管道煤气热式质量流量计研制及标定技术研究

Development and calibration of thermal gas mass flowmenter for pipe gas

为解决目前燃气计量中仪表下限以下测量精度差或无法计量而造成漏计等问题 ,基于强制对流换热理论和热线风速计原理 ,研制成功了新型气体质量流量计 .仪表中敏感元件和测速加热元件采用了微丝结构 ,测量线路中应用了副电桥技术 ,较大地提高了仪表的灵敏度 ,降低了仪表的死区 .由于煤气介质较特殊 ,影响因素多 ,采用了实流标定 .通过大量实流标定实验 ,分析了煤气导热系数对标定结果的影响 ,并提出了一种新的补偿方法 .经实验测试 ,仪表可做到几乎零下限 。

In order to solve the gas flowmeter's lower limit problems,such as low accuracy at lower limit or the small gas flow leakage,a novel gas flowmenter based on the compelled forced convection principle and the principle of hot-wire anemometer has been successfully developed,in which,micro hot-wires are used as sensitive elements,a resistive heater is used for measurement of gas flow rate,and a support bridge technology is adopted in the measuring circuit.The sensitivity of the meter has been improved and the dead space in it has been reduced.Pipe gas is an especial substance,its measurement precision is affected by many factors,the flowmeter must be calibrated before use.Based on lots of the actual process gas flow calibration experiments,and the analyses of the affection of thermal convection modulus,a new compensating method is proposed.Throungh these experiments,the instrument's lower limit nearly reach zero,successfully solve the problem of low flow rates leakage.