Mathematical model of time difference for Coriolis flow sensor output signals under gas-liquid two-phase flow

The features of Coriolis mass flow sensor output signal are analyzed, and a mathematical model of the time difference for the signals is built to evaluate the rationality and limitation of the proposed correction method when Coriolis mass flowmeter (CMF) is used to measure the gas-liquid two-phase flow. According to the experimental data of Coriolis mass flow sensor output signals under the gas-liquid two-phase flow condition, the time differences of the sensor output signals are extracted as a characteristic quantity to obtain the time difference sequence by adopting a digital zero-crossing detection method. The distribution pattern of the time difference sequence is analyzed with the probability density function, and the mathematical model of the time difference sequence is built by the correlation analysis. The mathematical model consists of a stable component and a fluctuating component. Correcting the stable component can improve the measurement accuracy of cumulative mass flow rate, and reducing the fluctuating component can enhance the measurement stability of instantaneous mass flow rate. Although the stable component cannot be completely corrected because its variation is nonlinear with the flow rate and drop in density, and the fluctuating component can only be reduced to a certain extent due to the real-time processing limitation of the instrument, CMF can provide relatively reliable measurement results of the liquid mass flow rate when the gas-liquid two-phase flow occurs.