Structured Methods for Improving Flow Measurement Accuracy in Pipelines
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MECHANICAL MEASUREMENTS STRUCTURED METHODS FOR IMPROVING FLOW MEASUREMENT ACCURACY IN PIPELINES G. N. Akhobadze
UDC 621.396.969.1
The issue of the development and creation of intelligent flow rate sensors of free-flowing and fluid substances carried on pipelines is considered timely during this era of digital conversion of production processes in industry and science. With this objective, this article presents new approaches to improving the measurement precision of microwave flow rate measuring units. Taking into account the characteristics of electromagnetic waves propagating along the pipeline, analysis was conducted of a wave scattered by the inhomogeneities of the medium being monitored. The features of the transformation of a polarized scattered wave, the limiting geometrical sizes of the pipeline, and optimization of the values of the true scattered signal, are revealed. The feasibility of picking up an information signal with orthogonal polarization of the scattered wave, and via a directional coupler, is substantiated. A methodology was developed to estimate measurement precision with an association to the signal-to-noise ratio at input to a processing unit. It has been shown that the results of the studies can be used in the cryogenic engineering industry to measure the volume and mass flow rates of liquid cryoproducts. Keywords: inhomogeneity, diffraction, scattering volume, the noise modulation, electromagnetic wave, signal collection, polarization, scattered wave.
Obtaining precise and continuous information on the flow rate of various media flowing on pipelines has great importance for automation of many industrial processes and their monitoring. At the current time, in measurements of the flow rate of substances in pipelines, the microwave method, based on using the characteristics of the propagation of electromagnetic waves of UHF range is the most popular [1]. However, precision measurements executed on the basis of this method do not always satisfy contemporary requirements. The author of this article has developed new principles for construction of primary transformers of microwave flow meters for fluid and friable media in order to improve the measurement precision of the flow rate in pipelines. In order to estimate the measurement precision of the flow rate, we will examine the nature of the propagation of the electromagnetic wave along the pipeline, and compare the errors caused by various modes of pick-up of the required information signal from the pipeline. In any homogeneous circular waveguide (pipeline) filled with a medium with inhomogeneities (particles), the voltage EZ of the electric field of the electromagnetic wave being distributed in the direction of the Z axis, can be written as [2]: EZ = Eme–iωt–γz, where Em is the amplitude of the electric field strength of the electromagnetic wave; ω is the angular frequency of oscillations, t is time, and γ is the propagation constant of the wave process under study. We will assume that the medium is immobile. Then a wave scattered by its p
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