Investigation of the flow velocity profile in a metering section of an invasive ultrasonic flowmeter

摘要

This paper describes a methodology for measurement and experimentally obtained results of local flow velocity components using invasive flow sensors (thermoanemometers) in the transit time ultrasonic flowmeter recesses. The investigations of the turbulent air flow (4000 < Re < 19 000 and flow rate from 14m{sup}3/h up to 55 m{sup}3/h) propagation through the metering section were performed. It was estimated that the flow profile in the pipe is asymmetric due to aerodynamic properties of the recesses. Therefore, due to air intake, the curve of the flow profile is inclined to the downstream recess. Bigger flow fluctuations were obtained close to the boundaries between walls of the pipe and cavities of the recesses. The flow velocity in the cavity of the recess has a complicated shape and depends on the flow velocity in the pipe. Near the surface of ultrasonic transducer the flow velocity is more than a few times bigger in the upstream recess. However, far away from the surface of the transducer, due to vortex motion in the cavity of the recess, the flow velocity is bigger in the downstream recess. The reduction in flow velocity in the metering section, due to recesses, was observed experimentally.