Abstract
Conventional diesel combustion (CDC) utilizes a centrally mounted multi-hole fuel injector spraying fuel into the piston bowl and towards the cylinder wall. This configuration is prone to jet/flame wall impingement causing wetting and flame quenching, higher coolant heat loss, and higher emissions of unburned hydrocarbons, soot, carbon monoxides, etc. Recently, we have introduced peripheral fuel injection (PeFI) whereby fuel is injected at an angle from the periphery of the cylinder head using multiple single-hole injectors. In this study, 3D computational fluid dynamics (CFD) analysis is utilized to investigate fuel-air mixing in the near-field of diesel sprays with the goal to compare CDC and PeFI strategies. The study utilizes experimentally determined rate of injection (ROI) profiles for multi-hole and single-hole injectors to replicate published data for non-evaporating CDC and PeFI sprays acquired in a pressurized test chamber. The CFD model thus validated is extended to investigate fuel-air mixing in an evaporating spray at ECN Spray A reference conditions of ambient pressure and temperature. Results show significant differences in the flow field in and around the fuel jet and within the chamber for CDC and PeFI cases. PeFI case with its faster initial ROI ramp-up increases initial mixing and achieves faster fuel vaporization compared to those for CDC case. Quantitative analysis reveals that PeFI case provides 20 to 40 percent increase in entrainment at quasi-steady conditions compared to that for CDC case.
