Research On Structure Analysis And Phase Difference Algorithm Of Coriolis Mass Flowmeter

Mass flow is the mass of fluid flowing through the pipe cross section per unit time,Coriolis mass flowmeters,hereinafter referred to as Coriolis flowmeters,are instruments that directly measure mass flow.Due to its high measurement accuracy,good stability and other advantages,market demand has increased in recent years.However,the accuracy and stability of domestic Coriolis flowmeters are still relatively large compared to similar foreign products.To improve the performance of Coriolis flowmeter is mainly to solve the two major difficulties of structural design and phase difference detection.This article will focus on these two aspects of research,the focus of which is the use of fluid-solid coupling analysis method for Coriolis flowmeter structural analysis.The main research contents of this topic are as follows:The Coriolis flowmeter modal analysis and bidirectional fluid-solid coupling analysis method are introduced.The natural frequencies and modes of each order are obtained through modal analysis,and the natural frequency is used as the excitation frequency.The Coriolis flowmeter is analyzed using the bi-directional fluid-solid coupling method to calculate the phase difference.The fluid-solid coupling experiment was completed to verify the reliability of Coriolis flowmeter analysis with bi-directional fluid-solid coupling at different flow rates.The focus is on structural performance studies of Coriolis flowmeters through modal analysis and bi-directional fluid-solid coupling analysis: The modal variation law of measuring tubes with different structures was analyzed,and the Coriolis flowmeter was analyzed by the method of fluid-structure coupling modal analysis.Based on the fluid-structure interaction modal analysis of different pipeline pressures and different fluid flow rates,the effect of pressure and velocity on the modal state is concluded.Based on the calculation of bi-directional fluid-solid coupling for different tubular shapes,the influence of structural changes on the phase difference and time difference of the Coriolis flowmeter was concluded.Fluid-solid coupling dynamics analysis was performed on measuring tubes with different inclination angles to study the velocity,stress,and deformation of fluids and solids.Developed a Coriolis flowmeter phase difference detection algorithm: Establish Coriolis flowmeter output signal model;select the Butterworth filter,ellipse filter,FIR filter and wavelet transform to filter the time-varying signal respectively,and the results show that the Butterworth bandpass filtering method is optimal.The phase difference detection of the signals is performed by digital correlation principle,discrete Fourier transform and Hilbert transform,respectively.Studies have shown that the accuracy of the phase difference detection of the three methods drops significantly during non-integer sampling.Therefore,this paper proposes an improved Hilbert transform to detect the phase difference.Through the detection effects of different signal-to-noise ratio noise interferences,different non-integer samples,and different phase difference detection results,it is shown that the improved Hilbert transform has the best detection effect.Through field tests,the correctness of the Coriolis flowmeter's fluid-structure coupled modal analysis method was verified.In addition,the output signal of the Coriolis flowmeter is collected,and the phase difference of the actual output signal is detected by applying the improved algorithm of this paper and the original algorithm.Experiments show that the improved algorithm of this paper has better detection effect.