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Swirl combustion is one of the most efficient approach to efficient combustion processes and therefore, it has received great interest particularly from aerospace industry. Swirl combustion has been studied in the past both experimentally and computationally. However, in spite of the extended studies, the swirl combustion is still not well understood and therefore, further studies are required. One of the open questions in the swirl combustion is the effect of the swirl number on the combustion efficiency and instabilities. Over decades, extensive experimental and computational studies of swirl combustion have been performed. The experimental studies of swirl combustion are quite challenging due to the unsteady nature of the combustion process. To overcome these challenges, computational studies have been used in the study of turbulent combustion. The present study concerns the effect of the swirl number on the combustion efficiency and flame stability. The combustion efficiency is assessed based on the temperature developed inside the combustion chamber and NOx levels. The effect of air/fuel blowing ratio on the combustion efficiency and instability is also investigated in this research. The computations are carried out using the large-eddy simulation (LES) approach along with the flamelet combustion model. The analysis reveals the unsteady nature of the flame and thus, its departure from the core of the combustor. The analysis also reveals the presence of a region of high level of temperature, NO and2CO , inside the combustor 

An investigation into emissions differences and their correlations with differing combustion characteristics between F24 and Jet-A was conducted. Raw emissions data was taken from a single stage jet engine by a FTIR gas analyzer. Measurements of H₂O, CO₂, CO, NOx, and total hydrocarbon emissions (THC) were taken at 60K, 65K, and 70K RPM. At 70K RPM Jet-A and F-24 the emissions were similar at approx.: 4% H₂O, 3% CO₂, 970 PPM CO, 28 PPM NOx. Jet-A THC emissions were approx.: 1200 PPM THC, F24 THC emissions were lower by over 60%. The significantly lower amount of THC emissions for F24 suggests more complete combustion compared to Jet-A. 

The Coal-To-Liquid (CTL) synthetic aviation fuel, Iso-Paraffinic Kerosene (IPK), was studied for ignition delay, combustion delay, pressure trace, pressure rise rate, apparent heat release rate in an experimental single cylinder indirect injection (IDI) compression ignition engine and a constant volume combustion chamber (CVCC). Autoignition characteristics for neat IPK, neat Ultra-Low Sulfur Diesel (ULSD), and a blend of 50%IPK and 50% ULSD were determined in the CVCC and the effects of the autoignition quality of each fuel were determined also in an IDI engine. ULSD was found to have a Derived Cetane Number (DCN) of 47 for the batch used in this experimentation. IPK was found to have a DCN of 25.9 indicating that is has a lower affinity for autoignition, and the blend fell between the two at 37.5. Additionally, it was found that the ignition delay for IPK in the CVCC was 5.3 ms and ULSD was 3.56 ms. This increase in ignition delay allowed the accumulation of fuel in the combustion chamber when running with IPK that resulted in detonation of the premixed air and fuel found to cause high levels of Ringing Intensity (RI) when running neat IPK indicated by the 60% increase in Peak Pressure Rise Rate (PPRR) when compared to ULSD at the same load. An emissions analysis was conducted at 7 bar Indicated Mean Effective Pressure (IMEP) for ULSD and the blend of 50% ULSD and 50% IPK. With the addition of 50% IPK by mass, there was found to be a reduction in the NO_x, CO₂, with a slight increase in the CO in g/kWh.