Flow Metering of Gases Using Ultrasonic Phased-Arrays at High Velocities

Abstract

We present an ultrasonic transit-time gas flow meter (UFM) based on our 40 kHz 8 8 phased-array. Besides single element receivers, the UFM uses×a waveguide-based phased-array with an inter-element spacing of half-lambda as sender, capable of electronic beam steering for an extra-large flow velocity range. The sound drift effect limits the measurement range of conventional UFMs, i.e. we compensate the sound-drift effect using beam steering. The UFM features a maximum measurable flow velocity up to 100 m s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> . The flowmeter body is a fully 3D-printed pipe with a length of 800 mm and an inner diameter of 315 mm. The receivers are arranged at inclination angles of 45 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">◦</sup> . The flowmeter is tested on a test rig for ventilation fans according to ISO 5801:2017(E). At zero flow velocity, the SNR for the downstream receiver is 64.1 dB. Without compensation of the sound-drift effect, at the full flow velocity of 100 m s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> , the SNR drops down to 18.0 dB (downstream). When the compensation is enabled, the SNR raises by 18.7 dB (downstream) at full flow velocity. These numbers proof that the usage of a phased-array in a UFM can significantly increase the maximum measurable flow velocity. Further advantages are the possibility of multi-path measurements for an improved meter factor, i.e. eccentric flow meter configurations.