# Patent

## Title
Compressed air bleed supply for buffer system

## Abstract

A gas turbine engine includes a fan, a compressor section fluidly connected to the fan, a combustor fluidly connected to the compressor section, a turbine section fluidly connected to the combustor, and a buffer system. The buffer system includes a heat exchanger having a first inlet, a first outlet, a second inlet, and a second outlet. The first outlet is configured to provide a cooled pressurized fluid. The buffer system includes first and second air sources that are selectively fluidly coupled to the first inlet, and a third air source that are fluidly coupled to the second inlet. Multiple fluid-supplied areas are located remotely from one another and are fluidly coupled to the first outlet. The multiple fluid-supplied areas include a bearing compartment. A method and a buffer system are also disclosed.

## Background
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation of U.S. application Ser. No. 13/362,499, filed Jan. 31, 2012.


BACKGROUND
This disclosure relates to a buffer system for a gas turbine engine.
Gas turbine engines typically require air from one of the compressor stages to provide buffer air to a bearing compartment, for example. One proposed system utilizes a valve in the buffer system that regulates the fluid flow from a high compressor stage and a low compressor stage. The regulated air is provided to a cooler and a bearing compartment.
Another system utilizes a dedicated centrifugal compressor to provide pressurized air to multiple bearing compartments and provide shaft ventilation. The centrifugal compressor is a separate compressor, discrete from the high pressure and low pressure compressor stages of the gas turbine engine.
SUMMARY
A gas turbine engine according to an example of the present disclosure includes a fan, a compressor section fluidly connected to the fan, a combustor fluidly connected to the compressor section, a turbine section fluidly connected to the combustor, and a buffer system. The buffer system includes a heat exchanger having a first inlet, a first outlet, a second inlet, and a second outlet. The first outlet is configured to provide a cooled pressurized fluid, first and second air sources that are selectively fluidly coupled to the first inlet, a third air source fluidly coupled to the second inlet, and multiple fluid-supplied areas located remotely from one another and fluidly coupled to the first outlet. The multiple fluid-supplied areas include a bearing compartment.
A further embodiment of any of the foregoing embodiments includes a first compressor and a second compressor. The second air source is provided by the second compressor, and the third air source is provided by the first compressor.
In a further embodiment of any of the foregoing embodiments, the first, second and third air sources are different than one another.
In a further embodiment of any of the foregoing embodiments, the first air source is configured to provide air at a first pressure and temperature state, and the second air source is configured to provide air at a higher pressure and temperature state than the first air source.
In a further embodiment of any of the foregoing embodiments, a valve is fluidly coupled to at least one of the first and second air sources. The valve is configured to regulate fluid flow from at least one of the one first and second air sources to the heat exchanger.
In a further embodiment of any of the foregoing embodiments, a mid-stage is provided fluidly between the first and second compressors. The first air source is provided by the mid-stage.
In a further embodiment of any of the foregoing embodiments, the second compressor includes a rotor, and the multiple fluid-supplied areas include the rotor.
In a further embodiment of any of the foregoing embodiments, the turbine section comprises a fan drive turbine including a shaft, and the multiple fluid-supplied areas include the shaft.
In a further embodiment of any of the foregoing embodiments, a pressure ratio across the fan is less than about 1.45.
In a further embodiment of any of the foregoing embodiments, fan drive turbine is configured to drive the fan. A pressure ratio across the fan drive turbine is greater than about 5.
In a further embodiment of any of the foregoing embodiments, the first inlet is fluidly connected to the first outlet, and the second inlet is fluidly connected to the second outlet.
In a further embodiment of any of the foregoing embodiments, the multiple fluid-supplied areas include a component of the gas turbine engine.
In a further embodiment of any of the foregoing embodiments, the component is one of a vane, a blade and a clearance control device.
A further embodiment of any of the foregoing embodiments includes a bypass flow path arranged between core and fan nacelles, the second outlet fluidly being coupled to the bypass flow path.
