Study of Brake Wear Particle Emissions: Impact of Braking and Cruising Conditions

Hagen, Ferdinand H. Farwick zum; Mathissen, Marcel; Grabiec, Tomasz; Hennicke, Tim; Rettig, Marc; Grochowicz, Jaroslaw; Vogt, Rainer; Benter, Thorsten

doi:10.1021/acs.est.8b07142

Cited by 98 publications

(73 citation statements)

References 25 publications

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“…The peak disc temperature is commonly suggested as an indicator for the onset of thermal release of material from the brakes [14,16,24]. However, this lumped parameter does not properly represent the actual temperature on the contact area between pads and disc.…”

Section: Discussionmentioning

confidence: 99%

“…Such a shift in the onset of their formation was observed with all pad materials tested. This behavior could simply reflect release of the more volatile compounds of the brake lining in the first run [16]. However, considering the relatively high temperatures achieved at the end of the sequence (~600 C), it is also possible that chemical restructuring of the brake pads took place.…”

Section: Discussionmentioning

confidence: 99%

“…It is not clear whether this systematic observation of volatile particles over the LACT is merely caused by differences in the pad formulations employed in the different studies or it reflects different emission behavior from the WLTP procedure. The LACT cycle includes more aggressive braking events and much higher braking durations [16].…”

Section: Discussionmentioning

confidence: 99%

“…Different approaches have been employed for the characterization of brake-wear emissions, ranging from on-road measurements [13] to chassis dynamometer [14], brake dynamometer [13,15,16] and pin-on disc configurations [17]. One of the major challenges in any measurement configuration relates to the inherent difficulties in sampling and transporting super-micron particles [13].…”

Section: Introductionmentioning

confidence: 99%

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Physical Characterization of Brake-Wear Particles in a PM10 Dilution Tunnel

et al. 2019

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A dilution tunnel was designed for the characterization of brake-wear particle emissions up to 10 µm on a brake dyno. The particulate matter emission levels from a single front brake were found to be 4.5 mg/km (1.5 mg/km being smaller than 2.5 µm) over a novel real-world brake cycle, for a commercial Economic Commission for Europe (ECE) pad. Particle Number (PN) emissions as defined in exhaust regulations were in the order of 1.5 to 6 × 10 9 particles per km per brake (#/km/brake). Concentration levels could exceed the linearity range of full-flow Condensation Particle Counters (CPCs) over specific braking events, but remained at background levels for 60% of the cycle. Similar concentrations measured with condensation and optical counters suggesting that the majority of emitted particles were larger the 300 nm. Application of higher braking pressures resulted in elevated PN emissions and the systematic formation of nano-sized particles that were thermally stable at 350 • C. Volatile particles were observed only during successive harsh braking events leading to elevated temperatures. The onset depended on the type of brakes and their prehistory, but always at relatively high disc temperatures (280 to 490 • C).

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Physical Characterization of Brake-Wear Particles in a PM10 Dilution Tunnel

et al. 2019

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“…Similarly, experimentally measured brake wear PM 2.5 EFs vary from 0.1 mg·km −1 to 5 mg·km −1 per vehicle [8,11,13]. Finally, particle number (PN) EFs reported by various researchers also appear to be inconsistent [12,[14][15][16]. This is probably due to more variations on the setup and measurement protocols when PN related studies are examined.…”

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confidence: 99%

Brake Wear Particle Emissions of a Passenger Car Measured on a Chassis Dynamometer

et al. 2019

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Brake wear emissions with a special focus on particle number (PN) concentrations were investigated during a chassis dynamometer measurement campaign. A recently developed, well-characterized, measurement approach was applied to measure brake particles in a semi-closed vehicle setup. Implementation of multiple particle measurement devices allowed for simultaneous measurement of volatile and solid particles. Estimated PN emission factors for volatile and solid particles differed by up to three orders of magnitude with an estimated average solid particle emission factor of 3·10 9 # km −1 brake −1 over a representative on-road brake cycle. Unrealistic high brake temperatures may occur and need to be ruled out by comparison with on-road temperature measurements. PN emissions are strongly temperature dependent and this may lead to its overestimation. A high variability for PN emissions was found when volatile particles were not removed. Volatiles were observed under high temperature conditions only which are not representative of normal driving conditions. The coefficient of variation for PN emissions was 1.3 without catalytic stripper and 0.11 with catalytic stripper. Investigation of non-braking sections confirmed that particles may be generated at the brake even if no brakes are applied. These "off-brake-event" emissions contribute up to about 30% to the total brake PM 10 emission.EFs depend on parameters like the type of the friction material, the type of the brake assembly, and the applied driving conditions [11]. Following the development of a WLTP-based braking cycle in 2018 [7], most studies focused on the application of realistic braking patterns, but still the range of reported EFs remained relatively wide [12][13][14]. Similarly, experimentally measured brake wear PM 2.5 EFs vary from 0.1 mg·km −1 to 5 mg·km −1 per vehicle [8,11,13]. Finally, particle number (PN) EFs reported by various researchers also appear to be inconsistent [12,[14][15][16]. This is probably due to more variations on the setup and measurement protocols when PN related studies are examined. One has to keep in mind that traffic related PN emissions, particularly ultrafine particle emissions, are becoming more relevant due to demonstrated negative health effects [17,18].One important reason for the observed inconsistencies in the measurement of PM and PN EFs is the lack of a standardized methodology for sampling and measuring brake wear particle emissions [7]. Indeed, in most references provided previously, different sampling and measurement setups were employed. Brake wear particles can be studied in a relatively controlled environment in the laboratory or under uncontrolled real-world conditions on the road [19,20]. Laboratory studies can be carried out at full vehicle level on a roller chassis bench [21], at brake couple level on a brake dynamometer [11,[22][23][24][25][26][27], or at brake component level on a pin-on-disc configuration [28][29][30][31][32]. Table 1 gives an overview of different methods applied by different researchers...

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Investigation of Brake Emissions of Different Brake Pad Materials with Regard to Particle Mass (PM) and Particle Number (PN)

Paulus¹

2019

Proceedings

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Study of Brake Wear Particle Emissions: Impact of Braking and Cruising Conditions

Cited by 98 publications

References 25 publications

Physical Characterization of Brake-Wear Particles in a PM10 Dilution Tunnel

Physical Characterization of Brake-Wear Particles in a PM10 Dilution Tunnel

Brake Wear Particle Emissions of a Passenger Car Measured on a Chassis Dynamometer

Investigation of Brake Emissions of Different Brake Pad Materials with Regard to Particle Mass (PM) and Particle Number (PN)

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