Research And Implementation Of Coriolis Mass Flowmeter For Measuring Two Special Flow Rates

Coriolis mass flowmeter has been widely used in industry applications because it can measure the mass flow rate directly and obtain the fluid density simultaneously.This paper focuses on the two special flow conditions encountered in the practical application of Coriolis mass flowmeter,namely the measurement of compressed natural gas and the measurement of gas-containing liquid flow.The corresponding signal processing algorithm,driving and error correction technologies were studied,and a transmitter system was developed to effectively solve the problem of Coriolis mass flowmeter measuring the compressed natural gas and the gas-containing liquid.From the aspects of calculation amount,resource occupation,dynamic response speed and actual cooperation with different driving methods,the two most practical signal processing methods in the current Coriolis mass flowmeter are analyzed and compared,and the application occasion of the two algorithms is indicated.The analysis results show that the DTFT algorithm is suitable for the measurement of steady single-phase flow in large elbow-type flow tubes with low frequency,and it is suitable for the occasions of high response speed,such as the measurement of compressed natural gas.The zero-crossing detection algorithm is suitable for the measurement of smooth single-phase flow in micro-bent flow tubes with high frequency,and it is suitable for the measurement of gas-containing liquid flow.For the problem that measuring compressed natural gas by Coriolis mass flowmeter,a mathematical model of the sensor output signal in the aerated process was established.Based on the mathematical model of the signal,the existing DTFT algorithm is improved from the perspective of dynamic response speed.The dynamic response speed of the algorithm is improved,and the accuracy of small flow measurement is ensured,which is suitable for the measurement of compressed natural gas.The algorithm is implemented in real time in a DSP-based digital Coriolis mass flow transmitter,and gasator calibration experiment is performed for the transmitter.The experimental results show that when measuring compressed natural gas,the developed transmitter can achieve 0.2 accuracy.For the problem that measuring gas-containing liquid flow by coriolis mass flowmeter,the best signal processing,driving and error correction methods are given,and the dual-core transmitter based on DSP and FPGA is developed.The support vector machine method based on grid search is adopted to establish the mass flow measurement error model,and then the error model parameters are transplanted into the dual-core transmitter to realize on-line real-time correction.After correction,the accuracy of the Coriolis mass flow meter for measuring gas-containing liquid flow is improved.