WO2006059991A1

WO2006059991A1 - Regeneratively cooled turbine blade for a tip turbine engine and method of cooling

Info

Publication number: WO2006059991A1
Application number: PCT/US2004/040098
Authority: WO
Inventors: Gabriel L. Suciu; Craig A. Nordeen; Brian Merry
Original assignee: United Technologies Corporation
Priority date: 2004-12-01
Filing date: 2004-12-01
Publication date: 2006-06-08

Abstract

A fan-turbine rotor assembly of a tip turbine engine includes a multitude of turbine blades which each define a turbine blade passage which bleed air from a diffuser section to provide for regenerative cooling. Regenerative cooling airflow is communicated from the radial core airflow passage through the diffuser passages, through diffuser aspiration passages and into the turbine blade passages. The regenerative cooling airflow exits from the turbine blade passage and transfers received thermal energy into an annular combustor. The received thermal energy is recovered at the highest temperature in the cycle.

Description

REGENERATIVELY COOLED TURBINE BLADE FOR A TIP TURBINE ENGINE AND METHOD OF COOLING

BACKGROUND OF THE INVENTION

The present invention relates to a gas turbine engine, and more particularly to airflow within a tip turbine engine to cool various sections thereof.

An aircraft gas turbine engine of the conventional turbofan type generally includes a forward fan, a low pressure compressor, a middle core engine, and an aft low pressure turbine all located along a common longitudinal axis. A high pressure compressor and a high pressure turbine of the core engine are interconnected by a high spool shaft. The high pressure compressor is rotatably driven to compress air entering the core engine to a relatively high pressure. This high pressure air is then mixed with fuel in a combustor and ignited to form a high energy gas stream. The gas stream flows axially aft to rotatably drive the high pressure turbine which rotatably drives the high pressure compressor through the high spool shaft. The gas stream leaving the high pressure turbine is expanded through the low pressure turbine which rotatably drives the fan and low pressure compressor through a low pressure shaft.

Although highly efficient, conventional turbofan engines operate in an axial flow relationship. The axial flow relationship results in a relatively complicated elongated engine structure of considerable longitudinal length relative to the engine diameter. This elongated shape may complicate or prevent packaging of the engine into particular applications.

A recent development in gas turbine engines is the tip turbine engine. Tip turbine engines locate an axial compressor forward of a bypass fan which includes hollow fan blades that receive airflow from the axial compressor therethrough such that the hollow fan blades operate as a centrifugal compressor. Compressed core airflow from the hollow fan blades is mixed with fuel in an annular combustor and ignited to form a high energy gas stream which drives the turbine integrated onto the radial outer tips of the hollow bypass fan blades for rotation therewith as generally disclosed in U.S. Patent Application Publication Nos.: 20030192303; 20030192304; and 20040025490. The tip turbine engine provides a thrust to weight ratio equivalent to conventional turbofan engines of the same class within a package of significantly shorter length.

The tip turbine engine utilizes a fan-turbine rotor assembly which integrates a turbine onto the outer periphery of the bypass fan. Integrating the turbine onto the tips of the hollow bypass fan blades provides an engine design challenge.

Conventional turbines operate in a high temperature environment and typically receive cooling airflow from cooler sections of the engine. Once the cooling airflow is communicated to the turbine to receive thermal energy therefrom, the elevated temperature cooling airflow is dumped overboard. This may be somewhat inefficient from a thermal standpoint which may reduce the engine operating efficiency. Tip turbine engines provide novel opportunities for cooling flow redirection.

Accordingly, it is desirable to provide a turbine for a fan-turbine rotor assembly of a tip turbine engine which provides regenerative cooling airflow while minimizing the effect on engine operating efficiency.

SUMMARY OF THE INVENTION

The fan-turbine rotor assembly according to the present invention includes a multitude of the hollow fan blades. Each fan blade includes an inducer section, a hollow fan blade section and a diffuser section. The diffuser sections form a diffuser surface about the outer periphery of the fan blade sections to provide structural support to the outer tips of the fan blade sections and to turn and diffuse the airflow from the radial core airflow passage toward an axial airflow direction. The turbine is mounted to the diffuser surface as one or more turbine ring rotors which include a multitude of turbine blade clusters.

