Signal processing of coriolis mass flowmeters under gas-liquid two-phase flow conditions

Under two-phase flow conditions, the performance of Coriolis mass flowmeters is significantly affected. A critical signal processing technique in Coriolis flowmeters is the estimation of resonance frequency and phase difference from sinusoidal vibration signals. This paper reviews three typical digital signal processing methods used to calculate phase difference, including Quadrature Demodulation, Hilbert Transform and Discrete Fourier Transform (DFT). These three methods are compared using simulated signals based on experimental results under two-phase flow conditions up to high GVFs (gas volume fractions) and low flow rate. The results indicate that, under two-phase flow conditions in particular for high GVFs and low flow rate, the three methods are affected in different degrees, and may need further modification to achieve better results under two-phase flow conditions.