نقش پارامترهای سیستم ترمز خودرو در انتشار گازهای ذرات On the influence of car brake system parameters on particulate matter emissions

1. INTRODUCTION Among road-traffic related pollutants, brakes have been estimated to contribute 55% by weight to the total non-exhaust PM10 emissions fraction (i.e. airborne particles with an aerodynamic diameter of less than 10 µm). Furthermore, they account for 21% of overall road-traffic related PM10 emissions [1]. In addition, particulate matter (PM) induces adverse health effects [2,3] and contributes to climate change. Previous studies also show existing relations with cardiovascular and respiratory diseases [4,5] and also classify this pollutant as carcinogenic [6]. Moreover, PM’s black-carbon content boosts global warming whereas other elements such as, e.g. organic carbon, may have a cooling effect [7]. So far, most of the scientific publications in the disc brake aerosol research community have focused on emissions characterization; that in order to better assess how particles can interact with human beings and the environment. Hence, a wide variety of studies, performed at different test scales, is available: real scale (field tests) [8,9], system scale (dynamic bench tests) [10–12] and model scale (pin-on-disc tribometers) [13–15], among which promising correlations have also been found [16,17]. These scientific studies provide a qualitative description of particle emission in terms of size distribution, emission factors, chemical composition and particle morphology. However, they do not explain how the brake system parameters affect the generation of PM. Nevertheless, some interesting observations are provided. Kukutschová et al. [10] noticed an increase in particle number concentration in the ultrafine fraction when the rotor temperature exceeded 300°C. Garg. et al. [11] also noticed a mass reduction in the airborne fraction and an increase in particle number for temperatures close to 400°C. Similarly, Wahlström et al. [18] found that the ultrafine number concentration in a pin-on-disc tribometer set-up increases by several magnitude orders for high load tests, i.e. the one with the highest disc temperature.