The detailed flame structure of highly stretched turbulent premixed methane-air flames
The detailed flame structure of highly stretched turbulent premixed methane-air flames
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DOI：
10.1016/s0010-2180(96)00070-3
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发表时间：
1996-11-01
影响因子：
4.4
通讯作者：
Mansour, MS
中科院分区：
文献类型：
--
作者：
Chen, YC;Peters, N;Mansour, MS
在一个喷嘴直径为12 mm、平均出口速度为65、50和30 m/s的预混式本生燃烧器上研究了甲烷湍流化学计量比火焰。先进的激光诊断的流场使用两个组件和两个点的激光多普勒测速仪（LDA），以及标量场的2-D瑞利测温和线拉曼/瑞利激光诱导预解离荧光（LIPF）-OH技术，被施加到获得瞬时和平均火焰结构的速度，温度，和主要物种浓度，以及湍流动能和长度尺度。就它们在燃烧图上的位置而言，三种火焰覆盖了从边界线到充分搅拌的反应器制度到小火焰制度的分布反应区制度的整个范围。测量范围为从喷嘴出口平面上方X/D = 2.5到下游X/D = 12.5。在未燃气体与引燃火焰的混合层内，由于停留时间短和燃烧器的热损失，瞬时温度远低于绝热壁温。随着停留时间的增加，平均火焰温度在轴向方向上增加。喷嘴射流和周围的先导流之间的剪切层产生的湍流的径向混合被抑制，使得湍流动能保持在中心线上几乎恒定。从二维（2D）温度场的瞬时等温线绘制显示了广泛的区域，已燃烧和未燃烧的气体部分混合。这些区域用猝灭尺度l（q）=（τ（c）（3））（1/2）来解释。火焰刷厚度的测量值是成比例的两个高速火焰的淬火规模，而低速火焰表现出基本的小火焰行为。版权所有（C）1996由燃烧研究所
The premixed stoichiometric turbulent methane flames are investigated on a piloted Bunsen burner with a nozzle diameter of 12 mm and mean nozzle exit velocities of 65, 50, and 30 m/s. Advanced laser diagnostics of the flow field using two-component and two-point laser Doppler anenometer (LDA), as well as of the scalar fields with 2-D Rayleigh thermometry and line Raman/Rayleigh laser-induced predissociation fluorescence (LIPF)-OH techniques, are applied to obtain both the instantaneous and mean flame structure in terms of velocity, temperature, and major species concentrations, as well as turbulent kinetic energy and length scales. In terms of their location on the combustion diagram, the three flames cover the entire range of the distributed-reaction-zones regime from the borderline to the well-stirred reactor regime to the flamelet regime. Measurements were from X/D = 2.5 above the nozzle exit plane to X/D = 12.5 downstream. Thus, a complete database is established for comparison with the numerical predictions.Within the mixing layer between the unburnt gas and the pilot flame, the instantaneous temperatures are much lower than the adiabatic dame temperature due to the short residence time and heat loss to the burner. With increasing residence time the mean flame temperature increases in the axial direction. The radial mixing of the turbulence generated with the shear layers between the nozzle jet stream and surrounding pilot stream is surpressed, such that the turbulence kinetic energy remains nearly constant on the centerline.From the two-dimensional (2D) temperature fields instantaneous iso-temperature contours are plotted showing broad regions where burnt and unburnt gas are partially mixed. These regions are interpreted in terms of the quench scale l(q) = (epsilon tau(c)(3))(1/2). The measured values of the flame brush thickness are proportional to the quench scale for the two high-velocity flames, whereas the low-velocity flame exhibits essential flamelet behavior. Copyright (C) 1996 by The Combustion Institute