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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There is a growing interest in the use of alternative fuels in gas turbine engines to reduce emissions. Testing of alternative fuels is expensive when done on a large-scale gas turbine engine. In this study, a re-commissioned small gas turbine auxiliary power unit (APU) has been used to test various blends of Jet A-1, synthetic paraffinic kerosene (SPK) and diesel with as well as eight other novel fuels. A detailed analysis of performance, gaseous emissions and particulate emissions has been presented in this study. It is observed that aromatic content in general as well as the particular chemical composition of the aromatic compound plays a vital role in particulate emissions generation. SPK fuel shows substantially lower particulate emissions with respect to Jet A. However, not all the species of aromatics negatively impact particulate emissions. Gaseous emissions measured are comparable for all the fuels tested in this study.