Analysis Of Flow Field And Hydraulic Characteristics Of Liquid-ring Pump As Vacuum Pump And Compressor

Liquid ring pump is a kind of fluid machinery used to pump and compress gas.It is widely used in petrochemical,electric power and mining industries due to its advantages of large flow and isothermal compression.Liquid ring pump commonly used to pump and compress gas.The same liquid ring pump can be used in vacuum pump,compressor and vacuum compressor conditions.However,at present,there is no complete design and selection method for liquid-ring compressor and liquid-ring vacuum compressor.Usually,the liquid-ring compressor and the liquid-ring vaccum compressor are designed and selected with reference to liquid ring vaccum pump.Therefore,it is of great significance to study the relationship between external characteristics and internal flow field between liquid-ring vacuum pump and liquid-ring vacuum compressor and liquid-ring compressor conditions.In this paper,the relationship between the external characteristics and the internal flow field characteristics of the same liquid-ring pump under the conditions of vacuum pump,compressor and vacuum compressor were compared and analyzed by combining experimental test and numerical simulation.The main contents and conclusions of this study are as follows:1.The liquid ring pump experimental system was designed and built.The external characteristics of 2BE liquid ring pump,the pressure pulsation characteristics of shell wall and the visualization of gas-liquid two-phase flow field in the liquid ring pump were studied experimentally under the conditions of vacuum pump and compressor.The performance relationship of liquid ring pump under different working conditions of vacuum pump and compressor was analyzed.The pressure pulsation characteristics of the inner wall of the vacuum pump and compressor under the same pressure ratio were tested and analyzed.Visualization test of gas-liquid two-phase flow in pump was carried out.The internal flow field and external characteristics of the liquid ring pump were studied by combining numerical simulation with experimental research.2.The hydraulic performance of vacuum pump,compressor and vacuum compressor were compared and analyzed.The analysis results show that the efficiency of vacuum compressor is the highest,and the efficiency of vacuum pump is the lowest.At low pressure ratio,the mass flow of the vacuum compressor and the compressor working condition under the same pressure ratio is close to and much larger than that of the vacuum pump working condition,the power capacity of the vacuum pump working condition is the lowest,and the volume flow of the compressor working condition is almost the same as that of the vacuum pump working condition but less than that of the vacuum compressor working condition.With the increase of pressure ratio,the limit pressure ratio of vacuum pump condition is much larger than that of the other two conditions,and the limit pressure ratio of vacuum compressor condition is the smallest.The volume flow ratio and efficiency ratio of vacuum pump to vacuum compressor and vacuum pump to compressor decrease gradually with the increase of pressure ratio.3.The internal flow field characteristics of liquid-ring pump were analyzed under the conditions of vacuum pump,compressor and vacuum compressor.The comparative results show that the structural characteristics of the internal flow field are basically the same under different working conditions The phenomenon of gas intrusion into liquid phase occurs in both vacuum compressor and compressor operating conditions under high pressure ratio,which indicates that the gas-liquid interface in vacuum pump operating conditions has the highest stability.Under the condition of the same pressure ratio,the local backflow strength of the exhaust outlet in the vacuum pump condition is higher than that in the compressor condition with the same pressure ratio,and the local backflow strength of the vacuum compressor is the weakest.At the same pressure ratio,the overall turbulence intensity distribution in the compressor condition is smaller than that in the vacuum pump condition but larger than that in the vacuum compressor condition.Under the same pressure ratio change,the inner wall pressure of the exhaust zone and the transition zone increases significantly with the increase of the pressure ratio in the compressor and vacuum compressor working conditions,while the change of the vacuum pump working conditions is not obvious.4.The pressure pulsation characteristics of pump shell under the condition of liquid-ring pump as vacuum pump,compressor and vacuum compressor were compared and analyzed.The analysis results show that the frequency domain characteristics of pump shell inner wall pressure under various working conditions have obvious zoning characteristics along the circumferential direction.The first-order dominant frequency characteristics of each monitoring point under different working conditions are basically the same In the case of the same pressure ratio,the amplitude of pressure pulsation at the monitoring point of the vacuum compressor and the compressor is almost the same,but both of them are larger than that of the vacuum pump.The amplitude of pressure pulsation in the inner wall of the shell increases significantly with the increase of pressure ratio under the conditions of vacuum compressor and compressor,but the change of pressure pulsation in the conditions of vacuum pump is not obvious.According to the time domain diagram,the pressure pulsation amplitude fluctuation of the monitoring points P₂and P₁₂under the three working conditions shows obvious periodicity,while the pressure pulsation amplitude fluctuation of P₆and P₈are small and does not show obvious regularity.