REVERSE CORE GEAR TURBOFAN

Abstract

A gas turbine engine comprises a fan at an axially outer location, the fan rotating about an axis of rotation, delivering air into an outer bypass duct, a radially middle duct, and a radially inner core duct. Air from the inner core duct is directed into a compressor, and then flows axially in a direction back toward the fan through a combustor section, and across a core turbine section, and is then directed into the middle duct. A gear reduction drives the fan from a fan drive turbine section. A method of operating a gas turbine engine is also disclosed.

Claims

1. A gas turbine engine comprising: a fan at an axially outer location, said fan rotating about an axis of rotation; said fan delivering air into an outer bypass duct, a radially middle duct, and a radially inner core duct; air from said inner core duct being directed into a compressor, and then flowing axially in a direction back toward said fan through a combustor section, and across a core turbine section, and then being directed into said middle duct; a gear reduction for driving said fan from a fan drive turbine section; and wherein said cold turbine section is in said radially inner core duct and is provided with a flow diverter that allows bypass of air around a rotor associated with said cold turbine section.

2. The gas turbine engine as set forth in claim 1, wherein a shaft downstream of said gear reduction relative to said fan drive turbine section also drives said booster fan.

3. The gas turbine engine as set forth in claim 2, wherein a shaft downstream of said gear reduction is also connected to rotate with said cold turbine.

4. The gas turbine engine a set forth in claim 3, wherein a fan booster delivering air into said radially middle duct and said radially inner core, and a cold turbine in said radially inner core rotating with a clutched shaft separate from a fan shaft driving said fan, and a clutch selectively connecting said clutched shaft to said fan shaft such that said fan shaft can selectively drive said clutched shaft.

5. A gas turbine engine as set forth in claim 4, wherein there are at least a plurality of core turbine sections, with one of said plurality of said core turbine sections driving said fan through said gear reduction and a second of said core turbine sections driving said fan booster.

6. The gas turbine engine as set forth in claim 1, wherein said compressor section includes at least a first compressor section and a second compressor section downstream of said first compressor section, and said core turbine section includes at least a first core turbine section and a second core turbine section, with said first core turbine section driving said second compressor section and said second core turbine section driving said first compressor section, with said second turbine section and said first compressor section operating at a slower speed and at lower pressures than said first turbine section and said second compressor section.

7. The gas turbine engine as set forth in claim 1, wherein a radially outer extent of blades associated with said cold turbine section is spaced inwardly of a radially outer position for said flow diverter to allow bypass of air radially outwardly of said radially outermost extent of the blades in said cold turbine section.

8. The gas turbine engine as set forth in claim 7, wherein there are a pair of flow diverters, with said pair of flow diverters being movable to a position allowing the bulk of the air delivered to the compressor section to bypass the turbine rotor by passing radially outwardly of the radially outermost extent of the blades, and said flow diverters being movable to an alternative position with a great bulk of the air delivered across said cold turbine section passes radially inwardly of the radially outermost extent of the fan turbine blades.

9. The gas turbine engine as set forth in claim 8, wherein said cold turbine section associated with said flow diverter is positioned adjacent to said booster fan.

10. The gas turbine engine as set forth in claim 8, wherein said cold turbine section associated with said flow diverter is positioned at a location adjacent to said compressor on an axial side of said compressor spaced away from said fan.

11. The gas turbine engine as set forth in claim 7, wherein said cold turbine section associated with said flow diverter is positioned adjacent to said booster fan.

12. The gas turbine engine as set forth in claim 1, wherein said cold turbine section associated with said flow diverter is positioned at a location adjacent to said compressor on an axial side of said compressor spaced away from said fan.

13. The gas turbine engine as set forth in claim 1, wherein said cold turbine section associated with said flow diverter is positioned adjacent to a booster fan.

14. A gas turbine engine comprising: a fan at an axially outer location, said fan rotating about an axis of rotation; said fan delivering air into an outer bypass duct, a radially middle duct, and a radially inner core duct; air from said inner core duct being directed into a compressor, and then flowing axially in a direction back toward said fan through a combustor section, and across a core turbine section, and then being directed into said middle duct; a gear reduction for driving said fan from a fan drive turbine section; and wherein a first cold turbine section is positioned adjacent a booster fan, and a second cold turbine section is positioned downstream of the first cold turbine section in the path of air flowing through said inner core duct, and upstream of said compressor section.

