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A new model has been developed to describe the size-dependent effects that are responsible for transient particle mass (PM) and particle number (PN) emissions observed during experiments of the active regeneration of Diesel Particulate Filters (DPFs). The model uses a population balance approach to describe the size of the particles entering and leaving the DPF, and accumulated within it. The population balance is coupled to a unit collector model that describes the filtration of the particles in the porous walls of the DPF and a reactor network model that is used to describe the geometry of the DPF. Two versions of the unit collector model were investigated. The original version, based on current literature, and an extended version, developed in this work, that includes terms to describe both the non-uniform regeneration of the cake and thermal expansion of the pores in the DPF. Simulations using the original unit collector model were able to provide a good description of the pressure drop and PM filtration efficiency during the loading of the DPF, but were unable to adequately describe the change in filtration efficiency during regeneration of the DPF. The introduction of the extended unit collector description enabled the model to describe both the timing of particle breakthrough and the final steady filtration efficiency of the hot regenerated DPF. Further work is required to understand better the transient behaviour of the system. In particular, we stress the importance that future experiments fully characterise the particle size distribution at both the inlet and outlet of the DPF.

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In this paper, we answer the question of whether polar curved aromatics are persistently polar at flame temperatures. We find, using electronic structure calculations and transition state theory, that the inversion barriers of curved aromatics (cPAH) of 0.9-1.2 nm in diameter are high and that they are not able to invert over the timescales and at the high temperatures found in sooting flames. We find a transition for smaller curved aromatics between 11-15 (≈ 0.8 nm) rings where the increasing strain introduced from the pentagonal ring increases the inversion barrier leading to rigidity. We then performed ab initio quantum molecular dynamics to find the molecular dipole fluctuations of a nanometre sized cPAH at 1500 K. We found the bending mode of the bowl shaped molecule gave rise to the largest fluctuations on the dipole moment by ±0.5-1 debye about the equilibrium value of 5.00 debye, indicating persistent polarity. We also observed binding of a chemiion at 1500 K over 2 ps, suggesting the molecular dipole of cPAH will be an important consideration in soot formation mechanisms.

A joint moment projection method and maximum entropy approach for treating the soot population balance equations is developed and presented in this work. The moment projection method is used to solve the population balance equations and generate moments that are supplied to the maximum entropy approach as a post-processing technique to reconstruct the soot particle size distribution. The particle size range required by the maximum entropy for particle size distribution reconstruction is determined based on the weighted particles generated in the moment projection method. The performance of the joint approach is first evaluated by solving a set of simplfied population balance equations on MatLab, then it is implemented into a Stochastic Reactor Model engine code to simulate the formation and oxidation of soot particles in a single-cylinder direct injection diesel engine. Results suggest