Modelling soot oxidation in DPF and modelling of PGM loading effect in a DOC

The aim of this PhD thesis is to develop a one-dimensional (1D) mathematical model to study in designing and improving emission control systems such as those in Diesel Oxidation Catalyst (DOC) and Diesel Particulate Filter (DPF). This was achieved by capturing the fundamental reaction kinetics from the microreactor data within the careful choice of concentrations/ temperatures domain; together with good understanding of the physical phenomena’s occurring in these systems. When considering a DOC, it is important to have a good description of the catalyst activity as a function of Platinum Group Metal (PGM) loading, which in this case is Pt, this enables mathematical models to be used in the optimization of the PGM loading. The work presented here looks at the design of a DOC based aftertreatment system through development of kinetics from data obtained from the microreactor for a wide range of PGM loadings (2.5-75g ft-3). The variation in catalyst activity with different PGM loadings for the key reactions was determined. The model developed in this study predicts well all the experimental data for the various loadings. DPF is another important aftertreatment technology that is used for the control of Particulate Matter (PM) emission from diesel engines. Under favourable conditions, the soot collected on the filter can be removed by oxidation with NO2 from temperatures as low as 200°C. The work presented in this thesis shows the fundamental modelling approach to develop kinetics for soot oxidation by NO2. The selectivity to CO was found to differ only marginally with temperature, and is independent of NO2 concentrations. By modelling these data using a 1D model, the rate equations for the soot-NO2 reaction were determined, and experimental data were predicted

Numerical simulation of mixing fluid with ferrofluid in a magnetic field using the meshless SPH method

In this study, a numerical investigation of the effect of different magnetic fields on ferrofluid-fluid mixing processes in a two-dimensional microchannel is performed An improved version of smoothed particle hydrodynamics, SPH, by shifting particle algorithm and dummy particle boundary condition, is implemented to solve numerical continuity, ferrohydrodynamics-based momentum and mass transfer equations. SPH is formulated through the irregular arrangement of the nodes where the fields are approximated using the fifth-order Wendland kernel function. After validating the computational approach, the influence of the number (from one to three) of parallel electrical wires positioned perpendicular to the microchannel on the mixing efficiency is studied for the first time. It has originally been found that the mixing efficiency highly non-linearly depends on the Reynolds number and the number of electrical wires. For Re ≤20, the mixing efficiency is almost the same for two and three electrical wires and about two times higher than one electrical wire. For Re ≥ 80, the mixing efficiency of three wires is much higher than one and two electrical wires. Optimum performance of the micromixer is achieved with three electrical wires, since the mixer performs well on a broader range of Re than the other two studied cases. The outcomes of this study, obtained by a meshless method, are important for the industrial design of micromixers