Variable injection direction nozzle using needle lift change

Abstract

This study proposed a simple configuration for a Variable Injection Direction (VID) nozzle for a diesel engine, which can change a direction of fuel injection according to the needle lift amount. Differently from a conventional one, the VID nozzle has a needle tip partly cylindrically shaped, and a divergent-shaped hole-end. The geometry enables to control internal nozzle flow. The needle tip increases the angle of the flow direction to a hole inlet with respect to an axis of nozzle hole at small needle lift, while it decreases the angle at large needle lift. The divergent-shaped hole-end allows for those direction change of injection. The internal nozzle flow was numerically simulated for exploring the nozzle geometry in detail, using the computational fluid dynamics (CFD). Also, for its validation, an eight-times enlarged nozzle was developed and water was injected. The observation was conducted using a high speed video camera. The CFD results showed good agreement with the measurements regarding not only the injection direction but also the needle lift amount when the injection direction switches. The investigations confirmed that the injection direction can be changed within one injection and a magnitude of injection angle is controllable by the nozzle geometry.