The diffuser includes a multitude of diffuser passages which turn and diffuse the airflow from a radial core airflow passage toward an axial airflow direction. A multitude of diffuser aspiration passages are in communication with the diffuser passages and through the diffuser surface. Diffuser aspiration passages communicate with the diffuser passages at a location which reduces separation of the airflow as the airflow is turned from the radial core airflow passage toward an axial airflow direction through airflow aspiration at the potentially turbulent locations.

Each of the multitude of turbine blades defines a turbine blade passage. The turbine blade passages bleed air from the diffuser to provide for regenerative cooling. Regenerative cooling airflow is communicated from the radial core airflow passage through the diffuser passages, through the diffuser aspiration passages and into the turbine blade passages. The regenerative cooling airflow receives thermal energy from the turbine blades and increases the centrifugal compression within the turbine while transferring the increased temperature cooling airflow into the annular combustor to increase the efficiency thereof through regeneration.

The received thermal energy is recovered at the highest temperature in the cycle. The engine is thereby benefited twice. Once by the cooling that allows elevated temperatures on the turbine blades and a second time by the regeneration of the thermal energy which would otherwise be lost downstream as per conventional application.

The present invention therefore provides a turbine for a fan-turbine rotor assembly of a tip turbine engine which provides regenerative cooling airflow while minimizing the effect on engine operating efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows: Figure l is a partial sectional perspective view of a tip turbine engine;

Figure 2 is a longitudinal sectional view of a tip turbine engine along an engine centerline;

Figure 3 is an exploded view of a fan-turbine rotor assembly;

Figure 4 is an expanded partial perspective view of a fan-turbine rotor assembly;

Figure 5 is an expanded partial perspective view of a fan-turbine rotor assembly illustrating a separated single fan blade segment; Figure 6A is an expanded exploded view of a segmented turbine rotor ring;

Figure 6B is an expanded exploded view of a complete turbine rotor ring;

Figure 7A is an expanded perspective view of a segment of a first stage turbine rotor ring; Figure 7B is an expanded perspective view of a segment of a second stage turbine rotor ring;

Figure 8 is a side planar view of a turbine for a tip turbine engine;

Figure 9 is an expanded perspective view of a first stage and a second stage turbine rotor ring mounted to a diffuser ring of a fan-turbine rotor assembly; Figure 1OA is an expanded perspective view of a first stage and a second stage turbine rotor ring in a first mounting position relative to a diffuser ring of a fan- turbine rotor assembly;

Figure 1OB is an expanded perspective view of a first stage and a second stage turbine rotor ring illustrating turbine torque load surface on each turbine rotor ring;

Figure 1OC is a side sectional view of a first stage and a second stage turbine rotor ring illustrating the interaction of the turbine torque load surfaces and adjacent stops;

Figure 1OD is an expanded perspective view of a first stage and a second stage turbine rotor ring illustrating the anti-back out tabs and anti-back out slots to lock the first stage and a second stage turbine rotor ring;

Figure HA is a partial phantom view of a single fan blade illustrating the diffuser section and aspirated flow therefrom;

Figure HB is a expanded view of a diffuser section illustrating an outer diameter aspirated flow passage;

Figure I IC is a expanded view of a diffuser section illustrating an inner diameter aspirated flow passage;

Figure HD is a sectional view through a diffuser section illustrating the inner and outer diameter aspirated flow passages; Figure 12A is an expanded perspective view of a segment of a first stage turbine rotor ring illustrating an airflow passage through a turbine blade; Figure 12B is an expanded perspective view of a segment of a second stage turbine rotor ring illustrating an airflow passage through a turbine blade;

Figure 13A is a side sectional view of a turbine for a tip turbine engine illustrating regenerative airflow paths through the turbine; and Figure 13B is a side sectional view of a turbine for a tip turbine engine illustrating another regenerative airflow path through the turbine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Figure 1 illustrates a general perspective partial sectional view of one embodiment of a tip turbine engine type gas turbine engine 10. The engine 10 includes an outer nacelle 12, a rotationally fixed static outer support structure 14 and a rotationally fixed static inner support structure 16. The engine 10 can also include a multitude of fan inlet guide vanes 18 mounted between the static outer support structure 14 and the static inner support structure 16. Each inlet guide vane 18 could include a separate variable trailing edge portion 18A which may be selectively articulated relative to the fixed inlet guide vane 18.

