domain.