为探索多孔介质内超绝热燃烧的特性,搭建了自由堆积多孔介质超绝热燃烧试验台架,测量了不同化学当量比(0.4-0.7)的甲烷/空气预混气体的超绝热燃烧特性.自由堆积多孔介质由直径为3和6 mm的Al2O3小球在陶瓷管(Φ38 mm×500 mm)中堆积而成,孔隙率为0.42.试验结果表明,在多孔介质中只有当燃烧波正向传播时才可能产生超绝热燃烧.在贫燃条件下超绝热燃烧的上限化学当量比为0.7,下限化学当量比为0.4;当化学当量比小于0.4或大于0.7时,在贫燃条件下的超绝热燃烧将不能实现.多孔介质中预混燃烧的火焰锋面速度约为7.82μm/s,最大燃烧锋面温度超过绝热燃烧温度139 K.
The super-adiabatic combustion of the pre-mixture of methane and air under different equivalence ratios (0.4-0. 7) was studied in order to probe into the characteristics of filtration combustion in freedumping porous media. The free-dumping porous media with a porosity of 0.42 was constructed by 3 mm and 6 mm diameter spherical alumina particles in a 38 mm inner diameter and 500 mm long ceramic tube. Experimental results showed that the upstream combustion wave caused under-adiabatic combustion and the super-adiabatic combustion could be obtain only when the direction of combustion wave was down- stream. The maximum temperature of the flame front exceeded the adiabatic one up to 139 K. The upper limit and minimal limit of equivalence ratio to maintain super-adiabatic filtration combustion under lean conditions were respectively 0.7 and 0.4, and the super-adiabatic combustion could not be obtained while the equivalence ratio was less than 0.4 or more than 0, 7. The flame front of the combustion inside the porous media propagated with a velocity of about 7.82 μm/s.