风排瓦斯的可燃极限及阻火问题研究

发布时间：2018-01-31 06:30

本文关键词： 风排瓦斯可燃极限绝热燃烧温度狭缝淬熄长度阻火器　出处：《中国科学技术大学》2014年硕士论文　论文类型：学位论文

【摘要】：风排瓦斯减排近年来逐步受到重视,为保障减排系统安全运行、消除安全隐患,需要对甲烷-氧气-氮气-二氧化碳的混合气体进行可燃极限研究,以及对混合气体被点燃后的阻火进行研究。因此,本文主要针对这两方面展开相关工作,为工业安全及阻火器设计提供参考。对于可燃极限方面,本文首先采用数值计算方法进行可燃极限预测,然后根据预测结果设计实验测量特定配比下的可燃极限。基于化学平衡方法,采用ChemKin软件求解不同配比下混合物的绝热燃烧温度。选取临界温度1450K作为混合气体是否可燃的判别标准,研究了氮气、氧化碳掺入对可燃极限的影响,并对甲烷与二氧化碳按特定比例混合的情况进行了可燃极限预测。在7L爆炸容器中,用光电传感器检测距离点火源100mm处是否有火焰信号,如果3次重复实验均未记录到火焰信号则认为混合物不可燃,否则认为是可燃的。据此对瓦斯突出后与空气混合的情况进行了可燃极限测量,并根据实验情况进行修正,得到了甲烷与二氧化碳按不同比例混合时在空气中的可燃极限。风排瓦斯减排系统中点火发生后,为阻止火焰在管道内传播,需要安装合适的阻火器。常用的波纹板型阻火器,其狭缝为三角形截面。不同截面形状的狭缝之间有对应的换算关系。本文通过对矩形截面狭缝内火焰传播淬熄的实验研究以及不同截面形状狭缝内火焰淬熄的数值模拟,为阻火器的选择及设计提供参考。在矩形截面激波管内,安装分布有不同宽度狭缝的装置,火焰经过加速段后进入狭缝。火焰进入狭缝时的速度通过改变预混气体中甲烷的含量进行调节。本文采用高速摄影记录下火焰在狭缝内的传播和淬熄过程,最终得到不同入口火焰速度下的淬熄长度-狭缝宽度关系,并给出了相应的经验公式。采用Fluent对火焰在狭缝内的传播和淬熄进行模拟,以1000K代表火焰阵面,作为火焰熄灭的临界温度,定性分析了不同入口火焰速度、不同狭缝宽度、不同截面形状对淬熄长度的影响。本文研究所得的瓦斯突出在空气中的可燃极限范围为工业安全提供了参考依据；得到的火焰在狭缝内的淬熄长度与火焰速度、狭缝宽度的关系,可以指导阻火器选择和设计,具有重要的应用价值。
[Abstract]:In order to ensure the safe operation of the emission reduction system and eliminate the hidden dangers, it is necessary to study the combustible limit of the mixture of methane, oxygen, nitrogen and carbon dioxide. Therefore, this paper mainly focuses on these two aspects of the relevant work to provide a reference for industrial safety and the design of fire arresters. For the flammable limit, this paper first uses the numerical calculation method to predict the flammable limit, and then designs experiments to measure the flammable limit under a specific ratio according to the predicted results. Based on the chemical equilibrium method, the adiabatic combustion temperature of the mixture was calculated by ChemKin software, and the critical temperature of 1450K was selected as the criterion for judging the flammability of the mixture. The influence of nitrogen and carbon oxide on the combustible limit was studied, and the combustible limit was predicted when methane and carbon dioxide were mixed in a specific proportion. In a 7L explosion vessel, the flame signal is detected by photoelectric sensor at 100mm distance from the ignition source. If the flame signal is not recorded in the three repeated experiments, the mixture is considered not combustible. Otherwise, it is considered combustible. Based on this, the combustible limit of the mixture of gas outburst and air is measured and modified according to the experimental results. The combustible limit of methane and carbon dioxide in the air was obtained when the methane and carbon dioxide were mixed in different proportions. In order to prevent the flame from spreading in the pipeline after the ignition occurs in the system of reducing gas emission from the wind, suitable fire arresters should be installed. The commonly used corrugated plate type fire arresters are needed. The slit is a triangular section. There is a corresponding conversion relationship between the slits with different cross-section shapes. In this paper, the experimental study of flame propagation quenching in the rectangular section slit and the number of flame quenching in the slit with different cross-section shapes are carried out. Value simulation. It provides reference for the selection and design of fire arresters. In the rectangular cross section shock tube, the device with different width slit is installed. The velocity of the flame entering the slit is adjusted by changing the methane content in the premixed gas. The flame propagation and quenching process in the slit is recorded by high-speed photography. Finally, the relationship between quenching length and slit width at different inlet flame velocities is obtained, and the corresponding empirical formulas are given. The flame propagation and quenching in the slit were simulated by Fluent. Using 1000K as the critical temperature of flame quenching, different inlet flame velocities were qualitatively analyzed. The influence of different slit width and section shape on quenching length. The flammable limit range of gas outburst in air obtained in this paper provides a reference for industrial safety. The relationship between the quenching length of flame in the slit and the flame velocity and slit width can guide the choice and design of the flame arrester and has important application value.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TD712

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