| The vertical axial-flow pumping system has the advantages of stable operation,high reliability,low investment and convenient installation and maintenance,and has accumulated rich experience in design,manufacture and operation management.Therefore,it is a typical pumping system type.It is widely used in large,medium and small pumping station projects.At present,the axial-flow pumping industry is moving towards wide operating efficiency,high operating efficiency,large-scale,and continuous development of automation,and at the same time puts forward higher requirements for ensuring the safe and stable operation of large axial-flow pumping units.The vertical axial-flow pumping system consists of an axial-flow pumping and a flow passage.The hydraulic flow interferes with the axial-flow pumping and the flow passage.The internal flow of the pumping system has three-dimensional unsteady flow characteristics.In actual engineering,some pump stations often have unit vibration,and the noise is relatively high.The large phenomenon affects the safe and stable operation of the pumping station.For this reason,for the hydraulic problems actually existing in the pumping station project,the vertical axial-flow pumping system as a whole research object is carried out,and the numerical and experimental research on the three-dimensional unsteady hydraulic characteristics of the pumping internal flow are carried out.The study of unsteady hydraulic characteristics in the axial-flow pumping system,especially the study of pressure pulsation characteristics,for the unsteady flow field prediction of the axial-flow pumping system,to realize the pumping system the low noise design has important practical significance.The commercial software CFD is used to calculate the three-dimensional full flow field of the vertical axial-flow pumping system,and its energy performance was predicted and compared with the test results.The internal flow field characteristics of each flow-through component of the pumping system under different flow conditions are analyzed.The pressure pulsation is studied by arranging pressure pulsation and velocity pulsation monitoring points on the characteristic section of the pumping system.And the relationship between velocity pulsation and monitoring point position and flow condition point.At the same time,the effects of different flow conditions on pressure pulsation and velocity pulsation intensity distribution,frequency characteristics and pressure pulsation peak-to-peak value of each monitoring point are analyzed.The internal pressure propagation law of the axial-flow pumping system is studied and analyzed.The flow noise in the outlet passage was tested by means of a hydrophone arranged inside the outlet passage of the pumping system,and the cause of the flow noise in the outlet passage was analyzed.The main conclusions are:(1)Four high pressure zones and four low pressure zones appear in the impeller inlet section to coincide with the number of impeller blades.As the flow rate increases,the axial force of the impeller decreases and the torque Mz gradually decreases.At the inlet of the vane body,the velocity from the rim to the hub gradually decreases;at the outlet of the vane,alternating high velocity region and low velocity region occur,and 5 high velocity regions and 5 velocity nips and vanes The number of leaves is consistent.As the flow rate increases,the average velocity of the outlet of the vane body gradually decreases.(2)With the increase of flow rate,the pressure pulsation amplitude of each monitoring point at the outlet of the inlet passage Both the value and the velocity pulsation amplitude are gradually reduced.As the flow rate increases,the pressure pulsation amplitude and velocity pulsation amplitude of each monitoring point of the impeller inlet gradually decrease.With the increase of flow rate,the pressure pulsation amplitude of each monitoring point of the impeller outlet first decreases and then increases.In the small flow condition,the pressure pulsation intensity is much larger than the optimal flow condition and large flow condition.As the flow rate increases,the vane body recovery speed loop is more obvious.With the increase of flow rate,the pressure pulsation amplitude of each monitoring point at the outlet of the outlet flow channel first decreases and then increases;the pressure pulsation amplitude and velocity pulsation amplitude of each monitoring point at the outlet of the outlet flow channel are mainly low frequency,and the flow conditions are different.Next,the maximum velocity pulsation amplitude of each monitoring point at the outlet of the outlet flow channel is at 0.5 times the frequency.(3)Under the same flow condition,the average pressure pulsation peak-to-peak value from the inlet flow channel outlet to the outlet flow channel inlet first increases and then decreases,and the average pressure pulsation peak-to-peak value at the impeller inlet is the largest;at the same position,with the flow rate increase,the average The peak and peak pressure pulsation showed a downward trend.With the increase of flow rate,the average total pressure of each characteristic section gradually decreases,and the axial pump lift gradually decreases with the increase of flow rate.(4)Under the same flow condition,with the increase of the rotational speed,the sound pressure level of the flow noise in the outlet flow channel gradually increases.When the speed is different for different flow conditions,the main frequency of the flow noise in the outlet flow channel is 427 Hz.Under the same running speed,with the increase of flow rate,the flow noise in the outlet flow channel first decreases and then increases.In the optimal operating condition,the flow noise in the outlet flow channel is the smallest. |
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