Pilot nozzle tips for extended lance of combustor burner

A burner for a combustor, the burner comprising:

• (a) a swirl generator enclosing a burner interior on an inlet side, the swirl generator comprising at least one tangential air inlet relative to a longitudinal center axis of the burner;
• (b) a mixing chamber enclosing the burner interior on an outlet side, the mixing chamber defining a burner outlet fluidly connecting the burner interior with a combustion chamber of the combustor;
• (c) a lance arranged coaxially with the longitudinal center axis of the burner, the lance comprising a nozzle tip at or near the burner outlet, the nozzle tip being configured and arranged to introduce fuel into the combustion chamber;
• wherein the nozzle tip comprises:
• a cartridge defining a center fuel passage;
• a first plurality of swirl vanes disposed within the center fuel passage at an outlet end of the nozzle tip;
• a first concentric tube surrounding the center fuel passage and defining a first annular fluid passage therebetween;
• a second concentric tube surrounding the first concentric tube and defining a second annular fluid passage, the second concentric tube having a non-uniform thickness from an inlet end to an outlet end;
• a second plurality of swirl vanes disposed in the second annular fluid passage;
• a third concentric tube surrounding an upstream portion of the second concentric tube and defining a third annular fluid passage therebetween, the third concentric tube defining a plurality of air channels in fluid communication with the third annular fluid passage, the plurality of air channels being disposed between a downstream end of the third concentric tube and the second concentric tube;
• and
• a fourth concentric tube disposed between the first concentric tube and the second concentric tube, wherein a fourth annular fluid passage is defined between the first concentric tube and the fourth concentric tube.