The measurement of brake emissions through inertia-dynamometer tests has been a focal point of research, garnering increased attention from various stakeholders interested in understanding particle emissions from foundation brakes. Over the years, different projects have utilized a variety of brake configurations, including full corner tests, chassis dynamometers, and tribometers. Furthermore, these projects have adopted various test methods, such as performance and duty cycles, alongside different measurement systems that assess particle sampling, size range, and quantification techniques. However, the lack of a practical means to correlate these varied approaches has often led to inconsistent and sometimes conflicting results.
The objective of the systematic testing plan outlined in this paper is to quantify the influence of test setup, test procedure, and friction material on brake emissions. This comprehensive study aims to provide clarity by measuring the number and mass concentrations of particles produced, as well as observing changes in particle size distribution during the tests. The assessments were conducted under controlled conditions to ensure repeatability and reproducibility, utilizing the same inertia dynamometer, testing personnel, rear brake assembly, control systems, and measurement devices that operate across a particle size range of 5.6 nm to 10 µm at a frequency of 10 Hz.
The test program incorporated a range of variables to gauge their effects on emissions:
- Friction Material Formulations: Two types were used: Non-Asbestos Organic (NAO) and low-metal friction materials.
- Emission Measurement Setups: Two distinct setups were employed: isokinetic measurements taken inside the air outlet duct and open-air sampling conducted near the brake caliper.
- Test Procedures: Six different procedures were implemented, including modified ISO 26867 friction behavior tests, modified SAE J2707-B block wear assessments, and duty cycles reflective of real-world driving conditions, such as Los Angeles City Traffic, Frankfurt City Traffic, the New European Driving Cycle (NEDC), and the Worldwide Harmonized Light Vehicles Test Procedure (WLTP).
The findings of this study reveal significant correlations between brake emissions and the various test factors examined. These insights not only clarify how different setups and materials influence emissions but also identify key areas that require further investigation and testing. The ultimate goal of this research is to assist the industry in establishing standardized test methods for characterizing brake emissions using inertia dynamometers. By promoting a more unified approach, stakeholders can better understand and regulate brake emissions, contributing to improved air quality and vehicle performance standards.