초록 ▼

A mid turbine frame is disposed between high and low pressure turbine assemblies. A cooling air system defined in the mid turbine frame of a gas turbine engine includes internal cavities for containing pressurized cooling air to cool the inter-turbine duct and the hollow struts, and discharges the u

A mid turbine frame is disposed between high and low pressure turbine assemblies. A cooling air system defined in the mid turbine frame of a gas turbine engine includes internal cavities for containing pressurized cooling air to cool the inter-turbine duct and the hollow struts, and discharges the used cooling air to further cool respective high and low pressure turbine assemblies.

대표청구항 ▼

1. A gas turbine engine comprising: a first turbine rotor assembly and a second turbine rotor assembly axially spaced apart from each other;a mid turbine frame (MTF) disposed axially between the first and second turbine rotor assemblies, including an annular outer case, annular inner case and annula

1. A gas turbine engine comprising: a first turbine rotor assembly and a second turbine rotor assembly axially spaced apart from each other;a mid turbine frame (MTF) disposed axially between the first and second turbine rotor assemblies, including an annular outer case, annular inner case and annular bearing housing with bearing seals, the annular bearing housing being connected to the annular inner case, a plurality of load spokes radially extending between and interconnecting the annular outer and annular inner cases to transfer loads from the annular bearing housing to the annular outer case; an annular inter-turbine duct (ITD) disposed radially between the annular outer and annular inner cases of the MTF, the ITD including an annular outer duct wall and annular inner duct wall, thereby defining an annular hot gas path between the annular outer and annular inner duct walls for directing hot gases from the first turbine rotor assembly to the second turbine rotor assembly, a plurality of hollow struts radially extending between and interconnecting the annular outer and annular inner duct walls, the load transfer spokes radially extending through at least a number of the hollow struts; andwherein the MTF defines a cooling air system, the system being formed with a first cavity between the annular outer case and the annular outer duct walls of the ITD with a first inlet defined in the annular outer case, a second cavity between the annular inner duet wall and the annular inner case, the first cavity, second cavity and the respective hollow struts being in fluid communication with the first inlet for receiving pressurized cooling air, the cooling air system including a cooling air discharge device at respective upstream and downstream sides of the MTF for discharging cooling air from the system to further cool the respective first and second rotor assemblies, and a flow restrictor supported between the annular inner duct wall and the annular inner case to defines an annular gap and configured for metering a cooling air flow escaping from the second cavity in order to provide a pressure margin within the first and second cavities in the MTF and the hot gas path to impede hot gas ingestion into the first and second cavities of the MTF. 2. The gas turbine engine as defined in claim 1 wherein the cooling air system further comprises a third cavity between the annular inner case and the annular bearing housing, and a cooling air passage in the annular bearing housing, the third cavity and the cooling air passage in the annular bearing housing being in fluid communication with a second inlet defined in a rotating shaft of the gas turbine engine for receiving pressurized cooling air. 3. The gas turbine engine as defined in claim 2 wherein the flow restrictor is in fluid communication with the second and third cavities to allow cooling air to escape from the second cavity while maintaining the first cavity, second cavity and a respective hollow struts pressurized with the cooling air. 4. The gas turbine engine as defined in claim 3 wherein the cooling air discharge device at the upstream side of the MTF defines a flow restricting/sealing arrangement for splitting the cooling air escaping from the flow restrictor, into a first air flow to be discharged from the cooling air system to cool the first turbine rotor assembly and a second air flow to be directed into the third cavity. 5. The gas turbine engine as defined in claim 4 wherein the flow restricting/sealing arrangement is formed in cooperation with the first turbine rotor assembly and the MTF, to allow the first air flow discharged from the cooling air system to pressurize a blade rim seal and to cool a blade back cavity of the first turbine rotor assembly. 6. The gas turbine engine as defined in claim 4 wherein the flow restricting/sealing arrangement comprises at least one annular, axial surface defined in each of the annular inner duct wall and the annular inner case, in cooperation with a seal component defined on an annular rear plate mounted on a rotor disc of the first turbine rotor assembly. 7. The gas turbine engine as defined in claim 4 wherein the second air flow directed from the flow restricting/sealing arrangement is mixed with a second inlet cooling air flow introduced from the second inlet, to form a mixed cooling air flow. 8. The gas turbine engine as defined in claim 7 wherein the cooling air discharge device at the downstream side of the MTF is configured to discharge the mixed cooling air flow from the third cavity to supply cooling air for the second turbine rotor assembly. 