Abstract:

The effects of the matching between the airflow characteristic and the fuel spray in the reentrant combustion chamber of a direct injection diesel engine under different fuel injection timings on the fields of air velocity, airfuel ratio, and temperature in the chamber were simulated using the 3-dimensional numerical simulation software FIRE. The behaviors of air-fuel mixture formation and combustion process under different conditions were studied and the effect of mixture formation on the engine performance was tested. The results showed that the matching between the airflow and the fuel spray under different fuel injection timings affects the premixed combustion phase, the diffusion combustion phase, and the combustion speed during the main combustion duration. For the matching of airflow and fuel spray in a given combustion chamber, there is an optimal fuel injection timing, which can adjust the proportions of premixed and diffusion combustion fuel quantities and the centroid crank angle position of heat release diagram, being of help for engine energy-saving and emission control.

Key words: power machinery and engineering, direct injection diesel engine, reentrant combustion chamber, airflow characteristic, fuel spray, fuel injection timing, combustion process, exhaust emission