Analysis of diesel engine in-cylinder air-fuel mixing with homogeneity factor: combined effects of pilot injection strategies and air motion

With a view to understanding the air-fuel mixing behavior and the effects of the mixture quality on the emissions formation and engine performance, a new quantitative factor of the in-cylinder air-fuel homogeneity named Homogeneity Factor (HF) has been developed. Its characteristics under various injection conditions and air swirl motions within the cylinder have been investigated with CFD simulation. The results have shown that air-fuel homogeneity is essentially affected by the spatial and temporal fuel distribution within the combustion chamber. Higher injection pressure, longer dwell time and increased pilot fuel quantities can contribute to better mixing quality resulting in increased HF and optimum engine performance with low fuel consumption and soot emissions. With regard to the in-cylinder air motion, increasing swirl ratio enhances the air-fuel mixing quality which has been relected in the variation of the HF. As a result, increased in-cylinder pressure and temperature caused by the optimized air-fuel mixing improved the combustion eficiency. CITATION: Dimitriou, P., Wang, W., Peng, J., Cheng, L. et al., "Analysis of Diesel Engine In-Cylinder Air-Fuel Mixing with Homogeneity Factor: Combined Effects of Pilot Injection Strategies and Air Motion," SAE Int. J. Engines 7(4):2014, doi:10.4271/2014-01-9052. 2014-01-9052 Published 10/01/2014 Copyright © 2014 SAE International doi:10.4271/2014-01-9052 saeeng.saejournals.org 2045 Downloaded from SAE International by Li Cheng, Wednesday, April 27, 2016