Research On Flow Field And Deformation Of SCO₂ Dynamic Pressure Seal Face

Dynamic pressure seal is an ideal seal form to solve the problem of high temperature and high pressure SCO2 seal.However,if the design is improper,the seal rings will be deformed too much due to the high temperature,high pressure and high speed.Therefore,in this paper,the flow field and deformation of SCO2 dynamic pressure seal are studied systematically and deeply by the method of numerical calculation and experiment.According to the typical spiral groove dynamic pressure seal structure of SCO2,the numerical analysis model of SCO2 fluid film considering Viscous dissipation was established.The SCO2 fluid temperature distribution and pressure distribution between the end faces of seal were analyzed,the seal performance parameters of SCO2 dynamic pressure seal were calculated,and the change rule of seal performance under different working conditions was discussed.The results show that the opening force is positively related to the speed and pressure;the leakage and the ratio of opening force to leakage change less with the increase of speed,which is greatly affected by the pressure;the friction power consumption increases exponentially with the increase of speed,and increases sharply with the increase of pressure.The leakage is positively related to the film thickness,and the other sealing performance parameters are negatively related to the film thickness.The numerical analysis model of SCO2 seal rings were established,the relevant parameters of thermal boundary are calculated,the steady-state temperature field and thermal deformation of seal rings end faces were analyzed,and the change rule of axial thermal deformation of seal end faces under different rotating speed and medium temperature were discussed.The results show that after the seal rings reach the thermal balance,the axial thermal deformation of the end face of the static ring is relatively uniform,and the deformation taper is small.The axial thermal deformation of the end face of the seal rings are positively related to the rotating speed and the medium temperature.The thermal deformation taper of the end face of the static ring is mainly affected by the rotating speed,and the medium temperature has a greater impact on the thermal deformation taper of the end face of the rotary ring.Based on the fluid film pressure of SCO2 obtained from the flow field calculation,the force deformation of the seal faces were analyzed,and the change rule of the axial force deformation of the end faces under various rotating speed and pressure were discussed.The results show that the axial deformation of the end face of the static ring is positively related to the pressure.The axial deformation of the end face of the rotary ring is negatively related to the pressure,and decreases first and then increases with the increase of rotating speed.Based on the analysis of force deformation and thermal deformation of seal end faces,the axial deformation of seal faces under the combined action of thermal force was analyzed,and the axial deformation of seal face in three cases was compared.The measures to control the deformation of the end faces were put forward from the aspects of material and structure.Designed and built a high-pressure and high-speed dynamic pressure seal test-bed,carried out the principle test of the sealing device,measured the air leakage of the dynamic pressure seal face and the temperature of the static ring face under different operating parameters.The results of the two experiments are consistent with the numerical analysis,which verifies the reliability of the numerical model.Through the research on the flow field and deformation of SCO2 dynamic pressure seal face in this paper,it can provide the structural design guidance for SCO2 thermodynamic system dynamic pressure seal and lay a certain foundation for the research of seal faces deformation under high parameters.