天然气大流量计量装置管路流场对检定的影响分析

Analysis of Influence of Pipeline Flow Field on Verification of Natural Gas Large Flow Metering Unit

在国家天然气计量站大流量检定系统的应用过程中,由于工作需开启不同的检定管路,所实施的核查级标准表和被检工作表具有多样化的组合方式,且工作流量较大,其检定结果准确度非常易受介质流场不稳定性的影响。为此,基于典型大流量检定装置的流程模型,通过采用FLUENT模拟不同检定口径在不同流量点下的不同工作组合模式,计算得到不同管路工作条件下的天然气体积流量测定误差值。研究分析结果表明:计量站的标准表不同组合方式工作条件对检定工作质量具有不同的影响,工作管路的口径越大而造成的介质流动不稳定性产生的检定结果准确度影响越明显,通过改善检定系统中标准表与检测表的管容和增大进、入口管路的间距可降低检定误差,从而一定程度地消除介质流动状态带给计量检定的影响,有效提高天然气计量检测的量传水平。

In the application process of the large flow verification system of national gas flow metering station,due to the need to open different calibrating pipelines in the work,the verification level standard table,the checked work table with a variety of combinations and the large working flow,the calibration accuracy is easily affected by the flow state of the medium. Therefore,based on the simplified flow model of the typical large flow verification device,the different working combinations of different calibrating calibre under different flow points are simulated by using FLUENT. In that way,the measurement of volume flow of natural gas and measurement error of natural gas in different working conditions are calculated. The reasonable distance between the standard table and the test meter and the tube capacity are analyzed. So the influence of the flow state of natural gas to the measurement verification is eliminated to the maximum.