The effect of initial temperature on flame acceleration and deflagration-to-detonation transition phenomenon
The effect of initial temperature on flame acceleration and deflagration-to-detonation transition phenomenon
复制标题
初始温度对火焰加速和爆燃-爆轰转变现象的影响
DOI：
10.2172/672036
复制
发表时间：
1998
期刊：
影响因子：
--
通讯作者：
A. Malliakos
中科院分区：
文献类型：
--
作者：
G. Ciccarelli;J. Boccio;T. Ginsberg;C. Finfrock;L. Gerlach;H. Tagawa;A. Malliakos
BNL 的高温燃烧设施用于进行爆燃到爆震转变 (DDT) 实验。周期性孔板安装在爆震管的整个长度内，以促进火焰加速。孔板的外径为 27.3 厘米，相当于管的内径，内径为 20.6 厘米。爆轰管长21.3米，孔板间距为一管直径。使用标准汽车柴油发动机电热塞来点燃管一端的测试混合物。氢气-空气-蒸汽混合物在高达 650K 的温度范围和 0.1 MPa 的初始压力下进行了测试。在大多数情况下，产生 DDT 的极限氢摩尔分数对应于爆轰单元尺寸 {lambda} 等于孔板内径 d 的混合物（例如 d/{lambda}=1）。唯一的例外是在 650K 的干燥氢气-空气混合物中，观察到 DDT 限值为 11% 氢气，对应于 d/{lambda} 值等于 5.5。对于 650K 时 10.5% 的氢气混合物，火焰加速至约 120 mIs 的最大速度，然后减速至 2 mIs 以下。通过将容器点火端前 6.1 米的温度保持在 400K，并将容器的其余部分保持在 650K，DDT 限值降低至 9.5% 氢气 (d/{lambda}=4.2)。这一观察表明，d/{lambda}=1 DDT 限制标准为充满障碍物的管道中 DDT 的发生提供了必要条件，但不是充分条件。在这种特殊情况下，混合物的初始条件（即温度）导致混合物无法将火焰加速到可能发生 DDT 的程度。还观察到，火焰加速到爆炸引发点所需的距离（称为助跑距离）是氢摩尔分数和混合物初始温度的函数。降低氢摩尔分数或提高初始混合物温度会导致更长的启动距离。发现火焰上的密度比和未燃烧混合物中的声速是影响助跑距离的两个参数。
The High-Temperature Combustion Facility at BNL was used to conduct deflagration-to-detonation transition (DDT) experiments. Periodic orifice plates were installed inside the entire length of the detonation tube in order to promote flame acceleration. The orifice plates are 27.3-cm-outer diameter, which is equivalent to the inner diameter of the tube, and 20.6-cm-inner diameter. The detonation tube length is 21.3-meters long, and the spacing of the orifice plates is one tube diameter. A standard automobile diesel engine glow plug was used to ignite the test mixture at one end of the tube. Hydrogen-air-steam mixtures were tested at a range of temperatures up to 650K and at an initial pressure of 0.1 MPa. In most cases, the limiting hydrogen mole fraction which resulted in DDT corresponded to the mixture whose detonation cell size, {lambda}, was equal to the inner diameter of the orifice plate, d (e.g., d/{lambda}=1). The only exception was in the dry hydrogen-air mixtures at 650K where the DDT limit was observed to be 11 percent hydrogen, corresponding to a value of d/{lambda} equal to 5.5. For a 10.5 percent hydrogen mixture at 650K, the flame accelerated to a maximum velocity of about 120 mIs and then decelerated to below 2 mIs. By maintaining the first 6.1 meters of the vessel at the ignition end at 400K, and the rest of the vessel at 650K, the DDT limit was reduced to 9.5 percent hydrogen (d/{lambda}=4.2). This observation indicates that the d/{lambda}=1 DDT limit criteria provides a necessary condition but not a sufficient one for the onset of DDT in obstacle laden ducts. In this particular case, the mixture initial condition (i.e., temperature) resulted in the inability of the mixture to sustain flame acceleration to the point where DDT could occur. It was also observed that the distance required for the flame to accelerate to the point of detonation initiation, referred to as the run-up distance, was found to be a function of both the hydrogen mole fraction and the mixture initial temperature. Decreasing the hydrogen mole fraction or increasing the initial mixture temperature resulted in longer run-up distances. The density ratio across the flame and the speed of sound in the unburned mixture were found to be two parameters which influence the run-up distance.