Influence of polydisperse distributions of both primary particle and aggregate size on soot temperature in low-fluence LII
Influence of polydisperse distributions of both primary particle and aggregate size on soot temperature in low-fluence LII
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DOI：
10.1007/s00340-006-2196-z
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发表时间：
2006-06-01
影响因子：
2.1
通讯作者：
Smallwood, G. J.
中科院分区：
文献类型：
--
作者：
Liu, F.;Yang, M.;Smallwood, G. J.
建立了一种改进的基于聚集体的低通量激光诱导白炽（LII）模型。利用等效传热球的概念，模拟了聚集烟尘颗粒与周围气体之间热传导的屏蔽效应。这种等效球体的直径是通过直接模拟蒙特卡罗计算在自由分子状态下确定的，作为集料尺寸和烟灰的热调节系数的函数。假设初级烟尘粒径和集料粒径分布均服从对数正态分布。基于400 nm和780 nm处烟尘颗粒总热辐射强度的比值，计算了不同初级颗粒直径和聚集粒径的烟尘颗粒系综在激光探针体积内的有效温度，模拟了实验测量的烟尘颗粒温度。一般来说，原始颗粒直径的多分散性的影响是重要的，应该加以考虑。当主要颗粒与周围气体之间的热传导发生在自由分子状态时，团聚体尺寸多分散性的影响相对不重要；然而，当热传导过程发生在近跃迁状态时，它开始变得重要。该模型还应用于常压层流乙烯扩散火焰中烟灰的热调节系数的再测定。
An improved aggregate-based low-fluence laser-induced incandescence (LII) model has been developed. The shielding effect in heat conduction between aggregated soot particles and the surrounding gas was modeled using the concept of the equivalent heat transfer sphere. The diameter of such an equivalent sphere was determined from direct simulation Monte Carlo calculations in the free molecular regime as functions of the aggregate size and the thermal accommodation coefficient of soot. Both the primary soot particle diameter and the aggregate size distributions are assumed to be lognormal. The effective temperature of a soot particle ensemble containing different primary particle diameters and aggregate sizes in the laser probe volume was calculated based on the ratio of the total thermal radiation intensities of soot particles at 400 and 780 nm to simulate the experimentally measured soot particle temperature using two-color optical pyrometry. The effect of primary particle diameter polydispersity is in general important and should be considered. The effect of aggregate size polydispersity is relatively unimportant when the heat conduction between the primary particles and the surrounding gas takes place in the free-molecular regime; however, it starts to become important when the heat conduction process occurs in the near transition regime. The model developed in this study was also applied to the re-determination of the thermal accommodation coefficient of soot in an atmospheric pressure laminar ethylene diffusion flame.