Combustion method and apparatus

Abstract

A combustion method and apparatus for gas turbine engines employs a combustion process and combustion liner structure adapted to promote complete combustion of liquid hydrocarbon fuel and minimize undesired combustion products. Compressed primary air flows radially inward into a prechamber into which fuel is sprayed. Except during start-up, the air is heated. Normally, the air mixes with and evaporates the fuel and the mixture flows through a throat into a reaction chamber. The upstream end of the reaction chamber is bounded by a biconical annular wall, the inner radial portion of which diverges sharply and the outer radial portion of which diverges less sharply. The liner wall downstream of the throat defines the reaction zone and a dilution zone to which secondary air is admitted. The areas of both the primary and the secondary air entrances are variable to maintain a lean fuel-air ratio in the reaction zone throughout the operating regime. The swirl angle of the entering primary air is variable. In starting combustion, the air is admitted with a very considerable degree of swirl, causing recirculation from the reaction chamber into the prechamber to facilitate ignition and promote fuel vaporization and stable combustion with a cold engine. After light-off, the quantity of primary air increases along with the fuel, and the primary air swirl is reduced or terminated so that the flame front is blown out of the prechamber into the reaction zone and no combustion takes place in the prechamber in the operating regime.