Browse Publications Technical Papers 2020-01-1637

Results of Brake PM Emissions Measurements on Six Different Vehicles Using a Large Inertia Dynamometer Study 2020-01-1637

Emissions of particulate matter (PM) due to brake wear are not well quantified in present air pollutant emission inventories. Current emission factor models need to be updated to reflect new technologies and materials and to incorporate the effects of vehicle driving cycles. This paper presents some results from the initiative of the California Air Resource Board (CARB) to update the emission factors for brake (non-exhaust) emissions from on-road light-duty vehicles. While emission regulations are significantly reducing PM emissions in vehicle exhaust, non-exhaust automotive emissions remain unregulated. Current emission factor models need to be updated to reflect the changes caused by new technologies, materials and speed-dependent vehicle usage. Most research regarding brake emissions conducts laboratory tests. These allow researchers, application engineers, data modelling engineers, and environmental agencies to generate large datasets for multiple vehicle configurations and friction couple designs. However, these results are inconclusive or difficult to compare at best, due to the lack of a standardized method. This paper reports on a six-vehicle campaign under standardized, repeatable and reproducible conditions. By relying on latest-technology speed control systems, the inertia dynamometer can recreate specific driving profiles, derived from field measurements. Six vehicles were tested with original equipment (OES) and aftermarket friction couples on an enclosed brake inertia dynamometer, using a driving cycle representative of vehicle usage in California. The project relied upon approved testing protocols, test system validation, adjustment of cooling airspeeds, and interlaboratory evaluation for filter weighing methods. The results from more than 80 tests show the effects of axle position, friction couple formulation, as well as vehicle size, type, and speed. These results are part of the updates to the CARB Emission Factors (EMFAC) model. These results show substantial variation in brake PM emissions by vehicle application and type of friction couple.


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