Gas turbine engine with intercooled cooling air and turbine drive
A gas turbine engine has a compressor section with a downstream most end and a cooling air tap at a location spaced upstream from the downstream most end. The cooling air tap is passed through at least one boost compressor and at least one heat exchanger, and then passed to a turbine section to cool the turbine section. The boost compressor is driven by a driveshaft which is driven by the turbine section. A boost turbine selectively drives the boost compressor.
1. A gas turbine engine comprising:
a compressor section having a downstream most end and a cooling air tap at an upstream location spaced upstream from said downstream most end;
cooling air from said cooling air tap being passed through at least one boost compressor and at least one heat exchanger, and then passed to a turbine section to cool said turbine section, said boost compressor being driven by a driveshaft which is driven by said turbine section, and a boost turbine for selectively driving said boost compressor; and
wherein an over-speed clutch between said driveshaft and said boost compressor, such that if said boost turbine rotates at a higher speed than a drive input from said driveshaft, said over speed clutch will disconnect said driveshaft from said boost compressor.
2. The gas turbine engine as set forth in claim 1 , wherein there are two of said heat exchangers, with a first heat exchanger between said cooling air tap and said boost compressor and a second heat exchanger downstream of said boost compressor.
3. The gas turbine engine as set forth in claim 2 , wherein said heat exchangers are in a bypass duct and cooled by bypass air from a fan rotor.
4. The gas turbine engine as set forth in claim 2 , wherein a mixing valve receives said cooling air from a location downstream of said boost compressor and selectively receives high pressure air, which has been compressed by said compressor section to a pressure higher than a pressure of compressor air at said cooling air tap, and said mixing valve controlling a mixture of said cooling air and said high pressure air to selectively deliver mixture of said two airflows to said turbine section.
5. The gas turbine engine as set forth in claim 2 , wherein said boost turbine receives air from a third location which has been compressed to a higher pressure than said upstream location wherein said cooling air is tapped.
6. The gas turbine engine as set forth in claim 2 , wherein a fan rotor is included and said fan rotor being driven by a fan drive turbine in said turbine section through a gear reduction.
7. The gas turbine engine as set forth in claim 2 , wherein the air driving said boost turbine is air from an air cycle machine system associated with an aircraft that includes the gas turbine engine.
8. The gas turbine engine as set forth in claim 1 , wherein when said boost turbine is driving said boost compressor, rotation passes back into said driveshaft from said boost turbine.
9. The gas turbine engine as set forth in claim 1 , wherein said at least one heat exchanger includes a plurality of heat exchangers, with a first heat exchanger between said cooling air tap and said boost compressor and a second heat exchanger downstream of said boost compressor.
10. The gas turbine engine as set forth in claim 9 , wherein said heat exchangers are in a bypass duct and cooled by bypass air from a fan rotor.
11. The gas turbine engine as set forth in claim 1 , wherein a mixing valve receives said cooling air from a location downstream of said boost compressor and selectively receives high pressure air, which has been compressed by said compressor section to a pressure higher than a pressure of compressor air at said cooling air tap, and said mixing valve controlling a mixture of said cooling air and said high pressure air to selectively deliver mixture of said two airflows to said turbine section.
12. The gas turbine engine as set forth in claim 1 , wherein said boost turbine receives air from a third location which has been compressed to a higher pressure than said upstream location wherein said cooling air is tapped.
13. The gas turbine engine as set forth in claim 1 , wherein a fan rotor is included and said fan rotor being driven by a fan drive turbine in said turbine section through a gear reduction.
14. The gas turbine engine as set forth in claim 1 , wherein the air driving said boost turbine is air from an air cycle machine system associated with an aircraft that includes the gas turbine engine.