Diversified fuel supplies and stringent environmental pollution regulations in the aviation sector have promoted the development of the alternative fuels industry. The chemical and physical properties of some of these diverse fuel substitutes lie outside of historical experience. Therefore, their combustion behavior cannot be judged via research of petroleum-derived jet fuel. Particulate matter (PM) emissions are important for future alternative fuels, although extensive results in relations to combustors are not available in the literature. Hence, large-scale experimental testing is essential for improving our understanding of alternative fuel effects on combustion performance and environmental impact. The aim of this study is to evaluate the impact of fuel properties and composition on the PM emission characteristics and flame sooty tendency profile on a Rolls-Royce Tay gas turbine combustor. Extractive sampling and in situ measurement methods have been used in this study. A total of 16 types of alternative fuels have been tested under two different operating conditions. PM emissions were measured via a differential mobility spectrometer (DMS 500 fast particulate spectrometer), and the soot propensity profile was analyzed via an innovative visual method based on flame luminosity high-speed imaging. The results indicate that a higher aromatic can be found as the main factor for insufficient burning and greater soot formation. In addition, for fuel properties, the density and surface tension were supposed to be key factors for soot formation. For chemical compositions, fuels with higher cycloparaffin content have the potential to induce soot promotion. In contrast, a fuel with a high hydrogen content can perform in a much more environmentally friendly way. Furthermore, it was observed that the results of PM emission measured by DMS 500 and sooting tendency computed via an imaging method (in situ) correlated particularly well for all of the tested fuels and conditions in this study. The in situ soot emission monitoring method presented in this study can be used for detailed, instantaneous investigation of PM emissions within the combustor. Thus, this method can be considered an alternative evaluation method for measuring qualitative soot emissions.

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Fuel formulation with particular selection of fuel components is a promising approach that offer the reduction of harmful emissions without altering the combustion system performance. Each fuel component has their own combustion characteristics and hence contribution in emissions. Aromatic is one of the main component of fossil based fuels and have a strong correlation with the formation of PM emissions. Besides aromatics presence in fuel is essential for compatibility of fuel with combustion system and maintaining the energy density of the fuel. In this regard, a Rolls Royce combustor rig was used to test 16 aromatics blended with jet fuels in three different proportions. Moreover, a novel approach of flame luminosity imaging is employed to measure the PM emissions through the soot propensity profile. The results show that PM emissions increase with the proportional increase of aromatics. The di- and cyclo-aromatics produced significantly higher PM emissions compared to alkyl-benzenes. 3-isopropylcumene has the tendency to lowest PM formation and thus is a consideration as a selection of aromatic type in future fuels for lower PM emissions. Furthermore, it was also observed that PM number concentration measured by extractive method with DMS500 instrument correlates well with imaging methods for all the tested fuels. The present study provides an information of particular selection of aromatic for future fuel development.

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