As an increasingly popular flow metering technology, Coriolis mass flowmeter exhibits high measurement accuracy under single-phase flow condition and is widely used in the industry. However, under complex flow conditions, such as two-phase flow, the measurement accuracy is greatly decreased due to various factors including improper signal processing methods. In this study, three digital signal processing methods—the quadrature demodulation (QD) method, Hilbert method, and sliding discrete time Fourier transform method—are analyzed for their applications in processing sensor signals and providing measurement results under gas-liquid two-phase flow condition. Based on the analysis, specific improvements are applied to each method to deal with the signals under two-phase flow condition. For simulation, sensor signals under single- and two-phase flow conditions are established using a random walk model. The phase difference tracking performances of these three methods are evaluated in the simulation. Based on the digital signal processor, a converter program is implemented on its evaluation board. The converter program is tested under single- and two-phase flow conditions. The improved signal processing methods are evaluated in terms of the measurement accuracy and complexity. The QD algorithm has the best performance under the single-phase flow condition. Under the two-phase flow condition, the QD algorithm performs a little better in terms of the indication error and repeatability than the improved Hilbert algorithm at 160, 250, and 420 kg/h flow points, whereas the Hilbert algorithm outperforms the QD algorithm at the 600 kg/h flow point.
科里奥利质量流量计作为一种日益流行的流量测量仪表, 在单相流条件下表现出较高测量精度, 并在工业上得到广泛应用. 但在复杂流动条件下, 例如两相流工况, 由于各种因素 (包括不合适的信号处理方法), 测量精度会大大降低. 本文分析了3种数字信号处理方法——正交解调 (QD)、 希尔伯特和滑动离散傅立叶变换法, 分别用于处理传感器信号并在两相流工况下测试算法性能. 在此基础上, 分别改进了两相流条件下的信号处理方法. 在仿真中使用随机游走模型分别建立单相流和两相流工况下的传感器信号, 评估这3种方法的相位差跟踪性能. 基于数字信号处理器, 在其评估板上完成转换器程序设计. 将转换器在单相流和两相流工况下测试, 根据测量精度和算法复杂度评估改进的信号处理方法性能, 结果表明QD算法在单相流工况下性能最佳. 在两相流条件下, QD算法在160、 250和420 kg/h流量点的测量指示误差和重复性能优于改进的希尔伯特算法, 而希尔伯特算法在600 kg/h流量点的性能优于QD算法.
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The authors would like to thank the technology support from both KROHNE UK and China. We would particularly like to acknowledge the discussion with Prof. Tao WANG from the University of Kent.
Chunhui LI, Lijun SUN, Jiarong LIU, Yang ZHANG, Haiyang LI, and Huaxiang WANG declare that they have no conflict of interest.
Project supported by the Scientific Research Project of Shanghai Municipal Bureau of Quality, China and the Technical Supervision Foundation of China (No. 2018-05)
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Li, C., Sun, L., Liu, J. et al. Improvement of signal processing in Coriolis mass flowmeters for gas-liquid two-phase flow. Front Inform Technol Electron Eng 22, 272–286 (2021). https://doi.org/10.1631/FITEE.1900558
- Coriolis mass flowmeter
- Digital signal processing method
- Two-phase flow condition
- Quadrature demodulation
- Sliding discrete time Fourier transform (SDTFT)
- Hilbert transform