流场因素对超声波气体流量计测量精度影响

Influence of flow field factors on measurement accuracy of ultrasonic gas flowmeter

采用超声波时差法进行气体流量测量时,流场快速变化或者管段结构造成的局部二次流、涡流及速度分布不对称等情况,是影响超声波气体流量计测量精度的关键因素。针对此问题,以DN50超声波气体流量计为研究对象,利用CFD对超声波流量计不同风速下进行数值模拟,并在低速回流风洞测试段进行风速测试实验。将计算流体力学与信号处理相结合,分析换能器安装结构引起的流速特性变化,以及流场扰动对超声波回波信号的影响。研究表明,在0~3 m/s流速范围内,随风速增大,超声波测速受流场变化与声束扰动影响也增大,同时超声波回波信号质量越差,流量计风洞测速实验验证了数值模拟的合理性。

When the ultrasonic time difference method is used to measure the gas flow,the rapid change of the flow field or the local secondary flow,the vortex and the asymmetric velocity distribution caused by the pipe section structure are the key factors that affect the measurement accuracy of the ultrasonic gas flowmeter.In view of this,the DN50 ultrasonic gas flowmeter is taken as the research object,and CFD(computational fluid dynamics)is used to conduct numerical simulation of ultrasonic gas flowmeter at different wind speeds,and the experiment of wind speed test is carried out at the section of the low⁃speed reflux wind tunnel test.By combining CFD and signal processing,the velocity characteristic change caused by installation structure of transducer and the influence of flow field disturbance on ultrasonic echo signals are analyzed.The results show that,in the flow velocity range of 0~3 m/s,with the increase of wind speed,the influence of flow field changes and acoustic beam disturbance on ultrasonic velocity measurement is increased,and the quality of ultrasonic echo signal is worse.The wind tunnel velocity measurement experiment of flow meter verifies the rationality of numerical simulation.