Study On The Variation Characteristics Of Axial Force Of Segmental Multistage Pump

Segmental multi-stage pump has the characteristics of high lift and variable series,and it is an indispensable fluid conveying equipment in engineering application.However,due to the series connection of impellers,a large axial force will be generated during the operation of the segmental multi-stage pump.The axial force will make the rotor parts of the pump move in the axial direction,resulting in wear and tear of the impeller and other components,affecting the safe and stable operation of the pump.In this paper,numerical simulation is used to study the axial force variation characteristics of DG155-67×5 multi-stage pump under two different operating conditions: stable operation and start-up.During the whole research process,the axial clearance B2 of the balancing disc remains unchanged.On the basis of the study of the axial force,the motion trend of the balancing disc is discussed.The main research work and conclusions are as follows:1.Firstly,the whole flow field of the multi-stage pump is simulated,and its external characteristic curve is obtained.Then,the comparison and analysis with the test results show that the simulation value and the test value are not very different,It is indicated that the numerical simulation method can be used to calculate the subsequent research in this paper.2.Segmental multi-stage pump models under different flow conditions are simulated with constant values.Through the analysis of the calculation results,it can be seen that the axial force decreases linearly with the increase of flow rate.The pressure in the balance disc is monitored.It is found that the pressure in the radial and axial clearances decreases in a straight line.The pressure in the balance chamber remains basically unchanged,and there will be a sudden drop in the pressure at the entrance of both clearances.By comparing the balance force generated by the balance disc with the total axial force of the pump,it is found that the balance force is greater than the total axial force.At this time,the residual axial force is a negative value,and then combined with the law of the reciprocating motion of the balance disc,it is indicated here.Under the axial clearance,the balance disc may have an acceleration motion or a deceleration motion.3.Under the design conditions,the unsteady numerical simulation of the multistage pump model shows that the axial force changes periodically with the running time,and in a stable change period,the axial force generated by the front cover plate of the impeller will have two wave peaks,and the axial force generated by the rear cover plate of the impeller will have two wave troughs.4.The transient numerical simulation of the segmental multi-stage pump is carried out by using linear starting and exponential starting.The impeller speed and pump inlet conditions are compiled by UDF.The external characteristic curve of the multi-stage pump is obtained by simulation calculation.It is found that the change trend of flow and head is greatly influenced by the increase of speed,and is consistent with the change rule obtained by similar theory.By comparing and analyzing the axial force of the pump and the balance force produced by the balancing disc under the two starting modes,it is found that the axial force produced by the straight-line starting mode is smaller in the whole starting process,but the axial force under the two starting modes is larger than the balance force,which indicates that the balancing disc will move to the left in the starting process.