Patent ID: 8355854

Claim:
A method of controlling variable extraction flow in a turbine engine that includes a compressor, a combustor and a turbine, wherein extraction flow comprises a supply of compressed air extracted from the compressor and supplied to the turbine while bypassing the combustor through one or more extraction conduits, and wherein at least one of the extraction conduits includes a variable extraction orifice that has a plurality of settings controlled by a control unit, the method comprising the steps of: measuring a plurality of turbine engine operating parameters, wherein the measured operating parameters include at least one associated with a temperature within the turbine, one associated with the setting of the variable extraction orifice, one associated with the level of extraction flow; one associated with a supply of fuel to the combustor; monitoring, by the control unit, the measured operating parameters of the combustion turbine engine; setting at least one variable extraction orifice to a setting that allows an approximate maximum level of extraction flow; calculating, by the control unit, at least one calculated operating parameter based upon model-based control and the measured operating parameters, including at least a current turbine inlet temperature and a maximum turbine inlet temperature; manipulating the setting for the supply of fuel to the combustor such that an increased and/or approximate maximum level of engine output is determined by comparing the values for the current turbine inlet temperature and the maximum turbine inlet temperature; determining if a system operator wants to increase and/or maximize engine output; setting at least one of the variable extraction orifices to a setting that allows an approximate maximum level of extraction flow; given any changes in the measured operating parameters that result from the setting that allows an approximate maximum level of extraction flow for the at least one variable extraction orifice, calculating the current turbine inlet temperature and the maximum turbine inlet temperature, wherein the calculation of the maximum turbine inlet temperature is based upon an approximate maximum combustor exit temperature at which the turbine engine may operate given the temperature limits of hot-gas path parts and the approximate level of extraction flow at the setting that allows an approximate maximum level of extraction flow for the at least one variable extraction orifice; and comparing the current turbine inlet temperature and the maximum turbine inlet temperature.