| Loop reactor is a new type of gas-liquid reactor that has been widely studied by many scholars in recent years and has been applied in many fields such as chemical industry,biology and environmental protection.The liquid-gas ejector is the most important component of the loop reactor,which directly determines the operating performance of the loop reactor.This thesis takes liquid-gas ejector as the research object,firstly,a set of experimental platform of liquid-gas ejector suction volume testing system is built,and the experimental data of suction volume at different nozzle outlet flow rates are used to verify the rationality of the simulation model.Then Fluent numerical simulation was used to investigate the effects of physical parameters and operating parameters on the suction performance of the liquid-gas ejector,and the mathematical model between physical parameters,operating parameters and suction volume was established based on Bernoulli’s equation.The results show that the suction volume and gas-liquid ratio are proportional to the liquid density and pressure difference,and inversely proportional to the liquid viscosity,gas density and gas viscosity;the suction volume is proportional to the nozzle outlet flow rate,while the gas-liquid ratio is independent of the nozzle outlet flow rate;the operating pressure has no effect on the suction volume and gasliquid ratio.Secondly,the structural parameters were optimized by response surface method with the maximum suction volume as the target.The results showed that the maximum suction volume and gas-liquid ratio were achieved when the mixing section length-todiameter ratio of the liquid-gas ejector was 0,the mixing section diameter ratio was2.50,the throat length ratio was 4,the diffusion section diameter ratio was 2.0,and the diffusion section length-to-diameter ratio was 14.Finally,the formation mechanism of liquid phase volume suction gas phase was clarified by analyzing the pressure cloud diagram,velocity cloud diagram and volume fraction cloud diagram of the liquid-gas ejector.The results show that the gas flow rate and the circulation area jointly determine the suction volume of the liquid-gas injector,the gas circulation area is determined by the area difference between the mixing section and the nozzle,and the gas flow rate is jointly determined by the liquid flow rate,the pressure difference and the structural parameters of the mixing section.The transformation characteristics of the flow patterns inside the mixing and diffusion sections of the liquid-gas ejector under different gas-liquid ratio conditions were investigated by means of high-speed dynamics,and the flow patterns of the mixing and diffusion sections were plotted on this basis.The results show that when the gas-liquid ratio is small,bubble flow and mist flow appear in both the mixing and diffusion sections;when the gas-liquid ratio is large,annular flow and stratified flow appear in the mixing section,and annular flow,lumpy flow,stratified flow and churning flow appear in the diffusion section.The conclusions obtained in this thesis,such as the mathematical model of suction volume,optimized structural parameters,flow pattern diagrams of mixing and diffusion sections,play a guiding role in the design theory and engineering application of liquidgas ejectors. |
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