A multi-zone, direct-injection (DI) diesel combustion model, the so-called RK-model, has been developed and implemented in a full cycle simulation of a turbocharged engine. The combustion model takes into account:
transient evolution of fuel sprays,
interaction of sprays with swirl and walls,
evolution of near-wall flow formed after spray-wall impingement depending on impingement angle and swirl, fuel-air mixing,
interaction of near-wall flows formed by adjacent sprays,
evaporation conditions for different zones.
In the model the fuel spray is divided into a number of zones with different evaporation conditions. The piston bowl is assumed to be a body of revolution of otherwise arbitrary shape. Submodels of soot and NOx formation are included. The model has been validated by experimental data obtained from high-speed and medium-speed engines over the whole operating range; a good agreement has been achieved without recalibration for different operating modes.
Predictions of spray tip penetration, spray angle and ignition delay were validated by the published data obtained for diesels with multiple injection system and injection timing after the TDC. Formulas for computation of these characteristics were derived.
Results obtained without recalibration of the RK-model demonstrate good agreement between the calculated and experimental heat release rate curves as well as between integral engine parameters for diesels with multiple injection being considered.
To make a computational research of multiple injection strategy possible, the full cycle thermodynamic engine simulation software DIESEL-RK has been supplied with an additional tool for parametric setting of multiple injection profile by specifying a fuel fraction and delay after previous injection for each fuel portion. These parameters can be used as arguments of optimization in a future research.