天然气在渐变型多孔介质中的预混燃烧启动特性

针对天然气在渐变型多孔介质燃烧器中的点火启动过程进行了试验研究,通过监测燃烧器壁面或气体温度在点火后的变化,得到了影响启动时间的因素及特性,对特定的燃烧器而言,启动时间与预混气体当量比、流速以及点火位置有关,在冷态下点火,随着当量比接近理论当量比,启动时间减小;混合气体流速增大,启动时间增大;点火位置从燃烧器外移到燃烧器人口时,启动时间可大大缩小,采用小流速、近理论当量比条件下点火,对多孔介质层预热,有利于火焰迅速向上游移动,然后再调整到需求当量比或流速,可以大大减小燃烧器启动时间,采用孔径变化率高的渐变型多孔介质结构,也可以达到缩短启动时间的目的。

Experimental Studies of the Startup Characteristics of Premixed Combustion of Natural Gas in the Gradually-Varied Porous Media

A series of experiments were conducted on the startup time of natural gas in the gradually-varied porous media (GVPM) burners.The wall or gas temperatures of the GVPM burners were measured under different startup conditions and different burners. For a given burner,the startup time was controlled by equivalence ratio,gas velocity,and the ignition position.For ignition under cool condition,the startup time became shorter as the equivalence ratio was closer to unity,and prolonged with the increase of gas velocity.The startup time was remarkably shorter when the ignition position was placed at the inlet instead of the outlet of the burner.To ignite the premixed gas with a low velocity and an equivalence ratio near stoichiometry,with better preheat of the po- rons media matrix,is favorable for the flame moving upwards.Through firstly preheating,and then adjusting the fuel and/or air flow into a given equivalence ratio or flow velocity,the startup time is reduced.If the pore size of the GVPM varies sharply along the same length,the startup time becomes shorter.