Reduction of Hydrodynamic Flow Measurement Error of Chordal Ultrasonic Flowmeter

Abstract

In this work, ways of reducing the hydrodynamic flow measurement error of chordal ultrasonic flowmeter for the distributed location schemes of their acoustic paths are investigated. The method of calculating optimal location coordinates of the acoustic paths of ultrasonic flowmeters is considered in detail, using the analytical-empirical power law of the distribution of the velocity of the undistorted flow. As a result of the work, the authors calculated the optimal arrangement of acoustic paths for chordal schemes of two-and three-path ultrasonic flowmeters. It was established that optimization of the location scheme of the acoustic paths of chordal ultrasonic flowmeters allows reducing the hydrodynamic flow measurement error to the value of 0.05 % (for two-path flowmeters) and 0.1 % (for three-path). The developed approach is convenient when designing multipath ultrasonic flowmeters and their research in laboratory conditions. Keywords: ultrasonic flowmeter; hydrodynamic error; power law; acoustic paths; chordal scheme. The purpose of the workSensitivity of ultrasonic flowmeters (USMs) to the profile of flow velocity is described in many domestic [1][2] and foreign [3-6] scientific works. Thus, in the case of USM under the conditions of undistorted flows, a hydrodynamic flow measurement error (HDE) occurs [5], and under the conditions of perturbation of the structure of the velocity profile of various local pipe fittings, an additional flow measurement error (AE) arises due to the distortion of the flow structure [6].The purpose of this work is to investigate one of the ways to reduce the HDE of the USM. Presentation of the materialThe occurrence of the HDE of the USM is due to the fact that the velocity of the flow, calculated from the value of passing of sound vibrations over and against the flow along its acoustic paths (APs) u L , is always different from the actual value of the flow velocity of the averaged over the diameter of the measuring pipeline (MPL) [5]. The relationship between these velocities does not depend on the angle of inclination of the AP to the axis of flow, but is determined by the number of Re and the location scheme of the APs USM (the number of APs and the way of their spatial arrangement).Currently, a significant number of location schemes of APs USM are proposed. We have carried out the classification of known location scheme of APs USM (see Fig. 1) and analysis of possible values the HDE of the USM for different location scheme.