Evolution of Gasoline Direct Injection System for Reduction of Real Mode Emission

Continuous improvement of gasoline engine emissions performance is required to further protect the global environment and also the impact of emissions on a local level. During real world driving, transient engine operation and variation in fuel injection, airflow, and wall temperature are key factors to be controlled. Due to the limited opportunity for optimization of engine control, generation of a well-mixed fuel spray is necessary to create a suitable combustion environment to minimize emissions. Optimum spray performance achieves minimum surface wetting as well as promoting evaporation and diffusion if wetting occurs. Improvement in spray homogeneity is an important step to achieve this. Higher fuel pressure is initially considered to achieve improvements, as it is expected to improve mixture formation by reduction of wall wetting due to high atomization and lower penetration, as well as improvement in spray homogeneity. However, excessive pressure should be avoided due to the associated increase in friction losses. This paper shows that improved injector nozzle technology is effective to reduce wall surface adhesion due to high spray dispersion and homogeneity, which will avoid losses due to excessive fuel pressure increase.