Abstract
Abstract
This paper presents the physical characterization of particle emissions from small two-stroke gasoline two-wheelers. Particle samples were drawn with a dedicated partial dilution system. They were analysed with various aerosol measurement instruments, including a scanning mobility particle sizer (SMPS), an electrical low-pressure impactor (ELPI), and a diffusion charger. Solid particles were discriminated by using a thermodenuder. Results suggest that small two-wheeled vehicles are significant emitters of both solid and volatile particles with the volatile fraction being the dominant one. The particle size distribution appears bimodal at high load and log-normal at lower load. The high concentration of condensable species in the exhaust also leads to the formation of volatile particles in the accumulation mode, which is typically not observed in diesel exhaust. Further comparison with a typical diesel passenger car revealed that some older technology two-wheelers emit even higher mass and solid particle counts than the car. However, the paper concludes that technology improvements such as oxidation catalysts and direct injection systems are expected significantly to reduce particulate matter emission rates.
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