In a further embodiment of any of the foregoing embodiments, the fan is configured to deliver a portion of air into the compressor section, and a portion of air into the bypass duct. A bypass ratio, which is defined as a volume of air passing to the bypass duct compared to a volume of air passing into the compressor section, is greater than about 6.
A method of designing a buffer system for a gas turbine engine according to an example of the present disclosure includes the steps of configuring a heat exchanger to define a first inlet and a first outlet fluidly coupled to each other and a second inlet and a second outlet fluidly coupled to each other, configuring the first inlet to receive air from first and second air sources that are selectively fluidly coupled to the first inlet, configuring the second inlet to receive air from a third air source fluidly that is coupled to the second inlet, and configuring the first outlet to provide cooled pressurized air to multiple fluid-supplied areas that are located remotely from one another and that are fluidly coupled to the first outlet. The multiple fluid-supplied areas include a bearing compartment of a gas turbine engine.
A further embodiment of any of the foregoing embodiments includes the steps of configuring a valve to be fluidly coupled to the first and second inlets, and designing the valve to regulate air from the first and second air sources, wherein the first and second air sources have different pressures.
A further embodiment of any of the foregoing embodiments includes the step of designing the first, second and third air sources to be different than one another.
A further embodiment of any of the foregoing embodiments includes the steps of configuring the first air source to provide air at a first pressure and temperature state, and configuring the second air source to provide air at a higher pressure and temperature state than the first air source.
A further embodiment of any of the foregoing embodiments includes the steps of configuring a compressor section to compress air and deliver it into a combustion section, the compressor section including first and second compressors; configuring the first compressor to provide the third air source; and configuring the second compressor to provide the second air source.
In a further embodiment of any of the foregoing embodiments, the step of configuring a compressor section includes arranging the first compressor to be upstream of the second compressor.
A further embodiment of any of the foregoing embodiments includes the steps of configuring a mid-stage to provide a flow path between the first and second compressors, and configuring the mid-stage to provide the first air source.
A further embodiment of any of the foregoing embodiments includes the step of designing the multiple fluid-supplied areas to include a component of the gas turbine engine. The component is at least one of a rotor of the second compressor and a shaft of a fan drive turbine driven by the compressor section.
A further embodiment of any of the foregoing embodiments includes the step of configuring the second outlet to be fluidly coupled to a bypass flow path. The bypass flow path is arranged between core and fan nacelles of a gas turbine engine.
A buffer system for a gas turbine engine according to an example of the present disclosure includes a heat exchanger configured for securing to a static structure. The heat exchanger has a first inlet and outlet and a second inlet and outlet, first and second air sources selectively fluidly coupled to the first inlet, and a third air source fluidly coupled to the second inlet and being provided by a first compressor. The first outlet is configured to provide a cooled pressurized fluid to multiple fluid-supplied areas fluidly coupled to the first outlet. The multiple fluid-supplied areas are located remotely from one another and include a bearing compartment.
In a further embodiment of any of the foregoing embodiments, the first air source is configured to provide air at a low pressure and temperature state, and the second air source is configured to provide air at a higher pressure and temperature state than the first air source.
In a further embodiment of any of the foregoing embodiments, the second air source is provided by a second compressor.
A further embodiment of any of the foregoing embodiments includes a valve configured for securing to the static structure, the valve being fluidly coupled to at least one of the first and second air sources. The valve is configured to regulate fluid flow from the first and second air sources to the heat exchanger.
In a further embodiment of any of the foregoing embodiments, the first inlet is fluidly connected to the first outlet, and the second inlet is fluidly connected to the second outlet.



BRIEF DESCRIPTION OF THE DRAWINGS
The disclosure can be further understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
FIG. 1 schematically illustrates a gas turbine engine.
FIG. 2 is a schematic of an example buffer system for a gas turbine engine.



