The development of jet engines with lower emissions than today is imperative from an environmental and public health perspective and for maintaining the competitiveness of European aviation industry. To this end, methods to use kerosene while producing lower NOx and particulate emissions are vital and innovations in this area can become very important for engine manufacturers. In addition, using low-carbon fuels is imperative. This project aims at the development of a new liquid fuel combustion concept based on "MILD" combustion principles, where the fuel and the air are significantly diluted with hot combustion products before they mix and burn, hence reducing the generation of pollutants. The particular configuration studied is the "Lean Azimuthal Flame" (LEAF) which has shown good emission reduction characteristics with natural gas. A liquid-fuel LEAF kerosene combustor has been demonstrated for the first time, which also works well with a range of other liquid fuels including Sunstainable Aviation Fuels, and measurements have shown it produces virtually no particulate emissions and very low NOx. The results also include new modelling capabilities that can be used not only for MILD combustion concepts in the future, but also for improved predictions of more conventional combustor concepts such as the Rich-Quench-Lean (RQL) configurations that are the workhorse of NOx reduction technologies at present. In the project, detailed measurements of NOx have demonstrated its low-NOx potential, with single-digit ppm NOx emissions feasible, while a new burner has been developed by the partners and has been tested at high pressures. Finally, the LEAF burner has operated with 100% hydrogen, producing very low NOx, hence promoting the use of this novel technology also for this important zero-carbon fuel. The results are important for aviation as they allow potentially low-soot and low-NOx to be achieved with a range of fuels (fossil kerosene, synthetic kerosene, hydrogen).
