Airblast fuel nozzle with swirl slot metering valve

Abstract

An airblast fuel nozzle has an injector head with an extension or support strut. An annular valve spool with a fuel discharge orifice is fixed to the head and a metering assembly surrounds the valve spool. The metering assembly includes an axially-slidable annular valve sleeve and a metal bellows. The bellows, a compression spring, and one or more shims between the valve spool and the injector head provide a preset bias on the valve sleeve such that the valve sleeve initially closes or minimizes the fuel metering area through longitudinally-extending fuel swirl slots spaced about the valve spool at the discharge orifice. When fuel under pressure flows through the injector, the fuel pressure overcomes the preset bias of the sleeve and moves the valve sleeve axially with respect to the valve spool, thereby increasing the fuel metering area through the fuel swirl slots and allowing fuel to flow (with a swirling component) therethrough. The fuel flows through a convoluted path through a fuel circuit surrounding the bellows and valve sleeve, around the bellows, and between the valve sleeve and valve spool to the fuel swirl slots. The convoluted fuel path and fuel metering at the tip of the fuel injector reduces vaporization and coking of the fuel. The bellows, springs and shims provide for easily configuring the metering valve assembly to optimize fuel flow for the particular requirements of the engine.