气流速度对晶体硼颗粒热氧化及点火燃烧特性的影响

Effect of airflow velocity on thermal oxidation and combustion characteristics of crystalline boron particles

利用热天平与激光点火装置,研究了不同气流速度下硼颗粒的热氧化特性和点火燃烧特性,在此基础上分析了对流换热对其影响规律。研究结果表明,气流速度对硼氧化反应的作用主要体现在对流换热项及扩散控制项两方面。气流速度对硼颗粒的点火燃烧过程的影响是双方面的。在流速较低时,其增大将促进硼颗粒的点火和燃烧,此时起主导作用的是氧扩散过程。随着流速的增加,对流换热对硼氧化反应的影响逐渐体现,超过某一程度后,其增大则不利于硼颗粒的点火和燃烧。研究还发现,硼颗粒的燃烧效率随气流速度的增大而增大,推测硼颗粒的燃烧效率的主要影响因素是氧扩散过程。

The thermal oxidation together with ignition and combustion characteristics of crystalline boron particles under differ- ent airflow velocity were studied by means of thermogravimetry analysis and a laser ignition apparatus. The effect of heat convection was analyzed based on experimental results. The results reveal that influence of airflow velocity on oxidizing reaction is mainly re- fleeted in form of heat convection and diffusion eontrol. The influence mechanism of airflow velocity on the ignition and combustion process is complex. When at a low level, the increase of airflow velocity promotes the ignition and combustion process, which is limited by oxygen diffusion process. As the velocity increases, the influence of heat convection on the boron oxidation process is gradually strengthened. When exceeding a certain value, the inerease of airflow velocity isnt benefit to the ignition and combustion. The results also show that combustion efficiency of boron particles increases monotonically as the airflow velocity increases. It is in- ferred that the combustion efficiency is mainly limited by oxygen diffusion process.