Abstract
Keywords Atomization, Nozzle, Fuel Injection, Hollow-cone like spray, Gasoline Engine
Abstract This paper deals with development of a fuel injector based on a new atomization phenomenon. Size-reduction of fuel spray droplets is one of the most effective measures to reduce polluted exhaust emission of SI engines. The authors have found a new atomization phenomenon that hollow-cone like liquid sheets are injected from each nozzle hole of multiple-hole nozzle. The phenomenon is applicable to fuel injector for SI engines and substantial size-reduction of spray droplets will be expected.
It was examined experimentally that the new atomization phenomenon was appropriate for fuel injection using real scale models of injectors. The new injector model had a flat nozzle plate with four nozzle holes and a flat duct channel that laid on the plate so as to control the liquid stream flowing into the nozzle holes. Photographic observations revealed that hollow-cone like liquid sheets were injected from each nozzle hole and disintegrated rapidly into many fine droplets, if the width of the flat duct was appropriate. Liquid flow in the new injector model was simulated numerically, and the mechanism of the liquid sheets injection was discussed. It was found that liquid flew into each nozzle holes with strong swirl, and the swirling motion was mainly due to parabolic velocity profile of liquid flow in the flat duct.
Based on these results, a new fuel injector for intermittent fuel injection was designed. Configuration of the flat duct was determined by the aid of numerical simulation so as to fulfil the new atomization phenomenon. A prototype of fuel injector was made. Behaviour of injected spray was observed in detail by flash photography and spray characteristics were investigated for various injecting pressures. It was confirmed that the hollow-cone like fine spray was injected from each nozzle hole of the prototype injector. It was remarkable that huge droplets were seldom found in the tip of spray, and the mean droplets size of the prototype injector was much smaller than that of the conventional injectors. Finally it was shown that the developed fuel injector based on the new atomization phenomenon is very useful for both intake-port fuel injection and in-cylinder direct fuel injection and will be instrumental to develop SI engines for low emission vehicles.