Burner Development for Light-Off Speed-Up of Aftertreatment Systems in Gasoline SI engines

Emission legislation for passenger cars is requiring a drastic reduction of exhaust pollutants from internal combustion engines (ICE). In this framework, achieving a quick heating-up of the catalyst is of paramount importance to cut down the cold start emissions and meet future regulation requirements. This paper describes the development and the basic characteristics of a novel burner for gasoline engines exhaust systems designed for being activated immediately at engine cold start. The burner is comprised of a fuel injector, an air system, and an ignition device. The design of the combustion chamber is first presented, with a description of the air-fuel interactions and mixture formation processes. Swirl is used along with a flame-holder concept to anchor the flame at the mixer exit. Spray-swirl and spray-walls interaction are also discussed. Computational Fluid Dynamics (CFD) analyses have been used to investigate these aspects. Prototypes have been built and tested in various conditions, ranging from cold start transients to steady-state lean operating conditions. High-speed videos have also been recorded in an optically accessible prototype burner, to investigate the spray behavior, the ignition kernel development, and the flame structure. Preparing an ignitable mixture in a short timeframe is extremely challenging, and the combination of CFD simulations with optical measurements revealed extremely important for understanding the system behavior. Preliminary data regarding emission performance and exhaust gas temperature have been also measured and reported. Overall, the burner technology here presented is capable of generating thermal power to warm up and to activate the catalyst faster than standard strategies in use.