Modelling of Particulate Matter Transformations and Capture Efficiency

In the current work, a comprehensive computational fluid dynamics (CFD) model is developed for an accurate description of the transport and transformation of automotive particulate matter (PM) in monolithic reactors. The model accounts for the developing gas flow, the evaporation of hydrocarbons (HCs) from the particles, and the adsorption of HCs in the washcoat, as well as motion, shrinkage, and deposition of particles in the channel. The comprehensive CFD model is used to validate a simplified tanks-in-series approach with a conceptual model for PM transformations. In the development of more detailed and accurate chemical kinetics for the reactions of PM in filters, it will be necessary to also predict the time-resolved properties of the particles collected in the filter (e. g., reactivity, amount of adsorbed HCs). It is shown in this work how the data necessary to construct such models can be obtained in situ with the aid of the conceptual model and PM measurements over an inert open substrate

New Directions in Advanced Modeling and in Situ Measurements Near Reacting Surfaces

Multidimensional numerical modeling and in situ spatially-resolved measurements of gas-phase thermoscalars over the catalyst boundary layer have fostered fundamental investigation of the heterogeneous and homogeneous chemical reaction pathways and their coupling at realistic operating conditions. The methodology for validating catalytic and gas-phase reaction mechanisms is firstly outlined for industrially-relevant fuels. Combination of advanced modeling and in situ near-wall species and velocity measurements is then used to address the intricate interplay between interphase fluid transport (laminar or turbulent) and hetero-/homogeneous kinetics. Controlling parameters of this interplay are the homogeneous ignition chemistry, flame propagation characteristics, competition between the catalytic and gaseous pathways for fuel consumption, diffusional imbalance of the limiting reactant, flow laminarization due to heat transfer from the hot catalytic walls, and fuel leakage through the gaseous reaction zone. Dynamic reactor operation and intrinsic flame dynamics driven by interactions between homogeneous kinetics and catalytic walls are outlined using detailed transient simulation. It is shown that the presence of catalytic reactions moderates flame instabilities. Future directions for transient modeling and for temporally-resolved in situ near-wall measurements are finally summarize

Surface Reaction Kinetics for Oxidation and Reforming of H2, CO, and CH4 over Nickel-based Catalysts

An experimental and kinetic modeling study of H2 and CO oxidation, as well as conversion of methane under oxidative and reforming conditions over nickel-based catalyst is presented. The numerical model is based on a newly developed surface reaction mechanism consisting of 52 elementary-steps reactions with 14 surface and 6 gas-phase species. The mechanism was evaluated against experimental data at varying operating conditions performed in this study and also taken from literature

A review of metal foam and metal matrix composites for heat exchangers and heat Sinks

Recent advances in manufacturing methods open the possibility for broader use of metal foams and metal matrix composites (MMCs) for heat exchangers, and these materials can have tailored material properties. Metal foams in particular combine a number of interesting properties from a heat exchanger's point of view. In this paper, the material properties of metal foams and MMCs are surveyed, and the current state of the art is reviewed for heat exchanger applications. Four different applications are considered: liquid-liquid, liquid-gas, and gas-gas heat exchangers and heat sinks. Manufacturing and implementation issues are identified and discussed, and it is concluded that these materials hold promise both for heat exchangers and heat sinks, but that some key issues still need to be solved before broad-scale application is possible

Experimental and numerical investigation of silicon carbide and refractory materials under extreme conditions

The chemical and mechanical aspects related to the use of refractory materials at high-temperatures and under oxidizing conditions were investigated. The behavior of silicon carbide and tantalum were studied with an emphasis on their performance as fuel cladding in nuclear power plants

Convection diffusion and reaction : bridging scales in science and engineering

Tese de doutoramento. Engenharia Química e Biológica. Faculdade de Engenharia. Universidade do Porto. 201