Influence of soot particle aggregation on time-resolved laser-induced incandescence signals
Influence of soot particle aggregation on time-resolved laser-induced incandescence signals
复制标题
烟灰颗粒聚集对时间分辨激光诱导白炽信号的影响
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
P. Bengtsson
中科院分区：
文献类型：
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作者：
H. Bladh;J. Johnsson;J. Rissler;Hussam Abdulhamid;Nils;M. Sanati;J. Pagels;P. Bengtsson
激光诱导白炽（LII）是一种多用途的技术，用于定量测量火焰和排气中的烟尘。当用于颗粒尺寸测量时，分析时间分辨信号，因为这些信号将显示取决于烟灰颗粒尺寸的衰减速率。这种分析传统上是基于孤立的初级粒子的假设。然而，火焰和废气中的烟灰颗粒通常聚集，这意味着表面积的损失，更少的热传导，因此估计的颗粒尺寸的误差。在这项工作中，我们提出了一个实验研究，旨在量化这种影响。一个煤烟发生器，基于丙烷扩散火焰，被用来产生一个稳定的煤烟流和煤烟的特征在于通过透射电子显微镜（TEM），扫描迁移率粒度仪（SMPS）和气溶胶粒子质量分析仪耦合后，微分迁移率分析仪（DMA-APM）串联。尽管三个选定的操作条件下几乎相同的初级颗粒尺寸分布，LII测量导致信号衰减与衰减速率的显着差异。然而，这三种情况下，被发现有相当不同的水平的聚集，如在TEM图像和迁移率的大小分布中所示，结果同意定性与预期的效果减少热传导从聚集的颗粒导致更长的LII信号衰减。在试图定量解释的差异，LII信号依赖于聚集建模使用的热量和质量传递模型LII给定的初级颗粒和聚集体的尺寸分布数据作为输入。没有达成定量协议，并讨论了这种差异的原因。
Laser-induced incandescence (LII) is a versatile technique for quantitative soot measurements in flames and exhausts. When used for particle sizing, the time-resolved signals are analysed as these will show a decay rate dependent on the soot particle size. Such an analysis has traditionally been based on the assumption of isolated primary particles. However, soot particles in flames and exhausts are usually aggregated, which implies loss of surface area, less heat conduction and hence errors in estimated particle sizes. In this work we present an experimental investigation aiming to quantify this effect. A soot generator, based on a propane diffusion flame, was used to produce a stable soot stream and the soot was characterised by transmission electron microscopy (TEM), a scanning mobility particle sizer (SMPS) and an aerosol particle mass analyzer coupled in series after a differential mobility analyzer (DMA-APM). Despite nearly identical primary particle size distributions for three selected operating conditions, LII measurements resulted in signal decays with significant differences in decay rate. However, the three cases were found to have quite different levels of aggregation as shown both in TEM images and mobility size distributions, and the results agree qualitatively with the expected effect of diminished heat conduction from aggregated particles resulting in longer LII signal decays. In an attempt to explain the differences quantitatively, the LII signal dependence on aggregation was modelled using a heat and mass transfer model for LII given the primary particle and aggregate size distribution data as input. Quantitative agreement was not reached and reasons for this discrepancy are discussed.