| Impeller is the basic element of centrifugal pump to achieve energy conversion.Good inflow is the key to ensure performance.In the design process of centrifugal pump impeller,it is generally assumed that the inflow of impeller is unifon.and stable along the circumference,that is,along the impeller inlet.The inflow of different circumferential channels is symmetrical and stable.However,in the actual operation of the centrifugal pump,the inlet of the elbow is often used due to the limited installation space.This inflow method will result in uneven flow and gradient of the flow rate of the centrifugal pump impeller.Large shear flows occur,that is,the contradiction between "uniform inflow in the design process" and "distortion inflow in actual operation",resulting in degraded performance of the centrifugal pump,increased vibration,and even threatening the safe operation of the entire pump system.In order to investigate the influence of distortion inflow on the internal flow of the pump,the overall performance and pressure pulsation characteristics of a double suction centrifugal pump were tested.The horizontal angle ?,straight pipe length L and turning radius R were studied,The influence of the inflow condition of the elbow on the external characteristics and pressure p.ulsation of the double suction centrifugal pump is analyzed.The influence of the inflow distortion induced by the bending of the inlet pipe on the external characteristics and pressure pulsation characteristics of the double suction centrifugal pump is analyzed.The test results show that:(1)The head and efficiency of the double-suction centrifugal pump will decrease with the increase of the horizontal angle ?,decrease first and then increase with the increase of the straight tube length L,and increase with the turning radius R.And increase;(2)the characteristic frequency of all pressrure measuring points in the pump will not change due to the parameter clhange,but as ? increases,the pressure pulsation in the pump inlet and the volute increases,and the leaf frequency pressure amplitude at the tongue The value and the low frequency pulsation in the pump increase significantly;as L grows,the pressure pulsation in the volute increases first and then decreases,and the low frequency pulsation in the pump increases first and then decreases;as R increases,the pressure pulsation in the suction chamber decreases.The low-frequency pulsation in the pump is reduced;(3)The special frequency of 123 Hz appears in the suction chamber,and the difference in pressure amplitude between the two sides of the suction chamber rises as ? increases,decreases as L increases,and increases with R(4)Inflow distortion causes the mean value of the pressure difference on both sides of the suction chamber to increase with increasing ?,increasing first and then decreasing as L increases,decreasing with increasing R;and axial frequency pressure amplitude difference As ? increases,L increases and decreases.In this paper,the numerical simulations of the flow under three horizontal angle inflow conditions are carried out.Firstly,the test and simulation are compared and the results are basically the same.Then the internal flow under the influence of the horizontal angle ? is simulated and found with the turning angle.Ascending,the difference of the inflow flow rate on both sides of the impeller increases,and the difference of the mean value of the pressure pulsation at the measuring point on both sides of the suction chamber increases,and the pressure distribution at the inlet of the pump is offset to the outside of the elbow,and the greater the angle,the greater the degree of deviation.The results show that the most important change caused by the inflow of the elbow is the change of the inflow flow on both sides caused by the shear flow.Finally,the research work of the paper can provide reference and support for the experimental and numerical simulation of the design and operation of the inlet pipe of the on-site water pump. |
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