Pneumatic cryogenic control valves(PCCV)are designed to meet the special requirements for the large cryogenic helium refrigeration system.Polychlorotrifluoroethylene(PCTFE)is adopted as the flat seal material of the v...Pneumatic cryogenic control valves(PCCV)are designed to meet the special requirements for the large cryogenic helium refrigeration system.Polychlorotrifluoroethylene(PCTFE)is adopted as the flat seal material of the valve seat.The leakage rates and compressive strain of the PCTFE gasket with different sealing stress are tested at both room temperature(293 K)and liquid nitrogen temperature(77 K).After 300 open/close cycles,the experimental results show that the sealing properties of the PCTFE gasket are improved.The leakage rates are about 10-8(293 K)and 10-4(77 K)Pam3 s-1 respectively.Finally,the effects of working pressure on sealing characteristics are discussed.The working pressure has little effect on compressive strain but it has a great influence on leakage rate.The leakage rate is linear with the working pressure of inlet at room temperature,but at liquid nitrogen temperature the leakage rate is linear with the square of the working pressure.展开更多
Valves are key components of the safety of fluid transportation systems because of induced disturbance and cavitation damage in them.In this study,a 2D model of a cryogenic globe valve with liquid nitrogen(LN_(2))as w...Valves are key components of the safety of fluid transportation systems because of induced disturbance and cavitation damage in them.In this study,a 2D model of a cryogenic globe valve with liquid nitrogen(LN_(2))as working fluid was established by Fluent,and thermal effects were specially considered in the simulation.The validity of the LN_(2) cavitation model was verified by the experimental data of hydrofoil LN_(2) cavitation from earlier studies by NASA.Cavitation characteristics of LN2 in the cryogenic globe valve under three typical working conditions were investigated.The average pressure and pressure pulse at different positions of the wall were further studied to reveal cavitation risks from fatigue and vibration.Results show that with similar valve structure and openings,the pressure pulsation frequencies of LN_(2) are lower than those of water,and the shape and location of the cavitation clouds also show significant differences.For LN_(2) cavitation,an extended period of valve opening at 66% should be avoided since its pressure pulse peak is the largest compared to openings of 33% and 100%,and reaches 5×10^(7) Pa.The opening of 33% should also be monitored because of the large torque caused by the pressure difference between the two sides of the valve baffles.To prevent resonance,a critical state for the valve opening and the connecting pipe length is proposed.These predictions of cryogenic cavitation in the globe valve are helpful for the safe and reliable operation of cryogenic fluid transport systems.展开更多
基金supported by the fund of the State Key Laboratory of Technologies in Space Cryogenic Propellants (Grant No. SKLTSCP1210)
文摘Pneumatic cryogenic control valves(PCCV)are designed to meet the special requirements for the large cryogenic helium refrigeration system.Polychlorotrifluoroethylene(PCTFE)is adopted as the flat seal material of the valve seat.The leakage rates and compressive strain of the PCTFE gasket with different sealing stress are tested at both room temperature(293 K)and liquid nitrogen temperature(77 K).After 300 open/close cycles,the experimental results show that the sealing properties of the PCTFE gasket are improved.The leakage rates are about 10-8(293 K)and 10-4(77 K)Pam3 s-1 respectively.Finally,the effects of working pressure on sealing characteristics are discussed.The working pressure has little effect on compressive strain but it has a great influence on leakage rate.The leakage rate is linear with the working pressure of inlet at room temperature,but at liquid nitrogen temperature the leakage rate is linear with the square of the working pressure.
基金This work is supported by the Research Fund of State Key Laboratory of Technologies in Space Cryogenic Propellants(No.SKLTSCP1601)the Key Research and Development Program of Zhejiang Province(No.2020C01029)+1 种基金the Key Program of National Natural Science Foundation of China(No.51636007)the Natural Science Foundation of Zhejiang Province(No.LQ21E060011),China.
文摘Valves are key components of the safety of fluid transportation systems because of induced disturbance and cavitation damage in them.In this study,a 2D model of a cryogenic globe valve with liquid nitrogen(LN_(2))as working fluid was established by Fluent,and thermal effects were specially considered in the simulation.The validity of the LN_(2) cavitation model was verified by the experimental data of hydrofoil LN_(2) cavitation from earlier studies by NASA.Cavitation characteristics of LN2 in the cryogenic globe valve under three typical working conditions were investigated.The average pressure and pressure pulse at different positions of the wall were further studied to reveal cavitation risks from fatigue and vibration.Results show that with similar valve structure and openings,the pressure pulsation frequencies of LN_(2) are lower than those of water,and the shape and location of the cavitation clouds also show significant differences.For LN_(2) cavitation,an extended period of valve opening at 66% should be avoided since its pressure pulse peak is the largest compared to openings of 33% and 100%,and reaches 5×10^(7) Pa.The opening of 33% should also be monitored because of the large torque caused by the pressure difference between the two sides of the valve baffles.To prevent resonance,a critical state for the valve opening and the connecting pipe length is proposed.These predictions of cryogenic cavitation in the globe valve are helpful for the safe and reliable operation of cryogenic fluid transport systems.
