Design of pipeline flow meter based on ultrasonic time difference method

Abstract

The traditional gas flow meter used in gas pipelines in coal mines has problems like blocking failure. The flow meter based on ultrasonic time difference method has high measurement accuracy and good repeatability of measurement results. However, it is not suitable for gas extraction pipeline flow measurement. Moreover, it is difficult to design ultrasonic driver circuit and signal processing circuit separately. Based on the characteristics of coal mine gas extraction pipelines, a pipeline flow meter based on ultrasonic time difference method is designed. In the context of fixed propagation distance, the propagation time of ultrasonic waves emitted by ultrasonic transducer in the fluid is functionally related to the gas flow rate. The product of the flow rate and the cross-sectional area of the pipeline is the flow, hence the pipeline gas flow is indirectly obtained. The pipeline flow meter uses a low-power microprocessor STM32F103 as the core control element, and uses the automatic differential flight time measurement method inside the time-to-digital conversion chip MAX35104 to calculate the ultrasonic wave downstream and upstream flow propagation time. The gas flow rate, instantaneous flow and cumulative flow are calculated through the propagation time. The test results show that the maximum absolute error of the pipeline flow meter based on ultrasonic time difference method is 0.15 m/s and the maximum repeatability error is 0.17%. The performance meets the requirements of level 2 accuracy in JJG 1030—2007 Verification Regulations Ultrasonic Flowmeters and also meets the requirements of the ultrasonic wind speed sensor basic error requirements in MT 448—2008 Wind speed sensor for mine.

Keywords

• gas extraction
• pipeline flow
• ultrasonic time difference method
• gas flow rate
• ultrasonic propagation time