Improvement of signal processing in Coriolis mass flowmeters for gas-liquid two-phase flow

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.

Flow-induced vibration characteristics of the U-type Coriolis mass flowmeter with liquid hydrogen

Compared with liquid nitrogen(LN_(2))and water,the density of liquid hydrogen(LH_(2))is more than one order of magnitude smaller,which leads to significantly different flow-induced vibration characteristics in the coriolis mass flowmeter(CMF).Based on the Euler beam theory,the complex set of equations of fluid-solid interactions for the U-type pipe Coriolis flowmeter with LH_(2)is solved.The calculation results are firstly validated by comparing the dimensionless frequency,displacement,and twist mode shape with the theoretical and experimental results in the other publications with water and kerosene as the working fluids.Then,the results of dimensionless frequency,phase difference,and time lag for LH_(2)are compared with those for LN_(2)and water,and the effects of the dimensionless flow velocity,sensor position,and the radius of the curved pipe are analyzed in detail for LH_(2).Results show that the time lag of LH_(2)is an order of magnitude smaller than that for LN_(2)or water.The excitation frequency for LH_(2)is much larger than that for LN_(2).Effects of geometric parameters on the time lag are also analyzed for the three fluids and the results contribute to the design optimization of a CMF for LH_(2).