Development of Dust Collectors to Reduce Brake Wear PM Emissions

Abstract

In this study, two different dust collectors, one based on an inertial separator and the other based on an electrostatic precipitator (ESP), were developed in order to reduce brake wear particulate matter (PM) emissions. Additionally, the collection efficiencies for brake wear particles (BWPs) of the inertial separator and the ESP were evaluated according to brake pad type. In the case of the inertial separator, the BWP collection efficiencies for the low-metallic (LM) and non-asbestos organic (NAO) pads were similar, and the cut-off size at 50% collection efficiency (D50) was 2.2 µm. The ESP was designed without an additional electrostatic charging device because naturally induced electrostatic charging occurred due to the friction between the brake disc and pad. The BWP collection efficiency of the ESP was higher for NAO pad than for LM pad because the BWPs generated from the NAO pad contained a relatively low iron (Fe) component compared to that of the LM pad, thereby generating more frictional electricity. The maximum ESP collection efficiencies of the BWPs generated from the LM and NAO pads were determined to be 60% and 75%, respectively, and the remaining BWPs that were not collected were presumed to be particles that were not frictionally charged.

Automotive braking is a source of highly charged aerosol particles

“…In addition to the role that charge may play in the transport and climatic impacts of BWPs, the observation that BWPs are mostly charged, and that most are highly charged, suggests that mitigation efforts such as that proposed by Woo et al ( 33 ) can be highly effective. This can have far-reaching consequences, since the environmental impacts of BWPs extend beyond the atmosphere to aquatic systems ( 64 ) and soils ( 65 ).…”

“…With regard to human health, several studies have shown that surface charges may enhance particle deposition onto lung airways ( 27 – 30 ), although this is still an area of active research ( 31 ). Brake pads have been studied as a tribological surface ( 32 ), and an electrostatic precipitator was recently proposed as a possible means by which to reduce primary BWP emissions ( 33 ). However, to the best of the authors’ knowledge, a study on the electrical charge characteristics of BWPs has yet to be reported and many open questions remain including the number of elementary charges per particle (hereafter referred to as charge state), ratios of charged-to-neutral particles, and the relationships between charge state, braking mechanisms, and particle size/composition.…”