Role of Piston Bowl Shape to Enhance Late-Cycle Soot Oxidation in Low-Swirl Diesel Combustion
Abstract Late-cycle soot oxidation in heavy-duty (HD) diesel engine low-swirl combustion was investigated using single-cylinder engine and spray chamber experiments together with engine combustion simulations. The in-cylinder flow during interactions between adjacent flames (flame-flame events) was shown to have a large impact on late-cycle combustion. To modify the flame-flame flow, a new piston bowl shape with a protrusion (wave) was designed to guide the near-wall flow. This design significantly reduced soot emissions and increased engine thermodynamic efficiency. The wave’s main effect was to enhance late-cycle mixing, as demonstrated by an increase in the apparent rate of heat release after the termination of fuel injection. Combustion simulations showed that the increased mixing is driven by enhanced flow re-circulation, which produces a radial mixing zone (RMZ).