The engine 10 can have a nose cone 20 located along the engine centerline A to direct airflow near the engine centerline A radially outward and into the engine 10.

The airflow enters the engine 10 through an axial compressor 22 ("core" or "primary" airflow) or through a fan-turbine rotor assembly 24 ("bypass" or "secondary" airflow"). The axial compressor 22 is mounted about the engine centerline A behind the nose cone 20.

The fan-turbine rotor assembly 24 is mounted for rotation about the engine centerline A aft of the axial compressor 22. The fan-turbine rotor assembly 24 includes a multitude of hollow fan blades 28 to provide internal, centrifugal compression of the compressed core airflow exiting the axial compressor 22 for distribution to an annular combustor 30 located within the rotationally fixed static outer support structure 14.

A turbine 32 includes a multitude of tip turbine blades 34 (two stages shown) which rotatably drive the hollow fan blades 28 relative a multitude of tip turbine stators 36 which extend radially inwardly from the static outer support structure 14.

Although two turbine stages are disclosed in the illustrated embodiment, it should be understood that any number of stages may be utilized by the instant invention. The annular combustor 30 is axially forward of the turbine 32 and discharges the combustion gases created by combusting a mixture of fuel and core airlow to the turbine 32. Referring to Figure 2, the rotationally fixed static inner support structure 16 includes a splitter 40, a static inner support housing 42 and an static outer support housing 44 located coaxial to said engine centerline A. An aft housing 45 can be attached to the static inner support housing 42 and the static outer support housing 44 through fasteners f such as bolts or the like. The static inner support housing 42, the static outer support housing 44, and the aft housing 45 are located about the engine centerline A to provide the non-rotating support structure for the engine 10.

The axial compressor 22 includes the axial compressor rotor 46 from which a plurality of compressor blades 52 extend radially outwardly and a compressor case 50. A plurality of compressor vanes 54 extend radially inwardly from the compressor case 50 between stages of the compressor blades 52. The compressor blades 52 and compressor vanes 54 are arranged circumferentially about the axial compressor rotor 46 in stages (three stages of compressor blades 52 and compressor vanes 54 are shown in this example). The axial compressor rotor 46 is mounted for rotation upon the static inner support housing 42 through a forward bearing assembly 68 and an aft bearing assembly 62.

The fan-turbine rotor assembly 24 includes a fan hub 64 that supports a multitude of the hollow fan blades 28. Each fan blade 28 includes an inducer section 66, a hollow fan blade section 72 and a diffuser section 74. The inducer section 66 receives core airflow from the axial compressor 22 generally parallel to the engine centerline A and turns the core airflow from an axial direction toward a radial direction. The core airflow is radially communicated through a core airflow passage 80 within the fan blade section 72 where the airflow is centrifugally compressed. From the core airflow passage 80, the core airflow is again turned, then diffused by the diffuser section 74. The core airflow is now directed in an axial direction toward the annular combustor 30. Preferably the core airflow is diffused axially forward in the engine 10, however, the airflow may alternatively be communicated in another direction. A gearbox assembly 90 aft of the fan-turbine rotor assembly 24 can provide a speed increase between the fan-turbine rotor assembly 24 and the axial compressor 22. Alternatively, the gearbox assembly 90 could provide a speed decrease between the fan-turbine rotor assembly 24 and the axial compressor rotor 46. The gearbox assembly 90 is mounted for rotation between the static inner support housing 42 and the static outer support housing 44. The gearbox assembly 90 includes a sun gear shaft 92 which rotates with the axial compressor 22 and a planet carrier 94 which rotates with the fan-turbine rotor assembly 24 to provide a speed differential therebetween. The gearbox assembly 90 is preferably an epicyclic gearbox that provides co-rotating or counter-rotating rotational engagement between the fan- turbine rotor assembly 24 and an axial compressor rotor 46. The gearbox assembly 90 is mounted for rotation between the sun gear shaft 92 and the static outer support housing 44 through a forward bearing 96 and a rear bearing 98. The forward bearing 96 and the rear bearing 98 are both tapered roller bearings and both handle radial loads. The forward bearing 96 handles the aft axial loads while the rear bearing 98 handles the forward axial loads. The sun gear shaft 92 is rotationally engaged with the axial compressor rotor 46 at a splined interconnection 100 or the like.

