Multi-Zone DI Diesel Spray Combustion Model and its application for Matching the Injector Design with Piston Bowl Shape 2007-01-1908
A multi-zone, direct-injection (DI) diesel combustion model, the so-called RK-model, has been developed and implemented in a full cycle turbocharged engine simulation code. 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;
interaction of near-wall flows formed by adjacent sprays.
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 with arbitrary side shape. Submodels of soot and NOx formation are included. The model has been validated by experimental data obtained for high-speed, medium-speed and low-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 different diesels including diesels with multiple injection system and injection timing after the TDC. Formulas for computation of these characteristics were derived.
Computational research and optimization of sprayer nozzles orientation for different piston bowl shapes has been performed. Analysis of fuel sprays evolution in contact with walls as well as distribution of fuel in characteristic zones has been done for part load and full capacity. Conclusion about dependence of optimal piston bowl shape on BMEP was made.