In photothermal power(solar energy)generation systems,purging residual molten salt from pipelines using highpressure gas poses a significant challenge,particularly in clearing the bottom of regulating valves.Ineffecti...In photothermal power(solar energy)generation systems,purging residual molten salt from pipelines using highpressure gas poses a significant challenge,particularly in clearing the bottom of regulating valves.Ineffective purging can lead to crystallization of the molten salt,resulting in blockages.To address this issue,understanding the gas-liquid two-phase flow dynamics during high-pressure gas purging is crucial.This study utilizes the Volume of Fluid(VOF)model and adaptive dynamic grids to simulate the gas-liquid two-phase flow during the purging process in a DN50 PN50 conventional molten salt regulating valve.Initially,the reliability of the CFD simulations is validated through comparisons with experimental data and findings from the literature.Subsequently,simulation experiments are conducted to analyze the effects of various factors,including purge flow rates,initial liquid accumulation masses,purge durations,and the profiles of the valve bottom flow channels.The results indicate that the purging process comprises four distinct stages:Initial violent surge stage,liquid discharge stage,liquid partial fallback stage,liquid dissipation stage.For an initial liquid height of 17 mm at the bottom of the valve,the critical purge flow rate lies between 3 and 5 m/s.Notably,the critical purge flow rate is independent of the initial liquid accumulation mass.As the purge gas flow rate increases,the volume of liquid discharged also increases.Beyond the critical purge flow rate,higher purge gas velocities lead to shorter purge durations.Interestingly,the residual liquid mass after purging remains unaffected by the initial liquid accumulation.Additionally,the flow channel profile at the bottom of the valve significantly influences both the critical purge speed and the efficiency of the purging process.展开更多
A new type regulating valve with the cooling mode of constant temperature difference water supply, temperature difference self operated regulating valve, was introduced into blast furnace cooling system to overcome s...A new type regulating valve with the cooling mode of constant temperature difference water supply, temperature difference self operated regulating valve, was introduced into blast furnace cooling system to overcome shortcomings of the cooling mode of constant flow rate water supply. The results show that the temperature difference between inlet and outlet water of cooling wall can be decreased greatly and steadily, and the water supply for blast furnace cooling can be reduced considerably.展开更多
A new type of pressure regulating valve for agriculture irrigation, which used spring to regulate pressure was studied. Through the spring regulating pres-sure test, it concluded that for the pressure regulating valve...A new type of pressure regulating valve for agriculture irrigation, which used spring to regulate pressure was studied. Through the spring regulating pres-sure test, it concluded that for the pressure regulating valve with same spring mod-el, the outer pressure became smal er than the inlet pressure of the system and with the changes of inlet pressure, the outlet pressure remained almost the same, and that when inlet pressure was constant, the valve with smal er spring diameter had lower outlet pressure, indicating that the pressure regulating effect of the spring was more obvious with smal er diameter.展开更多
A digital electro-hydraulic 4-port differential pressure control valve with a novel principle and structure is presented. The valve is designed by applying the regulating pressure technique of a capillary damping tube...A digital electro-hydraulic 4-port differential pressure control valve with a novel principle and structure is presented. The valve is designed by applying the regulating pressure technique of a capillary damping tube and also making full use of double freedom of the spool motion. Thevalve can implement digitizing interface easily. The theoretical analysis and experimental resultsshow that the valve is not only very simple in structure and convenient in use, but also has manygood properties, such as fast response, no-null-shift, etc.展开更多
