PhD Defense of Mr. Rafaël BARRELLON-VERNAY

BARRELLON-VERNAY Rafaël, PhLAM Laboratory- UMR8523 / ONERA- PMI Team 

Titre: Nucleation mechanisms of volatile particles in aircraft engine emissions and their links with fuel composition

Jury: C. FOCSA (PhLAM), I. ORTEGA COLOMER (ONERA Palaiseau), D. DELHAYE (ONERA Palaiseau), R. MIAKE-LYE (Aerodyne Research USA), B. CABANAS GALAN (Université de Castille, Espagne), X. MERCIER (Université Lille, PC2A), T. PETÄJÄ (Université d'Helsinki, Finlande), Y. MERY (SAFRAN Aircraft Engine, Villaroche)

Abstract:

One of the actual concerns of the aviation industry is to reduce fuel consumption and environmental footprint. Indeed, aviation emissions impact air quality in and around airports. As other transport sectors, aviation effluents need to be addressed to reduce greenhouse gases contribution (2% of these emissions are related to air transport worldwide), volatile and non-volatile Particulate Matter (vPM and nvPM) and indirect impact as condensation trails.

To reduce these emissions, different approaches have been investigated, in particular the use of Sustainable Aviation Fuels (SAF). Aims of SAF are to decrease the net CO2 emissions and nvPM. However, combustion of these fuels may lead to new pollutants that can react with atmosphere by formation of secondary aerosols. As part of the UNREAL project (Unveiling Nucleation mechanism in aiRcraft Engine exhAust and its Link with fuel composition), the objective of this work was to study the different molecular mechanisms of new particle formation from the exhausts of aircraft engines fed by fuels with different composition, from the standard Jet A-1 to 100 % SAF fuel.

The physicochemical characterisation of the particulate emissions from aircraft engines in real conditions is challenging both from the technical and economical point of view. Thus, a mini-CAST burner, suitable for the combustion of aeronautic liquid fuels, has been used as an alternative to obtain emissions comparable to some extent to those from aircraft engines. A decrease in nvPM emissions (number concentration, mass concentration and size distribution) can be observed in correlation with the quantity of aromatic compounds in the fuel. Moreover, the analysis by mass spectrometry revealed a decrease in the relative intensity of PAHs when alternative fuels were employed  . Emissions from the burner have been injected, with and without soot filtration, into an atmospheric chamber for ageing (CESAM chamber reproducing atmospheric conditions at ground level – LISA). For all fuels tested formation of vPM by homogeneous nucleation has been observed in the atmospheric chamber in absence of nvPM. This phenomenon is particularly highlighted for fuels with high amounts of sulphur in their compositions. However, in real cases (presence of soot), the formation of vPM is only observed for the fuels containing high amounts of sulphur. The concentration of gaseous precursors  formed for other fuels was not enough to produce vPM after being adsorbed on soot surface (heterogeneous nucleation). On-line characterisation techniques were completed by filter sampling and off-line mass spectrometry analysis, highlighting the presence of PAHs, oxygenated hydrocarbons, sulphur and nitrogen compounds. By employing semi-quantitative methods, it was possible to link the relative chemical composition (sulphur and PAH relative intensity) with vPM formation and their repartitions in particulate and gaseous phases.

This work benefited from the support of the project UNREAL ANR-18-CE22-0019 of the French National Research Agency (ANR).