基于数值仿真的涡街流量传感器优化_毕业设计论文.doc

毕业设计论文
基于数值仿真的涡街流量传感器优化
Optimizing vortex flow meter based on simulation
摘要
涡街流量传感器是一种速度式流量传感器,它依据流体振动频率与流速有对应关系的原理工作。涡街流量传感器输出的频率信号与流速成正比,且不受流体组分、密度、压力、温度的影响,具有可靠性高、压力损失小、量程比宽、结构简单牢固等优点,被广泛应用于管道流量测量。
传统涡街流量传感器旋涡发生体形状的确定,是基于频率与流速线性度的考虑,忽略了发生体形状对频率信号强度的影响,导致传统发生体形状涡街流量传感器在低流速下输出的频率信号不足以被检测,影响涡街流量传感器在低流速下的应用。
数字式仪表的大量应用,使对频率与流速的线性度要求已不再主要,涡街信号的强弱决定了涡街流量传感器在低流速下的应用。改进涡街流量传感器旋涡发生体形状,对提高涡街流量传感器在低流速下的应用价值,具有重要意义。
本论文主要完成了以下的工作:
利用计算流体仿真软件,运用两种仿真模型对涡街流场进行仿真计算,确定Realizable k-ε模型为涡街流场模拟的最佳仿真模型。
通过改变梯形旋涡发生体尾缘夹角角度、平行部分长度对旋涡发生体形状进行仿真研究。确定在水介质和空气介质涡街流场中能产生最强涡街信号的旋涡发生体最佳几何尺寸。
通过比较尾缘后部不同检测位置信号变化,对涡街信号最佳检测位置进行仿真研究。确定在水介质和空气介质涡街流场中涡街信号最佳检测位置。
针对几种尾缘夹角角度的旋涡发生体进行实流试验。验证了仿真结论,并提出在低流速测量中的最佳旋涡发生体形状。
关键词:涡街流量传感器;旋涡发生体;数值仿真;
ABSTRACT
Vortex flowmeter is a kind of velocity-type flowmeter; working depends on the linearity of frequency and velocity. The frequency signal, outputting from vortex flowmeter, is direct ratio with velocity, and have nothing to do with the form or density or pressure or temperature of the flow, so it has high stabilization, low pressure loss, wide measurement range and simple structure. It is widely used in pipeline flow measurement.
The confirmation of bluff body for traditional vortex flowmeter is based on the linearity of frequency and velocity. The influence of the bluff body shape to frequency signal was ignored. It results in the low velocity signal could not be measured by traditional bluff body, which effected the usefulness of vortex flowmeter in low velocity measurement.
The widely used of digital meter makes the key change to the strength of signal, not the linearity of frequency and velocity anymore. The strength of vortex is important to the usefulness of vortex flowmeter in low velocity. Optimizing vortex flowmeter bluff body shape has important meaning of the usefulness of vortex flowmeter in low velocity measurement.
The mainly research works of this thesis are as following.
Using putational fluid dynamics models. ensured a certain