DESIGN AND ASSESSMENT OF A TEST RIG FOR AIRBORNE BRAKE WEAR DEBRIS MEASUREMENTS

摘要

Particulate matter (PM) which originates from road vehicles can be generally divided into two categories; exhaust and non-exhaust emissions. Products of combustion from engines contribute primarily to exhaust emission. However, brake, tyre and road wear as well as resuspension of existing road debris are among the key sources of non-exhaust emissions. Among these sources, brake-related PM has become a major contributor. Stringent regulations regarding exhaust emissions have only been recently established and no proper regulations are in place regarding non-exhaust emissions; this means that they are effectively unregulated. As such, there is a need to better understand the behaviour of non-exhaust particulates, especially in light of the fact that they are known to adversely affect human health as well as the environment. Numerous studies have reported the relationship between negative health effects and the characteristics of PM, notably particulate size and concentration and their chemical composition. Accurate measurements of airborne brake-related PM in an open atmosphere is quite challenging because the airborne particles collected may originate from other sources. Therefore, characterising brake emissions is best conducted inside a laboratory with better control of the environment. Consequently, this paper focuses on the development of a new test rig for measuring real-time particulate concentration and mass distribution emanating from various friction pairs under drag-braking conditions. An existing disc brake dynamometer was redesigned to ensure all particles are generated solely from the brake assembly with a Dekati ELPI?+ unit, used to measure particle properties. An enclosed chamber was constructed around the brake assembly and ducting carefully designed to ensure the cleanliness of the intake air to the chamber. In parallel, Computational Fluid Dynamics (CFD) simulations were performed to investigate the velocity profile at the vicinity of the sampling point and also to gain knowledge on the behaviour of the air flow in the enclosed chamber, especially around the brake assembly. The initial promising results provide confidence and justification for utilising the test rig for measuring airborne brake wear debris in order to compare emissions from Plasma Electrolytic Oxidation (PEO) coated aluminium and standard grey cast iron rotors.