气体流量测量时密度补偿的研究
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摘要
气体流量测量常用的密度补偿是温度压力补偿。由于实际气体与理想气体之间的差异程度是用压缩因子描述的,因此,只考虑温度压力引起的密度补偿是不够的,一些气体的压缩因子因温度和压力的改变而偏离,当压缩因子的偏离值不等于1时,其对气体流量的影响就会超过精度的要求,从而产生误差。为此,针对通用的实际气体、天然气和蒸汽讨论了各种压缩因子的计算方法,并在计算机控制装置实施。因此,实际应用时,对气体流量测量必须要考虑压缩因子的影响。尤其是常用的蒸汽计量应用,提供的示例说明,当温度和压力改变时,密度的改变引起的精度有很大的改变,在实际应用时必须考虑。
The commonly used density compensation method for gas flow measurement is temperature and pressure compensation.Since the difference between the actual gas and the ideal gas exists, which is described by a compression factor, it is not correct only to consider the density compensation caused by temperature and pressure.When the deviation of the compression factor caused by the temperature and pressure is not equal to 1, the error will be introduced when measuring the gas flow rate. For this reason,the calculation methods of various compression factors for general gas, natural gas and steam were discussed in this paper, and meantime,the implementation in computer control devices were described. From the example presented, especially in measurement of steam flow, the effect of compression factor must be taken into account in practical application.
The commonly used density compensation method for gas flow measurement is temperature and pressure compensation.Since the difference between the actual gas and the ideal gas exists, which is described by a compression factor, it is not correct only to consider the density compensation caused by temperature and pressure.When the deviation of the compression factor caused by the temperature and pressure is not equal to 1, the error will be introduced when measuring the gas flow rate. For this reason,the calculation methods of various compression factors for general gas, natural gas and steam were discussed in this paper, and meantime,the implementation in computer control devices were described. From the example presented, especially in measurement of steam flow, the effect of compression factor must be taken into account in practical application.
引文
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[8]GB/T 17747.2-2011.天然气压缩因子的计算.第2部分:用摩尔组分进行计算[S].
[9]BS EN ISO 12213-2:2009.Natural gas-Calculation of Compression factor.Part 2:Calculation using molar-Composition analysis(ISO 12213-2:2006)[S].
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[2]臧福录,应金良.石油化工工艺工程师必读,第一册-物性、数据处理和优化[M].北京:中国石化出版社.1998.
[3]施海云.化工热力学[M].上海:华东理工大学出版社.2007.
[4]Smith J M,Van Ness H C,Abbott M M.Introduction to Chemical Engineering Thermodynamics.7th Edition.刘洪来,等译[M].北京:化学工业出版社.2008.
[5]彭瑜,何衍庆.IEC61131-3编程语言及应用基础[M].北京:机械工业出版社.2009.
[6]Chopey N P.Handbook of Chemical Engineering Calculations.3rd Edition.朱开宏译[M].北京:中国石化出版社.2005.
[7]周人,何衍庆.流量测量和控制实用手册[M].北京:化学工业出版社.2013.
[8]GB/T 17747.2-2011.天然气压缩因子的计算.第2部分:用摩尔组分进行计算[S].
[9]BS EN ISO 12213-2:2009.Natural gas-Calculation of Compression factor.Part 2:Calculation using molar-Composition analysis(ISO 12213-2:2006)[S].
[10]The IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam,J.Eng.Gas Turbines&Power122,150-182(2000)[S].
[11]Honeywell.Experion-Steamprop-pin.www.honeywellprocess.com.2014[Z].
[12]Emerson.Flow metering(AGA-SI)function block.Delta Vbooks online.2012[Z].