Method of operation for a gas turbine engine

Claim 1

A method for operating gas turbine engine having a compression section, a turbine section, an annular flow path for working medium gases which extends through the sections of the engine, a rotor assembly and a stator assembly, the engine further including a bearing housing which defines a bearing compartment in an inner cavity of the engine, a bearing disposed in the bearing compartment for supporting the rotor assembly, sealing means which extends from the housing into proximity with the rotor assembly, and a buffer region adjacent the sealing means, the improvement which comprises: flowing cooling air from the compression section through the inner cavity at pressures in excess of two-hundred pounds per square inch to the turbine section of the engine for cooling rotor blades in the turbine section; pressurizing the bearing compartment to a pressure in excess of one-hundred pounds per square inch to establish a difference in pressure across the sealing means which is less than a predetermined amount; flowing a lubricant to the bearing compartment and flowing a lubricant and air mixture from the bearing compartment at a flow rate which establishes a quench time characteristic for the lubricant and air mixture in the compartment; pressurizing buffer air in a region of the engine; flowing the pressurized buffer air to a buffer region adjacent the sealing means at a static pressure which is greater than the static pressure of the cooling air in the inner cavity adjacent the buffer region and greater than the static pressure of the bearing compartment under normal operative conditions; cooling the buffer air before the buffer air reaches the buffer air region to a temperature which establishes an autoignition time characteristic for the buffer air as the air passes through the sealing means into the bearing compartment which is greater than said quench time characteristic.

Claim 2

A method for operating gas turbine engine having a compression section, a turbine section, an annular flow path for working medium gases which extends through the sections of the engine, a rotor assembly and a stator assembly, the engine further including a bearing housing which defines a bearing compartment in an inner cavity of the engine, a bearing disposed in the bearing compartment for supporting the rotor assembly, sealing means which extends from the housing into proximity with the rotor assembly, and a buffer region adjacent the sealing means, the improvement which comprises: flowing cooling air from the compression section through the inner cavity at pressures in excess of two-hundred pounds per square inch to the turbine section of the engine for cooling rotor blades in the turbine section; pressurizing the bearing compartment to a pressure in excess of one-hundred pounds per square inch to establish a difference in pressure across the sealing means which is less than a predetermined amount; flowing a lubricant to the bearing compartment and flowing a lubricant and air mixture from the bearing compartment at a flow rate which establishes a quench time characteristic for the lubricant and air mixture in the compartment; pressurizing buffer air in a region of the engine; flowing the pressurized buffer air to a buffer region adjacent the sealing means at a static pressure which is greater than the static pressure of the cooling air in the inner cavity adjacent the buffer region and greater than the static pressure of the bearing compartment under normal operative conditions; cooling the buffer air before the buffer air reaches the buffer air region to a temperature which establishes an autoignition time characteristic for the buffer air as the air passes through the sealing means into the bearing compartment which is greater than said quench time characteristic.