单颗氢化铝的激光点火及燃烧特性

Laser-Induced Ignition and Combustion Charateristics of Single Aluminum Hydride Particle

为了揭示单颗氢化铝的着火和燃烧特性,采用近红外激光进行点火,利用高速摄像仪和红外热像仪获取颗粒表面温度、着火以及燃烧火焰演变过程,并结合热解特性对激光点火和燃烧机理进行分析。以20℃/min加热升温时,氢化铝经历两个主体失重阶段(80~175℃,363~565℃)和两个增重阶段(175~363℃,565~800℃)。在常温常压自然对流空气中,单颗粒径约1mm的氢化铝受功率密度为107W/m2量级的激光加热时,以104℃/s量级的速率快速升温后分解为氢气和金属铝。随后氢气被点燃,点火延迟时间约1ms,随着激光点火功率密度的提高,其点火延迟时间缩短。氢气燃烧火焰呈淡蓝色。金属铝被激光和气相火焰加热融化,温度基本保持不变;而后铝升温气化被点燃,分散在氢气火焰中燃烧,火焰呈棕红色。

To reveal the ignition and combustion characteristics of single aluminum hydride particle,the near infrared laser was used to ignite aluminum hydride. The high speed camera and the thermal imaging camera were utilized for recording the evolution of particle surface temperature,ignition and combustion flame. The laser-induced ignition behavior and the combustion mechanism of aluminum hydride were analyzed by combining the burning phenomena and the pyrolysis characteristics. At a heating rate 20℃/min,aluminum hydride suffers from two stages of weigth loss（80-175℃,363-565℃）and two stages weigth enhancement（175-363℃,565-800℃）. In the natural convection air at atmospheric pressure and temperature,the surface temperature of aluminum hydride in the diameter of about 1 mm elevates at the heating rate of 104℃/s,as aluminum hydride particle is heated by the laser with the power density of 107 W/m2. Aluminum hydride splits off hydrogen and aluminum particles. The released hydrogen is firstly ignited with the delay time of about 1 ms. The ignition delay time of aluminum hydride is shortened as ignition power density elevates. The combustion flame of released hydrogen is light blue. The decomposed aluminum partilces are then heated to melt by the laser and gas flame. During the melting of aluminum,the particle temperature keeps constant. After melting,the aluminum particles dispersed in the hydrogen flame are ignited and combust with brown red flame.