Yasukawa, Y., Okamoto, Y., Kobayashi, N., Saito, T. et al., "Multi-Swirl Type Injector for Port Fuel Injection Gasoline Engines," SAE Technical Paper 2014-01-1436, 2014, doi:10.4271/2014-01-1436.
The authors developed a multi-swirl type injector characterized by a short spray penetration length and fine atomization to improve exhaust emissions and fuel consumption for port fuel injection (PFI) gasoline engines. In PFI gasoline engines, fuel adhesion to an intake manifold causes exhaust emission. In addition, good mixing of fuel and air causes high combustion efficiency, and as a result the fuel consumption improves. Injectors therefore require two improvements: first, a short spray penetration to avoid fuel adhesion to the intake manifold, and second, a fine atomization spray to generate a good mixture formation of fuel and air. In this study, the authors developed a multi-swirl type injector equipped with multiple orifice holes featuring swirl chambers upstream of each orifice. The key feature of the proposed injector is “involute curve-formed swirl chambers” for generating a uniform thin liquid-film in the orifices. The authors performed experiments to obtain the Sauter mean diameter (SMD) of spray, a perspective image, and a magnified liquid-film image for multi-swirl type and multi-hole type injectors. The authors found that the multi-swirl injector generated a shorter spray penetration and finer atomization spray than the multi-hole injector. A magnification of the image showed that the multi-swirl type injector formed thin, uniform, cone-shaped liquid-films because of the swirl flow. Results of engine testing showed that using the multi-swirl injector improved the exhaust emissions and the fuel consumption.