Dual fuel mixer for gas turbine combustor

Abstract

A dual fuel mixer is disclosed as including a mixing duct having an upstream end, a downstream end, and a centerline axis therethrough, where the mixing duct has a circular cross-section defined by a wall. A shroud surrounds the upstream end of the mixing duct and contains therein a gas manifold in flow communication with a gas fuel supply and control. A set of inner and outer annular counter-rotating swirlers are located adjacent the upstream end of the mixing duct for imparting swirl to an air stream. The outer annular swirler includes hollow vanes with internal cavities which are in flow communication with the gas manifold, the outer swirler vanes also having a plurality of gas fuel passages therethrough in flow communication with the internal cavities to inject gas fuel into the air stream. A hub is provided for separating the inner and outer annular swirlers to allow independent rotation thereof. A fuel injector is substantially aligned with the centerline axis for injecting liquid fuel axially into the upstream end of the mixing duct. High pressure air from a compressor is injected into the mixing duct through the inner and outer swirlers to form an intense shear region so that gas fuel injected into the mixing duct from the outer swirler vane passages and/or liquid fuel injected into the mixing duct from the fuel injector are uniformly mixed therein, whereby minimal formation of pollutants is produced when the fuel/air mixture is exhausted out the downstream end of the mixing duct into the combustor and ignited.