轴流式止回阀关闭过程的可靠性数值模拟

发布时间：2018-01-11 17:10

本文关键词：轴流式止回阀关闭过程的可靠性数值模拟　出处：《北京工业大学》2012年硕士论文　论文类型：学位论文

【摘要】：止回阀作为管路系统中的关键部件，其性能优劣、寿命长短、工作可靠度高低直接影响到泵机组及管道的安全。在对阀门进行可靠性分析时，传统可靠性试验方法往往需要耗费大量的时间和金钱，既不经济且实现困难。所以必须探求新的试验方法，即利用目前较为成熟的液压类产品的数值仿真技术，在试验前通过有效的建模仿真来减少试验次数、降低试验费用等。在阀门关闭过程中，往往很容易发生水击问题；阀门的运动极其复杂，涉及到液动力和弹簧力相互作用的流固耦合问题，，不能用简单的方法反映其运动规律。本文以轴流式止回阀二维模型为研究对象，利用编程给定阀瓣运动的位移、速度、加速度和液动力等参数之间的相互关系，与CFD进行结合，从流场分析的角度分别对静水条件下和停泵条件下的轴流式止回阀关闭过程进行了数值模拟。并结合可靠性理论进行阀门关闭过程中产品的可靠性数值分析，对未来开展针对液压产品可靠性试验与评估提供可以借鉴的方法。论文的主要研究内容如下：（1）UDF及动网格技术很好的再现了二维轴流式止回阀在静水条件和停泵条件下的非稳态关闭过程。止回阀在关闭过程中，阀瓣瞬时响应并关闭阀门；阀瓣运动速度先开始增加到最大速度，之后开始下降直至关闭。（2）停泵后阀门关闭过程中，作用在阀瓣上的流体力先缓慢增加到某一值后波动下降，下降过程缓慢；在阀门即将完全关闭时，流体力出现振荡变化：流体力正反方向跳跃交替，且数值逐渐增大，最终流体力达到最大使阀门关闭。阀门关闭过程中，随着阀瓣的移动，阀内流场一直在变化。流场压力在阀瓣前后变化始终最大；阀门进口端和出口端的压差一直在增大；流体最大速度始终出现在阀瓣与阀体之间的流道中，在流体流经阀瓣后，由于流速较大的原因产生了漩涡，并出现回流，但回流速度不大；由于阀瓣的运动引起阀瓣附近的流体出现漩涡，且湍动能比下游流道出现的湍动能大。（3）运用Monte Carlo法进行可靠性概率分析和可靠性灵敏度分析，参考可靠性灵敏度分析结果，弹簧刚度、阀门直径和阀瓣厚度对系统可靠度影响较大。其中增加弹簧刚度、降低阀瓣厚度，可以提高系统的可靠度，从而实现系统的优化设计。
[Abstract]:Check valve as a key component in the pipeline system, its performance, life span, working reliability directly affect the pump unit and pipeline safety. In the valve reliability analysis. Traditional reliability test methods often cost a lot of time and money, which is not economical and difficult to realize. Therefore, we must explore a new test method, that is, using the more mature numerical simulation technology of hydraulic products. The effective modeling and simulation are used to reduce the number of experiments and reduce the cost of the tests before the experiment. In the process of valve closing, water hammer problem is always easy to occur. The movement of valve is extremely complex, which involves the fluid-solid coupling problem between hydraulic force and spring force, and can not be reflected by a simple method. In this paper, the two-dimensional model of axial flow check valve is taken as the research object. By programming the displacement, velocity, acceleration and hydrodynamic parameters of disc movement, the CFD is combined. From the point of view of flow field analysis, the closed process of axial flow check valve under static water condition and pump stop condition is numerically simulated, and the reliability numerical analysis of valve closure process is carried out by combining reliability theory. The main contents of this paper are as follows: (1) the methods of reliability test and evaluation for hydraulic products can be used for reference in the future. The UDF and dynamic grid technology can reproduce the unsteady state closure process of two-dimensional axial flow check valve under the condition of static water and stop pump. During the process of closing the valve, the valve disc can respond and close the valve. Disc motion increases first to maximum speed and then begins to decline until closed. (2) in the process of valve closing after pump stop, the flow force acting on the disc increases slowly to a certain value and then fluctuates and drops slowly; When the valve is about to be completely closed, the flow force oscillates: the flow force jumps alternately in the positive and negative directions, and the value increases gradually, finally the flow force reaches the maximum value to make the valve close. With the movement of the disc, the flow field in the valve is always changing. The pressure of the flow field always changes the most before and after the disc. The pressure difference between the inlet and outlet of the valve has been increasing; The maximum velocity of the fluid always appears in the passage between the disc and the valve body. After the fluid flows through the disc, the vortex is produced because of the high velocity of flow, and the reflux is not very fast. Because of the movement of the disc, the fluid around the disc appears whirlpool, and the turbulent kinetic energy is larger than that of the downstream passage. 3) using Monte Carlo method to analyze reliability probability and reliability sensitivity, referring to the result of reliability sensitivity analysis and spring stiffness. The valve diameter and disc thickness have great influence on the system reliability, in which increasing spring stiffness and reducing disc thickness can improve the reliability of the system and realize the optimal design of the system.
【学位授予单位】：北京工业大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TH134

【参考文献】