| In the pipeline transportation trade of tradable gas,time-difference ultrasonic gas flow meters have been widely used worldwide.Compared with traditional gas flowmeters,ultrasonic gas flowmeters have the advantages of ensuring higher accuracy,capable of repeating measurements in both directions,and no moving parts inside,so it has become the internationally recognized first choice for gas flow measurement.The number of internal channels of the flowmeter can be one or more,so the ultrasonic gas flowmeter can be divided into: a monophonic ultrasonic gas flowmeter and a multichannel ultrasonic gas flowmeter.As a legal measuring instrument for international trade in fuel and natural gas,the ultrasonic gas flow meter has greater development space and broad application prospects around the world.However,while the ultrasonic gas flow meter has this series of advantages,there are also many problems that cannot be overcome at present,such as various uncertainties in the flow state of the gas to be measured.Unfortunately,China’s research on this project is still in the emerging stage,so we must continue to innovate to solve various problems encountered in the research process.This article focuses on the flow state of the gas to be measured in a flat single elbow pipe,and further studies the measurement effect of the multi-channel ultrasonic gas flow meter in this case.The computational fluid dynamics simulation method is used to establish a reliable numerical simulation analysis model to study the flow characteristics of the gas in the pipeline and the measurement effect of the ultrasonic gas flow meter.In addition,it is also blessed by various other means,such as by installing a honeycomb rectifier and the multi-channel layout method is used to improve the measurement equipment.In addition,specific research and innovation are carried out by specifically improving the measurement accuracy.The specific research results obtained so far are as follows:1.Research on improving the measurement accuracy of ultrasonic gas flow meters by installing honeycomb rectifiers.According to the design standards of the honeycomb rectifier and the requirements of the pipeline conditions,the honeycomb rectifier model required for this project is designed.The inside of the honeycomb rectifier is a regular hexagon with a length of 20 mm and an inner diameter of the hexagon of 2.5mm.The honeycomb rectifier is installed at the front end of the inlet of the flowmeter.By comparing the flow velocity contour map of the gas to be measured in the pipeline without the rectifier and the pipeline conditions when the rectifier is installed,it is found that the installation of the rectifier can reduce errors that may exist during the measurement process,and thus can improve the measurement accuracy.2.Improve the measurement accuracy by increasing the number of channels and designing new channel arrangements.A new algorithm for calculating the cross-section flow velocity of a cross-channel arrangement is proposed;the influence of the ultrasonic gas flow meter on the measurement error of the ultrasonic gas flow meter when the cross-five channel arrangement is adopted and the upstream choke is a flat single elbow;and the effect of this cross-five-channel installation angle on the accuracy measurement of the gas flow to be measured.The calculation results show that the influence of the installation angle on the error is not obvious and irregular;in the case of a fixed installation angle,when the flow velocity is less than 2m / s(low flow velocity),the error at the straight pipe section after the bend is larger at 1 to 2D,does not meet the accuracy requirements;as the length and flow rate of the straight pipe section increase,the error decreases significantly.The straight pipe section after the bend can meet the precision requirements at 3 to5 D.(The required accuracy range is ± 2% in the low speed region and ± 1% in the high speed region). |
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