On the influence of bimodal size distributions in particle sizing using laser-induced incandescence

Time-resolved laser-induced incandescence (LII) is a technique for in-situ soot particle size distribution measurements with the limitation that the distribution function has to be assumed (often monodisperse or lognormal) in the signal analysis. Since it is established that size distributions sometimes are bimodal, it is of interest to understand the influence from such distributions on the LII signal, and consequently what information can be extracted from experimental LII signals. The influence of the parameters of the bimodal lognormal distribution on the evaluation using a monodisperse or lognormal distribution was investigated. A range of bimodal distributions were tested and it was found that a unimodal evaluation of a signal from a bimodal distribution is only slightly affected by its small-size mode, meaning that LII can be used to determine the approximate parameters of the large-size mode.