Lean prechamber outflow combustor with two sets of primary air entrances

A combustion apparatus for gas turbine engines particularly adapted to reduce emissions to meet automotive requirements. The fuel is laid on the wall of a cylindrical prechamber and evaporated from the wall by combustion air which is introduced through a swirler at the upstream end of the prechamber. The inner surface of the prechamber is artificially roughened by a grid of grooves to improve fuel evaporation. The fuel is laid on the wall from an annular manifold extending around the upstream end of the prechamber through tangential orifices leading from the manifold into the interior of the prechamber. The fuel manifold is cooled and shielded from heat by an air jacket. More air enters through entrance ports distributed around the prechamber toward its downstream end. The resulting lean fuel-air mixture is delivered past an annular flow dam at the outlet of the prechamber into a combustion or reaction zone which is abruptly enlarged from the prechamber. The structure causes turbulent flow, recirculation, and good mixing in the reaction zone. A dilution zone downstream of the reaction zone has a circumferential array of dilution air ports which are of such shape as to be varied nonlinearly in area by a sliding ring valve. The sliding ring valve is coupled to a second sliding ring valve which varies the area of the air entrance ports in the prechamber in reverse sense to the dilution air ports. A pilot fuel nozzle to aid in cold starts is mounted at the upstream end of the prechamber.