Quantification of braking particles emission by PIV analysis — Application on railway

The work focuses on particle trajectories from a railway braking device. We have developed an experimental method based on Particle Image Velocimetry analysis to evaluate the dispersion of the particulate matter. The motion of a train is simulated with an airflow imposed in a wind tunnel and a reduced-scale braking bench is embedded in the test section. The particle motion can be observed using a laser sheet in the rubbing contact plane. Images are recorded with cameras synchronized with braking bench measurements such as braking pressure, disc and pad temperature, sliding speed. The results demonstrate some correlation with particle counters and the stages of braking events regarding the concentration. They highlight opposing effects of the flow induced by the disc and by the wind tunnel. The particle motions are initially dominated by the disc induced airflow until they leave the boundary layer. The induced airflow becomes dominant. • PIV analysis allows tracking the trajectories of braking particles. • An indicator provides information on the presence of particles near the disc. • The presence indicator is correlated with particle counter measurements. • Emission phases are highlighted according to the braking steps.