This invention relates to a new injection nozzle system and a new method for effecting an improved degree of combustion of fuel by an internal combustion engine particularly of the diesel type. An especially significant feature of the invention is that of injecting pressurized cleaning air through the injection orifice structure into the combustion chamber after the step of injecting a pressurized premixture of fuel and air through that structure.
Although the invention has primary application for diesel engine design, it may also be useful in engines where burning is initiated by a electric spark.
Some early diesel engines employed pressurized air for breaking fuel up into minute particles (frequently called atomization) at the time of injection into the combustion cylinder, but with the advance of spray nozzle designs capable of sufficiently atomizing the diesel fuel by the use of fuel pressure only, the solid or airless type of injection became the generally accepted method of fuel injection for compression-ignition engines.
Recently the intensive drive toward energy independence has led many to consider plant oils as a extender or replacement for diesel fuel. The significantly higher viscosity of plant oils in comparison to conventional diesel fuel militates against accomplishing atomization or fine particle split up under typical fuel injection conditions. The higher viscosity fuel resists movement through injection orifices into a combustion chamber. Additionally some of the higher viscosity fuel remains in the injection cavity or sac volume and in the orifices after injection using conventional techniques. The residual fuel in the cavity and the orifices thermally decomposes during the burning or power stroke of the engine and causes an excessive carbonaceous buildup in the cavity and orifices of the nozzle tip. The buildup interferes with subsequent injection steps.
Reduction or elimination of the injection cavity or sac volume of an injection nozzle has been proposed, but such a change of design seriously influences the injection phenomena causing differences in the fuel spray at each spray hole as well as at each injection into the combustion chamber.