Holistic Diesel Combustion System Design - optimizing fuel-air mixing, heat transfer and combustion at low emissions level

摘要

Facing more and more stringent emission standard, Diesel combustion requires a fine optimization of the combustion chamber for reduced pollutants and improved thermal efficiency. Combustion system design must act simultaneously on all the parameters that are closely related to the air-fuel mixing and combustion efficiency, i.e. injections spray features, air motion, heat transfer and piston bowl shape. Advanced 3D CFD simulations on CSI CONVERGE platform provided analysis of fuel and air mixing, and supported the combustion development of a Euro6+ PC Diesel engine, based on a Fiat 1.6 I Diesel engine application. The increase of the bowl diameter, reduction of the swirl number and nozzle holes diameter aim at the reduction of heat transfer to bowl walls, and increased combustion speed. Engine operation of reference and optimized combustion system has been optimized by means of ICE~2 software for Design of Experiment. Model responses highlight the improved emissions and fuel consumption trade-off that can be obtained under stringent emission limits and noise restrictions; while combustion and energy analysis show the potential heat transfer reduction that is obtained. Overall, the optimized combustion system allows reduced fuel consumption, at low NO_x emissions without compromising full load performances.