Development and validation of an on-road sampling system for brake wear particles using a wheelhouse enclosure and clean-air supply

초록

Exhaust emissions from road vehicles have been reduced through advanced engine and after-treatment technologies and stricter emission regulations. However, non-exhaust emissions from brake wear, tire wear, and resuspended road dust have become increasingly important. With Euro 7 expected to introduce limits on nonexhaust particles, technologies for monitoring and reducing brake wear particles (BWPs) during on-road driving are needed. Although BWPs have been investigated using dynamometers, on-road measurements remain difficult because ambient particles enter the sampling region and BWPs are not fully collected. This study developed a novel methodology for selectively sampling BWPs during on-road driving using a wheelhouse enclosure and a clean-air supply. Airflow and particle transport around the wheel region were analyzed by numerical simulations considering vehicle motion, wheel-brake rotation, and steering conditions. The wheelhouse enclosure was designed to prevent BWP escape, while clean air was supplied to suppress external particle ingress. The system was implemented on a vehicle and evaluated through on-road measurements. CFD simulations predicted 100% BWP sampling efficiency and external particle ingress below 1% when the wheelhouse enclosure and clean-air supply were applied. On-road validation was conducted using one vehicle under limited driving conditions and with a small number of braking events. The standard deviation of normalized number concentration reached 0.184, indicating higher variability than in indoor tests, possibly due to uncontrolled driving factors. Nevertheless, particle size distributions and SEM images from on-road experiments agreed with indoor dynamometer measurements. These results are consistent with selective BWP sampling under real driving conditions while minimizing ambient particle influence.

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