Structural Velocity Measurement of Gas-Liquid Slug Flow Based on EMD of Continuous Wave Ultrasonic
Structural Velocity Measurement of Gas-Liquid Slug Flow Based on EMD of Continuous Wave Ultrasonic
复制标题
基于连续波超声EMD的气液弹流结构速度测量
DOI：
10.1109/tim.2018.2826858
复制
发表时间：
2018
影响因子：
5.6
通讯作者：
Dong Feng
中科院分区：
文献类型：
--
作者：
Shi Xuewei;Tan Chao;Dong Xiaoxiao;Dong Feng
气液段塞流广泛存在于许多工业过程中。段塞流的结构速度对于流体力学建模、科学研究和工艺保证具有重要意义。为了无创地测量段塞流的结构速度，将连续波超声多普勒传感器和电导传感器相结合，分别获得多普勒频移信号和持水率。由于相分数和速度的剧烈波动，段塞流不同区域的散射产生不同的多普勒频移。因此，多普勒信号是包含段塞流结构信息的多尺度波动信号。为了提取结构速度，利用经验模态分解将多普勒频移信号分解为多个本征模态函数（IMFs），并利用互相关法确定反映信号本质特征的主要IMFs。通过结合水含率信号，对主IMFs进行短时傅里叶变换（STFT），确定特定主IMFs与段塞单元结构之间的相关性。最后，从STFT结果中提取液塞流鼻部、液塞流和液膜的速度。为了验证模型的有效性，基于Dukler模型计算了理论结构速度，结果与提取的速度吻合较好，平均相对差为3.34%。为了进一步验证，采用二次阈值法计算了总体流量。与参考总容积流量相比，平均绝对百分比误差为3.53%。
Gas-liquid slug flow widely exists in many industrial processes. The structural velocities of slug flow are important for fluid mechanics modeling, scientific researches, and process assurance. To measure the structural velocities of slug flow nonintrusively, a continuous wave ultrasonic Doppler sensor and a conductance sensor are combined to obtain the Doppler shift signal and water holdup, respectively. Due to the intense fluctuation of phase fraction and velocity, the scatters in different regions of the slug flow produce different Doppler shifts. Therefore, the Doppler signal is a signal with multiscale fluctuations containing structural information of slug flow. To extract the structural velocities, the Doppler shift signal was decomposed into several intrinsic mode functions (IMFs) by the empirical mode decomposition, and the main IMFs that reflect the essential characteristics of the signal were determined by cross correlation method. By combining water holdup signal, the short-time Fourier transform (STFT) was applied to the main IMFs to determine the correlation between the specific main IMFs and the structure of a slug unit. Finally, the velocities of the liquid slug nose, the liquid slug, and the liquid film were extracted from the STFT results. To validate the proposed model, theoretical structural velocities were calculated based on Dukler's model, and the results showed good agreement with the extracted velocities with the average relative difference of 3.34%. For further validation, the total volume flow rate was calculated using a quadratic threshold method. Compared with the reference total volume flow rate, the mean absolute percentage error was 3.53%.