Research On The Hydraulic Performance And Pressure Pulsation Of Submersible Tubular Pumping System

The submersible tubular pump is a pump system that combines submersible motor and tubular pump technology.Due to its excellent hydraulic performance,compact structure,good noise immunity and low operating cost,it has good application prospects in urban rainwater pumping stations,flood control and drainage.The submersible tubular pump is suitable for low head pumping stations which is sensitive to changes in water level,flow rate,etc.The pump system does not necessarily operate under design condition in practical applications.For further studying the internal flow of the submersible tubular pump system under off-design conditions and improve the hydraulic performance and efficiency of the pump device,this paper uses numerical simulation and experimental research methods to study the internal flow characteristics of the submersible tubular pump system.It is of practical significance to understand and master the internal flow of the submersible pump device under off-design conditions.The ANSYS CFX software is used to simulate the three-dimensional unsteady simulation calculation of the submersible tubular pump system.This paper analyzes the internal flow and pressure pulsation characteristics of the pump system under off-design conditions.Due to the rotation of impeller blades,the axial velocity and static pressure distribution of the impeller inlet and the impeller outlet presents periodicity corresponding to the number of blades.At low flow rate,the flow of water has a larger angle of attack on the impeller blades,and there are unsteady flow phenomena such as de-flow,backflow and vortex near the surface of the blades and the hub.There are also unsteady flow phenomena such as backflow,outflow and vortex near the suction surface of the guide vane impellers and the hub,which reaches the maximum range in the middle section of the guide vane.The guide vane does not completely recover the loop amount this time,and the water flows through the guide vane passages to make a spiral flow of axial flow and circumferential rotation.At high flow rate,the flow in the impeller is better.The flow line distribution uniformity in the guide vane is high,and the vortex area exists near the vane pressure surface in the guide vane passage.The main frequency of the pulsation near the impeller chamber and the guide vane of the submersible pump device is mainly the leaf frequency and its multiplier.Under the same working condition,the pressure pulsation amplitude decreases continuously from the impeller inlet to the tail of the bulb body.At small flow rate,the pressure pulsation is larger than the design condition and the large flow condition.Therefore,the submersible flow pump device should be avoided as much as possible under low flow rate.Under different flow conditions,the impeller inlet and the impeller outlet section,the pressure pulsation gradually increases from the hub to the shroud.The external characteristics and pressure pulsation measurement at different speeds were carried out by the submersible pump-type closed test rig.The differences between the numerical simulation and the model test at different speeds were compared and analyzed.The time domain and frequency domain changes of the axial monitoring points of pumping equipment under different speeds,different monitoring points and different flow conditions are analyzed.The trend of the external characteristics of the three-stage repetitive test of the submersible pump device is completely the same,and the numerical results are very close under the similar working conditions,indicating the stability and reliability of the test results.Comparing the numerical simulation results and test results of the pump device,it can be found that the external characteristic trend is basically the same,and the numerical simulation and the experimental Q-H curve agree well.Under low flow conditions,numerical simulations are more efficient than tests,while large flow conditions are reversed.Through the amplitude analysis,it can be seen that when the rotational speed is 1200 r/min and 1450 r/min,the RMS value of the pulsating axial pulsation monitoring point of the submerged tubular pump device decreases continuously with the increase of the flow rate,and the outlet of the guide vane is occasionally increased;when the speed is 900 r/min,the RMS value of the impeller outlet pulsation decreases with the increase of the flow rate,the root mean square value of the middle section of the guide vane first decreases and then increases,the RMS value of the four axial pulsation monitoring points from the middle section of the guide vane is continuously increased.It can be seen from the frequency domain diagram analysis that under different speeds,the main frequency of the impeller exit section is the leaf frequency.With the increase of the rotational speed,the six axial monitoring points of the pump device are shifted to the small frequency direction.Compared with the same speed and different flow conditions,the amplitude of the main frequency of the impeller exit decreases with the increase of the flow rate,and the amplitude of the main frequency of the other monitoring points does not have obvious regularity.