| Many factors affect the performance of self-priming pump,such as the circumferential velocity of the impeller outlet,the gap between the tongue,the size of the gas-liquid separation chamber and the liquid storage chamber,the area of the reflux hole.The self-priming process of self-priming centrifugal pump includes complex processes.Changing the parameters affecting the self-priming performance of the pump based on the self-priming process is the main idea of the current study.This paper mainly studies the influence of the volume of the gas-liquid separation chamber of the pump on its self-priming performance.Self-priming height and self-priming time are the two main indicators for evaluating the self-priming performance.In this paper,three self-priming pumps with different volume of gas-liquid separation chamber were designed by using the control variable method.The pressure and flow of the inlet and outlet during the self-priming process of the pump are monitored to study the influence of the volume of the gas-liquid separation chamber on the performance of the pump.The internal flow process of pump gas-liquid mixing and gas-liquid separation was analyzed by numerical simulation to provide a theoretical basis for revealing the self-priming mechanism of self-priming pumps and the optimal design of self-priming pumps.The main research work and research results are as follows:1.Based on the 65ZB-40 C external mixing self-priming pump,three model pumps with a separation chamber volume of 1:1.5:2 were designed.Hydraulic performance tests were carried out on the model pumps to draw the hydraulic performance curves of the pumps during normal operation.Comparing the performance curves of the three pumps,the efficiency and head of the self-priming pump are slightly reduced under the same working condition with the increase of the volume of the separation chamber.The efficiency is reduced by about 7%,the head is reduced by about 10% while the volume of the gas-liquid separation chamber doubled,and the phenomenon is more obvious under high-flow conditions.2.The steady simulations were carried out for the three pumps under different working conditions.The simulation results were compared with the external characteristic test results to verify the reliability of the simulation.The pressure and streamline diagramsof the separation chamber and the impeller surface in the steady simulation result can be obtained.With the increase of the volume of the gas-liquid separation chamber,more vortices are generated when the self-priming pump is stably working,and the vortex distribution is wider,resulting in a loss of energy in the pump and a slight decrease in the hydraulic performance of the pump.3.The transient tests were carried out on the three pumps,and the curves of the inlet and outlet pressure,flow rate and gas content were monitored.Simultaneously,the unsteady simulation was carried out to monitor the pressure of key parts such as the impeller inlet.The results show that the volume of separation chamber has a great influence on the stable stage and suddenly change stage of the pump.The volume of the separation chamber increases,the vacuum degree in the inlet of impeller is higher,the self-priming height is higher,and the self-priming performance is better.As the volume of the gas-liquid separation chamber increases,the air volume fraction at the pump outlet first reaches the maximum value at the later stage of self-priming process,and then decreases to less than 0.1,and the self-priming time is relatively short.4.Using CFX software,the two-phase flow calculation was carried out to monitor the change of gas content and flow rate at the inlet and outlet of the pump,the inlet of the gas-liquid separation chamber and the reflux hole.The two-phase changing process of the self-priming process and the two-phase distribution diagram and velocity vector diagram inside the three pumps were analyzed.The results show that the larger the volume of the separation chamber is,the larger the space of gas-liquid flow inside the pump is.As the volume of the gas-liquid separation chamber increases,the gas-liquid mixture in the pump chamber is concentrated in the upper part of the pump body,making the gas more easily overflow and thus shortening the time of self-suction.The larger the volume of the gas-liquid separation chamber is,the larger the gas-liquid flow space inside the self-suction pump is.The distribution of the vortexes is wide and uniform.In addition,the upper and lower vortexes can be clearly seen in the gas-liquid separation chamber of model 3 when t=24s. |
