| CMF (Coriolis mass flow meter) can measure mass flow, volume flow, density and so on, has been widely used in petroleum, chemical, food, energy, Pharmaceuticals, trade and other industries. This paper involves several cutting-edge issues about the research areas of CMF, including signal processing methods of straight-tube CMF, applications of CMF in batch flow measurement and applications of CMF in three-phase flow measurement system without separation.It is difficult to achieve high accuracy measurement for straight-tube type CMF because of its characteristics of high resonance frequency and small phase difference. To solve this problem, two sets of algorithms, i.e., digital zero-crossing detection and DTFT considering negative frequency contribution, have been studied deeply to evaluate their measurement accuracy and processing speed. A CMF transmitter has been developed by using a TMS320C6726 chip as the core microprocessor to meet the requirement of real-time processing. The electrical signal tests and water flow calibrations of the transmitter are performed. Experimental results show that the developed transmitter possesses stable zero point, high processing speed and accuracy. And the experimental calibration results show that matching micro-bend flow tube of 15mm diameter, the mean error of the flowmeter is less than 0.07% with the turn-down ratio of 15:1, and the repeatability is better than 0.02%; matching triangular-bend flow tube of 25mm diameter, the mean error of the flowmeter is less than 0.08% with the turn-down ratio of 11:1, and the repeatability is better than 0.03%.Dynamic response speed is not fast enough when the CMF used in measuring batch flow. To solve this problem, the signal processing method is improved to shorten the dynamic response time; and experimental device had been designed to measure batch flow and test the batch measurement accuracy.Three-phase flow including oil, gas and water flows is difficult to be measured, and its measurement accuracy is very low. If using separating measurement method, it will be of the complex procedures and high costs of the separated measurement device. To solve this problem, a three-phase flow measurement experimental device based on CMF had been designed. The composition of three-phase flow can be measured and calibrated without separation. The detailed measurement principles, structure diagram of the device and calibration scheme are present to provide a reference for domestic scholars in this field. |
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