Over-compression Characteristics In Liquid Ring Pump And Working Mechanism Of Exhaust Check Valve

The liquid ring pump is widely used in coal,electric power,chemical industry,metallurgy,food and other industries due to its isothermal compression,compact structure and large pumping capacity,especially in the vacuum of large coal mine gas drainage and hypersonic multi-function wind tunnel equipment,nuclear power plant large-scale vacuum equipment for pumping and other major national needs.The complex gas-liquid two-phase flow structure inside the liquid ring pump causes a large hydraulic loss,resulting in a generally low efficiency of the liquid ring pump,generally between 30% and 50%.When the liquid ring pump is used as a compressor,it is extremely prone to over-compression phenomenon under low compression ratio conditions,which consumes excess energy.In order to prevent over-compression phenomenon in the liquid ring pump,a plurality of check valves are generally arranged in the front section of the exhaust port.In order to analyze the over-compression characteristics of the liquid ring pump and the working mechanism of the exhaust port check valve,VOF two-phase flow model is used to simulate the flow in liquid ring pump at compressor conditions.The influence of check valves internal flow characteristics and its area change on the flow structure and performance of the liquid ring pump is analyzed.The flow field distribution in the pump under different compression ratio conditions is analyzed.Main tasks as follows:1)The SY-type liquid ring pump was selected as the research object.The hexahedral structured grid and VOF two-phase flow model were used to simulate the unsteady gas-liquid two-phase flow,and the internal complex flow structure characteristics were analyzed and compared with the experimental results.The reliability of numerical simulation method for the liquid ring pump is verified.2)The open state and internal flow of the check valves at the front end of the exhaust port under different working conditions are analyzed.The flow field and external characteristics of the liquid ring pump with or without the check valves are analyzed.The numerical simulation results show that with the decrease of the pressure at the exhaust port of the liquid ring pump,the front end of the exhaust port of the liquid ring pump is prone to over-compression phenomenon,which will lead to the excess energy consumption of the liquid ring pump and reduce the efficiency of the liquid ring pump.The lower the outlet pressure,the greater the degree of over-compression.Under the condition of low compression ratio,the check valve installed at the front end of the exhaust port can automatically open,which can effectively avoid the over-compression phenomenon and improve the efficiency and suction capacity of the liquid ring pump.3)The area of the check valve at the front end of the exhaust port has a great influence on the performance of the liquid ring pump.In order to analyze the influence of the area change of the check valve on the performance of the pump,four different schemes of the area change of the check valve are put forward.The numerical simulation is carried out under different working conditions respectively.The analysis show that the diameter of the check valve is gradually increased along the rotation direction of the impeller,which can effectively increase the suction capacity of the liquid ring pump,reduce the flow rate of the check valve,and improve the performance of the liquid ring pump.