| Direct injection diesel engine is the most promising advanced combustion engine for vehicle due to its low fuel consumption and great torque. The investigation on the combustion process of DI diesel engine is a meaningful work for increasing the power and decreasing fuel and exhaust emission. Besides experimental investigation, numerical simulation is an effective tool to study the engine combustion process.The 3D numerical modeling of engine combustion process is introduced in this paper. The turbulence models, diesel engine spray models and combustion models are explained in detail. The 3D numerical package FIRE developed by AVL is adopted in this paper. Numerical investigation includes the in-cylinder turbulence flow, diesel engine spray and combustion process, temperature distribution and emission distribution.The numerical simulation in this paper is focused on two aspects of a vehicle-use 4100 DI diesel engine.①Combustion chamber geometric shape. Several shapes of combustion chambers are designed under the condition of compression ratioε=17.5. Comparison is made on the velocity field. Temperature and emission distribution are analyzed among different combustion chambers.②Injection parameters. The numerical simulation is conducted on different injection parameters, i.e. the protrusion size of nozzle tip into cylinder, injection advance angle and the relation position between the spray axis and the hole axis of the installing injector on the cylinder head. The numerical simulation indicates that proper protrusion size of the nozzle tip results in low NOx and low soot emissions. Injection delay results in reduction of NOx and rate of heat release. The optimum parameters are obtained through the simulation results. Comparison between the numerical simulation and the experimental results testifies the availability of numerical model, and numerical simulation is an effective tool to guide experiments.At last, the prospect is given on the 3D engine combustion simulation process.
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