DETAILED DESCRIPTION
FIG. 1 schematically illustrates a gas turbine engine 20. The gas turbine engine 20 is disclosed herein as a two-spool turbofan that generally incorporates a fan section 22, a compressor section 24, a combustor section 26 and a turbine section 28. Alternative engines might include an augmentor section (not shown) among other systems or features. The fan section 22 drives air along a bypass flowpath B while the compressor section 24 drives air along a core flowpath C for compression and communication into the combustor section 26 then expansion through the turbine section 28. Although depicted as a turbofan gas turbine engine in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of turbine engines including three-spool architectures.
The engine 20 generally includes a low speed spool 30 and a high speed spool 32 mounted for rotation about an engine central longitudinal axis A relative to an engine static structure 36 via several bearing systems 38. It should be understood that various bearing systems 38 at various locations may alternatively or additionally be provided.
The low speed spool 30 generally includes an inner shaft 40 that interconnects a fan 42, a low pressure compressor 44 and a low pressure turbine 46. The inner shaft 40 is connected to the fan 42 through a geared architecture 48 to drive the fan 42 at a lower speed than the low speed spool 30. The high speed spool 32 includes an outer shaft 50 that interconnects a high pressure compressor 52 and high pressure turbine 54. A combustor 56 is arranged between the high pressure compressor 52 and the high pressure turbine 54. A mid-turbine frame 57 of the engine static structure 36 is arranged generally between the high pressure turbine 54 and the low pressure turbine 46. The mid-turbine frame 57 supports one or more bearing systems 38 in the turbine section 28. The inner shaft 40 and the outer shaft 50 are concentric and rotate via bearing systems 38 about the engine central longitudinal axis A, which is collinear with their longitudinal axes.
The core airflow C is compressed by the low pressure compressor 44 then the high pressure compressor 52, mixed and burned with fuel in the combustor 56, then expanded over the high pressure turbine 54 and low pressure turbine 46. The mid-turbine frame 57 includes airfoils 59 which are in the core airflow path. The turbines 46, 54 rotationally drive the respective low speed spool 30 and high speed spool 32 in response to the expansion.
The engine 20 in one example a high-bypass geared aircraft engine. In a further example, the engine 20 bypass ratio is greater than about six (6), with an example embodiment being greater than ten (10), the geared architecture 48 is an epicyclic gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about 2.3 and the low pressure turbine 46 has a pressure ratio that is greater than about 5. In one disclosed embodiment, the engine 20 bypass ratio is greater than about ten (10:1), the fan diameter is significantly larger than that of the low pressure compressor 44, and the low pressure turbine 46 has a pressure ratio that is greater than about 5:1. Low pressure turbine 46 pressure ratio is pressure measured prior to inlet of low pressure turbine 46 as related to the pressure at the outlet of the low pressure turbine 46 prior to an exhaust nozzle. The geared architecture 48 may be an epicycle gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about 2.5:1. It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present invention is applicable to other gas turbine engines including direct drive turbofans.
