Caractérisation des particules de suies et de leurs précurseurs issus de la combustion de biocarburants. Etude couplée par diagnostics laser in-situ et par prélèvement on-line et désorption laser/ionisation laser/spectrométrie de masse.

Characterization of soot particles and their precursors from the combustion of biofuels. A study by in-situ laser diagnostic and on-line sampling following by laser desorption / ionization for mass spectrometry analysis.

The objective of this thesis is to study the influence of the nature of innovative biofuels on the soot formation in flames. The nature of soot precursors in the gaseous phase, the soot oxidation and the chemical composition of soot particle surface will be studied.

Selected fuels will be ignited either directly in liquid phase in the form of spray into a turbulent flame, or pre-vaporised in the form of a laminar flame in order to model the soot formation kinetics.

Soot and their precursors (gaseous polycyclic aromatic compounds, PAHs) will be mapped by non-intrusive laser diagnostics (laser-induced fluorescence and incandescence), to better understand their oxidation and formation mechanisms in the studied flames.

To study the chemical composition of the soot surface (responsible for many of their properties), the soot will be sampled by a microprobe in flames and diluted in an inert carrier gas. A transfer line will be used to prevent aging in the atmosphere. This line will allow the soot deposition onto a cold substrate directly under vacuum. The surface of the soot will be analyzed by mass spectrometry coupled to laser desorption and laser ionization in order to obtain the size distributions of the different molecular families adsorbed even at trace levels.

Innovative ionization schemes (REMPI or SPI in the VUV) will be used to selectively study the different classes of molecules. In a second step, the particles will be studied directly isolated in a molecular beam. To characterize the fate of the particles emitted into the atmosphere, these analyzes by mass spectrometry can be compared with those obtained for soot particles produced in the same conditions but having aged in the atmosphere.

Characterization of soot surface by ToF-SIMS and thermogravimetric will be also performed.

Directeur(s) et co-encadrant(s): Eric Therssen (PC2A) et Yvain Carpentier (PhLAM)

Laboratoire: PC2A