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Development of the Lean Azimuthal Flame as an Innovative aviation gas turbine low-NOX combustion concept

Periodic Reporting for period 2 - LEAFINNOX (Development of the Lean Azimuthal Flame as an Innovative aviation gas turbine low-NOX combustion concept)

Reporting period: 2020-01-01 to 2021-06-30

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. This project aims at the development of a new kerosene 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. In the first year of the LEAFINNOX project, a preliminary LEAF kerosene combustor has been demonstrated for the first time, and measurements have shown it produces virtually no particulate emissions. 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 second year, detailed measurements of NOx have demonstrated its low-NOx potential, with single-digit ppm NOx emissions feasible, while a new burner have been developed by the partners and is being tested at high pressures. The results are important for aviation as they allow potentially low-soot and low-NOx to be achieved.
The work is proceeding satisfactorily, with the key Milestone (i.e. the creation of the novel kerosene LEAF combustor) achieved. The partners have collaborated closely and the work has resulted in the following results:

1. A novel, soot-free kerosene flame has been developed. The preliminary visualisation and soot measurements performed show that the novel kerosene LEAF has great potential in producing low emissions from kerosene combustion. Further tests in the context of high-pressure, NOx and unburnt hydrocarbons in the 2nd year will reveal the extent to which this concept is truly of interest to industry to fully assess its potential for a practical device.

2. Novel ways to measure nanoparticles in gas turbine flames have been developed. The data assembled by the UNINA probe and analysis system in the UCAM conventional (RQL) burner and in the novel kerosene LEAF demonstrate, for the first time, the number of nanoparticles emitted by swirl flames and by kerosene MILD combustion concepts.

3. NOx and soot kinetic models have been implemented in CFD codes that can be used for LEAF but also for conventional combustor systems, hence allowing innovations.

The results are continually being communicated to industry through focused exchanges and participation to the Technical Reviews and the establishment of an Industrial Steering Committee.
Burning liquid fuels, and especially kerosene, has always been frought with high levels of soot production. It has been demonstrated in LEAFINNOX that the new kerosene LEAF combustor can produce virtually no soot. Preliminary measurements also show the Nox is low. This advantage will be explored further to produce a concept that has the potential to be used in aviation gas turbines. This will be achived until the end of the project through testing at more realistic conditions, modelling, and optimisation of the configuration.

Innovations in Low NOx and low soot kerosene combustion has a huge potential for European gas turbine manufacturers and the present project offers a novel combustion system that is promising for practical application. The expected results until the end of the project include: (i) optimised kerosene LEAF combustion system; (ii) guidelines on how to implement LEAF in an aviation jet engine; (iii) new modelling tools for conventional and unconventional gas turbine combustors. These will be welcome by engine manufacturers because they will allow innovations.