城市燃气用标准孔板流量计计量精度研究

发布时间：2018-05-21 01:41

本文选题：孔板流量计 + 计量精度　；参考：《西南石油大学》2014年硕士论文

【摘要】：标准孔板流量计因其结构简单,操作方便、技术成熟、性能稳定且无需标定,广泛应用于天然气计量。提高标准孔板流量计的计量精度,对控制因孔板流量计自身系统的原因造成的城市天然气系统输差和保证天然气交接计量公平性具有重要意义。利用FLUENT仿真软件进行流场模拟,通过模拟数据的定量分析,可为提高孔板流量计计量精度提供理论支撑和实际指导。首先分析了管径为DN80和DN150时流速、雷诺数、孔板自身的结构因素(直径比、斜角和孔板厚度)对孔板流量计流u系数的影响。通过模拟发现：(1)当流速在1-15m/s范围之内时,流出系数的相对误差都比较小,当流速大于15m/s时,流出系数的相对误差较大,因此,需将流速限制在15m/s以下；(2)直径比β在0.45～0.65之间时,流出系数的相对误差较小,建议孔板流量计直径比β尽量选择在0.45～0.65之间,最好选择中间值；(3)当斜角F=45°时模拟流出系数的相对误差最小,建议在使用孔板流量计时斜角F尽量为45°；(4)管径为DN80的孔板流量计的孔板厚度E为1～3mm时,流出系数的相对误差较小,当E4mm时模拟流出系数的相对误差较大,建议管径为DN80的孔板流量计在使用时孔板厚度E尽量小于4mm。在对流量计自身结构分析的基础上,结合国内外常见孔板流量计计量流程及整流装置,进一步分析计量系统对流量计计量精度的影响。讨论了孔板流量计上游的扩散管及汇管对天然气计量段流场影响的规律,确定孔板流量计在不同情况下直管段的安装长度。模拟结果表明：(1)在扩散管管路中安装19管束整流器孔板流量计前直管段长度为6倍管径,与不安装19管束整流器的扩散管相比孔板流量计前直管段长度缩短了11倍管径；(2)在进口相对的汇管管路中安装19管束的整流器,孔板流量计前直管段长度为8倍管径,与进口相对且无整流器的汇管管路相比孔板流量计前直管段长度缩短了17倍管径；在进口交错的汇管管路中安装19管束的整流器孔板流量计前直管段长度至少为10倍管径,与进口交错且无整流器的汇管管路相比孔板流量计前直管段长度至少缩短了20倍管径。本文主要利用FLUENT仿真软件对孔板流量计的计量精度进行研究,所得到的建议可以用于提高孔板流量计计量精度,也可以用于缩短孔板流量计前直管段长度,避免因站场的布局达不到标准的要求降低孔板流量计的计量精度。从而达到严格控制城市天然气系统因孔板流量计自身系统的原因造成的输差,保证天然气交接计量的准确性和公
[Abstract]:Standard orifice Flowmeter is widely used in natural gas measurement because of its simple structure, convenient operation, mature technology, stable performance and no need of calibration. It is of great significance to improve the measurement accuracy of the standard orifice plate Flowmeter to control the transportation difference of the urban natural gas system caused by the system of the orifice plate Flowmeter and to ensure the fairness of the measurement of the natural gas transfer. Using FLUENT software to simulate the flow field, the quantitative analysis of the simulated data can provide theoretical support and practical guidance for improving the measurement accuracy of the orifice plate Flowmeter. Firstly, the influence of flow velocity, Reynolds number and orifice plate structure factors (diameter ratio, angle and thickness of orifice plate) on flow coefficient of orifice plate Flowmeter is analyzed when the diameter of the tube is DN80 and DN150. It is found by simulation that the relative error of outflow coefficient is smaller when flow velocity is within the range of 1-15m/s, and when velocity is greater than 15m/s, the relative error of outflow coefficient is larger. Therefore, when the velocity of flow is limited below 15m/s, the diameter ratio 尾 is between 0.45 and 0.65. The relative error of efflux coefficient is relatively small. It is suggested that the diameter ratio 尾 of orifice plate Flowmeter should be chosen between 0.45 and 0.65 as far as possible, and the intermediate value should be chosen as low as 3.) when the angle is 45 掳, the relative error of simulated outflow coefficient is the smallest. It is suggested that when the orifice Flowmeter is used, the relative error of the efflux coefficient is smaller when the orifice thickness E of the orifice Flowmeter with the diameter of DN80 is 1~3mm, and the relative error of the simulated efflux coefficient is larger when the E4mm is used. It is suggested that the orifice plate Flowmeter with diameter of DN80 should be less than 4 mm in thickness. Based on the analysis of the structure of the Flowmeter, the influence of the metering system on the measuring accuracy of the Flowmeter is further analyzed by combining the flow chart of orifice Flowmeter at home and abroad and the rectifying device. The influence of the upstream diffusive tube and the sink tube on the flow field of the natural gas metering section is discussed, and the installation length of the straight pipe section of the orifice plate Flowmeter under different conditions is determined. The simulation results show that the length of the straight pipe section in front of the orifice plate Flowmeter of 19 tube bundle rectifiers is 6 times the diameter of the tube installed in the diffusion pipe line. Compared with the diffusion tube without the 19 tube bundle rectifier, the length of the straight pipe section in front of the orifice Flowmeter is reduced by 11 times the diameter of the tube). The rectifier of the 19 tube bundle is installed in the inlet relative manifold line. The length of the straight pipe section before the orifice Flowmeter is 8 times the diameter of the tube. The length of the straight pipe section in front of the orifice Flowmeter is reduced by 17 times compared with the inlet tube line with no rectifier, and the length of the straight pipe section in front of the rectifier orifice Flowmeter with 19 tube bundles installed in the inlet staggered pipe line is at least 10 times the diameter of the tube. The length of the straight pipe in front of the orifice Flowmeter is at least 20 times shorter than that of the inlet staggered and no rectifier manifold. In this paper, the measurement accuracy of orifice Flowmeter is studied by using FLUENT simulation software. The suggestions can be used to improve the metering accuracy of the orifice Flowmeter and to shorten the length of the straight pipe section in front of the Hole Plate Flowmeter. Avoid reducing the metering accuracy of orifice Flowmeter because the layout of the station is not up to the standard. Thus, the transportation difference caused by the orifice Flowmeter system in urban natural gas system can be strictly controlled, and the accuracy of natural gas transfer measurement can be ensured.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TH814

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