In operation, core airflow enters the axial compressor 22, where it is compressed by the three stages of the compressor blades 52 and compressor vanes 54. The compressed air from the axial compressor 22 enters the inducer section 66 in a direction generally parallel to the engine centerline A and is turned by the inducer section 66 radially outwardly through the core airflow passage 80 of the hollow fan blades 28. The core airflow is further compressed centrifugally in the hollow fan blades 28 by rotation of the hollow fan blades 28. From the core airflow passage 80, the core airflow is turned and diffused axially forward in the engine 10 into the annular combustor 30. The compressed core airflow from the hollow fan blades 28 is mixed with fuel in the annular combustor 30 and ignited to form a high-energy gas stream. The high-energy gas stream is expanded over the multitude of tip turbine blades 34 mounted about the outer periphery of the fan blades 28 to drive the fan- turbine rotor assembly 24. The fan-turbine rotor assembly 24 in turn drives the axial compressor 22 through the gearbox assembly 90. Concurrent therewith, the fan- turbine rotor assembly 24 compresses then discharges the bypass air axially aft to merge with the core airflow from the turbine 32 in an exhaust case 106. A multitude of exit guide vanes 108 are located between the static outer support housing 44 and the nonrotatable static outer support structure 14 to guide the combined airflow out of the engine 10 to provide forward thrust. An exhaust mixer 110 mixes the core airflow from the turbine blades 34 with the bypass airflow through the fan blades 28.

Referring to Figure 3, the fan-turbine rotor assembly 24 is illustrated in an exploded view. The fan hub 64 is the primary structural support of the fan-turbine rotor assembly 24 (also illustrated as a partial sectional view in Figure 4). The fan hub 64 supports an inducer 112, the multitude of fan blades 28, a diffuser 114, and at least one stage of the turbine 32.

Referring to Figure 5, the diffuser 114 defines a diffuser surface 116 formed by the multitude of diffuser sections 74. The diffuser surface 116 is formed about the radial outer periphery of the fan blade sections 72 to provide structural support to the outer tips of the fan blade sections 72 and to turn and diffuse the airflow from the radial core airflow passage 80 toward an axial airflow direction. The turbine 32 is mounted to the diffuser surface 116 as one or more turbine ring rotors 118a, 118b (Figure 6B) which could be assembled from a multitude of turbine blade clusters 119a, 119b (Figure 6A).

Preferably, each fan blade section 72 includes an attached diffuser section 74 such that the diffuser surface 116 is formed when the fan-turbine rotor 24 is assembled. It should be understood, however, that the fan-turbine rotor assembly 24 may be formed in various ways including casting multitude sections as integral components, individually manufacturing and assembling individually manufactured components, and/or other combinations thereof. Referring to Figure 6, a multitude of the turbine blade clusters 119a, 119b respectively can form the turbine ring rotor 118a, 118b defined about the engine centerline A. Alternative methods of manufacturing the rotors 118a, 118b are possible, including casting each rotor 118a, 118b in one piece. As discussed herein, turbine rotor ring 118a is a first stage of the turbine 32, and turbine ring 118b is a second stage of the turbine 32, however, other turbine stages will likewise benefit from the present invention. Furthermore, gas turbine engines other than tip turbine engines will also benefit from the present invention. Referring to Figures 7A and 7B, each turbine blade cluster 119a, 119b includes an arcuate tip shroud 120a, 120b, at a radially outer location, an arcuate base 122a, 122b and a multitude of turbine blades 34a, 34b mounted between the arcuate tip shroud 120a, 120b and the arcuate base 122a, 122b, respectively. The arcuate tip shroud 120a, 120b and the arcuate base 122a, 122b define generally flat planar rings which extend axially about the engine centerline A. The arcuate tip shroud 120a, 120b and the arcuate base 122a, 122b provide support and rigidity to the multitude of turbine blades 34a, 34b.

