COMBUSTION EQUIPMENT FOR A GAS TURBINE ENGINE

Abstract

Combustion equipment for a gas turbine engine operating on the pre-mix lean combustion bases comprises a flame tube having a plurality of alternately arranged main and pilot air ducts each having a respective fuel injector and receiving axially directed air from downstream of part span outlet guide vanes. The fuel and air in each duct are substantially pre-mixed before entry into the flame tube and the outlets of the pilot ducts direct the fuel and air mixture into the recirculation zone in a single vortex. At engine idle the air fuel ratio (AFR) is substantially stoichiometric to prevent the formation of unburnt hydrocarbons (UHC) and carbon monoxide (CO). As the engine accelerates the fuel flow to the pilot air ducts remains near constant so that the AFR in the re-circulation zone progressively weakens, and fuel is introduced into the main air ducts, the outlets of which direct the air fuel mixture into the flame tube with a substantial downstream component. The equivalence ratio of the main air fuel mixture is kept below 0.7 to keep NOx emissions at an acceptable level. Air direct from the engine compressor with a large swirl component is used to cool the flame tube walls with a high degree of effectiveness due to the scrubbing action of the air. Ducting for outer dilution air and bleed air can also be provided interdigitated with the main and pilot air ducting, and the flame tube can also have a catalyst block which allows the re-circulation zone to run weak at engine idle without excessive UHC and CO being produced.

Source: Google Patents

35 USC §181 Secrecy Order

Inventor

• 1ERIC A. ALEXANDER

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