Emissions characterization tests for hydrotreated renewable jet fuel from used cooking oil and its blends

Experimental trials have been conducted using an optical swirl burner to compare the heat release and emission profiles from the application of four different aviation fuel blends with changing inlet conditions. The mixtures comprised fossil Jet A-1 and a HRJ (Hydrotreated Renewable Jet fuel) batch produced from used cooking oil processing, and blended in discrete ratios. Changes in the produced emissions were quantified with varying combustor pressure and equivalence ratio, in addition to analysing the distribution of combustion heat release using OH∗ chemiluminescence, and monitoring operational rig temperatures. Results suggest the presence of HRJ can reduce emissions and lead to a more compacted and homogenous heat release zone, beneficial as localised hot-spots can lead to the generation of soot and thermal NOx. An increase in pressure was also shown to compact the flame brush at constant thermal power, due to density changes in the combustion air, and reduced bulk flow. The presented heat release distributions and experimental data are useful for the validation of numerical simulations, particularly for the use of alternative fuels. The work also highlights the correlation of flow/acoustic perturbations with heat release, crucial in characterising global combustion behaviour.