Study On Plasma Flow Control Of Axial Tip Leakage F Low In Liquid Ring Pump

Liquid ring pump is a general machine used to pump gas by taking liquid as the medium of energy conversion.In the process of pumping gas,the pump has the advantages of small temperature change,no rotor metal surface contact and so on,it has great advantages in the transportation of toxic and condensable gas,which is widely used in petrochemical,mining and electric power and other important fields of national economy.At present,the technology of liquid ring pumps in China started relatively late,and currently there are still some special liquid ring pumps facing the "bottleneck" dilemma in the fields of petrochemical and nuclear power.The liquid ring pump has unique structure and performance characteristics,under the pressure difference between the exhaust and suction zones,the leakage occurs at the axial tip clearance of the impeller,the interaction between the leakage fluid in the outflow gap and the mainstream in the impeller flow channel produces a complex turbulent structure in the near-wall region,which further increases the hydraulic loss and hydraulic excitation force in the pump and reduces the performance of the liquid ring pump;based on the above problems,this study proposes a plasma excitation control method for gas phase leakage flow in axial clearance of liquid ring pump impeller,the numerical simulation method is used to analyze the effect of plasma excitation on the hydraulic performance and hydraulic excitation characteristics of the pump,and to analyze the coupling characteristics of the plasma excitation induced flow field and the gap leakage flow;it provides a theoretical reference for the research and development of high performance liquid ring pump in China.The main work and conclusions of this paper are as follows :(1)Comparing the experimental and numerical simulation results,the simulation accuracy of RNG k-ε turbulence model and VOF gas-liquid two-phase flow model for gas-liquid two-phase flow in liquid ring pump is verified;based on the above calculation model,the numerical simulation of plasma-excited flow control of axial tip clearance leakage flow in liquid ring pump is carried out by coupling plasma excitation effect;it is found that under the action of plasma excitation,a wall jet opposite to the direction of the gap leakage flow is generated at the excitation position,which can effectively suppress the strength of the gap leakage high-speed jet,at the same time,it is coupled with the leakage flow to generate wall-induced vortex,which will increase the hydraulic loss in the near-wall region to a certain extent.(2)The control effect of plasma excitation on gap leakage flow is closely related to the excitation position;when the plasma excitation position is in the axial tip region of the impeller,the clearance leakage flow is obviously suppressed,the leakage flow velocity flowing out of the axial clearance is reduced,and the interference to the downstream mainstream is reduced;when the excitation position is in the flow passage between the blades,the interaction between the leakage high-speed jet in the outflow gap and the plasma-induced reverse wall jet appears obvious vortex-vortex coupling characteristics;when the plasma excitation position gradually moves downstream of the leakage flow,the flow control effect gradually weakens.(3)The influence of the flow effect of the liquid ring pump on the hydraulic performance and pressure pulsation characteristics of the plasma control is analyzed,it is found that the plasma excitation of 15 k V excitation voltage can effectively regulate the hydraulic performance of the liquid ring pump at the suction flow rate of 0.03kg/s;it can effectively suppress the pressure fluctuation characteristics of the axial clearance leakage flow of the impeller under the flow condition of the pump,and has a significant effect on the stability expansion;it has no obvious effect on the hydraulic performance regulation and the pressure pulsation suppression of the leakage flow when the suction flow rate of the pump is 0.05kg/s;the hydraulic performance and leakage flow pressure pulsation suppression effect of 15 k V plasma excitation on the flow rate of 0.01kg/s are between 0.03kg/s and 0.05kg/s.