Investigating the effect of spray included angle on thermally stratified compression ignition with wet ethanol using computational fluid dynamics

•TSCI with wet ethanol provides cycle-by-cycle control over heat release in LTC.•The spray included angle is critical to thermal stratification development in TSCI.•Narrow spray included angles are less effective than wide spray included angles.•Narrow included angles must overcome the natural thermal stratification.•Wide spray included angles work with (enhance) the natural thermal stratification. Computational fluid dynamics (CFD) modeling was used in this study to explore the effect of spray included angle in a diesel engine with a re-entrant bowl piston. Previously, it was shown that thermally stratified compression ignition (TSCI) has the ability to control the heat release rate and extend the upper load limit of advanced combustion compared to Homogenous Charge Compression Ignition. TSCI can be achieved using either the direct injection of water into a premixed mixture of air and fuel or using a split direct injection strategy of a water-fuel mixture. The current study focuses on the latter variation of TSCI using wet ethanol as the direct injected water-fuel mixture. The CFD model implemented in CONVERGE with SAGE detailed chemistry solver was first validated using experimental results collected on a single-cylinder research engine. Then, the model was used to simulate different spray included angles to explore the effect of spray included angle on the thermal and equivalence ratio stratification that develops in the cylinder. The spray included angle was varied from 60° to 150° and the results indicate that the broader spray included angles targeted the regions of the cylinder outside of the piston bowl while the narrower angles targeted mostly inside of the piston bowl. Since the charge inside the piston bowl is naturally hotter due to spatial differences in heat transfer losses and the natural thermal stratification that occurs, when the bowl region is targeted, the difference between the temperature inside and outside piston bowl reduces. However, when targeting the region outside of the piston bowl (i.e., the squish region), the natural and forced thermal stratifications work together and the temperature difference between the bowl and squish regions increases. This results in higher thermal stratification for the broader included angles, which results in better control over the heat release rates.