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Towards Lean Combustion

Final Report Summary - TLC (Towards Lean Combustion)

The mitigation of aviation emissions in terms of their environmental impact is a priority for both air quality (local impact) and the greenhouse effect (global impact). For a fixed engine cycle, the margin of progress depends on the combustor technology. Lean combustion is the breakthrough, which should enable high-level reductions in NOx emissions both during the LTO cycle (air quality) and at cruise speeds (global impact). In addition, lean combustion also enhances particulate reduction. Injection systems form the most critical issue in achieving a satisfactory level of lean combustion and will be the technological focus for the project.

Within this framework, a wide range of experiments will be carried out on mono-sector or tubular combustors. This program was a crucial effort in achieving sufficient maturity for the single annular combustor application. The objectives was an 80 % reduction in NOx emissions in relation to the CAEP2 regulation limit during the LTO cycle, and low NOx emission indices at cruise speed (EINOx = 5 g/kg as target). Other gaseous emissions and soot performance characteristics were also precisely evaluated.

In this prospect, the project supported the adaptation of most advanced, non-intrusive laser-based measurement techniques to combustors actual conditions and their application (in addition to intrusive techniques) to experiments of various concepts of injection systems. The injection systems tested was derived from the Lopocotep program or other projects and from advanced CFD optimisation of new concepts. The entire range of operating conditions was experimentally evaluated (LTO points, cruise speeds). Auto-ignition and flashback risk issue as well as lean extinction limit were assessed. Advanced CFD simulation exploited the data from the fundamental experiments, thereby enabling calibration of the latest codes in emissions predictions.

The TLC consortium gathers 19 partners from 6 countries (France, Germany, Italy, Sweden, Spain and Poland). Main European actors in aero-engine combustor technology are involved (Snecma, Rolls-Royce Deutschland, MTU, Avio, Turboméca). The two main national research centres in aeronautics (DLR, ONERA) and best universities and laboratories in measurement and computation participate to TLC (Ulund, CORIA, ECN, ITS, EBI, Gen-U, Na-U, Cerfacs, LITEC, DMA , IMP).