Brake wear emissions gained significant relevance with the upcoming Euro7 type
approval within the European Union for brake emission measurement on the test
bed. While the controlled brake test bed approach provides consistent results,
real-driving emission (RDE) measurements are needed to better understand actual
emission behavior due to varying vehicle and environmental conditions. The EU
has already announced its interest in RDE testing. Here we present the results
of an RDE brake wear sampling system with minimal thermal impact, where
particles are only sampled from one side of the brake disc, characterized on a
laboratory sampling system. The investigations aim to validate symmetric
particle release and to confirm that doubling the measured RDE results
effectively represents the reference emissions on the test bed. The discovered
positive correlation between brake temperature and PN, PM2.5, and
PM10 emissions under different cooling settings emphasizes the
importance of our system with minimal interference with the vehicle's cooling
behavior to maintain accurate emission results. Following the Trip-10 test
cycle, we found deviations between the test bed and RDE sampling system ranged
from -18% to +9% for PM2.5, -12% to +24% for PM10, and
-23% to +0% for PN. Reasons could be potential particle losses, unequal wear of
the inner and outer brake side, or particle crosstalk between both sides of the
brake. Finding the optimum sampling flow within the tested range will lead to
the desired agreement of results. Evaluating this brake’s emissions with both
sampling systems following the WLTP-Brake cycle (used for the upcoming Euro7
legislation) resulted in 1.4-1.8 mg/km and 5.2-5.5 mg/km per front brake for
PM2.5 and PM10, respectively. This would exceed the
upcoming Euro7 limit more than twice on a vehicle basis.
