Experimental testing and mathematical modelling of diesel particle collection in flow-through monoliths

Abstract

The honeycomb monolith is the most prevalent geometry in automotive exhaust aftertreatment, with applications including oxidation catalysts, partial-flow and wall-flow filters. Particle collection mechanisms at the leading edge of honeycomb monoliths and in open channels are usually neglected by engineers of these devices. Under specific conditions however, these phenomena can make an appreciable contribution to overall particle collection and deposits on channel walls may affect catalyst performance. In the current study, experimental measurements of deposit loading, capture efficiency and pressure drop at constant flow conditions are presented for three flow-through monoliths with different cell densities and lengths, while particle distribution is varied in an additional case. The processed results reveal the evolution of deposit distribution at the leading edge, the entry zone inside the channel and the remaining part of the monolith. Next a one-dimensional transient mathematical model is proposed, which takes into account interception at the edge and coupled diffusion–interception inside the channel. After fitting the model parameters, all experimental cases are predicted with sufficient accuracy with the exception of loadings extended beyond 12 hours. Finally, further application of the model reveals the negative effect of flow rate on collection efficiency and the potential to maximize or minimize collection efficiency using various cell designs.