A significant amount of thrust is provided by the bypass flow B due to the high bypass ratio. The fan section 22 of the engine 20 is designed for a particular flight condition—typically cruise at about 0.8 Mach and about 35,000 feet. The flight condition of 0.8 Mach and 35,000 ft, with the engine at its best fuel consumption—also known as “bucket cruise Thrust Specific Fuel Consumption (‘TSFC’)”—is the industry standard parameter of lbm of fuel being burned divided by lbf of thrust the engine produces at that minimum point. “Low fan pressure ratio” is the pressure ratio across the fan blade alone, without a Fan Exit Guide Vane (“FEGV”) system. The low fan pressure ratio as disclosed herein according to one non-limiting embodiment is less than about 1.45. “Low corrected fan tip speed” is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(Tambient deg R)/518.7)^0.5]. The “Low corrected fan tip speed” as disclosed herein according to one non-limiting embodiment is less than about 1150 ft/second.
An example buffer system 60 is illustrated in FIG. 2. The system 60 includes first, second and third air sources 62, 64, 66, which are different than one another in the example. In one example, one of the first and second air sources 62, 64 is provided by the high pressure compressor 52. The third air source 66 is provided by the low pressure compressor 44. A pressurized region 100 between the exit of the low pressure compressor 44 and the entrance of high pressure compressor 52 is referred to as “mid-stage” (100 in FIG. 1) and is arranged fluidly with the low and high pressure compressors 44, 52 within the compressor section 24. In the example, the first and second air sources 62, 64 are provided within the high pressure compressor but could be representative of any two differing pressure supplies. Thus, in one example, the first air source 62 provides air at a low pressure and temperature state, the second air source 64 provides air at a higher pressure and temperature state, and the third air source 66 provides low pressure compressor air.
The first and second air sources 62, 64 are selectively fluidly coupled to a heat exchanger 72. In one example, a valve 68 is fluidly coupled to the first and second air sources 62, 64 and is configured to regulate fluid flow from the first and second air sources 62, 64 to the heat exchanger 72.
The heat exchanger 72 includes a first inlet and outlet 69, 70 and a second inlet and outlet 71, 73. The first outlet 70 provides cooled pressurized air 74. Passages are provided between respective inlets and outlets and are configured to transfer heat between the passages. In the example, the valve 68 is fluidly coupled to the first inlet 69, and the third air source 66 is fluidly coupled to the second inlet 71. The second outlet 73 is fluidly coupled to the bypass flow B so that low pressure compressor air expelled from the heat exchanger 72 may be used to supplement the thrust provided by the bypass flow B.
The first outlet 70 is fluidly coupled to multiple fluid-supplied areas that are located remotely from one another. The multiple fluid-supplied areas include multiple bearing compartments 76A, 76B, 76C, 76D. The multiple fluid-supplied areas may also include a component 78 that requires thermal conditioning, such as a vane, blade or clearance control device. The multiple fluid-supplied areas may also include a rotor 80 in the high pressure compressor 52 and/or a low pressure turbine section shaft 82.
In operation, a method of providing pressurized air to the gas turbine engine 10 includes selectively providing pressurized air from multiple air sources to the heat exchanger 72 to cool the pressurized air. The cooled pressurized air 74 is distributed to multiple fluid-supplied areas within the gas turbine engine. In one example, air from first and second air sources 62, 64, which are different from one another, are regulated. The pressurized air is cooled by providing low pressure compressor air from a third air source 66 to the heat exchanger 72. The cooled pressurized air 74 is distributed to multiple bearing compartments 76A, 76B, 76C, 76D, high pressure compressor section rotor 80, low pressure turbine section shaft 82, and/or a component 78.
Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.

