Matthieu Ems thesis defense (mechanical engineering department)

Reducing particulate emissions, particularly PM10, PM2.5 and ultrafine particles (<100nm), has become an environmental and public health issue. Their dispersion in the immediate environment during friction braking is linked, on the one hand, to thermomechanical stresses at the lining-disc interface, and on the other hand, to the under-vehicle footprint that will influence their initial trajectory.

This thesis is part of the BREAQ project aimed at reducing exposure to fine particles from rail braking.

The work presented in this thesis is specifically interested in linking particle production to thermomechanical parameters in the contact of a disc brake and assessing their trajectory using a visualization technique.

A scaled-down braking test rig is dimensioned to maintain equivalence on dissipated heat flux density and is integrated into a wind tunnel to emulate train motion.

Airflow conditions are combined with braking conditions to be representative of real urban journeys.

Particles of different sizes are quantified by real-time counters and spectrometers, as a function of braking and flow parameters.

The data show an influence of tribological conditions on the emissions profile.

The results highlight particle emission phases (contact, force maintenance, withdrawal).

A PIV (Particulate Imaging Velocimetry) analysis, usually used to calculate the velocity field of a seeded fluid, is adapted to our study to estimate particle dispersion close to the braking system.

The estimated particle velocity fields are consistent with meter measurements.

PIV analysis has enabled us to propose a temporal and spatial indicator of the presence of emitted particles during the various phases of braking.

These results are intended as an experimental database for the validation of CFD models of particle transport: they should ultimately enable the development of innovative tools for predicting/controlling the environmental impact of rail rolling stock (metro, regional trains, TGV).

Rapporteurs

• RICHARD Caroline, University Professor, University of Tours (GREMAN UMR CNRS 7347).
• DAZIN Antoine, University Professor, ENSAM, Lille (LMFL UMR CNRS 9014).

Examiners

• TRUNFIO SFARGHIU Ana Maria , Research Fellow, INSA, Lyon (LAMCOS UMR CNRS ).
• BOHER Christine , University Professor, IMT, Albi (ICA UMR CNRS 5312).

Co-Thesis supervisors

• DUBAR Laurent, Professeur des Universités, Université Polytechnique Hauts-de-France, Valenciennes (LAMIH UMR 8201).
• KEIRSBULCK Laurent, Professeur des Universités, Université Polytechnique Hauts-de-France, Valenciennes (LAMIH UMR 8201).

Co-supervisors

• BASLEY Jérémy, Maitre de conférences, Université Polytechnique Hauts-de-France, Valenciennes (LAMIH UMR 8201).
• MERESSE Damien, Associate Professor, Université Polytechnique Hauts-de-France, Valenciennes (LAMIH UMR 8201).
• WATREMEZ Michel, Associate Professor, Université Polytechnique Hauts-de-France, Valenciennes (LAMIH UMR 8201).

Invited

• PAJOT Karine, Doctor, Engineer, Alstom, Saint-Ouen-sur-Seine.

Particulate Matter, Railway braking, Particle tracking
.