【作者】 孙志强；

【导师】 周孑民； 张宏建；

【作者基本信息】 中南大学 ， 热能工程， 2004， 硕士

【摘要】 在热工、化工、冶金等诸多工业过程检测中，流量检测占有很高的份额，也是过程检测的一大难点。本论文主要研究目前发展势头十分良好的涡街流量计中的关键技术问题——旋涡频率的检测。 为了解决目前涡街流量计中存在的某些突出问题，使旋涡频率的检测更准确、抗干扰性更强，作者提出通过检测旋涡发生体后管壁处的差压信号的频率来检测涡街流量计旋涡频率的新方法。 基于这一基本思想，本论文采用理论分析—数值仿真—实验验证相结合的方法，以基于差压原理的涡街流量计旋涡频率检测方法为主要研究对象，以计算流体力学软件FLUENT为辅助研究工具，最后通过实验实现了利用管壁差压法对涡街流量计旋涡频率的准确检测。主要完成了以下工作： 1) 通过大量阅读国内外相关文献，对涡街流量计的发展历程、测量原理、组成结构、优缺点进行了概括，对国内外涡街流量计研究的现状和趋势进行了总结。 2) 评述了涡街流量计旋涡频率各种常用检测方法的特点，针对现有方法存在的不足，提出通过检测尾流中贴近管壁处的差压周期变化的频率来检测旋涡频率的新方法，即管壁差压法。并且对该方法的可行性做了理论上的分析，对实现的技术难点提出了解决方案。 3) 针对涡街流量计内旋涡产生和脱落的特点，建立了涡街流量计流场的数值仿真模型，应用FLUENT软件对涡街流量计流场进行了仿真，对流场中的几个特定点的静压波动情况进行了监测、分析和比较。 4) 在数值仿真结果的基础上，使用空气和水两种不同流动介质进行了实验，结果表明：管壁差压法能够准确检测涡街流量计旋涡频率，测量误差均小于仪表的允许误差。并对管壁差压取压孔位置的选取做了比较，发现管壁差压取压孔选取在距旋涡发生体迎流面较近位置较好。更多还原

【Abstract】 The flow measurement accounts for a large share of many process measurements in the industry, such as thermal engineering, chemical engineering and metallurgy. It is one of the greatest difficulties in process measurement technology. The dissertation is focusing on the detection of vortex frequency, which is the key technical problem of vortex flowmeter, a sort of promising and rapidly developing flowmeter.In order to solve some key problems of vortex flowmeter and to detect vortex frequency more accurately with stronger anti-disturbance, a new method for vortex frequency detection has been put forward by the author. By this method, the vortex frequency of vortex flowmeter is obtained by detecting frequency of differential pressure near duct wall downstream bluff body.Based on this idea, the combinative technique of theoretical analysis, numerical simulation and experimental verification is adopted. In the dissertation, detecting vortex frequency of vortex flowmeter based on differential principle is the main research object, Computational Fluid Dynamics(CFD) software FLUENT is used as auxiliary tool, and at last the method is realized by experiments. The main contribution and results are as follows:1) By reading home and foreign relevant literature extensively, the development process, measurement principle, configuration, merits and drawbacks of vortex flowmeter were summarized; its present status and progress tendency were generalized.2) The commonly used vortex frequency detection methods were commented. To overcome shortcomings of existing methods, a newmethod has been put forward. By this method, the vortex frequency of vortex flowmeter is obtained by detecting frequency of differential pressure near duct wall downstream bluff body. Its feasibility was theoretically analyzed and some proposals were brought forward to solve its technical difficulties.3) According to the characteristics of vortex yielding and shedding, a numerical simulation model for flow field in vortex flowmeter was established. Flow in vortex flowmeter was simulated with FLUENT, and static pressure on some given points near duct wall was monitored, analyzed and compared.4) On the basis of numerical simulation results, experiments were separately carried out using two different types of fluid, air and water. The results show that vortex frequency can be properly detected by duct-wall differential pressure method, and the errors are all less than the permissible error of the vortex flowmeter. Some efforts were also made to compare the performances of static pressure at different sampling positions, and it reveals that the better result is achieved by the sampling position near the against-flow face of bluff body.更多还原