Analysis of the Accuracy of Liquid Flow Measurements by the Means of Ultrasonic Method in Non-standard Measurements Conditions

The article presents the results of ultrasonic flow measurements performed after the hydraulic elbow. Ultrasonic flowmeter with applied head set in accordance with the Z-type was used to carry out the measurements. The results of flow measurements after the hydraulic elbow were referenced to measurements made on a straight section of the pipeline before the elbow, where the flow was stabilized, and the velocity profile was symmetrical with respect to the pipe-line axis. Measurements, with the maintaining a constant volumetric stream flow, were made for 12 different angles of the flowmeter head settings in 16 distances from the hydraulic elbow. The results of the measurements were compared with the velocity values obtained from the flow simulation performed in the ANSYS CFX program. On the basis of the comparison of the measurement results with the simulation results, and also based on the analysis of the velocity profiles, it was found that at the appropriate angle of the head setting, measurements can be made using the ultrasound method at a distance smaller than the one described in the standards. The optimal location of the measurement can be selected on the basis of a computer flow simulation, which is a representation of geometry and measurement conditions. This action scheme can be used in the flow measurements, which are carried out after the obstacle which is disturbing the flow, in the pipelines with large diameters (for example power plants, electrical power and heating plant, chemical industry) where finding a straight section with a length of 15–20 pipeline diameters is problematic.