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本文采用数值模拟方法研究了重力对甲烷/空气同轴射流层流扩散火焰烟黑生成特性的影响,数值分析中将详细的气相化学反应机理、复杂的热物性和输运特性关系、半经验的双方程烟黑生成模型和非灰体辐射模型耦合到燃烧场的计算中。同时考虑烟黑经O_2、OH和O的氧化途径。热辐射计算采用与统计窄波段调K(SNBCK)模型相耦合的离散坐标法求解。烟黑的谱带吸收系数根据小颗粒的Rayleigh理论计算。结果表明,随着重力水平的降低,火焰峰值温度降低,微重力下烟黑浓度的最大值约为正常重力下相应火焰的两倍。这一计算结果与已有的试验数据符合较好。计算结果还表明,重力也影响烟黑成核和表面生长的位置和强度。
In this paper, the numerical simulation method is used to study the influence of gravity on the formation characteristics of methane / air coaxial laminar flow and diffusion flame smoke black. The numerical analysis will be based on the detailed chemical reaction mechanism, the complex thermal properties and transport characteristics, semi-empirical The dual-equation smoke generation model and the non-gray body radiation model are coupled to the calculation of the combustion field. At the same time, the oxidation path of O 2, OH and O via black smoke is considered. Thermal radiation calculations are solved using the discrete ordinate method coupled with the statistical narrow band tuning K (SNBCK) model. Spectral absorption coefficients of soot are calculated based on the Rayleigh theory of small particles. The results show that as the gravity level decreases, the peak temperature of the flame decreases, and the maximum of the concentration of soot under microgravity is about twice that of the corresponding flame under normal gravity. This result is in good agreement with the existing experimental data. The results also show that gravity also affects the location and intensity of soot nucleation and surface growth.