15. The gas turbine engine as set forth in claim 14, wherein one of said first and second cold turbine sections is provided with a flow diverter that allows bypass of air around a rotor associated with said one of said cold turbine sections.

16. The gas turbine engine as set forth in claim 15, wherein a radially outer extent of blades associated with said one of said cold turbine sections is spaced inwardly of a radially outer position for said flow diverter to allow bypass of air radially outwardly of said radially outermost extent of the blades of said one of said cold turbine sections.

17. The gas turbine engine as set forth in claim 16, wherein there are a pair of flow diverters, with said pair of flow diverters being movable between a position allowing the bulk of the air delivered to the compressor section to bypass the turbine rotors by passing radially outwardly of the radially outermost extent of the blades, and said flow diverters being movable to an alternative position wherein the great bulk of the air delivered across said one of said cold turbine sections passes radially inwardly of the radially outermost extent of the fan turbine blades.

18. The gas turbine engine as set forth in claim 17, wherein said flow diverter is associated with said first cold turbine section.

19. The gas turbine engine as set forth in claim 15, wherein said flow diverter is associated with said first cold turbine section.

20. The gas turbine engine as set forth in claim 15, wherein said flow diverter is associated with said second cold turbine section.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1 shows a first embodiment.

[0032] FIG. 2 shows a second embodiment.

[0033] FIG. 3 shows a third embodiment.

[0034] FIG. 4A shows a feature which may be incorporated into any one of the FIG. 1-3 embodiments.

[0035] FIG. 4B shows the first embodiment feature in a second operative position.

[0036] FIG. 5A shows another embodiment feature which can be incorporated into any of the FIGS. 1-3 embodiments.

[0037] FIG. 5B shows the second embodiment feature in a second operative position.

[0038] FIG. 6A shows another embodiment feature which can be incorporated into anyone of the FIGS. 1-3 embodiments.

[0039] FIG. 6B shows the third embodiment feature in a second mode of operative position.

[0040] FIG. 7A shows a fourth embodiment feature which can be incorporated into any one of the FIGS. 1-3 embodiments.

[0041] FIG. 7B shows the fourth embodiment feature and a second operative position.

DETAILED DESCRIPTION

[0042] FIG. 1 shows a gas turbine engine 20 having a fan 22 delivering air into three flowpaths, as an outer bypass propulsion flowpath 24, a middle flowpath 26 wherein the air will mix with exhaust from an exhaust duct 54, and an inner flow duct 28 which will deliver air into a core inlet duct 32 for the reverse core engine 20.

[0043] A fan booster 50 is positioned downstream of the fan 22 and further drives the air into the flowpaths 26 and 28. A turbine 52(or cold turbine) receives the air from the inner flowpath 28 and extracts energy from the air as it is driven to rotate.

[0044] The air from the turbine 52 passes into the inner core flowpath 28, the duct 32, and into a low pressure compressor 30. The air is compressed and delivered into a high pressure compressor 34. The air is mixed with fuel in a combustion section 36 and ignited.

[0045] Products of the combustion pass downstream over a high pressure turbine 38, a low pressure turbine 40 and another low pressure turbine 44. Downstream of the low pressure turbine 44, exhaust gases exhaust from the duct 54, and into the middle airflow duct 26.

[0046] The turbine 40 drives a spool 42 to drive the low pressure compressor 30. The high pressure turbine 38 drives a spool 39 to in turn drive a high pressure compressor 34.

[0047] The turbine 44 is a fan drive turbine, and drives a gear reduction 46 to in turn drive a shaft 48. The shaft 48 is operatively connected to drive the fan blade 22, the fan booster 50 and the turbine 52. Notably, the turbine 52 may also extract energy from the air delivered by the fan booster 50 to rotate the shaft 48.

[0048] The provision of a turbine driven by the cold air downstream of the fan booster 50 provides greater efficiency to the overall arrangement.

[0049] FIG. 2 shows another embodiment 120. In embodiment 120, components which are generally the same as the FIG. 1 embodiment bear like numbers, however, increased by 100. Embodiment 120 differs in that the gear reduction 146 drives a shaft 147. The shaft 147 is clutched by clutch 160 to a shaft 148 which drives the fan booster 150, and the turbine 152.

[0050] The clutch may be engaged to provide greater efficiency by either capturing the rotation of the turbine 152, or allowing it to free rotate and drive the fan booster 150 on its own.

[0051] FIG. 3 shows yet another embodiment 220. A turbine 256 drives the gear reduction 260 to drive the fan rotor 222. Again, components which are similar to those in FIGS. 1 and 2 are identified by the same reference numeral, only increased by 200.

