Research On Two-Phase Flow In Water Filling Device Of Centrifugal Pump Without Bottom Valve

Water pumps are the most commonly used liquid conveying machines in oil,coal mine,water supply and drainage,and agricultural irrigation and drainage.Centrifugal pumps are the most widely used pumping products in China.According to statistics,20%of the national power generation is used for the operation of pumping machines.The water filling device without bottom valve is widely used in social production activities,which can avoid the problems caused by adding bottom valve.At present,the literature about the water filling device without bottom valve is mainly about the structure design and the use method,but the research on the quantitative design parameters is lack.When the bottomless valve centrifugal pump water filling device is running,the bubbles generated in the water tank are easy to be transported to the pump,thus affecting the pump performance.In this paper,the self-made water filling device without bottom valve of centrifugal pump is used to study the problems and phenomena found in the actual operation of the device.According to the pipe diameter of water tank outlet,determine the minimum water depth of water tank outlet.By changing the water temperature and the initial water depth of the water tank,the operation process of the device without bottom valve under different flow conditions is studied.Analyze the phenomenon of the device in different conditions and the change of water depth in the water tank,find the lowest initial water depth of the water tank under different flow rates,so as to ensure that there is no surface vortex on the water surface of the water tank.Analyze whether the water depth of the water tank has a threshold value when the device operates under different flow rate.The results show that the minimum initial water depth of the tank increases with the increase of flow rate and the influence of temperature on the minimum initial water depth of the tank increases with the increase of flow rate.When the flow is small,the water depth of the tank is basically stable during operation,and there is no threshold value for the water depth during operation.When the flow increases,there is a threshold value for the water depth of the tank during operation due to gas-liquid two-phase flow in the outlet pipe of the tank.Analyze the water depth change of the water tank before and after the operation of the device,determine the water depth reduction of the water tank during multiple operations,and explore the number of repeated operations after the device is filled with water in combination with the threshold value.Finally,the influence degree of factors on the operation of the device is determined by orthogonal experiment analysis.The results show that the flow rate and the initial water depth of the water tank have the greatest influence on the operation of the device.When the flow is0.0009 m~3/s,the initial water depth of the water tank is 170 mm,and the water temperature is25℃,the air bubble content in the outlet pipe of the water tank is the largest during operation.The results of this paper can provide some help for the design of the size of the water tank and the selection of the initial water depth of the water tank in the bottomless valve filling device.