LNG低温球阀的模拟研究及热应力分析

发布时间：2018-06-20 04:30

本文选题：LNG球阀 + 传热　；参考：《兰州交通大学》2017年硕士论文

【摘要】：近年来,随着我国能源政策的调整,LNG(液化天然气)产业在我国得到了快速的发展,其使用量也在急剧增加。而在天然气的液化及液化天然气的运输、贮存等方面都需要大量的低温阀门,因此随着LNG产业的迅速发展,LNG低温阀门的需求量也会越来越大,所以LNG低温阀门也将在我国得到空前的发展。目前,传统的LNG低温阀门在设计上和安全性上都存在很多不足之处,如阀杆阀盖过长、无法安全泄压、过临界设计等问题。针对传统LNG低温阀门存在的上述问题,首先,本文从传热的角度分析,采用散冷翅片技术解决阀盖、阀杆过长问题。即在LNG超低温阀门长颈阀盖上加装一组散冷翅片,增大阀盖颈部与环境的换热面积,强化阀盖颈部与环境的对流换热,延缓并阻止冷量继续向上传递,以此达到降低阀盖和阀杆的高度,减小阀门启闭时阀杆的扭矩,延长阀门的受用寿命。其次,应用LNG自增压原理及低温预紧应力与输送压力匹配的原理,解决LNG球阀无法安全泄压及过临界设计问题。即在球体上安装LNG压力调节阀,用于导出LNG球阀启闭后盲区内的LNG,达到安全泄压目的,从而提高LNG过程控制效率和阀门的安全性;此外因LNG压力调节阀及时泄压,可降低阀门及系统的设计压力,提高阀门和系统运行的安全性与可靠性。最后,根据低温阀门设计手册及相关标准,对LNG球阀及LNG压力调节阀结构进行了合理设计,并基于传热学理论,结合数值模拟对所设计的带有散冷翅片的长颈阀盖及LNG压力调节阀进行了以下研究:(1)对带有散冷翅片的长颈阀盖结构组件建立物理模型。首先根据传热学相关理论,对LNG超低温球阀的保冷层厚度进行理论计算和模拟计算,之后将两种结果进行对比分析得出保冷层最佳厚度;其次运用Solidworks软件中的Simulation插件对长颈阀盖结构组件温度场分布进行模拟研究,得出散冷翅片位置最佳模型及片数最佳模型,最终确定出长颈阀盖结构最佳模型及加装散冷翅片后阀颈的实际高度。(2)根据流体力学相关理论,运用Solidworks软件中的Flow Simulation插件对LNG压力调节阀的流场进行模拟,得出其流场温度、压力、速度及密度分布规律。(3)根据传热学和热力学相关理论,采用热-结构耦合模型对长颈阀盖结构组件进行热应力分析,得出其应力、位移、应变变化规律;此外,对LNG压力调节阀的预紧弹簧进行了热应力分析,得出了其抗剪应力及轴向位移的变化,并进行了理论验证。本文基于理论计算和模拟分析的方法,以LNG低温球阀为研究对象,对如何降低长颈阀阀盖的高度,如何安全泄压等关键问题进行了分析和研究,并得出了一些对有实际意义的结论,为LNG低温阀门的发展提供参考。
[Abstract]:In recent years, with the adjustment of China's energy policy, LNG (liquefied natural gas) industry has been rapidly developed in China, its use is also increasing rapidly. In the aspects of liquefied natural gas and transportation and storage of LNG, a large number of cryogenic valves are needed. Therefore, with the rapid development of LNG industry, the demand for LNG cryogenic valves will also be increasing. So LNG low-temperature valve will also get unprecedented development in our country. At present, there are many shortcomings in the design and safety of the traditional LNG cryogenic valve, such as the valve stem cover is too long, the pressure can not be safely released, and so on. In view of the above problems existing in traditional LNG cryogenic valves, firstly, this paper analyzes the heat transfer from the point of view of the use of cold fin technology to solve the valve cap, the stem is too long. That is, add a group of cold fins to the long neck cover of LNG ultra-low temperature valve, increase the heat transfer area between the cover neck and the environment, strengthen the convection heat transfer between the cover neck and the environment, delay and prevent the further transfer of cold volume up, It can reduce the height of valve cover and stem, reduce the torque of valve stem when opening and closing, and prolong the service life of valve. Secondly, the principle of LNG self-pressurization and the matching principle of low-temperature pre-tightening stress and conveying pressure are applied to solve the problems of safe pressure relief and over-critical design of LNG ball valve. That is to install LNG pressure regulating valve on the ball, which can be used to derive LNGin in the blind area after opening and closing of LNG ball valve, so as to achieve the purpose of safely releasing pressure, thus improving the control efficiency of LNG process and the safety of valve, in addition, because LNG pressure regulating valve releases pressure in time, It can reduce the design pressure of valve and system, and improve the safety and reliability of valve and system operation. Finally, according to the low temperature valve design manual and related standards, the structure of LNG ball valve and LNG pressure regulating valve is designed reasonably, and based on the theory of heat transfer, Based on the numerical simulation, the physical model of the long necked bonnet with cooling fin and the LNG pressure regulating valve is studied as follows: 1) the physical model of the long necked valve cap with cold fin is established. Firstly, according to the theory of heat transfer, the thickness of insulation layer of LNG ultra-low temperature ball valve is calculated theoretically and simulated, and then the optimum thickness of insulation layer is obtained by comparing and analyzing the two results. Secondly, the simulation plug-in of Solidworks software is used to simulate the temperature field distribution of the long neck bonnet structure, and the optimum model of the position of the fin and the best model of the number of pieces are obtained. Finally, the optimal structure model of the long neck valve cover and the actual height of the valve neck after adding the distributed cold fin are determined. According to the relevant theory of fluid mechanics, the flow simulation plug-in Solidworks software is used to simulate the flow field of LNG pressure regulating valve, and the flow field temperature is obtained. According to the theory of heat transfer and thermodynamics, the thermo-structural coupling model is used to analyze the thermal stress of the long neck valve cover structural assembly, and the variation of stress, displacement and strain are obtained. The thermal stress analysis of pressure-spring of LNG pressure regulating valve is carried out, and the variation of shear stress and axial displacement is obtained, and the theoretical verification is carried out. Based on the method of theoretical calculation and simulation analysis, this paper analyzes and studies the key problems, such as how to reduce the height of the valve cover of long neck valve and how to release pressure safely, taking LNG cryogenic ball valve as the research object. Some conclusions of practical significance are obtained, which provide references for the development of LNG cryogenic valves.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE974.3

【参考文献】