Importance

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Abstract

Combustion is improved in a cylinder of a direct-injection stratified charge-type engine such as a diesel engine by injecting the fuel into the cylinder in the form of a rapidly expanding cloud. The expanding cloud is produced by a very short duration injection of rapidly falling velocity as close as possible to top dead center. The expanding cloud rapidly disperses the fuel droplets in a substantially uniform air/fuel ratio for efficient fast diffusion burning. The very short duration of injection close to top dead center substantially eliminates undesirable premixed burning, while the expanding cloud separates the droplets so they cannot agglomerate into large particles and cause wall wetting and consequent undesirable liquid fuel burning late in the cycle. The invention includes a system for damping the injector needle at the ends of both of its opening and closing strokes, enabling a lightweight, very fast-moving needle to be employed so that the full benefits of the short duration, rapidly falling injection velocity are achieved over most of the injection event.

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First Claim