【作者】 任少峰；

【导师】 王玉杰； 陈先锋；

【作者基本信息】 武汉理工大学 ， 采矿工程， 2012， 博士

【摘要】 随着国家经济的高速发展和能源结构的调整,可燃性气体得到了广泛应用,是工业发展必不可少的燃料与原料,且今后将进一步发展以液化石油气和天然气为主的工业、生活能源结构。但是可燃性气体在开采、输送、贮存、加工和使用过程中或者因为管道泄露,可燃性气体爆炸事故时有发生,特别是煤矿经常发生瓦斯爆炸事故,造成重大的财产损失和人员伤亡。根据可燃性气体发生爆炸的环境和场所,选择开口泄爆管道对可燃性气体的传播规律和其内在机理进行研究,为防止可燃性气体爆炸事故和减小爆炸事故带来的危害提供依据。预混火焰在开口泄爆管道内传播,是一个高速、流动的动力学过程,受到许多因素的制约和影响,导致火焰阵面结构、火焰传播特性参数发生不稳定的改变,因此课题将从甲烷-空气预混火焰传播的几个影响因素进行实验和理论分析。首先建立了一套长方体开口泄爆管道实验平台,利用高速纹影系统清晰的捕捉到预混火焰在不同实验工况下的动态传播过程和火焰阵面结构的变化,并以此得出了火焰阵面的传播速度；利用建立的数据采集系统测试了预混火焰在传播过程中的流场压力值并得到了对应的压力上升速率。针对预混火焰传播特性的参数值,进行理论分析和数值模拟验证,揭示无约束泄爆管道内预混火焰传播的动力学机理和传播规律。研究了不同泄压口比率下,预混火焰在长50cm的开口泄爆管道中的传播特性,得出了随着泄压口比率的增大,预混火焰的传播速度峰值随之增大,而流场压力和压力上升速率的峰值随之降低,并得出了他们与泄压口比率的关系式。当泄压口比率小于30%时,预混火焰的传播速度和流场压力峰值随泄压口比率急剧变化；而大于30%时,传播速度和流场压力峰值的变化都很小,故泄压口比率30%可看作是可燃性气体在开口泄爆管道的一个拐点比率,并可作为泄爆设计的重要参考值。通过三种不同当量比浓度的预混气体,研究得出在开口泄爆管道内,当量比浓度为1.26(富燃)时,速度和压力值均达到最大值,且达到最大值所需的时间也最短,这主要是因为开口导致空气进入管道内,当量比浓度发生改变,使其接近或等于化学当量比浓度,管道内可燃性气体反应较充分,单位体积内化学放热量增大,从而加快了火焰传播速度和增大了流场压力。而最佳浓度即当量比浓度为1.06时则处于“贫燃”状态,火焰传播速度和压力峰值降低。从而得出在开口泄爆管道内的当量比浓度是一个可变参数。同一长方体障碍物的截面不同,即阻塞比率的不同,会导致火焰传播特性的变化,阻塞比率越大,火焰燃烧爆炸产生的速度和压力就越大,因此应尽量将长方体障碍物的最小截面与火焰传播方向相同。长方体障碍物到点火端的距离与火焰的传播速度和流场压力峰值存在着一个先增大后减小的指数关系,得出了长径比在5.8～6.3之间为“位置危险区域”,火焰的传播速度和压力峰值最大。长方体障碍物的数量与火焰的传播速度和流场压力峰值存在着一个先增大后减小的变化规律,也就是在障碍物的截面一定的条件下,障碍物的长度与火焰传播特性的参数存在着这样的规律。更多还原

【Abstract】 Combustible gas is the absolutely necessary fuel and raw material of industrial development, and would be widely used in future with the rapid development of national economy and the adjustment of energy structure. But combustible gas explosion occur from time to time in the mining, transportation, storage, process and using process, especially mine gas explosion, which always lead to big property losses and casualties. In order to prevent these explosion accidents and reduce these hazards, study the propagating law and the inner mechanism of flame accelerating with the explosion venting tube, according to the environment and places.The dynamic process between flame and flow usually involves flame acceleration, flame structure variation and flame instability during the premixed flame accelerating propagation in the explosion venting tube, and is subjected to different restriction and influence. Accordingly, the study in this topic focuses on these influencing factors of methane-air premixed flame with experiments and theoretical analysis.Firstly, the experimental system on explosion venting tube was built up, The high speed schlieren photograph method was used to record the dynamic process of flame propagation clearly, including the precise flame front position, flame structure in the various experimental conditions, and that velocity of the flame front was obtained. The data acquisition system was establishment which was using to test the flow pressure, and the corresponding rate of pressure rise was calculated. Theory analysis and numerical simulation were carried out to describe the parameters of flame propagation, to explore the dynamic behavior of premixed flame propagation and propagation law in the unconstrained tube.Through the experiments studied the influences of different pressure-orifice ratios on the propagation characteristics in the long50cm tube. The velocity increased as the ratio rose, but the pressure and the rate of pressure rise decreased, by which to figure out the relation between the ratio and the propagation characteristics. Both peak velocity and pressure had a rapid change when the pressure-orifice ratio was less than30%, however, they changed was very little with the ratio for more than30%. So inflection point ratio was obtained when the pressure-orifice ratio was30%, and could be used as the important reference value for designing of explosion venting.The experiments studied the influences of the three concentration equivalence ratios. When the equivalence ratio was1.26, the value of velocity and pressure were up to maximum, and it took shortest time to reach the peaks. The main cause of the conclusion was the changed equivalence ratio in venting tube, and made them close to or equal to stoichiometric concentration ratio, then the reaction of premixed gas was more complete, heat output per unit volume was increased to maximum, so could speed up the flame propagation and increase pressure. But the optimum concentration was transformed into "lean-burn" state, so both the propagation velocity and pressure were decreased. Thus the concentration equivalence ratio was a variable parameter in the explosion venting tube.When the blockage ratio was different because of the same cuboids for the different placement direction, the flame propagation characteristics could change. The propagation velocity and pressure was increased with blockage ratio. So should keep the same direction between the least cross section and flame propagation.It was the exponential relationship for increases firstly then decreases between the distance and the flame propagation characteristics, and the distance was from the obstacle to ignition point. It was the "dangerous area of position" when the aspect ratio is5.8-6.3, the peak of the propagation velocity and pressure were the maximum.It was the variation for increases firstly then decreases between the length of obstacle and the flame propagation characteristics, the length was increased with the quantity of obstacle under the invariable cross section.更多还原