Research And Optimization Analysis Of Double-row Spiral Dynamic Pressure Seal In High-speed Cryogenic Medium

With the development of aerospace science and technology,cryogenic liquid hydrogen and oxygen fuel with high specific impulse,no pollution,high heat and low density has been deeply studied and widely applied in aerospace engines.The sealing performance of the turbopump of a liquid fuel engine with high speed and low temperature as the main working environment directly determines whether the turbopump can operate normally.Cryogenic fuel medium is very easy to undergo vaporization phase change and generate vibration,which leads to seal failure and further makes the application conditions of turbopump seal device more severe.This paper will study and discuss the vaporization phase transition characteristics and sealing performance of the fluid film on the dynamic pressure seal end face of cryogenic sealing medium under high rotating speed and low temperature conditions.The change rule of vaporization phase change characteristics and sealing performance of fluid film on the end face of double helix seal under extreme working conditions such as high rotating speed and low temperature is discussed.The results show that the pressure of the fluid film in the seal end gap increases with the increase of operating pressure and operating speed,and the temperature of the sealing fluid medium has little influence on the maximum pressure of the end face.The degree of vaporization phase change of fluid film increases with the increase of rotating speed and inlet medium temperature,and decreases with the increase of operating pressure.The opening force,friction power consumption and fluid film stiffness increase with the increase of rotating speed and pressure,while the leakage decreases with the increase of operating speed and increases with the increase of operating pressure.The influence of the structural parameters of the double helix seal end face,such as helix angle,groove depth,groove number and inner and outer groove diameter ratio,on the phase change characteristics and sealing performance of the fluid film on the seal end face under high rotating speed was studied.It is found that the structural parameters of the sealing face have significant effects on the phase change and sealing performance.The influence of groove bottom roughness on phase change characteristics and sealing performance is analyzed.With the increase of roughness,the absolute value of relative deviation of opening force,leakage,friction power consumption and fluid film stiffness increases.A targeted multi-parameter comprehensive performance optimization scheme for the end face of double helix seal is proposed.When considering the three special requirements of realizing low phase change while realizing low friction power consumption,realizing high starting force while realizing low leakage,realizing low leakage while realizing large fluid film rigidity,and considering the comprehensive performance of the seal,the structural parameters of the double helix seal end face are respectively optimized and analyzed,and the optimal combination of the structural parameters of the double helix dynamic pressure seal end face is obtained,which is suitable for high rotating speed and low temperature working conditions.The double helix dynamic pressure seal is designed and a high-speed cryogenic medium dynamic pressure seal test bed is built to carry out operation experiments of different rotating speeds,pressures,medium temperatures and types.The experimental results show that the seal design is reasonable and operates normally,and the experimental results are consistent with the theoretical analysis results.The leakage volume flow measured when the experimental medium is 75℃ water is between 25℃ water and air experiments,indicating that the sealing medium has undergone vaporization phase change.Through the research on the vaporization phase change characteristics and sealing performance of fluid film in high-speed cryogenic medium dynamic pressure seal,the influence of working condition parameters and seal end surface structure parameters on the vaporization phase change characteristics and sealing performance of fluid film is obtained,and an effective optimization scheme for special working conditions is proposed,which provides certain theoretical and technical references for the design and application of such high-speed cryogenic medium seals.