Patent ID: 8820089
Filing Date: 2014-09-02
Classification: F02C,F05D,F23N,F23R

Abstract:
1. A method for controlling an operating point of a gas turbine that includes a compressor, a combustor and at least a turbine, the method comprising: determining an exhaust pressure drop at an exhaust of the turbine; measuring a compressor pressure discharge at the compressor; determining a turbine pressure ratio based on the exhaust pressure drop and the compressor pressure discharge; calculating a primary to lean-lean mode transfer threshold reference curve as a function of the turbine pressure ratio, wherein the primary to lean-lean mode transfer threshold curve includes operating points of the gas turbine at which an operation of the gas turbine is changed between a primary mode and a lean-lean mode; determining, at a first time, when an exhaust temperature associated with at least one of the operating points is higher than an exhaust temperature associated with the primary to lean-lean mode transfer threshold reference curve for the same turbine pressure ratio; and after a predetermined time after the first time, changing a split fuel quantity from a first value to a second value if the exhaust temperature associated with the operating point remains higher than the exhaust temperature of the primary to lean-lean mode transfer threshold reference curve; wherein the primary mode is defined as providing more than half of the fuel to primary burners of the combustor and igniting the provided fuel in a primary region of the combustor only, the primary region being adjacent to a secondary region; wherein the lean-lean mode is defined as providing fuel to both the primary burners and the secondary burner and burning the provided fuel both in the primary region and the secondary region; and wherein the split fuel quantity describes in percentages a first amount of the total fuel that is received by the primary burner and a second amount of the total fuel that is received by the secondary burners.