Study On The Influence Of Inlet Bend Pipe On The Internal Flow Of Centrifugal Pump

Pump design and selection are generally carrnied out according to the uniform straight pipe inflow conditions.However,in practical engineering,due to the installation space limitation,sedimentation at the inlet and structural design caused the inhomogeneity of inlet flow in practical engineering,which leads to the reduction of pump efficiency,increases the cavitation risk,increased pressure pulsation and affects the safe operation of the pump system.Elbow inflow is one of the most common reasons causing the inlet distortion flow.The influence of inlet conditions of different elbow pipe on the internal flow characteristics of centrifugal pump is analyzed by means of experiment and numerical simulation in this paper The results have an important practical significance for installation of inlet pipe to improve the efficiency and operation stability of centrifugal pump.Firstly,the extrnal characteristics and pressure pulsation of centrifugal pump were tested.A single-stage single-suction centrifugal pump was designed and processed according to the existing test system,The external characteristics of centrifugal pump were tested under different inflow conditions of elbow pipe.The high frequency signafic pressure sensor was connected with pressure pulsation data of centrifugal pump.The external and prtssure pulsation characteristics under different inflow conditions were compared.The results show that the inflow of elbow pipe has a significant influence on the external characteristics of centrifugal pump.The maximum head loss is 0.56m and the maximum efficiency loss is 3.7%.The intensity of pressure pulsation is obviously increases with the increases of bend angle and the decreases of length of straight pipe section.In particular,the influence is greater under the condition of low flowrate.Secondly,the centrifugal pump model was established under different inflow conditions.The steady and unsteady numerical calculation of centrifugal pump under different inflow conditions were carried out.The inflow patterns of the inlet,impeller and volute of centrifugal pump under different inflow conditions were compared and analyzed,as well as the pressure pulsation laws of the inlet and the impeller were compared and studied.The results show that the numerical simulation of centrifugal pump shows a same trend as the test results.Under different inflow conditions,the flow of the inlet pipe in centrifugal pump is greatly influenced by the angle of bend and the length of straight pipe under different inflow conditions.The intensity of secondary flow increases with the increase of bend angle and the decrease of length straight section.Both the internal flow and the turbulent kinetic energy intensity increases with the increases of turning angle.In particular,the flow in the impeller near upper cover side is the greatest influences.Finally,the variation rule of experimental pressure pulsation was analyzed through the distribution of internal flow pattern by combined with the experimental testing and numerical simulation analysis.The influence of different inlet conditions on flow pattern and pressure pulsation distribution in centrifugal pump was obtained.The current research work in this paper is hoping that providing a reference for the layout of inlet pipe of centrifugal pump in practical engineering,improving the performance of centrifugal pump to reduce the centrifugal pump pressure pulsation and provide a certain data support.