Study On Transient Thermal Structure Coupling And Impact Effect On High Temperature Quick Closing Butterfly Valve Sealing Pair

Quick closing butterfly valve is one of the most critical devices for handling system emergencies,and widely used in thermal power,nuclear power,metallurgy and petrochemical industries for cut off the emergency.Quick closing butterfly valve not only directly withstands high temperature and pressure load from the system medium,but also withstands the transient impact shock loads caused by the quick closing.With the development of emergency shutoff system towards maximization and high parameterized,the problem of strength and seat sealing are becoming increasingly prominent under the transient thermal load and transient impact load.The safety and reliability of the whole system depends on the long-term stable operation of the quick closing butterfly valve.A series of studies have been carried out in this paper,The main research contents are as follows:(1)An analytical method for sealing and impact of quick closing butterfly valve is proposed based on the Hertz theory and rotational dynamics theory,based on the method and considering the non-linearity of sealing contact,the force acting on the quick closing butterfly valve at the moment of closing is analyzed.The mechanical model of the seal pair under impact was established,which provides a theoretical basis for the numerical simulation of the quick closing butterfly valve.(2)Steady-state and transient thermal-structural coupling analysis of quick closing butterfly valve was finished by finite element multiphase field coupling method,it shows that the sealing performance of the quick closing butterfly valve meets the sealing requirements under both sealing test and design conditions.Based on the steady-state analysis,transient thermal-structural coupling analysis is carried out.The effects of six heating rates and twenty-seven heating and holding times on the sealing performance and structural strength of quick closing butterfly valves were studied.The results show that the heating rate,heating and holding time have great influence on the sealing performance and structural strength of the high-temperature quick-closing butterfly valve.The greater the heating rate,the stronger the thermal shock effect,then the greater the damage to the structure.In the process of heating the valve with different heating and holding time,the speed of the final stage heating time has the greatest influence on the sealing performance and structural strength of the quick closing butterfly valve.(3)Based on the implicit dynamic method,numerical simulation of transient dynamics of quick closing butterfly valve closing process was carried out.The instantaneous impact velocity and the total displacement of the quick closing butterfly valve are analyzed and compared with the theoretical results,the error is less than 5%,on this basis,the variation of the joint stress and the contact pressure on the sealing surface with impact time on the contact surface between butterfly plate and valve seat is studied.The results show that the effect of quick closing impact on butterfly disc is greater than that of seat.Further research has drawn the influence of key parameters such as impact velocity,impact area and over-closing angle on valve impact.The results show that the impact speed has the greatest impact on the quick-closing butterfly valve,followed by the over-closing angle and the smallest impact area.Through the above research,the theoretical basis and research method are provided for the research of transient thermal seal and structural strength and sealing performance of quick closing butterfly valve under impact load.It provides reference and guidance for optimum design of quick closing butterfly valve to avoid the harm caused by transient impact load.