Three-Dimensional Numerical Simulation on Fuel Preparation and Stratified Combustion in a Direct Injection Gasoline Engine

摘要

Fuel preparation and mixture stratified combustion are studied for a gasoline direct injection (GDI) engine by computer simulations. A modified version of the KIVA-3V multi-dimensional CFD code that includes the improved sheet atomization model, spray breakup model, droplets distribution model, initial air tumble model, droplets evaporation model and combustion model is used. Numerical studies of spray and mixture stratification are applied to both a constant pressure combustion bomb and a GDI combustion chamber at a partial load operating condition. The effects of different spray injection conditions, injector orientations, reverse tumble strengths and injection timings on mixture quality near the spark plug are analyzed. The spray computational result from these models coincides with the experimental one very well. The GDI engine simulation results reveal that these parameters significantly influence the fuel stratification pattern, ignition process and the combustion characteristics, improper parameters will make the mixture too lean or too rich near the spark plug and the combustion can be poor in these cases. For a GDI engine, an optimization in chamber structure, in tumble flow and in injection timing tare important for the successful stratified combustion at i partial load condition.