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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). The main margin for progress is in the field of combustor technology. Lean combustion technology is the breakthrough that should enable high-level reductions in NOx emissions, both at airports and in cruise. In addition, lean combustion also assists the reduction of particulates. Injection systems are the most critical issue in achieving a satisfactory level of lean combustion, and are the focus of this project.

Project objectives

The project aims to achieve sufficient maturity in lean combustion for the single annular combustor application. The objectives will be an 80% reduction in NOx emissions in relation to the CAEP2 regulation limit during the LTO (Landing and Take-Off) cycle, and low NOx emission indices at cruise speed (EINOx=5g/kg as a target). Other gaseous emissions and soot performance characteristics will also be precisely evaluated. In addition, significant progress is expected on non-intrusive measurements and numerical diagnostics.

Description of the work

A wide range of experiments will be carried out on mono-sector or tubular combustors. The injection systems tested will be of LPP/LP (Lean Premixed Prevaporised/Mean Premixed) type, derived from the LOPOCOTEP 5th Framework Programme project or other projects, and from advanced CFD optimisation of new concepts. The entire range of operating conditions will be experimentally evaluated (LTO points, cruise speeds). Auto-ignition and flashback risk issues as well as lean extinction limits will be assessed.

The project will support, in parallel, the adaptation of advanced, non-intrusive laser-based measurement techniques to combustor actual conditions and their application (in addition to intrusive techniques) to experiments of the various concepts of injection systems. Advanced CFD simulation will also exploit the data from the fundamental experiments, thereby enabling calibration of the latest codes in emission predictions.

The project is composed of four Work Packages: on non-intrusive measurements, including in particular LIF, CARS, LDA/PDPA and LII techniques; on experimental campaigns to assess new LPP/LP injection systems performance; on injection systems designs and optimisation; on numerical exploitation (RANS and LES) and diagnostics.

Expected results

The project will result in the achievement of satisfactory maturity on lean injection systems with high pollutant level reduction, the development of appropriate non-intrusive laser-based measurement techniques, the calibration of the most modern CFD tools and the establishment of rigorous optimisation procedures for lean injection systems.