Introduction

Accurate flow measurement has become increasingly important for many key industrial sectors including oil & gas, aerospace, automotive, chemical and pharmaceutical process industries, as well as various military and government operations. While ultrasonic flow measurement techniques offer numerous advantages such as non-intrusive design, wide turndown ratio, fast response time, there still remain many challenges that need to be overcome while making ultrasonic measurement techniques both accurate & reliable, especially for applications in gas flow measurements. In practical transit-time gas flow measurement applications there is often a change in the received signal shape between upstream and downstream signals, which will cause an error in the transit time and transit time difference calculation, both of which are fundamental to the flow calculation.

Flow measurement facilities

A dedicated air flow test-bench experiment has been setup to enable transit time ultrasonic data collection under varied flow conditions. The test setup comprises of pairs of conventional air coupled ultrasonic transducers pairs, with nominal operating frequency of 200kHz, positioned strategically on a pipe (approx. 6 inch inner diameter) in such a way that ultrasonic signal (both up and down stream) from a variety of propagation path layout is recorded. This multi-path measurement approach is extremely important to mitigate against the presence of swirls or any asymmetric flow profiles that are typically found in a gas flow. The flow itself is created by a powerful suction fan down-stream from the metering setup and varied flow profiles are introduced by the way of introducing bends and pipe size variations up-stream.

Air flow test-bench schematic

A dedicated closed loop water flow facility was obtained from Prof Roger Baker and rebuilt at Warwick at the end of summer 2013. The following timelapse video shows the progress of the build over a period of a couple of weeks.

Timelapse Video. Few flowrig installation days.

CAD fly through video of the CIU water flow rig, with a prototype wetted ultrasonic flow meter using low cost transducers, done as part of a final year undergraduate project - an excellent example and indication of the quality of work that our undergraduates can produce. [Thanks to the group - Lewis McGregor, Franek Zajak, James Fotheringham, Nikal Gulati, Jamie Grifferty, Seetal Pankhania, Dan Willoughby and Dan Edwards]