The effect of spray targeting on exhaust emissions, especially soot and carbon monoxide (CO) formation, were investigated in a single-cylinder, high-speed, direct-injection (HSDI) diesel engine. The spray targeting was examined by sweeping the start-ofinjection (SOI) timing with several nozzles which had different spray angles ranging from 50 o to 154 o. The tests were organized to monitor the emissions in Premixed Charge Compression Ignition (PCCI) combustion by introducing high levels of EGR (55%) with a relatively low compression ratio (16.0) and an open-crater type piston bowl. The study showed that there were optimum targeting spots on the piston bowl with respect to soot and CO formation, while nitric oxide (NOx) formation was not affected by the targeting. The soot and CO production were minimized when the spray was targeted at the edge of the piston bowl near the squish zone, regardless of the spray angle. Targeting this spot is believed to enhance the pre-ignition mixing of air and the spray effectively with the help of the squish flow. The results from the narrow angle nozzles (50 o and 85 o) indicated that soot could be optimized when the spray was targeted at the bottom of the piston bowl which provided the longest spray travel distance. However, CO emission increased but was significantly reduced when the spray was targeted at the inner surface of the bowl with a corresponding increase in soot emission. In the standard diesel combustion regime, the soot and CO increased as SOI was retarded, and the minimum soot was achieved with SOI of about-20 degree ATDC. This SOI timing provides a rough boundary between conventional diesel and PCCI combustion as seen from the heat release rate data.
The objectives of this study were 1) to evaluate the characteristics of rich diesel combustion near the stoichiometric operating condition, 2) to explore the possibility of stoichiometric operation of a diesel engine in order to allow use of a three-way exhaust after-treatment catalyst, and 3) to achieve practical operation ranges with acceptable fuel economy impacts. Boost pressure, EGR rate, intake air temperature, fuel mass injected, and injection timing variations were investigated to evaluate diesel stoichiometric combustion characteristics in a singlecylinder high-speed direct injection (HSDI) diesel engine. Stoichiometric operation in the Premixed Charge Compression Ignition (PCCI) combustion regime and standard diesel combustion were examined to investigate the characteristics of rich combustion. The results indicate that diesel stoichiometric operation can be achieved with minor fuel economy and soot impact. The fuel consumption at stoichiometric operation increases about 7% compared to the best fuel economy case of standard diesel combustion. However, NOx emissions decrease to around 0.1 g/kW-hr due to oxygen deficiency at stoichiometric condition. Variations of injection timing, intake air temperature, EGR, and boost pressure did not affect the fuel consumption significantly. In general, emissions and fuel consumption were dependent strongly on the equivalence ratio under high EGR and rich operating conditions. Extending the operating range will be the subject of future studies.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.