Bowl geometry effects on turbulent flow structure in a direct injection diesel engine
In swirl-supported diesel engines, piston bowl geometry can affect mixing controlled heat release rates and thereby thermal efficiency. These effects may also depend on parameters such as injection timing, engine speed, and load, but a fundamental understanding of how bowl geometry and injection timing/duration influence turbulent mixing rates is lacking. This computational study compares engine behavior with two pistons representing competing approaches to combustion chamber design: a conventional, re-entrant piston bowl and a stepped-lip piston bowl. Simulations are performed for a conventional diesel combustion operating point with a pilot-main injection strategy under non-combusting conditions. Injection timing and duration are varied and the simulation results are analyzed to provide insight into bowl geometry effects on turbulent flow structure and mixing behavior.