Clarification of Pattern Formation Mechanism in Microcombustion

火焰图案的形成进行了检查的发展，微燃烧装置。预混合的甲烷-空气混合物被引入到两个平行的圆形石英板的中心，所述圆形石英板以毫米尺度距离（<5 mm）分开。两个板用外部加热器加热，以沿流动方向沿着产生正温度梯度条件。主要结果如下：1）除了在径向位置观察到稳定的预混火焰阵面外，还观察到多种非稳态火焰传播模式。对于较低的混合物流量和混合物当量比的范围内，径向火焰传播模式观察到同时存在两个圆形火焰在不同的径向位置。对于更高的流量，观察到旋转螺旋火焰传播模式。除了径向和螺旋火焰传播模式，随机和不对称的火焰振荡也被观察到。观察了螺旋火焰锋面的旋转速率， ...更多信息 o从28到83 Hz变化。对稳态圆形火焰形成螺旋火焰的过程进行了简单的分析。2）根据实验结果绘制了具有温度梯度的径向微通道内火焰斑图的综合状态图。在由两个平行的圆形石英板形成的微通道的中心处引入预混合的甲烷-空气混合物，所述石英板用外部多孔燃烧器加热以在流动方向上产生正温度梯度条件。在这些微通道的通道宽度为0.5，1.0，1.5，2.0，2.5，和3.0毫米的燃烧行为进行了实验研究。获得了各种稳定和不稳定火焰模式的状态图，证实了火焰模式是混合物当量比、入口混合物速度和通道宽度的强函数。此外，还研究了单、三重火焰的旋转频率、稳定圆形火焰阵面的半径以及单、二重火焰主要燃烧产物的比较等燃烧特性，并通过二维数值模拟成功地再现了部分实验结果。结果提交给期刊。少

Flame pattern formation was examined for the development of microcombustion devices. Premixed methane-air mixture is introduced at the center of two parallel circular quartz plates separated by a millimeter scale distance (<5mm). Two plates are heated with an external heater to create a positive temperature gradient condition along the flow direction. Main result are as follows.1) In addition to the general perception of a stable premixed flame front at a radial location, a variety of nonstationary flame propagation modes are observed. For lower mixture flow rates and a range of mixture equivalence ratios, a radial flame propagation mode is observed with simultaneous presence of two circular flames at different radial locations. For higher flow rates, a rotating spiral flame propagation mode is observed. In addition to radial and spiral flame propagation modes, random and unsymmetrical flame oscillations are also observed. The rotational rates of the spiral flame fronts were observed t … More o vary from 28 to 83 Hz. A simple analysis is carried out to describe the formation of spiral flames from a steady circular flame.2) Comprehensive regime diagrams of flame pattern formation in radial microchannels with temperature gradients were drawn based on experimental findings. A premixed methane-air mixture was introduced at the center of microchannels formed by two parallel circular quartz plates that were heated with an external porous burner to create a positive temperature gradient condition in the direction of flow. Combustion behavior in those microchannels at channel widths of 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mm were experimentally investigated. Regime diagrams of various stable and unstable flame patterns were obtained, confirming that the flame pattern is a strong function of mixture equivalence ratio, inlet mixture velocity, and channel width. Furthermore, some combustion characteristics, such as the rotating frequency of the single pelton-like flame and the triple flame, the radius of the stable circular flame front, and comparison between the major combustion products of the single and double pelton-like flames, were also investigated.After careful examinations, some of the experimental pattern formations were successfully reproduced by computational two-dimensional modeling. Results are submitted to a journal. Less