(주)에이피엠엔지니어링

Characteristic of Brake Wear Particles under Various Test Driving Cycles

Abstract

Brake wear particles (BWPs) were measured using a brake dynamometer to understand the characteristics of

fine dust generated by brake wear under various driving cycles. WLTC (word harmonized light-duty vehicle test cycle), Novel braking cycle which was specialized for brake particles measurement, and NIER (national institute of environment research) driving cycles which was used to determine the exhaust emission factor in Korea were utilized. The experimental results showed that emission factors of PM10 and PM2.5 in three driving modes were ranged with 0.21~0.61 mg/km/brake and 0.12~0.36 mg/km/brake, respectively. NIER driving cycle showed the highest number of braking among the three cycles, which caused the highest emission factor. However, the braking dissipation energy of each stop in the test cycle rather than the number of braking had a greater effect on the generation of BWPs. Although the same pad and disc were used, it was confirmed that the particle size distributions were different for each test cycle. The BWPs showed a unimodal distribution with mode diameter of around 2~3 μm based on aerodynamic diameter and showed a bimodal distribution with mode diameters of 600 nm and 2.8 μm based on optical diameter. Comparing the 15 NIER test cycles classified by average driving speed, the faster the speed, the smaller diameter of BWPs generated. The ratio of BWPs generated by brake drag varied by 4~53% according to the steps of NIER test cycle. Specialized new driving cycle or modified NIER driving cycle in consideration of the driving speed and brake dissipation energy are required to measure the emission factor of BWPs.

key words: Non-exhaust particulate matter, Brake wear particles, Test driving cycle, Dissipation energy

▶Sources: Journal of Korean Society for Atmospheric Environment Vol. 36, No. 3, June 2020