Tertiary fuel, injection system for use in a dry low NOx combustion system

Claim 1

A method of suppressing combustion dynamics during transfer from a primary mode to a premixed mode of operation in a dual stage gas turbine combustor which includes primary and secondary combustion chambers separated by a venturi and supplied with fuel from primary and secondary fuel nozzles respectively and wherein, in a primary mode fuel is fed to the primary combustion chamber by said primary fuel nozzles for burning in the primary combustion chamber only, and in a premixed mode fuel is fed to the primary combustion chamber by said primary fuel nozzles for premixing with air and for burning in the secondary combustion chamber, comprising the steps of: a) during transfer from the primary to the premixed mode of operation, diverting 100% of the fuel to a plurality of tertiary fuel nozzles arranged in circular array about a longitudinal axis of the combustor, proximate but not upstream of a throat portion of the venturi, for injection into the secondary combustion chamber, thereby causing flame out on the primary combustion chamber and providing a stable diffusion flame on the secondary combustion chamber; and (b) upon flame out in the primary combustion chamber, diverting a portion of the fuel back to the primary fuel nozzles for injection of fuel into the primary combustion chamber for premixing with air, and diverting the remaining portion of the fuel to the secondary fuel nozzle for injection into the secondary combustion chamber.

Claim 2

A method of suppressing combustion dynamics during transfer from a primary mode to a premixed mode of operation in a dual stage gas turbine combustor which includes primary and secondary combustion chambers separated by a venturi and supplied with fuel from primary and secondary fuel nozzles respectively and wherein, in a primary mode fuel is fed to the primary combustion chamber by said primary fuel nozzles for burning in the primary combustion chamber only, and in a premixed mode fuel is fed to the primary combustion chamber by said primary fuel nozzles for premixing with air and for burning in the secondary combustion chamber, comprising the steps of: a) during transfer from the primary to the premixed mode of operation, diverting 100% of the fuel to a plurality of tertiary fuel nozzles arranged in circular array about a longitudinal axis of the combustor, proximate but not upstream of a throat portion of the venturi, for injection into the secondary combustion chamber, thereby causing flame out on the primary combustion chamber and providing a stable diffusion flame on the secondary combustion chamber; and (b) upon flame out in the primary combustion chamber, diverting a portion of the fuel back to the primary fuel nozzles for injection of fuel into the primary combustion chamber for premixing with air, and diverting the remaining portion of the fuel to the secondary fuel nozzle for injection into the secondary combustion chamber.