| The pressure of supercritical carbon dioxide（SCO2）decreases rapidly on both sides of the dynamic pressure seal,and the phase state between the seal end faces changes drastically.At the same time,the thermal elastic deformation of the sealing end face under the high temperature,high pressure and high speed working conditions of the SCO2 dynamic pressure sealing application cannot be ignored,which greatly affects the stability and reliability of the seal.Therefore,this paper analyzes and discusses the transcritical flow and thermoelastic deformation of the SCO2 dynamic pressure sealing fluid film,and carries out experimental research at the same time.The ANSYS software is used to establish a dynamic pressure sealing thermo-fluid-solid coupling numerical analysis model.In Fluent,the actual gas effect,inertia effect and turbulence effect are considered to solve the fluid film transcritical flow,and the fluid film pressure distribution is obtained.Analyze the heat balance of the seal,calculate the viscous shear heat,stirring heat,and convective heat transfer coefficient,and get the temperature distribution of the seal ring.Analyze the force of the seal ring,and couple the temperature and the fluid film pressure to the seal ring to solve the thermoelastic deformation,and get the seal face thermoelastic deformation.Analyzing the influence of temperature,pressure and speed on the transcritical phase change of the sealing fluid film,the results show that low temperature is not conducive to the stability of the sealing phase,and the risk of liquefaction and solidification will occur.The higher the pressure,the closer the phase change interface is to the sealing outlet,which is nearly critical.The lower the speed of the point working condition,the higher the risk of multiphase condensation flow.Analyzing the impact of operating case on sealing ability,it is concluded that for the high-speed dynamic pressure seal with external grooves,the pumping effect of the fluid promotes the seal leakage,and the centrifugal effect inhibits the seal leakage.The index of reducing the leakage can be achieved by reducing the pumping effect.The impact of operating case on the thermoelastic deformation of seal is analyzed,and the rule of the maximum deformation gap of the seal face is obtained.It is proposed that the temperature difference of the sealing ring should be reduced under high temperature,high pressure and high speed,the use of high elastic modulus materials and the coordination of the thermal and elastic deformation of the moving ring to reduce the total deformation.In order to achieve the effect of deformation coordination of the dynamic pressure seal,the influence of the structural parameters of the seal ring on the stability of the thermoelastic deformation of the seal end face was explored,and the orthogonal optimization method was used to obtain that the seal face is still approximately after the thermoelastic deformation.Optimal sealing ring structure in parallel state.Develop a comprehensive sealing test platform integrating SCO2 preparation system,dynamic pressure sealing auxiliary system and test system,and carry out dynamic pressure sealing static pressure test and variable speed and variable pressure operation test.Obtain the change law of the leakage,the fluid film thickness,the bearing and the seal face temperature of seal under different speed and pressure.The results prove the correctness of the thermalfluid-solid coupling calculation for SCO2 dynamic pressure sealing.Through the study of this article,the mechanism of the transcritical flow of the SCO2 dynamic pressure sealing fluid film is obtained,and the impact of different operating case on the seal transcritical phase change and sealing performance is obtained.The optimization method of deformation coordination is proposed for thermoelastic deformation and provides technical support for the design,optimization and development of supercritical fluids and high-parameter dynamic pressure seals. |
