基于虚拟仪器的超声Doppler管道低流速测量

传统的超声Doppler流量计在管道流量测量中会遇到无法判断流速方向和低流速测量困难等问题。该文基于虚拟仪器平台,将Doppler信号解调到15kHz的中心频率,并运用Zoom-FFT算法对其进行高精度选带频谱分析,然后进行加权平均频率估计,得到被测流体的平均流速及方向,实现了一个新的超声Doppler流量测量系统。超声波探头外夹安装在充满流体介质的不锈钢管道上进行流量测量,实验结果表明该系统不仅可以正确分辨流速方向,还能测量低达0.02m/s的流速,在判断流速方向和低流速测量上比传统超声Doppler流量计更为有效。

Virtual-instrument based ultrasonic Doppler flowmeter for low velocities measurement

Conventional ultrasonic Doppler flowmeters can not easily measure low flow velocities and directions. A low speed Doppler flowmeter was developed using virtual-instrument technology to demodulate the echo signal to an intermediate frequency of about 15 kHz. A Zoom-FFT estimator is used to analyze the spectrum of the demodulated Doppler shift signal with high frequency resolution, and a weighted averaging algorithm is used to calculate the average Doppler frequency. The flow direction and average velocity can then be determined from the results. The new Doppler system was tested with transducers clamped on a stainless-steel pipe to measure the flow. The results indicate that the system can measure the flow direction and velocity at velocities as low as 0.02 m/s. Therefore, the system is more effective than a conventional ultrasonic Doppler flowmeter for measuring low flow velocities.