Study of Brake Wear Particle Emission

A special issue of Atmosphere (ISSN 2073-4433). This special issue belongs to the section "Air Quality".

Deadline for manuscript submissions: 21 June 2024 | Viewed by 4965

Special Issue Editor

College of Mechanical and Electronic Engineering, China University of Petroleum, Qingdao 266500, China
Interests: friction-induced vibration and noise; tribology performance of brake materials; eco-friendly brake friction materials; brake wear particle emissions
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Special Issue Information

Dear Colleagues,

The traffic-generated PM emissions are classified into exhaust PM emissions and non-exhaust PM emissions. Due to the strict regulations for vehicle exhaust emissions and the rapid growth of electric vehicle (EV) sales, the contribution of non-exhaust PM emissions to the total traffic-generated PM emissions will reach 90% by the end of the current decade.

Brake wear particle emissions are a primary source of non-exhaust traffic-generated emissions. In November 2022, the European Commission proposed new Euro 7 standards to reduce the brake wear particle emissions so that the limit for M1 (passenger cars) and N1 (light commercial vehicles) vehicles is 7 mg/kg/vehicle until 2035, and 3 mg/km/vehicle afterwards. However, there are many knowledge gaps regarding brake wear particle emissions. The Special Issue aims at improving the knowledge of brake wear particle emissions including the tribological formation mechanisms, PM measurement methods, adverse health effects of brake wear particles, and brake wear mitigation approaches. A special focus is given to the brake wear particle emissions from EVs. Both experimental and simulation studies are welcome.

Dr. Long Wei
Guest Editor

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Keywords

  • brake wear
  • emissions
  • non-exhaust
  • particular matter

Published Papers (4 papers)