## Claims

1. A gas turbine engine comprising:
a fan;
a compressor section fluidly connected to the fan, the compressor section including a first compressor and a second compressor each downstream of the fan;
a combustor fluidly connected to the compressor section;
a turbine section fluidly connected to the combustor; and
a buffer system comprising:
a heat exchanger having a first inlet, a first outlet, a second inlet, and a second outlet, the first outlet configured to provide a cooled pressurized fluid;
first and second air sources that are selectively fluidly coupled to the first inlet;
a third air source fluidly coupled to the second inlet, the third air source being provided by the compressor section; and
multiple fluid-supplied areas located remotely from one another and fluidly coupled to the first outlet, the multiple fluid-supplied areas including a bearing compartment.

2. The gas turbine engine according to claim 1, wherein the second air source being provided by the second compressor, and the third air source being provided by the first compressor.

3. The gas turbine engine according to claim 2, wherein the first, second and third air sources are different than one another.

4. The gas turbine engine according to claim 3, wherein the first air source is configured to provide air at a first pressure and temperature state, and the second air source is configured to provide air at a higher pressure and temperature state than the first air source.

5. The gas turbine engine according to claim 4, wherein a valve is fluidly coupled to at least one of the first and second air sources, the valve configured to regulate fluid flow from at least one of the one first and second air sources to the heat exchanger.

6. The gas turbine engine according to claim 5, wherein a mid-stage is provided fluidly between the first and second compressors, the first air source being provided by the mid-stage.

7. The gas turbine engine according to claim 6, wherein the second compressor includes a rotor, and the multiple fluid-supplied areas include the rotor.

8. The gas turbine engine according to claim 1, wherein the turbine section comprises a first turbine including a shaft, and the multiple fluid-supplied areas including the shaft.

9. The gas turbine engine according to claim 8, wherein a pressure ratio across the fan is less than 1.45.

10. The gas turbine engine according to claim 9, wherein the first inlet is fluidly connected to the first outlet, and the second inlet is fluidly connected to the second outlet.

11. The gas turbine engine according to claim 8, wherein the multiple fluid-supplied areas include a component of the gas turbine engine.

12. The gas turbine engine according to claim 11, wherein the component is one of a vane, a blade and a clearance control device.

13. The gas turbine engine according to claim 12, comprising a bypass flow path arranged between core and fan nacelles, the second outlet fluidly coupled to the bypass flow path.

14. The gas turbine engine according to claim 4, wherein a mid-stage is provided fluidly between an exit of the first compressor and an entrance of the second compressor, the first air source being provided by the mid-stage.

15. The gas turbine engine according to claim 4, wherein the first air source being provided by the second compressor.

16. The gas turbine engine according to claim 15, comprising a bypass flow path arranged between core and fan nacelles, and the fan being configured to deliver a portion of air into the compressor section, and a portion of air into the bypass flow path.

17. The gas turbine engine according to claim 16, wherein the turbine section comprises a first turbine including a shaft connected to the fan through a geared reduction to drive the fan at a relatively lower speed than the first turbine.

18. The gas turbine engine according to claim 17, wherein a valve is fluidly coupled to each of the first and second air sources, the valve configured to regulate fluid flow from each of the first and second air sources to the heat exchanger.

19. The gas turbine engine according to claim 18, wherein the second compressor includes a rotor, and the multiple fluid-supplied areas include the rotor.

20. The gas turbine engine according to claim 19, wherein the multiple fluid-supplied areas includes the shaft.

21. A buffer system for a gas turbine engine comprising:
a heat exchanger configured for securing to a static structure, the heat exchanger having a first inlet and outlet and a second inlet and outlet;
first and second air sources selectively fluidly coupled to the first inlet; and
a third air source fluidly coupled to the second inlet and being provided by a first compressor downstream of a fan;
wherein the first outlet is configured to provide a cooled pressurized fluid to multiple fluid-supplied areas fluidly coupled to the first outlet, the multiple fluid-supplied areas being located remotely from one another and including a bearing compartment.

22. The buffer system according to claim 21, wherein the first air source is configured to provide air at a low pressure and temperature state, and the second air source is configured to provide air at a higher pressure and temperature state than the first air source.

23. The buffer system according to claim 21, wherein the second air source is provided by a second compressor.

24. The buffer system according to claim 21, comprising a valve configured for securing to the static structure, the valve being fluidly coupled to at least one of the first and second air sources, and the valve being configured to regulate fluid flow from the first and second air sources to the heat exchanger.

25. The buffer system according to claim 21, wherein the first inlet is fluidly connected to the first outlet, and the second inlet is fluidly connected to the second outlet.

26. The buffer system according to claim 22, wherein the second air source is provided by a second compressor, the second compressor being downstream of the first compressor and the fan.

27. The buffer system according to claim 26, wherein a mid-stage is provided fluidly between an exit of the first compressor and an entrance of the second compressor, the first air source being provided by the mid-stage.