Air injection system in a gas turbine engine

A method for operating a gas turbine engine comprising:

• compressing air in a compressor section of the engine;
• mixing fuel and at least a portion of the compressed air and burning the mixture in a combustion section of the engine to create hot combustion gases;
• expanding the hot combustion gases to extract energy therefrom in a turbine section of the engine, wherein at least a portion of the extracted energy is used to rotate a turbine rotor during a first mode of engine operation comprising full load operation;
• injecting primary path air extracted from the engine into a rotor chamber through at least one rotor cooling pipe during the first mode of engine operation, the injected primary path air providing cooling to structure to be cooled within the turbine section;
• during a second mode of engine operation comprising less than full load operation:
• enabling operation of a blower system to:
• extract secondary path air from a combustor shell through at least one outlet port located in an engine casing portion that surrounds the combustion section;
• convey the extracted secondary path air through a piping system to the at least one rotor cooling pipe;
• and
• inject the extracted secondary path air into the rotor chamber through the at least one rotor cooling pipe.

A gas turbine engine comprising:

• a compressor section where air pulled into the engine is compressed;
• a combustion section where fuel is mixed with at least a portion of the compressed air from the compressor section and burned to create hot combustion gases;
• a turbine section where the hot combustion gases from the combustion section are expanded to extract energy therefrom, wherein at least a portion of the extracted energy is used to rotate a turbine rotor during a first mode of engine operation comprising full load operation;
• a rotor chamber in communication with structure to be cooled within the turbine section;
• at least one rotor cooling pipe that injects primary path air extracted from the engine into the rotor chamber during the first mode of engine operation;
• and
• an air injection system comprising:
• at least one outlet port through which secondary path air is extracted from the engine only during a second mode of engine operation comprising less than full load operation, the at least one outlet port located in a portion of an engine casing that surrounds the combustion section;
• the at least one rotor cooling pipe, which is used to inject the secondary path air extracted from the at least one outlet port into the rotor chamber during the second mode of engine operation;
• a piping system that provides fluid communication between the at least one outlet port and the at least one rotor cooling pipe;
• a blower system for extracting the secondary path air from the engine through the at least one outlet port and for conveying the extracted secondary path air through the piping system and the at least one rotor cooling pipe into the rotor chamber;
• and
• a valve system that is:
• closed during the first mode of engine operation to prevent secondary path air from being extracted from the engine and conveyed through the piping system by the blower system;
• and
• open during the second mode of engine operation to allow secondary path air to be extracted from the engine and conveyed through the piping system by the blower system.