A new method to assess vehicle airborne non-exhaust particles: Principle, application and emission evaluation

Abstract

A method that could assess the whole vehicle non-exhaust particle (NEP) emission from the whole vehicle level was proposed by combining sealed housing with the chassis dynamometer. The intake and exhaust systems were connected to the out of the chamber to avoid possible effects on NEP emissions. The most distinguishing feature of the proposed method is the whole vehicle assessment of the NEP. Based on the proposed method, three vehicles were tested under various conditions. The results proved that the total NEP from the US06 cycle could be four orders of magnitude higher than that of the WLTC cycle due to the higher thermal load. The transient NEP concentration is highly associated with the friction pairs' temperature, and there are two critical temperatures respectively for volatile particles and solid particles. Mechanical friction-dominated test (WLTC) tends to produce larger particles, while thermal process-dominated tests (US06) tend to emit smaller particles. Solid particles occupy <10% of the total particles, and solid particle is dominated with the size at 10– 23 nm. The higher the brake temperature, the higher the solid particle emissions (both concentration and portion). NEP emission decreases when vehicle miles travelled increase. Total NEP number emission factors could be two orders of magnitude higher than the current PN limit for exhaust particles (6*1011#/km). The solid particle emission factor could also be ten times higher than the current PN limit. O and Fe element distribution matches well with the SEM image, which means the proposed method could successfully sample the brake particles. The carbon element weight is dominated by the organic carbon, which might mean that it's the mechanical abrasion dominate the carbon mass. The top 5 dominant element during ICP/MS analysis is Si, Na, Mg, Zn, and Al.