Research of the metrological model of optic-thermal method of natural gas flow measurement

Abstract

The article substantiates the importance of research aimed at the development and study of contactless method of natural gas flow measurement.On the basis of the developed mathematical model of contactless optic-thermal method of gas flow measurement and key provisions of the uncertainty theory the metrological model analysis is made. The component of the combined standard uncertainty due to the uncertainty of uncorrelated input parameters of the measurement equation is researched and evaluated. The dominant components and the ways of reducing their impact on the combined standard uncertainty are selected. The greatest contribution to combined standard uncertainty of the method makes the uncertainty of interference fringes number measurement, the uncertainty of the distance between the cross-sections of the pipeline measurement and uncertainty of the coefficient determination, which characterizes the velocity distribution of the gas flow.The components of combined standard uncertainty (thermophysical parameters of the gas and the pipeline material, the geometric characteristics of the pipeline), which are correlated with each other due to the temperature dependence, are identified. The uncertainty budget of correlated measurements is compiled. Quantitative assessment showed that the correlation between certain input parameters does not have large impact on the combined standard uncertainty of the measurement.Analysis of the metrological model of the contactless optic-thermal method of gas flow measurement allowed estimating the relative combined standard uncertainty of the method and substantiating the perspective applications of the method for measuring gas flow in large diameter pipelines.