Abstract
Keywords - Internal combustion engine, Emission, Measurement, Nano-particle, PM
Abstract - Recently particulate matter (PM) emission from internal combustion engines especially from the diesel engines is becoming a sever problem. Specially, particles having diameter of less than 100 nm are usually called as Nano-particle are considered to be seriously hazardous for human health. Due to very smaller in size these nano-particles are very difficult to measure by the conventional gravimetric measurement system with sampling in a filter paper. More over it is assumed that more attention should be given to the effect of number and surface area of nano-particles to human health rather than to the effect of total mass of PM. However, emission behaviour of nano-particles, especially the Nuclei-mode of nano-particles having diameter less than 30 nm is very sensitive to the engine operating condition, measurement conditions and others. Therefore motivation of this research is to confirm the behaviour of nano-particles emitted from engine and recommendation of a precise measuring method for nano-particles.
Measurements of nano-particles emitted from an 8 little DI diesel engine with common rail injection system were performed at four different points from the exhaust pipe upstream (just behind the turbo charger) to the exit of the full dilution tunnel. Number distribution of nano-particles was measured by SMPS, ELPI and NanoMet type measuring systems. A rotary type or an ejector type diluter was used for measurement of high concentration and high temperature exhaust gas at the upstream part of the exhaust pipe.
It was found that, generation of the nuclei mode particles having the peak at 10 nm size increases with decreases in the exhaust gas temperature. Particle number concentration during accumulation mode does not depend on exhaust gas temperature. But the nucleation mode particle generation at the low temperature upstream region becomes higher and the number concentration decreases with increases in the exhaust gas temperature. Especially the concentration of nano-particles generated at the upstream part does not vary even when travelling to the low temperature downstream part of the exhaust pipe. Generation of nuclei mode particles is significantly influenced by the cooling history of the exhaust gas just after the exhaust valve.