November 2024
In a joint measurement campaign of the NEX-EL project by VTT, Tampere University, and the Finnish Meteorological Institute, particle emissions from car brakes were studied. The experimental work was carried out in Espoo using VTT’s brake testing equipment, which is based on an electric motor dynamometer and a passenger car brake system. The brake is enclosed, and the internal airflow of the enclosure carries particles from the brake to the measuring devices.
The study investigated how different parameters affect particle emissions from brakes. The impact of electric powertrain regeneration and vehicle mass was studied by simulating their effect on the required braking force. Additionally, differences between two different brake pad materials were compared.
The particles from the brakes were analyzed for their number, mass, size, and chemical composition. Mainly, micrometer-sized particles, typical of street dust, were released from the brakes. A significant number of small particles, comparable in size to exhaust particles, were observed when the brake disc heated above 200°C. The particles from the brakes contained various metals and organic compounds. The highest concentrations of metals were measured for iron, copper, zinc, tin, chromium, and barium. The brake pad material was found to affect particle emissions. When low-metal brake pads were used instead of regular ones, particle emissions decreased significantly (30-90%).
