Influence of Flow Disturbances behind the 90° Bend on the Indications of the Ultrasonic Flow Meter with Clamp-On Sensors on Pipelines

Abstract

The subject matter of the article concerns velocities/flow rate measurements in the area of disturbed flows-behind the 90° bend. They were conducted by means of an ultrasonic flowmeter with clamp-on sensors on pipeline, for water and two different Reynolds numbers of 70,000 and 100,000, corresponding to two velocities of approximately 1.42 m/s and 2.04 m/s. The tests were carried out at 12 distances from the disturbance. Sensors on the circumference of the pipeline were mounted 30° each. The correction factor values were calculated for the given measurement geometry. The measurements have shown that the values of this coefficient are always greater than 1, which means that the ultrasonic flow meter understates the speed values. They also showed that already at a distance of 8 nominal diameters from the disturbance, the correction factor does not exceed 1.02, so the measurement errors are within the maximum permissible error (MPE) of a typical ultrasonic flow meter. For distances less than eight nominal diameters from the disturbance, not taking the correction factor value into the account can lead to systematic errors of up to 10.8%. Studies have also proved that in each measurement plane behind the disturbance there are two mounting angles for the ultrasonic sensors, 60° and 240° respectively, for which the correction factor values are minimal. Additionally, using the laser Doppler anemometry (LDA) method, velocity solids were determined at individual distances from the disturbance, and the projections of velocity blocks on the appropriate plane represented velocity profiles and indicated the distances from the disturbance at which these profiles stabilise.

Experimental Determination Influence of Flow Disturbances behind the Knife Gate Valve on the Indications of the Ultrasonic Flow Meter with Clamp-On Sensors on Pipelines

“…The K* factor is a dimensionless parameter reflecting changes in the velocity distribution on the section between the ultrasonic sensors. The K* factor is used by the authors in many articles on ultrasonic flow measurement [ 7 , 9 , 11 , 12 ]. …”

“…For that reason, there are many limitations in the use of instruments of a certain type in given conditions which deviate from the standard conditions accepted and described in normative acts (norms, instructions). This was the reason for the authors of this article to perform a comprehensive study connected to the use of the ultrasonic method of measurement in customized measurement conditions, i.e., behind different elements which disturb the flow [ 6 , 7 , 8 , 9 ]. Hydraulic elbows of different sizes and shapes, as well as a throttle, were the obstacles in the available literature.…”

Influence of elbow pipe on gas measurement accuracy of ultrasonic flowmeter and improvement

“…Direct -pointing and reflection are the two most common mono layout. Using in-line arrangement, vortex flow and cross flow resistance is weak, and reflection type track decorate can effectively overcome the negative influence of complex flow field, the length of the track at the same time increase the measurement of transit time is more accurate, so in small pipe flow measurement using this arrangement can play to the advantages of large [7]. In this paper, the channel is used in the reflective channel layout.…”