초록 ▼

A mid-turbine frame is disposed between high and low pressure turbine assemblies. A secondary air system is defined in the mid-turbine frame (MTF) to provide cooling to the turbine section of the engine. The secondary air system may be used to cool and pressurize seals to assist with oil retention i

A mid-turbine frame is disposed between high and low pressure turbine assemblies. A secondary air system is defined in the mid-turbine frame (MTF) to provide cooling to the turbine section of the engine. The secondary air system may be used to cool and pressurize seals to assist with oil retention in bearing cavities. The temperature gain of the secondary air may be reduced by flowing the secondary air through one or more external lines and then generally radially inwardly through air passages defined in the MTF.

대표청구항 ▼

1. A gas turbine engine comprising first and second axially spaced-apart turbine rotor assemblies mounted for rotation on bearings housed in a bearing housing, the bearings having seals to restrict lubricant leakage from the bearing housing, and a mid-turbine frame disposed axially between the first

1. A gas turbine engine comprising first and second axially spaced-apart turbine rotor assemblies mounted for rotation on bearings housed in a bearing housing, the bearings having seals to restrict lubricant leakage from the bearing housing, and a mid-turbine frame disposed axially between the first and second rotor assemblies, the mid-turbine frame having structurally interconnected radially outer and inner cases, the bearing housing being mounted to the radially inner case of the mid-turbine frame and being disposed radially inwardly of the mid-turbine frame, said mid-turbine frame having a first air system for pressurizing and cooling the seals of the bearings in the bearing housing, said first air system comprising at least one air inlet defined in the radially outer case of said mid-turbine frame for receiving pressurized cooling air from at least one first external line disposed outside of a core casing of the engine where engine temperatures are lower, and a cooling air passage extending from said air inlet radially inwardly through said mid-turbine frame to said bearing housing, said cooling air passage comprising an inner plenum bounded at a front axial end thereof by a baffle configured to direct a first portion of the pressurized cooling air to a first front seal of said seals of the bearings, the inner plenum being bounded at a rear axial end thereof by a wall through which flow calibrating holes are defined, the flow calibrating holes being in flow communication with an enclosed space which is in turn in fluid flow communication with at least two other seals of the bearings. 2. The gas turbine engine defined in claim 1, wherein the first air system further comprises an air cooler for cooling the air prior to directing the same into the bearing housing. 3. The gas turbine engine defined in claim 1, wherein the mid-turbine frame further comprises an inter-turbine duct disposed between the radially outer case and the radially inner case, the inter-turbine duct having inner and outer annular walls and an array of circumferentially spaced-apart struts extending radially between the inner and outer annular walls, the inner and outer annular walls defining a hot gas path therebetween for directing hot gases from the first turbine rotor assembly to the second turbine rotor assembly, and wherein the cooling air passage comprises at least one internal pipe extending from said air inlet radially inwardly through at least a corresponding one of said struts. 4. The gas turbine engine defined in claim 3, wherein the inner plenum is defined between the inner case and the bearing housing, the at least one internal pipe directing the pressurized cooling air into said plenum. 5. The gas turbine engine defined in claim 3, wherein said mid-turbine frame has a second air system integrated thereto, said second air system comprising at least one second air inlet defined in said radially outer case of the mid-turbine frame, an outer plenum defined between the radially outer case and the outer annular wall of the inter-turbine duct, the outer plenum being connected in fluid flow communication with said at least one second air inlet for receiving pressurized cooling air therefrom, an intermediate plenum defined between the radially inner case and the inner annular wall of the inter-turbine duct, said outer and intermediate plenums being connected in fluid flow communication through at least one of said struts, and wherein said intermediate plenum is connected in fluid flow communication with both said first and second turbine rotor assemblies. 6. The gas turbine engine defined in claim 5, wherein the at least one internal pipe of the first air system extends through the outer and intermediate plenums of the second air system, and wherein the pressurized cooling air flowing through the second air system flows over said at least one internal pipe as it travels from said outer plenum to said intermrnediate plenum. 7. The gas turbine engine defined in claim 5, wherein said at least one internal pipe of the first air system extends through said at least one of said struts connecting the outer and intermediate plenums of the second air system. 8. The gas turbine engine defined in claim 5, wherein said at least one second air inlet is connected in fluid flow communication to at least one corresponding second external line. 9. The gas turbine engine defined in claim 8, wherein said at least one first and second external lines are disposed radially outwardly relative to the mid-turbine frame and extend outwardly therefrom to a source of compressor bleed air. 10. The gas turbine engine defined in claim 2, wherein the air cooler is mounted outside of the mid-turbine frame in said at least one first external line. 11. The gas turbine engine defined in claim 3, wherein the internal pipe has an outlet end connected to a port in said radially inner case, and wherein said port constitutes an inlet of the inner plenum. 12. A gas turbine engine comprising: a high pressure turbine (HPT) rotor assembly; a low pressure turbine (LPT) rotor assembly; a mid-turbine frame disposed axially between the HPT rotor assembly and the LPT rotor assembly, the mid-turbine frame comprising a radially outer case, a radially inner case and an inter-turbine duct between the radially outer and radially inner cases, the inter-turbine duct defining a gas path for directing hot gases from the HPT rotor assembly to the LPT rotor assembly, said inter-turbine duct including a set of circumferentially hollow struts extending radially across said gas path; a first secondary air system including at least one first air inlet defined in the radially outer case of the mid-turbine frame, at least one internal pipe connected in fluid flow communication with said at least one first air inlet and extending radially inwardly through a corresponding one of said hollow struts, and a first plenum disposed radially inwardly relative to said radially inner case, said first plenum being connected in fluid flow communication with said at least one internal pipe and with a bearing housing of said HPT and LPT rotor assemblies; and a second secondary air system comprising at least one second air inlet defined in said radially outer case of said mid-turbine frame, a second plenum defined between said radially outer case and said inter-turbine duct, said second plenum being connected in fluid flow communication with said at least one second air inlet, a third plenum defined between the inter-turbine duct and the radially inner case, the third plenum being connected in fluid flow communication with said second plenum via said hollow struts, and wherein said third plenum is connected in fluid flow communication with a rotor rear cavity of the HPT rotor assembly and a rotor front cavity of the LPT rotor assembly. 13. The gas turbine engine defined in claim 12, wherein the at least one first and second air inlets are connected to a source of pressurized cooling air via respective external supply lines disposed radially outwardly of a core case of the engine. 14. The gas turbine engine defined in claim 12, wherein the first secondary air system comprises an air cooler disposed upstream of the at least one first air inlet. 15. The gas turbine engine defined in claim 12, wherein a back wall of the third plenum includes a baffle defining openings to allow air to flow in a generally downstream direction from the third plenum to the rotor front cavity of the LPT rotor assembly.