Unveiling soot volume fraction trends in model gas turbine RQL combustor at varying pressure using in-situ LII calibration technique

Formation and oxidation of soot in combustion processes have long concerned researchers due to its impact on nature and life. Reducing soot emissions in ground vehicles, power plants, and aircraft requires a thorough understanding of the real-time phenomenon. On the one hand, the world is advancing aviation sustainability with greener fuels like hydrogen/hybrid fuels or modifying the processes with Lean Direct Injection (LDI), while on the other hand, the community is working to mitigate soot in Rich burn - Quick quench - Lean burn (RQL) combustion strategy. Present work highlights the soot volume fraction trends observed in an industrial scale RQL gas turbine combustor by utilizing Laser Induced Incandescence (LII) with in-situ calibration, at pressures of 2 bar and 4 bar and varying fuel-to-air ratios (FARs). Soot volume fraction (\((f_v)\)) is quantified from experimental measurements in the primary (rich) and secondary (lean) zones of the combustor in planes along the axis and perpendicular to the axis for different FARs. Key results indicate increase in FAR increases \((f_v)\) in the primary (rich) zone at 2 bar while not much soot is formed in the secondary (lean) zone. At 4 bar, there is some soot seen in the secondary zone. As the FAR increases, the \((f_v)\) decreases in the primary zone while it increases in the secondary zone. This variation of soot along the length of the combustor appears to be a consequence of local fuel distribution and temperature in these zones.