The gaseous fuel-fired can combustor for a gas turbine include a generally cylindrical housing, and a generally cylindrical liner disposed coaxially within the housing to define with the housing a radial outer flow passage for combustion air, the-liner also defining inner combustion and a dilution zone, the dilution zone being axially distant a closed housing end relative to the combustion zone. A fuel/air mixing apparatus disposed at the closed housing end includes a plurality of swirl vanes defining passages each having constant cross-section flow areas along the vanes, and an increasing aspect ratio from the passage inlet to the outlet. An impingement cooling sleeve coaxially disposed in the combustion air passage between the housing and the liner cools the portion of the liner defining the combustion zone. Channeling apparatus is disposed between a downstream end region of the sleeve and the mixing apparatus and includes a diffuser section with a ratio of the outlet flow area to the inlet flow area in a range of 1.3-1.5.