9. The gas turbine engine as defined in claim 2 wherein the cooling air passage in the annular beating housing comprises a radial section to direct a second inlet cooling air flow introduced from the second inlet, to pass between a rear seal of a first bearing of the first turbine rotor assembly and a front seal of a second bearing of the second turbine rotor assembly, thereby pressurizing the respective seals. 10. The gas turbine engine as defined in claim 9 wherein the cooling air passage in the annular bearing housing comprises a forward section and a rearward section to split the cooling air flow having passed through the radial section, into a forward cooling air flow for pressurizing a front seal of the first bearing of the first turbine rotor assembly and a rearward cooling air flow for pressurizing a rear seal of the second bearing of the second turbine rotor assembly. 11. The gas turbine engine as defined in claim 2 wherein the annular inner case comprises an arch structure defining a chamber for receiving a portion of a first inlet cooling air flow which has passed through the first cavity, the plurality of hollow struts and the second cavity and a portion of a second inlet cooling air flow which has passed through the cooling air passage in the annular bearing housing, the portions of first and second inlet cooling air flows being mixed in the chamber and discharged through the third cavity for supplying cooling air to the second turbine rotor assembly. 12. The gas turbine engine as defined in claim 1 wherein the cooling air discharge device at the upstream side of the MTF is located at a front axial end of the annular outer duct wall for supplying cooling air to a turbine shroud of the first turbine rotor assembly. 13. The gas turbine engine as defined in claim 1 wherein the cooling air discharge device at the upstream side of the MTF is located at a front axial end of the annular inner duct wall for supplying cooling air to pressurize a blade rim seal and to cool a back cavity of the first turbine rotor assembly. 14. The gas turbine engine as defined in claim 1 wherein the cooling air discharge device at the downstream side of the MTF is located at a rear axial end of the annular outer duct wall for supplying cooling air to a turbine shroud of the second turbine rotor assembly. 15. The gas turbine engine as defined in claim 1 wherein the cooling air discharge device at the downstream side of the MTF is located at a rear axial end of the annular inner duct wall for supplying cooling air to a rotor of the second turbine rotor assembly. 16. A gas turbine engine comprising: a first turbine rotor assembly and a second turbine rotor assembly axially spaced apart from each other;a mid turbine frame (MTF) disposed axially between the first and second turbine rotor assemblies;a cooling air system including a first inlet defined in the MTF and a second inlet defined in a rotating shaft of the gas turbine engine for receiving pressurized cooling air from separate passages, the cooling air system having a first cavity between an outer case and an outer duct wall of an inter-turbine duct (ITD) disposed inside the outer case, a second cavity between an inner duct wall of the ITD and an inner case, a third cavity between the inner case and a bearing housing mounted to the inner case, a cooling air passage in the bearing housing, and a chamber defined by an arch structure integrated with the inner case and communicating with the first inlet through a first flow path, the first flow path extending from the first cavity through a hollow passage in the ITD to the second cavity, the chamber communicating with the second inlet through a second flow path, the second flow path extending through the cooling air passage in the bearing housing, the chamber also communicating with the third cavity, and at least one of the first, second and third cavities including a cooling air discharge device located at respective upstream and downstream sides of the MTF for discharging cooling air from the system to the respective first and second rotor assemblies. 17. The gas turbine engine as defined in claim 16 wherein the cooling air passage in the bearing housing comprises a radial section, a forward section and a rearward section, the radial section directing the second inlet cooling air flow to pass between a rear seal of a first bearing of the first turbine rotor assembly and a front seal of a second bearing of the second turbine rotor assembly, thereby pressurizing the respective seals, the forward section and the rearward section splitting the second inlet cooling air flow which has passed through the radial section, into a forward cooling air flow for pressurizing a front seal of the first bearing of the first turbine rotor assembly and a rearward cooling air flow for pressurizing a rear seal of the second bearing of the second turbine rotor assembly. 18. The gas turbine engine as defined in claim 16 wherein the cooling air discharge device at the upstream side of the MTF is located at a front axial end of the inner duct wall for supplying cooling air to pressurize a blade rim seal and to cool a back cavity of the first turbine rotor assembly. 19. The gas turbine engine as defined in claim 16 wherein the cooling air discharge device at the downstream side of the MTF is located at a rear axial end of the outer duct wall for supplying cooling air to a turbine shroud of the second turbine rotor assembly. 20. The gas turbine engine as defined in claim 16 wherein the mixed portions of the first inlet cooling air flow and the second inlet cooling air flow are discharged from the third cavity for supplying cooling air to a rotor of the second turbine rotor assembly.