Improvement of gas ultrasonic flowmeter measurement non‐linearity based on ray tracing method

Gas ultrasonic flowmeters are widely used in natural gas industry. When flow velocity achieves to tens of meters per second, the measurement error may appear significant non‐linearity with flow velocity increased. In order to solve this problem, reasons of non‐linearity are discussed based on the ray acoustics theory. First, the two‐dimensional ray tracing method is introduced and realised by Matlab. Second, both DN100 and DN500 diametric single path gas ultrasonic flowmeters are simulated, respectively. The ultrasonic wave propagation trajectory, transit time, path angle and receiving position of transducer are analysed with increasing flow velocities 1–50 m/s. Third, it is noted that the assumption of traditional velocity measurement model is not consistent with the actual ultrasound propagation. Therefore, a corrected model is proposed. Through comparing results of traditional and corrected models, the measurement error is reduced up to 4%, and the measurement non‐linearity is improved.