[0052] A separate turbine 258 is connected to the cold turbine 262, and the booster fan blade 250 by a spool 260. In this regard, the power delivered to the fan booster 250, and how the power generated by the turbine 262 is utilized, has some additional freedoms.

[0053] FIG. 3 also shows a second fan air turbine section 304 which is positioned downstream of the duct 232 and leading into the inlet for the compressor section 302. The turbine section 304 is operable to rotate with a shaft 307 that rotates with the low pressure turbine 256 and the low pressure compressor 302.

[0054] FIG. 4A shows another feature which can be incorporated into any one of the three above-referenced embodiments. As shown, the turbine blades 262 have a relatively short radially outer edge 270. A flow diverter, which could be a bypass door 272 of some sort is shown in an operative position to increase power flow. This position may be utilized such during takeoff of an associated aircraft on a hot day.

[0055] Notably, while the features of FIGS. 4-7 are shown associated with the FIG. 3 embodiment, they would have application into any one of the embodiments illustrated in this application.

[0056] FIG. 4B shows another operative position wherein the door 272 is pivoted outwardly to create a bypass flowpath 274 which avoids the blades in the turbine section 262. The bypass door could be opening during cruise conditions. In either case, the bypass flow 274 is still directed into the inner flow path 228, and to the inlet duct 232 (for example, shown in FIG. 3).

[0057] FIG. 5A shows a second embodiment feature wherein a pair of flow diverters or doors 272 and 276 are utilized. During a cruise condition as shown in FIG. 5A the door of 272 is pivoted outwardly as is the door 276. Now, all air is diverted away from the turbine section 262 and through the bypass path 274.

[0058] FIG. 5B shows an alternative operative position where the doors 272 and 276 are pivoted inwardly such that the great bulk of the air would now be directed across the turbine section 262. This position would be utilized during high power conditions such as a takeoff on a hot day.

[0059] FIG. 6A shows yet another embodiment 300. In embodiment 300, the turbine 302 is positioned downstream of the inlet duct 232, and upstream of the low pressure compressor 302. Door 308 operates similarly to the FIG. 4A/4B embodiment to direct all air across the turbine blades in turbine 304, and within the radial extent of the blades (that is, radially inwardly of the radially outermost extent 306).

[0060] FIG. 6A would be utilized in high power conditions such as during takeoff of an associated aircraft on a hot day.

[0061] FIG. 6B shows the door 308 pivoted radially outwardly to provide a bypass flowpath 310 which is outward of the radially outer end 306 of the blades in the turbine 304. This would be utilized at low power conditions such as cruise.

[0062] FIG. 7A shows another embodiment 350. Again, the turbine 304 is positioned downstream of the duct 232, but upstream of the low pressure compressor 302. A second door 354 is provided in addition to the door 352. In the FIG. 7A position, the bypass 356 is opened, such as may be utilized during cruise conditions. The lower door 354 ensures that the great bulk of air avoids the turbine blades in turbine section 304.

[0063] FIG. 7B shows the position of the doors 352 and 254 during high power conditions such as takeoff on a hot day. In this position, the great bulk of the air is directed radially inward of the radially outermost extent 306 of the blades in the turbine section 304.

[0064] A schematic control 800 is illustrated in the figures and would operate to control the various components disclosed across this application. The control can be incorporated into a FADEC for the entire engine. A worker of ordinary skill in the art would be able to design such a control given the teachings of this disclosure.

[0065] For purposes of this application, the terms low or high relative to pressure or speed, and in core turbine and compressor sections simply are to be taken as relative terms. That is, the high would rotate at higher pressures and typically higher speeds than would the low, although both might be at objectively high speeds and pressures. In addition, the term cold for the turbine sections downstream of the booster fan simply imply they are not part of the core engine. They may well operate at very high temperatures, even though they are referred to as cold in this application. The turbine sections which are in the core engine could be called core turbine sections for purposes of this application. The core turbine sections would typically be seeing higher temperature and pressure gases than would the cold turbine sections.

[0066] As should be understood, all of the gas turbine engines illustrated in all of these figures rotate about a central axis of rotation. The figures are generally illustrating only the upper half of that engine, and there is an axis of rotation shown generally in dashed line in each of the figures.

[0067] A worker of ordinary skill in this art would recognize that many modifications would come within the scope of this disclosure. For that reason, the following claims should be studied to determine the true scope and content of this application.