Pneumatic control valve is a throttling depending on the local resistance change to achieve components, is usually made up of actuator and control valve, pneumatic control valve of the automatic process of offshore oi...Pneumatic control valve is a throttling depending on the local resistance change to achieve components, is usually made up of actuator and control valve, pneumatic control valve of the automatic process of offshore oil platform during the specific choice, needs to focus on analysis of pneumatic control valve stroke, pneumatic control valve structure and combining with the Marine climate environment of material aspects, such as selection of effects.展开更多
The existing researches of stepless capacity regulation system by depressing the suction valve for reciprocation compressor always adopt hypothesis that the compressor valves are open or close instantaneously,the valv...The existing researches of stepless capacity regulation system by depressing the suction valve for reciprocation compressor always adopt hypothesis that the compressor valves are open or close instantaneously,the valve dynamic has not been taken account into thermal cycle computation,the influence of capacity regulation system on suction valves dynamic performance and cylinder thermal cycle operation has not been considered.This paper focuses on theoretical and experimental analysis of the valve dynamic and thermal cycle for reciprocating compressor in the situation of stepless capacity regulation.The valve dynamics equation,gas forces for normal and back flow,and the cylinder pressure varying with suction valve unloader moment during compression thermal cycle are discussed.A new valve dynamic model based on L-K real gas state equation for reciprocating compressor is first deduced to reduce the calculation errors induced by the ideal gas state equation.The variations of valve dynamic and cylinder pressure during part of compression stroke are calculated numerically.The calculation results reveal the non-normal thermal cycle and operation condition of compressor in stepless capacity regulation situation.The numerical simulation results of the valve dynamic and thermal cycle parameters are also verified by the stepless capacity regulation experiments in the type of 3L-10/8 reciprocating compressor.The experimental results agree with the numerical simulation results,which show that the theoretical models proposed are effective and high-precision.The proposed theoretical models build the theoretical foundation to design the real stepless capacity regulation system.展开更多
This paper mainly studied how to determine the best location of the self-operated flow control valve at the heating system entrance.Since the location of regulating valve directly affects the pipe network performance,...This paper mainly studied how to determine the best location of the self-operated flow control valve at the heating system entrance.Since the location of regulating valve directly affects the pipe network performance,the simulation and analysis of pressure change in heating system was carried out with Computational Fluid Dynamics(CFD)software.The study shows the best location of regulating valve varies with the change of the supply and return pipe length when the heating area of each user is small,and when the heating area of each user is large(2000000~3000000 m2),the best location is on the supply pipe.展开更多
Factors that cause the self-discharge in valve-regulated sealed lead-acid batteries are discussed and measures to inhibit the self-discharge are put forward.
目的基于呼吸力学、心肌损伤、术后肺部并发症来探讨压力控制容量保证通气模式(PRVC)用于心脏瓣膜手术的价值。方法前瞻性纳入2024年1月至2025年10月徐州医科大学附属医院收治的择期行心脏瓣膜置换或修复术患者,严格纳入与排除标准后最...目的基于呼吸力学、心肌损伤、术后肺部并发症来探讨压力控制容量保证通气模式(PRVC)用于心脏瓣膜手术的价值。方法前瞻性纳入2024年1月至2025年10月徐州医科大学附属医院收治的择期行心脏瓣膜置换或修复术患者,严格纳入与排除标准后最终入组100例,以分层区组随机化方法按1∶1比例将患者分配至PRVC组(n=50)与对照组(n=50,容量控制通气模式),比较两组手术不同时间呼吸力学、氧合状态,测定术前术后肌酸激酶同工酶(CK-MB)、乳酸脱氢酶(LDH)、超敏肌钙蛋白T(hs-cTnT)、N端脑钠肽前体(NT-proBNP)水平,记录术后7 d内肺部并发症发生情况。结果不同时间点,PRVC组Ppeak、Pplat、△P均低于对照组,Cdyn高于对照组,存在组间与时间效应(P<0.05),Ppeak存在交互效应(P<0.05);不同时间点,PRVC组PaO_(2)、OI均高于对照组,RI、PA-aO_(2)低于对照组,存在组间与时间效应(P<0.05),其中PaO_(2)、PA-aO_(2)存在交互效应(P<0.05);术后6、24 h两组CK-MB、LDH、hs-cTnT、NT-proBNP均高于同组术前,PRVC组术后6、24 h CK-MB、LDH、hs-cTnT、NT-proBNP低于对照组,存在组间、时间及交互效应(P<0.05);PRVC组拔管时间、ICU停留时间及总住院时间短于对照组(P<0.05),术后总肺部并发症发生率显著低于对照组(P<0.05)。结论PRVC模式用于心脏瓣膜手术较VCV模式对呼吸力学、氧合影响更小,肺保护作用显著,可减轻心肌损伤,减少肺部并发症。展开更多
