Thesis of Antoine Berthier

Impact of fuel composition on aeronautic emissions, a multi-scale approach Abstract : The transportation-related economic sector is responsible for nearly 56% of greenhouse gas emissions in Europe, of which up to 2% is due to air transport. Internal combustion engines represent the majority of propulsion sources and generate gaseous and particulate matter (PM) emissions. The emitted particles (commonly called soot) are complex, mainly consisting of carbon, and may have numerous compounds adsorbed on their surface, such as sulfates, polycyclic aromatic hydrocarbons (PAHs) and metals. These emissions have a significant impact on air quality, human health and the Earth’s radiative balance. Numerous efforts to reduce pollutant emissions and fuel consumption have been implemented in recent decades by engine manufacturers, in particular through the deployment of new fuels, so-called alternative fuels, and new technologies, to meet the emission standards for gases (CO2, NOx) and non-volatile particulate matter (nvPM).
The main objective of this thesis work was to understand the link between the particulate and gas emissions of a turbojet engine and the fuel chemical composition, the engine configuration and its power. To achieve this, this work aimed to characterize the emissions of different aerosol sources burning aircraft fuels. This study stood out for its multi-technical and multi-scale approach. The characterization of the different combustion sources was done by coupling “physical” nvPM measurements, on a line developed according to the SAE (Society of Automotive Engineers) recommendations, and “chemical” ones via sample collection on filters and subsequent analysis by mass spectrometry. Emissions characterization techniques were deployed from the laboratory scale on a mini-CAST burner adapted for liquid fuel combustion, to the turbomachine scale on a helicopter engine from Safran Helicopter Engines (SHE), after passing through the combustion bench scale on ONERA’s installations.
The mini-CAST laboratory burner adapted to burn liquid fuels and the M1 combustion bench were used as a part of the European JetScreen project to achieve the combustion of common and alternative fuels to link the fuel composition to nvPM emissions and the chemical composition of emissions. It was possible to observe a reduction in nvPM emissions (number concentration, mass concentration, size distribution) according to the level of aromatic compounds present in the fuel. In addition, mass spectrometry analysis showed a reduction in the PAH relative intensity when using alternative fuels. Using ONERA’s MICADO test bench as a source of representative aerosols, allowed the analyses of the impact of a catalytic stripper on the chemical composition of emissions, this device being commonly used to isolate nvPM in the emissions. The suppression of the organic layer on the surface of soot particles was so evidenced. Finally, characterization techniques were deployed at the exit of a helicopter engine, allowing the characterization on the emissions in various engine configurations (release of lubricating oils, used or new injectors…) and as a function of its power. Filters sampling made possible to highlight the presence of PAHs, oxygenated hydrocarbons, sulfur and nitrogen compounds, as well as metal compounds resulting from the wear of rotating parts in the engine. By applying semi-quantitative approaches, it was possible to link the relative chemical (PAH relative intensity) and physical (nvPM mass concentration) with the power regime of the engine. Keywords : emissions,non-volatile particulate matter,physico-chemical characterization,test bench,turbojet engine