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Research

27 pages, 11172 KiB  
Article
A Practical Approach for On-Road Measurements of Brake Wear Particles from a Light-Duty Vehicle
by Jon Andersson, Louisa J. Kramer, Michael Campbell, Ian Marshall, John Norris, Jason Southgate, Simon de Vries and Gary Waite
Atmosphere 2024, 15(2), 224; https://doi.org/10.3390/atmos15020224 - 13 Feb 2024
Viewed by 963
Abstract
Brake wear particles are generated through frictional contact between the brake disc or brake drum and the brake pads. Some of these particles may be released into the atmosphere, contributing to airborne fine particulate matter (PM2.5). In this study, an onboard [...] Read more.
Brake wear particles are generated through frictional contact between the brake disc or brake drum and the brake pads. Some of these particles may be released into the atmosphere, contributing to airborne fine particulate matter (PM2.5). In this study, an onboard system was developed and tested to measure brake wear particles emitted under real-world driving conditions. Brake wear particles were extracted from a fixed volume enclosure surrounding the pad and disc installed on the front wheel of a light-duty vehicle. Real-time data on size distribution, number concentration, PM2.5 mass, and the contribution of semi-volatiles were obtained via a suite of instruments sub-sampling from the constant volume sampler (CVS) dilution tunnel. Repeat measurements of brake particles were obtained from a 42 min bespoke drive cycle on a chassis dynamometer, from on-road tests in an urban area, and from braking events on a test track. The results showed that particle emissions coincided with braking events, with mass emissions around 1 mg/km/brake during on-road driving. Particle number emissions of low volatility particles were between 2 and 5 × 109 particles/km/brake. The highest emissions were observed under more aggressive braking. The project successfully developed a proof-of-principle measurement system for brake wear emissions from transient vehicle operation. The system shows good repeatability for stable particle metrics, such as non-volatile particle number (PN) from the solid particle counting system (SPCS), and allows for progression to a second phase of work where emissions differences between commercially available brake system components will be assessed. Full article
(This article belongs to the Special Issue Study of Brake Wear Particle Emission)
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20 pages, 3347 KiB  
Article
Feasibility of Measuring Brake-Wear Particle Emissions from a Regenerative-Friction Brake Coordination System via Dynamometer Testing
by Hiroyuki Hagino
Atmosphere 2024, 15(1), 75; https://doi.org/10.3390/atmos15010075 - 7 Jan 2024
Cited by 1 | Viewed by 1082
Abstract
Emissions of brake-wear particles are commonly associated with vehicular traffic. We investigated the feasibility of quantifying brake-wear particle emissions under realistic vehicle driving and braking conditions with a currently used regenerative friction brake coordination system. We used a braking system installed in commercially [...] Read more.
Emissions of brake-wear particles are commonly associated with vehicular traffic. We investigated the feasibility of quantifying brake-wear particle emissions under realistic vehicle driving and braking conditions with a currently used regenerative friction brake coordination system. We used a braking system installed in commercially available plug-in hybrid electric vehicles and found that it reduced emissions by 85% for PM10, 78% for PM2.5, and 87% for particle numbers (PNs) compared with the system installed in vehicles with internal combustion engines. Brake friction work showed a linear relationship with PM10 and PM2.5. Nanoparticle PM emissions tended to increase slightly with regenerative braking but did not contribute significantly to the overall PM percentage. The emission events of high concentrations of nuclei-mode particles (<20 nm in diameter) in electric vehicle brake assemblies designed for regenerative braking use under high-temperature, high-load braking conditions with full-friction brakes. The nuclei-mode particles amplified the PN emissions and led to high variability. In strict regulatory certification tests where measurement reproducibility and stability are required, it is appropriate to measure PNs under brake conditions appropriate for the actual use of electric vehicles rather than under full-friction brake conditions or to remove particle measurements smaller than 20 nm. Full article
(This article belongs to the Special Issue Study of Brake Wear Particle Emission)
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14 pages, 1724 KiB  
Article
Iron Oxide and Hydroxide Speciation in Emissions of Brake Wear Particles from Different Friction Materials Using an X-ray Absorption Fine Structure
by Hiroyuki Hagino, Ayumi Iwata and Tomoaki Okuda
Atmosphere 2024, 15(1), 49; https://doi.org/10.3390/atmos15010049 - 30 Dec 2023
Cited by 1 | Viewed by 900
Abstract
Iron (Fe), the main component of non-exhaust particulates, is known to have variable health effects that depend on the chemical species of iron. This study characterized the possible contribution of iron oxides and hydroxides to airborne brake wear particles under realistic vehicle driving [...] Read more.
Iron (Fe), the main component of non-exhaust particulates, is known to have variable health effects that depend on the chemical species of iron. This study characterized the possible contribution of iron oxides and hydroxides to airborne brake wear particles under realistic vehicle driving and braking conditions with different brake pad friction materials. We found significant differences in wear factors and PM10 and PM2.5 emissions between non-asbestos organic (NAO) and European performance (ECE) brake pads. Iron was the dominant contributor to PM10 and PM2.5 brake wear particles for both NAO and ECE. The iron concentration ratio in the particle mass (PM) was comparable to the disc-to-pads ratio measured by wear mass. The fact that magnetite, which is of interest with respect to health effects, was less abundant in NAO than in ECE suggested that tribo-oxidations occurred in NAO. Metallic iron is generated not only from abrasive wear but also from tribo-chemical reduction with magnetite as the starting material. We found that there were differences in PM emissions between brake friction materials, and that the phase transformations of iron differed between friction materials. These differences were apparent in the distribution of iron oxides and hydroxides. Heat, tribo-oxidation, and tribo-reduction are intricately involved in these reactions. Full article
(This article belongs to the Special Issue Study of Brake Wear Particle Emission)
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30 pages, 4659 KiB  
Article
Analysis of Parameters Influencing the Formation of Particles during the Braking Process: Experimental Approach
by Saša Vasiljević, Jasna Glišović, Jovanka Lukić, Danijela Miloradović, Milan Stanojević and Milan Đorđević
Atmosphere 2023, 14(11), 1618; https://doi.org/10.3390/atmos14111618 - 28 Oct 2023
Cited by 2 | Viewed by 1236
Abstract
Knowing and understanding the parameters influencing the concentration of particles created by brake wear, as one of the main contributors to non-exhaust emissions from vehicles, is important for the further development of systems on vehicles to reduce the concentration of particles, and also [...] Read more.
Knowing and understanding the parameters influencing the concentration of particles created by brake wear, as one of the main contributors to non-exhaust emissions from vehicles, is important for the further development of systems on vehicles to reduce the concentration of particles, and also for further research in the field of developing new friction pairs. In this research, a brake inertial dynamometer was used to measure brake particles, and four different brake pads were examined. Based on a previous review of the applied tests and driving cycles, the braking parameters were determined, i.e., the initial simulated speed of the vehicle, the load of one-quarter of the vehicle, and the brake pressure. The ambient temperature, air humidity, coefficient of friction between friction pairs, deceleration, and braking time can have an influence depending on the brake pad. Further, during the measurement, the temperatures of the brake pads were also measured, where the initial temperature of the brake pads was always the same. In order to process the data, several methods were used, including the presentation of the obtained results in a time domain, the application of the Taguchi design of the experiment with the analysis of the parameters, and a correlation analysis using the Pearson and Spearman correlation coefficients. In this research, the authors concluded that the influences of the parameters primarily depend on the applied brake pads. The vehicle speed turned out to have a large influence in all cases, as did the load, i.e., the influence of the vehicle weight (indirectly through the kinetic energy of the vehicle). In this case, the pressure showed less influence on the particle concentration. An important braking parameter that has a significant impact on the concentrations of PM2.5 and PM10 particles is the final temperature of the brake pads. Full article
(This article belongs to the Special Issue Study of Brake Wear Particle Emission)
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