文摘In photothermal power(solar energy)generation systems,purging residual molten salt from pipelines using highpressure gas poses a significant challenge,particularly in clearing the bottom of regulating valves.Ineffective purging can lead to crystallization of the molten salt,resulting in blockages.To address this issue,understanding the gas-liquid two-phase flow dynamics during high-pressure gas purging is crucial.This study utilizes the Volume of Fluid(VOF)model and adaptive dynamic grids to simulate the gas-liquid two-phase flow during the purging process in a DN50 PN50 conventional molten salt regulating valve.Initially,the reliability of the CFD simulations is validated through comparisons with experimental data and findings from the literature.Subsequently,simulation experiments are conducted to analyze the effects of various factors,including purge flow rates,initial liquid accumulation masses,purge durations,and the profiles of the valve bottom flow channels.The results indicate that the purging process comprises four distinct stages:Initial violent surge stage,liquid discharge stage,liquid partial fallback stage,liquid dissipation stage.For an initial liquid height of 17 mm at the bottom of the valve,the critical purge flow rate lies between 3 and 5 m/s.Notably,the critical purge flow rate is independent of the initial liquid accumulation mass.As the purge gas flow rate increases,the volume of liquid discharged also increases.Beyond the critical purge flow rate,higher purge gas velocities lead to shorter purge durations.Interestingly,the residual liquid mass after purging remains unaffected by the initial liquid accumulation.Additionally,the flow channel profile at the bottom of the valve significantly influences both the critical purge speed and the efficiency of the purging process.
文摘A new type regulating valve with the cooling mode of constant temperature difference water supply, temperature difference self operated regulating valve, was introduced into blast furnace cooling system to overcome shortcomings of the cooling mode of constant flow rate water supply. The results show that the temperature difference between inlet and outlet water of cooling wall can be decreased greatly and steadily, and the water supply for blast furnace cooling can be reduced considerably.
文摘A new type of pressure regulating valve for agriculture irrigation, which used spring to regulate pressure was studied. Through the spring regulating pres-sure test, it concluded that for the pressure regulating valve with same spring mod-el, the outer pressure became smal er than the inlet pressure of the system and with the changes of inlet pressure, the outlet pressure remained almost the same, and that when inlet pressure was constant, the valve with smal er spring diameter had lower outlet pressure, indicating that the pressure regulating effect of the spring was more obvious with smal er diameter.
文摘A digital electro-hydraulic 4-port differential pressure control valve with a novel principle and structure is presented. The valve is designed by applying the regulating pressure technique of a capillary damping tube and also making full use of double freedom of the spool motion. Thevalve can implement digitizing interface easily. The theoretical analysis and experimental resultsshow that the valve is not only very simple in structure and convenient in use, but also has manygood properties, such as fast response, no-null-shift, etc.
文摘Pneumatic control valve is a throttling depending on the local resistance change to achieve components, is usually made up of actuator and control valve, pneumatic control valve of the automatic process of offshore oil platform during the specific choice, needs to focus on analysis of pneumatic control valve stroke, pneumatic control valve structure and combining with the Marine climate environment of material aspects, such as selection of effects.
