Research And Application Of Flow Measurement Technology For Small Axial Pump Horn Pipe

The pump station is widely used in China.It is an important subject for the scientific management of the pump station to conduct field measurement at the pump station.Measurement of the flow rate has always been a key and difficult point,especially for the axial pumps commonly used in small and medium-sized pump stations.The axial flow pump is different from the centrifugal pump and the mixed flow pump.The medium and small axial flow pumps only have inlet horn tubes(large-scale axial flow pumps generally adopt inlet conduits in situ construction),and the outlet tubes are also short.Therefore,research on the method of flow measurement of small and medium axial flow pumps is of great significance.The main research results of this paper are as follows:1.Summarize the technical characteristics of the commonly used methods for on-site testing of pump flow,and optimize the flow measurement method based on the analytic hierarchy process(AHP)to measure flow accuracy,investment cost,installation straight pipe requirements,flow measurement range,pressure loss,whether calibration is needed,The current measurement object is the criterion layer,and the commonly used nine measurement methods are used as the solution layer.The preferred order are trumpet differential pressure flow measurement,ultrasonic flowmeter,salt concentration method,turbine flowmeter,electromagnetic flowmeter,and bypass tube method.The flow meter method,five-hole probe method,differential pressure flowmeter,and the preferred results have certain guiding values for the selection of flow measurement methods for small axial flow pumps in irrigation areas.2.The pilot test of the differential pressure flow measurement of the trumpet tube was performed by using an outdoor 150ZB-4 axial flow meter flow measurement device and an indoor 100ZB-3A axial flow pump test device.It mainly discusses the influence of variable head on the flow coefficient,the average flow rate coefficient of the same pressure measuring section to calculate the error analysis of the water flow,and the influence of the water level change of the inlet water tank on the flow of the water pump.The test results show that:① For a section of the same piezometric tube,there is a fixed coefficient of the ratio of the flow measured through the differential pressure at the inlet of the trumpet to the water surface and the actual flow rate of the channel;② The position of the pressure measurement section through error analysis should be at 1/2H.～2/3H range;③ In order to ensure that the axial pump horn tube is submerged,the change of water level in the inlet tank has little effect on the flow.The test demonstration provided the basis for the development of the axial flow pump horn tube flow measurement device.3.Based on the test,the axial flow pump horn tube differential pressure flow measurement system was field-tested,and the method of on-site calibration using a flow meter was introduced.The system mainly includes a pressure sensor and a data acquisition system.The trials at two axial-flow pumping stations in Gaoyou Irrigation Area showed that the flow-measuring device is stable in operation and can be used for small axial-flow pumping stations to measure flow.