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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Increasing emissions and depleting fossil fuel resources have led to concerns over the sustainability of conventional jet fuel and growth in research on alternative fuels. One of the strategies in the field for further research is to check the performance and emissions of gas turbine engines by using different alternative fuels. 100 % SPK and Fully Formulated Synthetic Jet Fuel appear to be attractive alternative fuels for gas turbine engines due to their similar properties as Jet fuel. This paper presents the results of an experimental study done on a small gas turbine engine, burning conventional Jet A-1 fuel, thermally stressed % SPK and Fully Formulated Synthetic Jet Fuel. Emissions have been measured at engine exit plane. Comparison of emissions and performance parameters of different alternative fuels have been presented in the paper. A detailed analysis on emissions (CO, CO 2 , NO, NO 2 , NO x , Smoke and particulate) and performance of % SPK, Fully Formulated Synthetic Jet Fuel, Jet A-1 has been presented and compared. Substantial reduction in smoke and particulate emissions is observed for % SPK as compared to conventional Jet A-1 and Fully Formulated Synthetic JetFuel due to lower aromatic content. Nomenclature CLD = Chemi Luminescence Detection FID = Flame Ionization Detector FTIR = Fourier-Transform Infra-Red Detector H 2 = Hydrogen H 2 O = Water NDIR = Non-Dispersive Infra-Red Detector NO x = Nitrogen oxides SPK = Synthetic Paraffinic Kerosene UHC = Unburned Hydro-Carbons

It is a well-known fact that NO2 has far more harmful effects as compared to NO. NO2 creates ozone, which causes eye irritation and exacerbates respiratory conditions. This leads to an increased emergency departments’ visits and hospital admissions for respiratory issues, especially asthma. Under current situation, majority of regulations deal with total NOx emissions, without looking at the break-up of NO2 and NO. However, there is a feeling in emissions regulation community to implement regulations on NO2 emissions. There are standards to measure total NOx emissions. However, these standards are not equipped enough to measure NO2 emissions accurately. The effect of sample line length on NO2 emissions is not fully understood to date. Also, the standards only suggests maximum of 10 seconds residence time regardless of what the line length is. In this study, a systematic experimental test campaign has been conducted to understand the effect of sample line length on NO2, NO distribution. The residence time was maintained below 10 seconds in accordance with the SAE ARP1256D standards. A Rolls-Royce gas turbine combustor and different calibration cylinders have been used to study the effect of sample line length. A numerical study has also been done to predict the conversion of NO2 to NO. It has been found that with increasing sample line length, more NO2 gets converted to NO and overall NO2 emissions show a reduction, whereas this would not be the case at engine exhaust. This effect of sample line length can be used as a loophole in giving lower NO2 emissions readings.