Low-nox, rich-lean combustor

A low-NO.sub.x combustor for heating compressor discharge gases to drive a turbine, comprising:

• a basket having a wall for containing combustion therein and further having an upstream zone for fuel rich, diffusion flame combustion and a downstream zone for fuel-lean combustion with a necked-down quench zone connecting said cumbustion zones;
• means for injecting fuel into the upstream end of said basket;
• means for enabling fuel-rich combustion of the fuel injected by said injecting means in said fuel-rich combustion zone;
• means for introducing a quench air flow into said combustor quench zone to assure downstream fuel-lean combustion of gaseous products produced in said fuel-rich combustion zone without need for dilution air admission;
• said basket wall having disposed about its inner side and along said rich zone a first ceramic enclosure means to support combustion without wall cooling air;
• means for admitting oxidant to said rich zone including openings through said basket wall and said first ceramic enclosure means to ensure that the fuel equivalence ratio within said rich zone is greater than 1.0;
• means for igniting the injected fuel;
• a first section at the upstream end of said quench zone gradually decreasing in diameter in the downstream direction;
• a second section at the downstream end of said quench zone gradually increasing in diameter in the downstream direction;
• a third section between said first and second sections having a substantially constant inner diameter and a plurality of annularly disposed cooling ports extending radially therethrough for supplying cooling air to said quench zone;
• and
• a second ceramic enclosure substantially continuous with said first ceramic enclosure being disposed along the inner side of the first, second and third wall sections of said quench zone.