Patent ID: 8726671

Claim:
A method of operating a combustor apparatus in a turbine engine comprising: transitioning from a first operating mode to a second operating mode corresponding to a lesser load than the first operating mode, the method comprising: reducing an amount of fuel provided to a primary fuel injection system of the combustor apparatus, the primary fuel injection system providing fuel to a main combustion zone; reducing an amount of fuel provided to a secondary fuel/air injection system of the combustor apparatus, the secondary fuel/air injection system providing fuel to a secondary combustion zone downstream from the main combustion zone; reducing a total amount of air provided to the combustor apparatus, wherein a first portion of the air is provided to the primary fuel injection system and a second portion of the air is provided to the secondary fuel/air injection system; upon reaching operating parameters corresponding to the second operating mode: increasing the amount of fuel provided to the primary fuel injection system; reducing the amount of fuel provided to the secondary fuel/air injection system to a predetermined value; increasing the total amount of air provided to the combustor apparatus; maintaining an air to fuel ratio in the combustion zone which is ideal for reducing carbon monoxide (CO) and nitrous oxides (NOx) emissions during the first operating mode, the second operating mode and the transition from the first to the second operating mode; transitioning from the second operating mode to a third operating mode corresponding to a lesser load than the second operating mode; reducing the amount of fuel provided to the primary fuel injection system during the transition from the second operating mode to the third operating mode; maintaining the amount of fuel provided to the secondary fuel/air injection system at the predetermined value during the transition from the second operating mode to the third operating mode; and continuously reducing the total amount of air provided to the combustor apparatus during the transition from the second operating mode to the third operating mode.