Janghee Lee

Characterization of non-exhaust coarse and fine particles from on-road driving and laboratory measurements.

We investigated the physical and chemical properties of non-exhaust coarse and fine particles generated by on-road driving and in a laboratory setting using a mobile sampling system. The on-road driving and laboratory measurements performed under constant speed driving revealed that particles produced by tire wear had a size distribution in the range of 2-3 μm, while roadway particles (RWPs) measured behind the front tire during on-road driving largely comprised crustal materials such as road surface wear particles and road dust as well as tire wear particles (TWPs). The mode diameters of particles obtained from on-road driving under cornering conditions were similar to those obtained under constant speed conditions, but with higher concentrations of crustal elements. Under braking conditions, the particulate matter (PM) concentrations of brake wear particles (BWPs) sampled near the brake pad increased significantly and were much higher than the concentration of RWPs during deceleration, indicating that BWPs are one of the main sources of non-exhaust emissions. In addition, BWPs observed from on-road and laboratory measurements had a broader PM size range (1-10 μm) than RWPs. Size-segregated chemical analysis of PM samples indicated that the concentrations of Fe and Ca were highest in the coarse fraction emitted under constant speed and cornering conditions, while Fe, Ba, and Ti were most abundant in the fine fraction emitted during braking events.

Laboratory study of the generation of nanoparticles from tire tread

ABSTRACT An experimental study was carried out to investigate the formation process of airborne nanoparticles from tire tread. The formation of nanoparticles by volatilization of the tire tread was simulated in a reaction chamber. The number concentration of nanoparticles in the reaction chamber suddenly increased when the tire tread surface temperature reached above 160°C. The generated nanoparticles have a unimodal distribution and the number of nanoparticles increased as the heating rate increased. The geometric mean diameter and size distribution of the generated particles can be controlled by adjusting the cooling rate since the cooling rate is directly related to the growth of particles. From the morphological and elemental analyses, the main components of the tire nanoparticles were C, O, S, and Si and the particles had an irregular shape. Based on these observations, we concluded that the formation mechanism of nanoparticles from the tire tread was volatilization and condensation of the organic materials in the tire tread. Copyright

Applicability of Fuel Supply System for HCNG Engine

Abstract : CNG buses has contributed to improve air quality in cities. But it is difficult to meet the next emission regulations such as EURO-VI without the help of additional post-processing device. Hydorgen has higher flame speed and lower combustion temperature that make it thermal efficiency increase with leaner operation. Using hydrogen natural gas blend (HCNG) fuel is promising technology which can reduce NO x and CO 2 emissions for a natural gas vehicle. However, fuel flow rate of HCNG should be increased since hydrogens energy density per volume is much smaller than natural gas. In the present study, the characteristics of fuel supply system and its applicability were evaluated in a heavy duty natural gas engine. The results showed that the potential of fuel pressure regulator and fuel metering valve had enough capacity with HCNG. Employed mixer did not affect the distribution characteristics of mixture. Key words : Hydrogen natural gas blend(HCNG, 수소-천연가스 혼합연료), Fuel pressure regulator(레귤레이터), Fuel metering valve(연료분사기), Mixer(믹서), Distribution characteristics(분배특성)