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Combustion has played a key role in the development of human society; it has driven the evolution in the manufacturing processes, transportation, and it is used to produce the vast majority of the global energy consumed. The emission of pollutants from the combustion of fossil fuels in power plants lead to the development of advanced clean energy technologies, such as carbon capture and storage. Oxyfuel combustion is part of the carbon capture and storage techniques, and consists in the replacement of the air as oxidiser in the reaction with a mixture of oxygen and recycled flue gas, thus allowing a rich CO2 out-flow stream that can subsequently be compressed, transported and safely stored. The number of phenomena in combustion that are inherently dynamic impede the convention of a unique conception of flame stability. However, the quantification of the flow repeatability can produce insights on the efficiency of the process. This thesis presents the assessment of the stability in swirling flows through the calculation of their spatiotemporal coherence. The experimental data obtained from a 250 kWth combustor allows the assessment of the flame by means of spectral and oscillation severity analyses. A similar methodology is developed to analyse the data from large eddy simulations. The spectral analysis, the proper orthogonal decomposition and the dynamic mode decomposition have been employed to account for the temporal, spatial and spatiotemporal coherence of the flow, respectively. The spatiotemporal coherence is employed as a comprehensive term for the characterisation of the dynamic behaviour in the swirling flows and as a measurable indicator of the stability. This concept can be incorporated into the design of novel combustion technologies that will lead into a sustained reduction in pollutants and to the mitigation of the noxious effects associated to them.

A range of bisphenol based epoxy resin monomers were cured with a range of amines to investigate the influence of nuanced chemical changes of constituent molecules upon the chemical performance of networks. Initially, the curing process was optimised in order to reduce the influence of oxidation and carbamation. Moving away from a stoichiometric formulation was found to result in a slight decrease in chemical performance. Networks cured under an air atmosphere swelled faster, and were more vulnerable to failure. Networks based on DGEBF monomers rather than DGEBA were generally found to exhibit an improved chemical performance. Chain extension of epoxy resin monomers was demonstrated to result in less dense networks which showed lower and slower solvent uptake. Aromatic amines were found to give denser networks which showed reduced and slower sorption (vs. aliphatic analogues). 1,3- substitution of six-membered rings was found to produce networks of a higher performance than 1,4- analogues, irrespective of similar densities. Across the work it was demonstrated that none of the individual physical/thermal properties probed (glass transition temperature, density, crosslink density, beta transition temperature) offered an effective indicator (in isolation) of chemical performance, though a combination of properties indicating a well-packed network gave a good indication of performance. Density was shown to be the most important of these factors.

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