不同背压下多孔介质燃烧器的燃烧特性研究

多孔介质燃烧技术是实现低热值气体稳定燃烧、清洁利用的有效解决方案。为了观测不同背压下多孔介质燃烧器的燃烧特性、考察火焰的稳定性,掌握其系统流动和阻力损失特性分布规律,进而实现系统装置结构的优化设计和高效运行,搭建了泡沫陶瓷多孔介质燃烧装置实验台,分别进行了无背压以及两种不同背压工况下燃烧器的冷态阻力和热态燃烧特性实验。结果表明:1多孔介质极强的热回流作用能对预混气体进行有效预热,易获得稳定火焰,燃烧当量比较之于传统燃烧器要小。且烟气中污染物含量远低于国家标准;2泡沫陶瓷的摩阻系数随空气流量增大而减小。且降幅逐渐趋缓;3空气低流速时,流动阻力项以黏性项为主,摩阻系数与流量呈反比关系;4随着空气流速增大,流动阻力项以惯性项为主,摩阻系数主要受泡沫陶瓷粗糙度及陶瓷缝隙的影响;5导入二次空气后多孔介质燃烧器能够达到的最小当量比远小于未加入二次空气时的最小当量比,与传统燃烧器相比极大地拓宽了当量比的范围。

Combustion characteristics of porous media burners under various back pressures

The porous media combustion technology is an effective solution to stable combustion and clean utilization of low heating value gas. For observing the combustion characteristics of porous media burners under various back pressures, investigating flame stability and figuring out the distribution laws of combustion gas flow and resistance loss, so that an optimized design and efficient operation of the device, a bench of foamed ceramics porous media combustion device was set up to test the cold-state resistance and hot-state combustion characteristic of burners in working conditions without back pressures and with two different back pressures. The following results are achieved. (1) The strong thermal reflux of porous media can preheat the premixed air effectively, so the flame can be kept stable easily, the combustion equivalent ratio of porous media burners is lower than that of traditional burners, and its pollutant content of flue gas is much lower than the national standard value. (2) The friction coefficient of foamed ceramics decreases with the increase of air flow rate, and its decreasing rate slows down gradually. (3) When the flow rate of air is low, viscosity is the dominant flow resistance, and the friction coefficient is in an inverse relation with the flow rate. (4) As the flow rate of air increases, inertia is the dominant flow resistance, and the friction coefficient is mainly influenced by the roughness and cracks of foamed ceramics. (5) After the introduction of secondary air, the minimum equivalent ratio of porous media burners gets much lower and its range of equivalent ratio is much larger than that of conditional burners.