Numerical Analysis on the Effect of Piston Bowl Geometry in Gasoline-Diesel Dual-Fuel Combustion 2019-01-1164
As the emissions regulation becomes stricter, a variety of advanced combustion concepts which can achieve the emissions reduction and higher thermal efficiency have been suggested. Dual-fuel combustion is one of the alternatives which has both premixed and non-premixed combustion characteristics. It is important to know the effect of mixture formation in dual-fuel combustion because it determines the ignition spot and following combustion phase. Hence a thorough investigation on related factors such as engine hardware or fuel spray is required.
Meanwhile, Computational Fluid Dynamics (CFD) is a good apparatus to visualize the in-cylinder phenomena and enables to investigate the detailed combustion characteristics quantitatively.
In this paper, 3-dimensional Computational Fluid Dynamics (CFD) was used to investigate the effect of mixture formation in dual-fuel combustion. The combustion model consists of two parts; the Representative Interactive Flamelet (RIF) model was used to solve the auto-ignition of direct injected fuel, and level-set approach was used to mimic the flame propagation. The reduced Primary Reference Fuel (PRF) mechanism with 73 species and 296 reactions is used. The combustion model was validated with the experimental results under gasoline-diesel dual-fuel combustion in single cylinder diesel engine where the injection timing and EGR rate are varied. After that, the effects of mixture formation on the combustion and emissions characteristics were investigated by changing the piston bowl shape and spray angle. The model showed a good agreement with the experimental results, and it could quantitatively analyze how the spray targeting affects to the emissions reduction and thermal efficiency.
Sunyoung Moon, Gyujin Kim, Sanghyun Chu, Jaegu Kang, Hoimyung Choi, Taehun Ha
Seoul National Univ., Seoul National University, Gachon University