Study On Liquid Oxygen Phase Transformation And Sealing Performance Of Mechanical Seal Microtexture

Turbopump is the core power component of liquid rocket engines,pneumatic hydraulic servo systems,and liquid hydrogen liquid oxygen expansion cycle engines.Its main function is to increase the pressure of propellant in the storage tank and deliver it to the main thrust chamber to generate gas according to the requirements of the engine system.As an important component of a liquid rocket engine turbopump,the rotating shaft has the characteristics of high speed,high pressure,and low temperature when working.The key to achieving higher performance of the turbopump is to form a stable fluid film lubrication through the micro molding of the sealing end surface.The commonly used rotary shaft seals mainly include labyrinth seals,lip seals,floating ring seals,and mechanical seals.The spiral groove liquid film seal of the rotary shaft is a typical non-contact mechanical seal that can provide excellent comprehensive performance for turbopumps operating under extreme conditions.Based on the evaporation and condensation model of the multiphase flow model in ANSYS,a numerical analysis model for a single groove was established.The degree and distribution of liquid film vaporization phase change under operating conditions were analyzed,as well as the impact of liquid film vaporization phase change on pump opening force and leakage.The results show that with the increase of rotating ring speed and medium pressure,phase transformation is inhibited,and the average vapor volume fraction occurs at the pressure outlet and gradually decreases in range.The maximum phase transformation pressure gradually increases,and the opening force and leakage amount continuously increase.The increase in medium temperature will promote the occurrence of phase change,with the average vapor volume fraction occurring at the pressure outlet and gradually increasing in range.The maximum phase change pressure continues to decrease,and the opening force and leakage amount continue to decrease.The vaporization phase transition of the liquid film will have a direct impact on the sealing performance.Reasonable selection of sealing conditions can effectively utilize and control phase transitions and improve sealing performance.A numerical analysis model for dynamic pressure sealing of composite grooves was established to investigate the effects of operating parameters on the vaporization phase transition and sealing performance of the composite groove liquid film.The results show that with the continuous increase of rotating ring speed,phase change is inhibited,the maximum phase change pressure gradually increases,the maximum phase change pressure increase ratio gradually increases,the opening force continuously increases,and the leakage amount continuously decreases.With the continuous increase of medium pressure,the vaporization phase transition of the liquid film is inhibited,and the average vapor volume fraction decrease ratio first increases and then decreases,then increases and then decreases.The maximum phase change pressure gradually increases,the maximum phase change pressure increase ratio first decreases and then increases,and the opening force and leakage amount continue to increase.As the inlet temperature continues to rise,the vaporization phase transformation of the liquid film is promoted,the average vapor volume fraction increase ratio first rises and then decreases,the maximum phase change pressure gradually decreases,the opening force first decreases and then increases,and the leakage amount first decreases and then increases.A dynamic pressure sealing device for mechanical seals was designed and a dynamic pressure sealing test rig was built.Operating experiments were carried out under two types of groove type constant pressure variable speed and constant speed variable pressure conditions.The numerical simulation results and experimental results were compared and analyzed.Through experiments on two types of grooves with constant pressure and variable rotational speed,it is found that the experimental value of a single groove is slightly larger than the theoretical value and the maximum error is 12.2%.The experimental value of the composite groove is slightly larger than the theoretical value and the maximum error is 12.7%.Through experiments on two types of grooves with constant rotational speed and variable pressure,it was found that when the medium pressure increased,the experimental value of a single groove was slightly larger than the theoretical value,and the maximum error was 14.1%.The experimental value of the composite groove is slightly larger than the theoretical value and the maximum error is 11.9%.Through the study of the vaporization phase transition characteristics and sealing performance of composite and single groove liquid membranes using liquid oxygen as the medium,the effects of operating conditions on the vaporization phase transition characteristics and sealing performance of the liquid membrane were obtained,providing some theoretical and technical basis for the design and use of dynamic pressure seals for liquid oxygen.