【作者】 张建华；

【导师】 宋学官； 王宣平；

【作者基本信息】 大连理工大学 ， 机械工程（专业学位）， 2022， 硕士

【摘要】 一体式弹性热阀瓣具有密封性能良好,结构可靠性高等优点,代表着安全阀弹性热阀瓣技术的先进水平,其工作性能对安全阀乃至整个压力系统的稳定运行有着重要影响。本文通过数值模拟和试验研究的方法对安全阀关闭状态下的密封状态、安全阀回座冲击下的阀瓣受力情况进行了研究,并通过代理模型技术和遗传算法对一体式弹性热阀瓣进行了结构优化设计,旨在提高密封性能及阀瓣的结构强度。希望本文能够给安全阀弹性热阀瓣的设计人员提供一些参考,下面是本文的研究内容:(1)建立了安全阀关闭状态下的热力耦合有限元模型,对不同介质压力下阀瓣受力情况、密封面的接触状态及接触压力进行了研究。在介质压力从0MPa逐渐增加至整定压力的过程中,阀瓣的最大应力呈现先减小,再增大的趋势,密封面的最大接触压力的变化趋势也是相同的。同时在介质压力增大的过程中,阀瓣与阀座的实际接触位置由密封面的外圈过渡到内圈,即密封中径逐渐减小,这种接触状态的变化趋势是柔性阀瓣的特点,这个特点也使得柔性阀瓣的结构更有利于安全阀密封。(2)搭建了安全阀回座冲击试验平台,并进行了安全阀回座冲击试验,通过传感器及数据采集软件,对试验进行数据采集。试验测得的介质压力为仿真计算提供了边界条件,同时试验结果中的阀瓣位移及冲击力也验证了仿真方法的可行性。由于试验条件的限制,只能进行低压(0.85MPa)刚性阀瓣的回座冲击试验,但所确定的有限元仿真模型对本文所研究的高压(18.5MPa)柔性阀瓣的仿真计算同样适用,间接性的验证了高压柔性阀瓣仿真计算的合理性,通过仿真计算与试验研究结合的方法,最终得到了阀瓣回座冲击时的最大应力值,该应力超过了阀瓣材料的屈服极限,需要对阀瓣结构进行优化设计。(3)使用代理模型及遗传算法对阀瓣结构进行了优化设计,优化目标是保证阀瓣结构强度的同时,尽可能提升安全阀的密封性能。首先确定了密封性能指标——密封强度W,此参数同时考虑了接触压力和接触宽度对密封性的影响。优化的阀瓣结构参数为:密封唇内侧最大距离、密封面宽度、密封唇厚度、密封唇内侧关键角度和密封唇内侧关键半径,通过最优拉丁超立方(OLHS)方法进行取点,使用克里金(KRG)方法构建目标函数和约束的代理模型,所构建的代理模型R~2均超过0.95。然后通过遗传算法在样本空间内找到最优的阀瓣结构,最后通过仿真验证优化结果的精度。结果表明,优化后的阀瓣密封强度提升了78.09%,阀瓣的最大应力降低了14.96%。更多还原

【Abstract】 The integrated elastic thermal valve disc has the advantages of good sealing performance and high structural reliability.It represents the advanced level of the pressure relief valve(PRV)elastic thermal valve disc technology.Its working performance has an important impact on the stable operation of the safety valve and even the whole pressure system.By means of numerical simulation and experimental research,this paper studies the sealing state of the PRV when it is closed and the stress of the valve disc under the impact of reseating of the PRV,and optimizes the structure of the integrated elastic thermal valve disc through surrogate model technology and genetic algorithm,in order to improve the sealing performance and structural strength of the valve disc.It is hoped that this paper can provide some references for the designers of the elastic thermal disc.The research content of this paper is as follows:(1)The thermal mechanical coupling finite element model under the closed state of the PRV is established,the stress of the valve disc,contact state and contact pressure of sealing surface under different fluid pressures are studied.It is found that the maximum stress of the valve disc decreases first and then increases in the process of the fluid pressure gradually increasing from 0MPa to the set pressure,and the change trend of the maximum contact pressure of the sealing surface is the same.At the same time,in the process of increasing the fluid pressure,the actual contact position between the valve disc and the valve seat gradually transits from the outer diameter of the sealing surface to the inner diameter,that is,the sealing pitch diameter is gradually decreasing.The change trend of this contact state is the characteristic of the flexible valve disc,which also makes the structure of the flexible valve disc more conducive to the sealing of the PRV.(2)A PRV reseating impact test platform was built and a PRV reseating impact test was carried out.The test data were collected through sensors and data acquisition software The fluid pressure measured in the test provides boundary conditions for the fluid structure coupling simulation calculation.At the same time,the valve disc displacement and impact force in the test results also verify the feasibility of the fluid structure coupling simulation method.Due to the limitation of experimental conditions,only the reseating impact test of low-pressure(0.85MPa)rigid valve disc can be carried out,but the determined finite element simulation model is also applicable to the simulation calculation of high-pressure(18.5MPa)flexible valve disc studied in this paper.It indirectly verifies the correctness of the simulation calculation of high-pressure flexible valve disc.Through the combination of simulation calculation and experimental research,the maximum stress of valve disc reseating impact is finally obtained.The stress exceeds the yield limit of the disc material,so it is necessary to optimize the disc structure.(3)The surrogate model technology and genetic algorithm are used to optimize the valve disc structure.The optimization goal is to improve the sealing performance of the PRV as much as possible on the premise of ensuring the structural strength of the valve disc.Firstly,the sealing performance evaluation index-sealing contact strength W is determined,which can take into account the influence of contact pressure and contact width on sealing performance.The optimized design variables are five key parameters of the valve disc: the maximum distance inside the sealing lip,the width of the sealing surface,the thickness of the sealing surface,the sealing inclination and the key radius of the sealing lip.The optimal Latin hypercube(OLHS)method was used to pick points,and the kriging(KRG)method was used to construct proxy models with objective functions and constraints.The R~2 of the constructed proxy models were all over 0.95.Then the optimal valve disc structure is found in the sample space by genetic algorithm.Finally,the accuracy of the optimization results is verified by simulation.The results show that the sealing contact strength of the optimized disc is increased by 78.09%,and the maximum stress of the disc is reduced by 14.96%.更多还原