A fuel injector having a body with a bore, which defines a fuel manifold. The injector also has a variable-area injector arrangement having a pintle with a conical head and a pintle spring connected to the body. The pintle spring urges a tip of the pintle to seal against an exit orifice of the body, such that application of pressurized fuel within the body causes the pintle to move. Above some threshold pressure, the pressurized fuel causes the conical head to move out of contact with the exit orifice of the body. This, in turn, provides a corresponding variable area for passage of the pressurized fuel through the exit orifice about the conical head of the pintle. The injector further includes a swirler configured to create a swirling action in the flow of pressurized fuel through the fuel manifold, wherein the manifold is upstream of the exit orifice.

Co-firing a combustor with gas fuel and ammonia using various approaches is disclosed. Each method fires a gas fuel in a primary combustion zone using a head end fuel nozzle, in a secondary combustion zone using a first axial fuel stage (AFS) injector set, and/or a tertiary combustion zone using a second AFS injector set over a particular combustor load range, and transitions to firing with ammonia using an ammonia atomizer. The methods may transition to ammonia combustion alone or ammonia with gas fuel combustion. The cross flow of the first AFS injector set stabilizes combustion of ammonia, and the second AFS injector set provides a quenching effect, each of which contributes to efficient ammonia combustion with or without gas fuel combustion.

Co-firing a combustor with gas fuel and ammonia using various approaches is disclosed. Each method fires a gas fuel in a primary combustion zone using a head end fuel nozzle, in a secondary combustion zone using a first axial fuel stage (AFS) injector set, and/or a tertiary combustion zone using a second AFS injector set over a particular combustor load range, and transitions to firing with ammonia using an ammonia atomizer. The methods may transition to ammonia combustion alone or ammonia with gas fuel combustion. The cross flow of the first AFS injector set stabilizes combustion of ammonia, and the second AFS injector set provides a quenching effect, each of which contributes to efficient ammonia combustion with or without gas fuel combustion.