超声脉冲反射法和激光吸收光谱法同步测量流动液膜厚度

Synchronous thickness measurements of flowing liquid film on horizontal surface by ultrasonic pulse-echo and laser absorption spectroscopy methods

液膜流动现象在工业过程中广泛存在,对流动液膜厚度测量方法的测量研究至关重要。首先利用已知液膜厚度的标准具(100~1000μm)对超声脉冲反射法和激光吸收光谱法精度进行验证;结果表明,超声脉冲反射法测量液膜厚度的平均测量误差为1.07%,激光吸收光谱法测量液膜厚度的平均测量误差为1.29%。同时结合两种方法对流动液膜进行研究,结果表明,当液膜在低速/中速/高速流动时,两种方法测量流动液膜的平均厚度吻合良好,平均厚度差值分别为16.59、16.26、13.36μm,流动液膜厚度的标准方差的相对偏差分别为0.29%、7.71%、25.37%,且在三种不同速度下两种方法测得在1s的周期内液膜波动次数一致。

Because of common existence of liquid film flow in industrial processes, it’s crucial to study methods for measuring thickness of moving liquid film. Measurement accuracy of both ultrasonic pulse-echo and laser absorption spectroscopy methods was validated by calibration standards of known film thicknesses （100-1000 μm）. The coefficient of variation was 1.07% for ultrasonic pulse-echo method and 1.29% for laser absorption spectroscopy method. Then, thickness of flowing liquid film was measured by these two methods. The average film thicknesses were in good agreement for two methods when liquid film flow was at low/medium/high velocity. At three corresponding velocities, the difference of average film thicknesses between these two methods were 16.59, 16.26 and 13.36 μm, and the relative standard deviation of film thickness was 0.29%, 7.71% and 25.37%, respectively. Furthermore, both methods detected same number of fluctuations of liquid film within 1 s cycle at three different velocities.