Compressed Natural Gas Mass Flow Meter Development

Compressed natural gas as a clean and efficient high-quality fuel, has been widely applied to people’s daily lives and economic spheres. Natural gas flow measurement is undoubtedly occupy an important position in its use. Due to the special nature of compressed gas,it is highly susceptible to the influence of external factors such as temperature、pressure, so the common volumetric gas flow meter generally faced that the measurement accuracy is not high. Natural gas as a commodity, and sometimes faces a huge amount of the transaction, so there is a very high demand on the measurement accuracy.This paper studies the natural gas flowmeter based on the Coriolis principle which achieved a direct mass measurement, eliminated the serious deviation of temperature, pressure and other factors on the measurement results,it has a very high measurement accuracy and reliability in a similar gas flow meter, and has a great prospect in the field of compressed natural gas metering.This paper focuses on the working principle of the Coriolis mass flowmeter, demonstrates its feasibility for compressed natural gas measurement. Before making the the flowmeter system design,this paper emphasis the importance of needs analysis according to the requirements of the standard product development process, and proposed a "SMART" principle for needs analysis, it has a practical value.Aiming to the development difficulties, this paper focuses on flow meter measuring tube drive, the phase difference detection methods, and a variety of instrument communication interface designMeasuring tube driven is used the mature closed-loop analog drive method to improve the skills of analog circuit applications. In the study of the phase difference detection method, we break the traditional DSP platform for data processing, use the MCU+FPGA platform to do phase difference detection, making full use of the advantages of the FPGA parallel processing, doing FFT algorithm、real-time signal acquisition and module control,however MCU use its rich set of peripherals to communicate and response to the interrupts timely, MCU+FPGA system platform greatly improve the entire flowmeter real-time and reliability of the instrument with the reference value. Account to the diversity of embedded instrumentation application, the flowmeter specially designed multiple communication interfaces, meetting the different needs of the external system as possible, we innovatively provided the gas flowmeter a CAN communication interface, facilitated its application in the field of industrial automation. This article also describes the most important part of the development of the flowmeter instrument calibration experimentation link,we stressed that a complete product development should be concerned about the details from the requirements of engineering practice again. Finally, experiments show that the designed flow meter in this paper is to meet the application requirements, provides a reference design for mass flow meter in the field of natural gas measurement applications.