Gas turbine firing temperature control with air injection system

A method of operating a gas turbine engine equipped with an air injection system at a desired firing temperature, comprising:

• determining an exhaust temperature of said gas turbine engine when said gas turbine engine is operating without air injection;
• calculating a firing temperature of said gas turbine engine when said air injection system is not injecting air into said gas turbine engine;
• injecting air into said gas turbine engine at an air injection flow rate using said air injection system;
• and
• using a controller of said gas turbine engine to:
• determine a bias to be added to an exhaust temperature control curve of said gas turbine engine based on a gas turbine inlet temperature;
• and
• operating said gas turbine engine along a curve that is a function of said bias and said exhaust temperature control curve to achieve said desired firing temperature during air injection;
• wherein, said desired firing temperature is generally equal to said firing temperature.

A method of achieving a desired firing temperature of a gas turbine engine during air injection, comprising:

• injecting compressed air into said gas turbine engine using an external source, said external source comprising a compressor and a recuperator;
• using a controller of said gas turbine engine to:
• determine an air injection exhaust bias gain using an inlet temperature of said gas turbine engine;
• calculate, based on said air injection exhaust bias gain, an air injection exhaust curve bias;
• and
• operating said gas turbine engine along said air injection exhaust curve bias to achieve said desired firing temperature during air injection.