Abstract
Ultrasonic wave carries the information for flowing velocity when it is propagating in flowing fluids. Flowrate can be obtained by measuring the propagation time of ultrasonic wave. The principle of transit-time ultrasonic flowmeters used today was based on that the velocity is uniform along the propagation path of the ultrasonic wave. However, it is well known that the velocity profiles in a pipe are not uniform both in laminar flow and turbulent flow. Emphasis on the effects of velocity profiles across the pipe on the propagation time of ultrasonic wave, theoretical flowrate correction factors considering the real velocity profile were proposed for laminar and turbulent flow to obtain higher accuracy. Experiment data of ultrasonic flowmeter and weighting method are compared to verify the proposed theoretical correction factors. The average relative error of proposed correction factor is determined to be 0.976% for laminar flow and 0.25% for turbulent flow.
Highlights
Flow measurement is necessary in engineering field for fluid metrology and process control [1,2].A variety of flow measurement techniques were invented, such as differential pressure flowmeter [3], float flowmeter [4], volumetric flowmeter [5], electromagnetic flowmeter [6], and vortex shedding flowmeter [7]
The flowrate Q1 is measured by the ultrasonic flowmeter, while Q2 is measured by the weight discharged within a certain period of time
From Equations (15) and (18), it is clearly indicated that the theoretical correction factor for laminar flow is 0.75
Summary
A variety of flow measurement techniques were invented, such as differential pressure flowmeter [3], float flowmeter [4], volumetric flowmeter [5], electromagnetic flowmeter [6], and vortex shedding flowmeter [7]. The common disadvantage of these flow measurement techniques is that the fluid properties are tightly restricted due to direct contact with the flowmeters. In order to overcome the above disadvantage, non-contact ultrasonic flowmeter was developed, which is immune to temperature, causticity, and conductivity of measured fluid [8]. There is a great variety of ultrasonic flowmeters for measurement of liquid and gas flow [9,10,11,12]. Due to the simplicity of the measurement principle, the ultrasonic transit-time method is one of the most common techniques in industrial applications
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