| 摘要 |
A direct injection fuel system for internal combustion engines is disclosed, which relies on a novel device for preparing, injecting and igniting a stratified air-fuel charge inside the cylinder of an internal combustion engine. A single, preferably electrically triggerable, injection and ignition device prepares, supplies and ignites the stratified air-fuel charge. The device of the invention favorably uses the variable pressure existing inside the cylinder, during the compression stroke, to control fuel flow and fuel jet penetration. The injection and ignition device of the invention divides the total amount of fuel injected per cycle into a main fuel dose and a pilot fuel dose. The main fuel dose is injected into the combustion chamber through a set of main injection ports, forming a lean mixture therein. The pilot fuel dose is a small fraction of the total fuel dose and it is injected, through a set of pilot injection ports, in the proximity of the ignition source of the device. One preferred embodiment of the device of the invention has a combustion shell, which physically defines a predetermined volume inside the combustion chamber. The combustion shell surrounds both the pilot ports and an ignition source. The combustion shell has a plurality of torch nozzles cut through its walls. Thus, a stratified charge is formed in the cylinder, with a rich mixture kernel being created in the vicinity of the injection and ignition device, and a lean mixture field being created in the remaining volume of the combustion chamber. When a high voltage is applied to one of the two electrodes of the injection and ignition device, at least one electric spark is created between two electrodes. In the preferred embodiment, the electrodes are designed to create a plurality of sparks, in a circular pattern surrounding the central injection valve. The spark or sparks easily ignite the rich mixture kernel. As the fuel burns inside the combustion shell, the pressure therein will rise and the combustion flames will be ejected through torch nozzles into the combustion chamber. Other embodiments do not use a combustion shell, but rely solely on the kinetic energy of the flames to initiate and propagate combustion through the lean mixture field. Thus torch ignition of the lean mixture field occurs, permitting the engine to run efficiently on an overall leaner mixture than a homogenous charge spark ignition engine.
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