基金supported by China National Key Technology R&D Program(Grant No.2008BAF34B13)China Postdoctoral Science Foundation Funded Project(Grant No.2011M501363)
文摘The existing researches of stepless capacity regulation system by depressing the suction valve for reciprocation compressor always adopt hypothesis that the compressor valves are open or close instantaneously,the valve dynamic has not been taken account into thermal cycle computation,the influence of capacity regulation system on suction valves dynamic performance and cylinder thermal cycle operation has not been considered.This paper focuses on theoretical and experimental analysis of the valve dynamic and thermal cycle for reciprocating compressor in the situation of stepless capacity regulation.The valve dynamics equation,gas forces for normal and back flow,and the cylinder pressure varying with suction valve unloader moment during compression thermal cycle are discussed.A new valve dynamic model based on L-K real gas state equation for reciprocating compressor is first deduced to reduce the calculation errors induced by the ideal gas state equation.The variations of valve dynamic and cylinder pressure during part of compression stroke are calculated numerically.The calculation results reveal the non-normal thermal cycle and operation condition of compressor in stepless capacity regulation situation.The numerical simulation results of the valve dynamic and thermal cycle parameters are also verified by the stepless capacity regulation experiments in the type of 3L-10/8 reciprocating compressor.The experimental results agree with the numerical simulation results,which show that the theoretical models proposed are effective and high-precision.The proposed theoretical models build the theoretical foundation to design the real stepless capacity regulation system.
基金Supported by the projects of Beijing Municipal Educational Committee(KM200710016012)Beijing Municipal Office of Philosophy and Social Science(06BaJG0095)Beijing Municipal Organization Committee(20071D0501700235)
文摘This paper mainly studied how to determine the best location of the self-operated flow control valve at the heating system entrance.Since the location of regulating valve directly affects the pipe network performance,the simulation and analysis of pressure change in heating system was carried out with Computational Fluid Dynamics(CFD)software.The study shows the best location of regulating valve varies with the change of the supply and return pipe length when the heating area of each user is small,and when the heating area of each user is large(2000000~3000000 m2),the best location is on the supply pipe.
文摘Factors that cause the self-discharge in valve-regulated sealed lead-acid batteries are discussed and measures to inhibit the self-discharge are put forward.
文摘目的基于呼吸力学、心肌损伤、术后肺部并发症来探讨压力控制容量保证通气模式(PRVC)用于心脏瓣膜手术的价值。方法前瞻性纳入2024年1月至2025年10月徐州医科大学附属医院收治的择期行心脏瓣膜置换或修复术患者,严格纳入与排除标准后最终入组100例,以分层区组随机化方法按1∶1比例将患者分配至PRVC组(n=50)与对照组(n=50,容量控制通气模式),比较两组手术不同时间呼吸力学、氧合状态,测定术前术后肌酸激酶同工酶(CK-MB)、乳酸脱氢酶(LDH)、超敏肌钙蛋白T(hs-cTnT)、N端脑钠肽前体(NT-proBNP)水平,记录术后7 d内肺部并发症发生情况。结果不同时间点,PRVC组Ppeak、Pplat、△P均低于对照组,Cdyn高于对照组,存在组间与时间效应(P<0.05),Ppeak存在交互效应(P<0.05);不同时间点,PRVC组PaO_(2)、OI均高于对照组,RI、PA-aO_(2)低于对照组,存在组间与时间效应(P<0.05),其中PaO_(2)、PA-aO_(2)存在交互效应(P<0.05);术后6、24 h两组CK-MB、LDH、hs-cTnT、NT-proBNP均高于同组术前,PRVC组术后6、24 h CK-MB、LDH、hs-cTnT、NT-proBNP低于对照组,存在组间、时间及交互效应(P<0.05);PRVC组拔管时间、ICU停留时间及总住院时间短于对照组(P<0.05),术后总肺部并发症发生率显著低于对照组(P<0.05)。结论PRVC模式用于心脏瓣膜手术较VCV模式对呼吸力学、氧合影响更小,肺保护作用显著,可减轻心肌损伤,减少肺部并发症。
