Abstract
A new structure is proposed for a DN25-type ultrasonic gas flow meter with a V-shape double sound channel arrangement. The flow field characteristics are analyzed including velocity curves for the four channel lines, velocity profiles for different cross-sections of the flow meter, and streamlines of the transducer channel sections. The metering characteristics of the flowmeter are measured using a Venturi nozzle device. When the pipeline flow rate is less than 2.26 m/s, the pipe installation does not have a significant effect on the velocity profile and the velocity in the channel lines. However, the error in the low-flow region is large, and the flow distortion directly affects the measurement accuracy. When an ultrasonic gas flow meter with an accuracy class of 1.5 is used with pipes containing a single or double bend upstream, the linear error doubles, low-flow error becomes a negative deviation, and reference error in the low-flow region becomes approximately 700%–949%. The installation structure of the first pair of transducers also affects the signal propagation of the transducers behind it. Therefore, it is critical to process the ultrasonic signal according to the flow field distribution and adopt different weighted algorithms to obtain accurate pipeline flow rates to improve the measurement accuracy of the ultrasonic flow meter.
Highlights
The natural gas market is developing rapidly; there is an increasing demand for accurate and reliable natural gas measurements
Under condition III, the velocity curve was more distorted, similar to a ladder, the velocity along the z-axis was greater than the average flow velocity, and the negative velocity along the z-axis was significantly lower than the average flow velocity. This occurred due to secondary vortex flow caused by the double bend
The proposed ultrasonic gas flow meter has two sound channels consist of four channel paths, and the channel velocities were computed for each of the three conditions, as shown in Figures 8 to 10
Summary
The natural gas market is developing rapidly; there is an increasing demand for accurate and reliable natural gas measurements. Most ultrasonic gas flow meters use the transit-time method, where the time interval of acoustic propagation is measured and used to calculate the fluid velocity in the sound channel, which is converted to the pipe velocity. This study presents a design for a twochannel ultrasonic gas flow meter with DN25 diameter, and the flow field and measurement characteristics under different pipe installation conditions are investigated.
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