Experimental and Numerical Analysis of a Swirled Fuel Atomizer for an Aftertreatment Diesel Burner

Emission legislation for light and heavy duty vehicles is requiring a drastic reduction of exhaust pollutants from internal combustion engines (ICE). Achieving a quick heating-up of the catalyst is of paramount importance to cut down cold start emissions and meet current and new regulation requirements. This paper describes the development and the basic characteristics of a novel burner for diesel engines exhaust systems designed for being activated immediately at engine cold start or during vehicle cruise. The burner is comprised of a swirled fuel dosing system, an air system, and an ignition device. The main design characteristics are presented, with a detailed description of the atomization, air-fuel interaction and mixture formation processes. An atomizer prototype has been extensively analyzed and tested in various conditions, to characterize the resulting fuel spray under cold-start and ambient operating conditions. The geometrical shape of the spray was investigated by imaging, while droplet size and velocity were measured by a Phase Doppler Anemometer (PDA). Computational Fluid Dynamics (CFD) analyses have been used to investigate these same quantities and predict the air-fuel mixing process. Preparing an ignitable mixture in a short timeframe is extremely challenging, particularly under low temperature conditions and with a low volatility fuel. The combination of CFD models with optical measurements revealed extremely important for understanding the burner behavior and for supporting further developments of the system through predictive and reliable simulations.