亚毫米通道内的氢氧预混合燃烧

Premixed Combustion of Hydrogen and Oxygen in Sub-Millimeter Channels

在亚毫米尺度,尺寸效应带来散热损失的激增和燃烧驻留时间的急剧减少,使燃烧室内预混合气的着火和燃烧条件恶化.针对碳化硅材质的亚毫米矩形燃烧室,改变混合气的流量和当量比,测出了不同高度燃烧室内氢氧预混合气的着火界限分布,并通过燃烧室外壁面和出口温度的测量,分析得出亚毫米通道内氢氧预混合燃烧的特性.结果表明,亚毫米尺寸与常规尺寸相比氢氧预混合气的稀燃界限明显升高,但仍能在一定条件下实现稳定燃烧;测试条件下,外壁面温度随氢气流量的增加而升高,但燃烧的充分性降低;少量的过量氧气能提高外壁面的温度,并使温度分布更均匀;由于导热系数较高,碳化硅材质的燃烧室外壁面温度分布比石英材质的要更均匀.

The miniaturization of combustors results in the surge of heat loss and the sharp decline of combustion residence time,which exerts a negative impact on the conditions of ignition and combustion,especially in the case of sub-millimeter scale.This work tested experimentally ignition limits for sub-millimeter rectangular combustors with carborundum material by changing three major parameters on ignition and combustion,namely hydrogen to oxygen mixing ratio,hydrogen volumetric flow rate and height of combustor.The combustion characteristics were then investigated by analyzing temperature distribution of outside wall and exit of the combustor.The results show thatstable combustions can be obtained under a proper condition although the lean ignition limit in sub-millimeter scale is higher than that in regular scale.High average wall temperature can be achieved at slightly oxygen rich mixing ratios.The outside wall temperature distribution of the combustor built with carborundum material is more uniform than that with quartz for different thermal conductivityies.