Patent ID: 8056344

Claim:
A method for operating a gas turbine engine having a compressor joined to a turbine by a core rotor, with at least one combustor disposed therebetween for receiving compressed air from said compressor and fuel for providing combustion gas discharged to said turbine, said method comprising: supplying a hydrocarbon fuel to the combustor; and injecting hydrogen into said combustor in response to a power output level of said gas turbine engine; wherein, said gas turbine is operable at least in a high-power condition, a mid-power condition, and a low-power condition; said method further comprises, i) supplying said hydrocarbon fuel to said combustor during said high-power, mid-power and low-power conditions; ii) starting an injection of hydrogen into said combustor when changing from one of said high-power and the mid-power conditions to said low-power condition; and iii) stopping said hydrogen injection when changing from said low-power condition to one of said high-power and mid-power conditions; said gas turbine engine is operable in an output power range ranging from a minimum power output to a maximum power output and including said high-power, mid-power and low-power conditions and further including a low-power subrange ranging from said minimum power output to a switch power level within a lower half of said output power range, said low-power subrange including said low-power condition; said supplying step comprises supplying said hydrocarbon fuel to the combustor in the whole output power range; said starting step comprises starting an injection of hydrogen into the combustor when entering said low-power sub-range; and said stopping step comprises stopping said injection of hydrogen when leaving said low-power sub-range; said method further comprises, x) detecting an actual power condition; and y) comparing the actual power condition with said switch power level; said detecting an actual power condition includes detecting an ambient pressure, detecting an ambient temperature, and detecting a speed of said core rotor; and said method further calculating a combustor inlet temperature from detected values of the ambient pressure, ambient temperature and core rotor speed.