论文部分内容阅读
空气中水的存在会严重影响烷烃类扩散火焰中烟黑的生成,研究氧化剂流中水对烷烃类火焰的影响,对污染物控制及火灾扑救具有重要意义。模拟采用24步简化机理的有限速率化学反应模型、Moss-Brookes烟黑模型及Discrete Ordinates(DO)辐射模型,研究在空气中加入水对甲烷/空气层流伴流扩散火焰的影响,其中烟黑模型包括烟黑的成核、表面增长和氧化。结果表明,伴流空气中的水蒸气会降低火焰的温度、抑制烟黑的生成。这是因为:一方面,水蒸气降低了甲烷燃烧的温度,火焰温度的降低导致化学反应速率减慢,烟黑成核和表面生长速率随之降低,火焰中烟黑质量分数便减少;另一方面,由于水蒸气的加入使化学反应OH+H_2 H+H_2O(R(15))逆向反应加速,继而导致OH生成量增加。但由于氧气浓度降低使火焰体积增大,OH的浓度降低。从而导致烟黑的氧化速率降低,烟黑生成量增加。由于水蒸气的化学效应小于其温度效应,总体上烟黑质量分数降低。最后对比了模拟结果和试验结果。
The presence of water in the air will seriously affect the generation of smoke black in the flame of alkane diffusion flame. Studying the influence of water in the oxidant flow on the flame of alkane flame is of great significance for pollutant control and fire fighting. The effects of adding water to methane / air laminar flow with stream diffusion flame were investigated by using a 24-step simplified mechanism of limited rate chemical reaction model, Moss-Brookes smoke black model and Discrete Ordinates (DO) radiation model. The effects of smoke black The model includes the blackening nucleation, surface growth and oxidation. The results show that the water vapor in the air stream will reduce the flame temperature, inhibit the formation of black smoke. This is because: on the one hand, the steam reduces the temperature of methane combustion, and the decrease of the flame temperature leads to the slowdown of the chemical reaction rate, the decrease of the nucleation rate of the black smoke and the growth of the surface, and the decrease of the mass fraction of the black smoke in the flame; As a result, the reaction of OH + H_2H + H_2O (R (15)) accelerates due to the addition of water vapor, which leads to the increase of OH. However, the concentration of OH decreases due to the increase of the flame volume due to the decrease of oxygen concentration. As a result, the oxidation rate of soot is reduced and the generation of soot is increased. As the chemical effect of water vapor is less than its temperature effect, the overall mass fraction of smoke decreases. Finally, the simulation results and experimental results were compared.