Abstract
Keywords
Fuel Injection, Internal Combustion Engine, Spray Structure, Injector, Atomization
Abstract
In gasoline direct injection engines, the fuel-spray pattern that is injected directly into the combustion chamber is one of the most important factors for stable combustion and lower HC exhaust emissions. In order to achieve stable stratified-charge combustion, as many former studies reported, a wall-guided system in which fuel spray is transported toward the spark plug via a piston crown has been developed. However, the wall-guided approach has a negative effect on HC exhaust emission because the fuel spray impinges on the piston crown surface. Our main goal is to develop a suitable fuel-spray pattern for improving combustion stability and reducing fuel spray impingement on the piston crown surface. First, we considered a desirable spray pattern and developed a V-groove nozzle injector. The V-groove nozzle injector was based on a straight-orifice nozzle injector that is equipped with a swirler for better atomization. After that, we investigated the characteristics of the spray pattern by an experiment that takes into account the influences of ambient pressure and fuel pressure. The fuel-spray pattern was illuminated by a YAG-laser sheet and its images were captured by CCD cameras. The resulting fuel-spray pattern was evaluated in terms of spray angle and penetration length. Atomization of spray droplets was investigated and compared with the conventional one. As a result, it was confirmed that the V-groove nozzle injector could generate a flat and robust fuel-spray pattern under ambient pressure fluctuation. And the controllability of the spray angle was strongly affected by the orifice length. These characteristics improve combustion stability and HC exhaust emissions in gasoline direct injection engines.