Real Driving Emissions Sampling System for Brake Wear Particle Measurement

Brake wear is well recognized as one of the dominant sources of traffic-induced particulate matter emissions. A first standardized measurement methodology is currently being developed by UNECE's Particle Measurement Program. The approach is based on isolated single brakes on dedicated brake test beds, where the test conditions can be tightly controlled. However, the actual real-world emission behavior of a brake system is influenced by many changing factors depending on the vehicle and a multitude of surrounding conditions. This makes real driving emissions measurement of brake dust a highly relevant but also very challenging task, considering minimal impact of the measurement setup on the emission behavior. In this paper, we show the design of a novel brake particle sampling system with minimal influence on the thermal behavior of the brake, supported by numerical simulation studies. The proposed setup covers only part of the brake disc on one side and allows for installation with minimal interventions at the brake mount and rim. The particle-collecting grommet and the sampling line were carefully designed to minimize larger particle losses. The sampling system was implemented in a commercial passenger car and equipped with particulate matter measurement instruments, closely following the ongoing standardization for brake dyno emission testing. Repeated real driving tests on a test track were successfully performed with different sampling flow rates. The results demonstrate the validity of the proposed approach, indicating promising particulate matter collection efficiency with sufficiently high sampling flow.