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Journal of Combustion
Volume 2017, Article ID 9702625, 8 pages
https://doi.org/10.1155/2017/9702625
Research Article

Effects of Injection Rate Profile on Combustion Process and Emissions in a Diesel Engine

1Key State Lab of Engines, Tianjin University, Tianjin, China
2School of Engineering and Technology, University of Hertfordshire, Hertfordshire, UK
3Faculty of Creative Arts, Technologies and Science, University of Bedfordshire, Luton, UK

Correspondence should be addressed to Zhijun Peng; ku.ca.sdeb@gnep.nuj

Received 3 February 2017; Accepted 7 May 2017; Published 21 June 2017

Academic Editor: Kalyan Annamalai

Copyright © 2017 Fuqiang Bai et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

When multi-injection is implemented in diesel engine via high pressure common rail injection system, changed interval between injection pulses can induce variation of injection rate profile for sequential injection pulse, though other control parameters are the same. Variations of injection rate shape which influence the air-fuel mixing and combustion process will be important for designing injection strategy. In this research, CFD numerical simulations using KIVA-3V were conducted for examining the effects of injection rate shape on diesel combustion and emissions. After the model was validated by experimental results, five different shapes (including rectangle, slope, triangle, trapezoid, and wedge) of injection rate profiles were investigated. Modeling results demonstrate that injection rate shape can have obvious influence on heat release process and heat release traces which cause different combustion process and emissions. It is observed that the baseline, rectangle (flat), shape of injection rate can have better balance between NOx and soot emissions than the other investigated shapes. As wedge shape brings about the lowest NOx emissions due to retarded heat release, it produces the highest soot emissions among the five shapes. Trapezoid shape has the lowest soot emissions, while its NOx is not the highest one. The highest NOx emissions were produced by triangle shape due to higher peak injection rate.