초록

A cooling system 46 for a turbofan gas turbine 10 is disclosed. Various construction details which increase the effectiveness of a heat exchanger 48 located in the secondary flow path 24 are developed. In one embodiment, the cooled air is used for protecting a bearing compartment.

대표청구항 ▼

1. In an axial flow, turbofan gas turbine engine of the type having a fan section, a compressor section, a primary flow path for working medium gases which extends through the compressor section and a secondary flow path for working medium gases which extends through the fan section, and further of

1. In an axial flow, turbofan gas turbine engine of the type having a fan section, a compressor section, a primary flow path for working medium gases which extends through the compressor section and a secondary flow path for working medium gases which extends through the fan section, and further of the type having a rotor assembly, a stator assembly which is spaced from the rotor assembly, an inner cavity adjacent the rotor assembly filled with gases from the working medium flow path, and a bearing disposed between the stator assembly and the rotor assembly for supporting the rotor assembly, and having a bearing housing which includes a casing extending circumferentially about the bearing to define a bearing compartment, the housing having at least one end adjacent the rotor assembly, the engine having a first seal means at said end of the housing which extends into proximity with the rotor assembly, the improvement which comprises: a bearing housing disposed in said inner cavity which is spaced from the rotor assembly leaving a buffer cavity therebetween adjacent the seal means, the buffer cavity being in flow communication through a first leak path with the bearing compartment and in flow communication through a second leak path with the inner cavity; a first flow path for cooling air for the turbine section which extends through the inner cavity from the compressor section to the turbine section, the cooling air having a pressure and a first temperature in the inner cavity; and, a cooling system for providing pressurized cooling air at a temperature which is less than the first temperature of the cooling air flowed in the inner cavity from the compressor section to the turbine section, the cooling system including a heat exchanger in flow communication with the working medium gases of the secondary flow path, a duct for flowing pressurized air to the heat exchanger from a rear stage of the high pressure compressor, a duct for flowing cooled air from the heat exchanger to the bearing compartment, and means for discharging said cooled air into said buffer air cavity. 2. The gas turbine engine as claimed in claim 1 wherein the engine further has a shield spaced axially from the surface of the casing leaving an annular manifold therebetween which is in flow communication with the buffer air cavity and wherein the duct for flowing pressurized air from the fan air heat exchanger to the buffer cavity is in flow communication with said manifold. 3. The gas turbine engine as claimed in claim 1 wherein the heat exchanger is disposed in the fan duct such that at least one wall of the heat exchanger is adjacent the annular flow path for secondary gases and wherein the heat exchanger includes passages through which the hot gases from the compression section are flowed to cause convective cooling of the gases as heat is transferred from the gases through the wall adjacent the working medium flow path and to the gases in the working medium flow path. 4. In an axial-flow, turbofan gas turbine engine of the type having a fan section, a compressor section, a primary flow path for working medium gases which extends through the compressor section and a secondary flow path for working medium gases which extends through the fan section, having a rotor assembly, a stator assembly which is spaced from the rotor assembly, an inner cavity adjacent the rotor assembly filled with gases from the working medium flow path, and a bearing disposed between the stator assembly and the rotor assembly for supporting the rotor assembly, and having a bearing housing which includes a casing extending circumferentially about the bearing to define a bearing compartment, the housing having at least one end adjacent the rotor assembly, the engine having a first seal means at said end of the housing which extends into proximity with the rotor assembly, the improvement which comprises: a bearing housing disposed in said inner cavity which is spaced from the rotor assembly leaving a buffer cavity therebetween adjacent the seal means which is in flow communication through the leak path with the bearing compartment and in flow communication through a second leak path with the inner cavity; and, a cooling system for providing pressurized cooling air at a temperature which is less than the temperature in the inner cavity which includes a heat exchanger in flow communication with the working medium gases of the secondary flow path, a duct for flowing pressurized air to the heat exchanger from a rear stage of the high pressure compressor, a duct for flowing cooled air from the heat exchanger to the bearing compartment, and means for discharging said cooled air into said buffer air cavity; wherein the heat exchanger is a strut disposed in the fan duct which extends radially across the working medium flow path having a leading edge, a trailing edge, a first side wall adjacent to the annular flow path for secondary gases and a second side wall joined to the first side wall at the leading edge and the trailing edge leaving a cavity therebetween which defines a pressure containment vessel for containing the hot, pressurized working medium gases from the compressor section, wherein the strut includes a second pressure containment vessel disposed within said first pressure containment vessel having an interior which is in flow communication with the hot, pressurized gases for impinging the hot, pressurized gases on the leading edge region of the heat exchanger, and, wherein the strut further includes passages in the strut through which the hot gases from the compression section are flowed to cause convective cooling of the gases as heat is transferred from the gases through the wall adjacent the working medium flow path and to the gases in the working medium flow path. 5. The gas turbine engine as claimed in claim 4 wherein said second pressure containment vessel is a plurality of impingement tubes, and wherein the heat exchanger includes a base section in flow communication with the hot, pressurized gases and an airfoil section which forms the second pressure containment vessel.