对长、宽、高为650 mm×400 mm×12 mm的半闭口狭窄矩形通道（海伦-肖装置）内的甲烷/空气层流预混火焰传播过程进行了实验研究，探究当量比φ在0.6~1.2范围内、火焰传播角度ω在垂直向下-90°至垂直向上90°区间对火焰前锋轮廓发展及非标准层流火焰速度的影响。结果表明：火焰在通道内的传播分为热膨胀、准稳态传播和端壁效应3个阶段，每个阶段具有各自不同的前锋轮廓特征。由于瑞利-泰勒不稳定性机制的作用，所有当量比工况下向上传播的火焰均在准稳态传播阶段中呈现出明显的锋面褶皱与胞状结构；对向下传播的火焰而言，其在贫燃工况（φ为0.6，0.8）下的胞状不稳定性得到了有效抑制，而在当量比φ=1.0及富燃工况（φ=1.2）下，该稳定性效应并不显著。火焰瞬时速度与标准层流速度的比值Ui/UL，在φ=0.6的极贫燃工况与其他当量比工况下展现出明显不同的发展特性，极贫燃工况火焰向上传播时（ω=90°），Ui/UL随着传播过程的进行一直增大，直到火焰触碰壁面末端熄灭，整个过程Ui/UL与火焰传播方向呈正相关关系；而对于其他当量比工况，Ui/UL在传播过程中均先升高后下降，火焰触碰壁面末端熄灭前其值趋于稳定，其平均速度与标准层流速度的比值Ua/UL在水平传播（ω=0°）时达到最大值。

The propagation process of premixed methane/air laminar flames in a semiclosed, rectangular narrow channel in 650 mm length, 400 mm width and 12 mm height, respectively was experimentally studied. Focuses were placed on the effects of fuel/air equivalence ratios (φ=0.6 to 1.2) and flame propagation angle ω (from -90° to 90° in vertical direction) on the flame front profiles as well as nonstandard laminar flame speeds. Results show that the flame propagation process within the channel can be divided into three stages such as thermal expansion stage, quasisteady state propagation stage and endwall effect stage, and each stage exhibits different flamefront profiles. Owing to the RayleighTaylor instabilities, flame fronts of the upwardpropagating ones are found to show remarkably wrinkled and cellular structures at their quasisteady state propagation stages, for all the equivalence ratios investigated; for the downwardpropagating flames, the cellular instabilities can be effectively suppressed at the fuellean conditions (φ=0.6, 0.8), while this stabilizing effect is not noticeable at both the stoichiometric (φ=10) and fuelrich conditions (φ=1.2). Ratio of instantaneous velocity to standard laminar flame velocity Ui/UL has quite divergent features between the extralean (φ=0.6) and higher-φ conditions. For an upwardpropagating flame (ω=90°) at the former condition (φ=0.6), Ui/UL increases during the propagation process, till touching the end of the closedwall and ending up with extinction. Also, Ui/UL during the whole process shows a positive correlation with the flame propagation angle; however, for the higher equivalence ratios (φ=0.8, 1.0 and 1.2), Ui/UL increases first and then decreases, while eventually levels off, till touching the end walls. In these cases, ratio of averaged speeds to standard laminar flame velocity Ua/UL reaches its maximum value for a horizontally propagating flame (ω=0°).

TK16

国家自然科学基金（51806158）