December 15, 2009

Characteristics Of Ultrafine Particles From An Engine Fueled

The Key Laboratory for Power Machinery and Engineering of M. O. E, Shanghai Jiao Tong University (SJTU) in Shanghai, showed that the characteristics of ultrafine particles from a compression- ignition engine fueled with low sulfur diesel and evaluated the effects of diesel fuel sulfur on particulate matter from a compression-ignition engine. The study is reported in Volume XX, Issue 23 (December, 2009) of the Chinese Science Bulletin because of its significant research value.

Ultrafine particles can contain much more trace amounts of toxic substances (As , Se, Pb , Cr etc.) and organic pollutants (PAHs, PCDDPFs etc.) and penetrate deep into the lung and enter interstitial tissues, causing severe respiratory inflammation and acute pulmonary toxicity. Diesel vehicles are a major source of fine particles in urban atmosphere. Diesel particle emissions range from about 3 nm to 1 ÃŽ¼m in diameter and show high number concentration of about 107 particles/cm3. Therefore, the ultrafine particles from diesel vehicles have attracted extensive attention because of health problems caused by them. Many studies have found that sulfates may have significant effect on particle number emissions. However, because sulfates form only a small fraction of the particulate mass (PM) emissions, lowering fuel sulfur levels has very limited potential to become an effective means to control PM. Hence, the effects of diesel fuel sulfur on particle emission have been neglected for a long time.

In this work, number size distributions (NSDs, 10-487nm) and composition of nanoparticles emitted from an engine fueled with ordinary diesel (OD) and low sulfur diesel (LSD) fuel were comparatively studied. The results indicate that, compared with the OD, the LSD was found to slightly decrease the mass concentration, and significantly reduce the number concentration of the total particles. The NSD for the two fuels showed similar bimodal structure under all test engine conditions. Under the same engine conditions, the nucleation mode for LSD fuel was significantly lower than those of ordinary diesel. The element composition of exhaust particles included C, O, Cl, S, Si, Ca, Na, Al and K. The S element was not detected in LSD fuel case. The main component of soluble organic fraction (SOF) of exhaust particles for the two fuels included saturated alkane (C15-C26), ester and polycyclic aromatic hydrocarbons (PAHs). However PAHs were not found in LSD fuel case.

"This paper focuses on number size distributions and composition of ultrafine particles from engine. The effects of diesel fuel sulfur on particulate matter from a compression-ignition engine were investigated. The result is of academic and practical significance. " said one journal reviewer. A series of papers about ultrafine particles from engine written by Dr. Liu and Prof. Huang have been published in Energy& Fuels., Chin. Sci. Bull, etc. " It is a good attempt to reduce exhaust particle number concentration, and it has certain reference value for establishing future emission regulations and environmental standards for ultrafine particles." said another reviewer.


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