Staging fuel nozzle
A main swirler of a triple annular configuration that is partitioned by a pre-filmer and a separator is installed in an inlet port of a main air flow channel. The vicinity of the inner wall of the main air flow channel provided with a main fuel injection port is bulged radially outward from the innermost surface (innermost surface of a small swirler) of a main swirler. Further, a distance from the main fuel injection port and the pre-filmer is set such that an effective opening area between the pre-filmer and “the inner wall of the main air flow channel provided with the main fuel injection port” is equal to an effective opening area of the small swirler. The swirling directions of the swirlers of the main swirler are “clockwise”-“counter-clockwise”-“clockwise” respectively along the radial outward direction when the swirling direction of the innermost swirler is taken as “clockwise”.
1. A staging fuel nozzle having, in the center thereof, a pilot fuel injection portion and a main fuel injection portion of a pre-mixing type that has a main swirler and a liquid film forming body around the pilot fuel injection portion, wherein
the main swirler comprises a plurality of swirlers,
the plurality of swirlers comprises an innermost swirler that is arranged closest to a central axis of the fuel nozzle, an intermediate swirler, and an outermost swirler,
a fuel injection port of the main fuel injection portion is provided in an inner wall surface of a main fuel injection portion air flow channel located downstream of the plurality of swirlers,
a wall surface in the vicinity of the fuel injection port includes a convex wall surface that protrudes radially outward from an innermost surface of the innermost swirler,
the convex surface is formed at least as far as a downstream end of the liquid film forming body,
and the liquid film forming body extends downstream between the innermost swirler and the intermediate swirler,
the innermost swirler and the intermediate swirler swirl in an opposite direction to each other,
the innermost swirler and the outermost swirler swirl in the same direction,
the plurality of swirlers are combined to obtain swirling of an intensity that enables the formation of a stable recirculation flow in the entire configuration, and
the main swirler is a triple annular swirler.
2. The staging fuel nozzle according to claim 1 , wherein an effective opening area between the convex surface and the liquid film forming body is substantially equal to an effective opening area of the innermost swirler.
3. The staging fuel nozzle according to claim 1 , wherein a backward-facing step flame stabilizer is provided between the main air flow channel and a pilot air flow channel.
4. The staging fuel nozzle according to claim 3 , comprising:
a structure that introduces air from an upstream side of the pilot fuel injection portion and the plurality of swirlers of the main fuel injection portion to cool a pilot flare portion and the backward-facing step flame stabilizer from a back side thereof and jets out the air in the form of a film from the inner wall surface in the vicinity of an outlet of the main air flow channel.