The arcuate tip shroud 120a, 120b each include a tip seal 126a, 126b extending therefrom. The tip seal 126a, 126b preferably extend perpendicular to the arcuate tip shroud 120a, 120b to provide a knife edge seal between the turbine ring rotor 118a, 118b and the nonrotatable static outer support structure 14 (also illustrated in Figure 8) during rotation of the turbine ring rotors 118a, 118b. It should be understood that seal arrangements other than knife seals may alternatively or additionally be utilized.

The arcuate base 122a, 122b includes attachment lugs 128a, 128b. The attachment lugs 128a, 128b are preferably segmented to provide installation by axial mounting and radial engagement of the turbine ring rotor 118a, 118b to the diffuser surface 116 as will be further described. The attachment lugs 128a, 128b preferably engage a segmented attachment slot 130a, 130b formed in the diffuser surface 116 in a dovetail-type, bulb-type or fir tree-type engagement (Figure 8). The segmented attachment slots 130a, 130b preferably include a continuous forward slot surface 134a, 134b and a segmented aft slot surface 136a, 136b (Figure 9).

The arcuate base 122a preferably provides an extended axial stepped ledge 123a which engages a seal surface 125b which extends from the arcuate base 122b. That is, arcuate bases 122a, 122b provide cooperating surfaces to seal an outer surface of the diffuser surface 116 (Figure 9).

Referring to Figure 1OA, assembly of the turbine 32 to the diffuser surface 116 will be describe with reference to the turbine ring rotors 118a, 118b which include a multitude of separate turbine blade clusters 119a, 119b (Figure 6A). Assembly of the blade clusters 119a, 119b to the diffuser surface 116, begins with the first stage turbine blade cluster 119a which are first axially mounted from the rear of the diffuser surface 116. The forward attachment lug engagement surface 129a is engaged with the continuous forward slot engagement surface 134a by passing the attachment lugs 128a through the segmented aft slot surface 136a. That is, the attachment lugs 128a are aligned to slide through the lugs of the segmented aft slot surface 136a. All first stage clusters 119a are then installed in this fashion. Next, the second stage blade clusters 119b are axially mounted from the rear of the diffuser surface 116. The forward attachment lug engagement surface 129a is engaged with the continuous forward slot engagement surface 134b by passing the attachment lugs 128b through the segmented aft slot surface 136b. That is, the attachment lugs 128b are aligned to slide between the lugs of the segmented aft slot surface 136b.

The extended axial stepped ledge 123a of the arcuate base 122a receives the seal surface 125b of the arcuate base 122b. The second stage turbine blade cluster 119b rotationally locks with the first stage turbine blade cluster 119a through engagement between anti-backout tabs 140a and anti-backout slots 140b (also illustrated in Figure 10D). The remaining second stage airfoil clusters 119b are installed in the same manner.

A multitude of radial stops 138a, 138b are located upon the diffuser surface 116 to correspond with each of the turbine blade clusters 119a, 119b. Once all of the pairs of clusters 119a, 119b are installed the turbine ring rotors 118a, 118b are completed. The turbine ring rotors 118a, 118b are then rotated as a unit within the segmented attachment slot 130a, 130b so that a torque load surface 139a, 139b (Figures lOB-lOC) on each turbine cluster 119a, 119b contacts a radial stop 138a, 138b to radially locate the attachment lugs 128a, 128b adjacent the lugs of the segmented aft slot surface 136a, 136b of the segmented attachment slots 130a, 130b. The completed turbine ring rotors 118a, 118b are rotated together toward the radial stops 138a, 138b in a direction which will maintain the turbine ring rotors 118a, 118b against the radial stops 138a, 138b during operation. It should be understood that a multitude of torque load surface 139a, 139b and radial stop 138a, 138b may be located about the periphery of the diffuser surface 116 to restrict each turbine blade cluster 119a, 119b. It should be further understood that other locking arrangements may also be utilized. Once the turbine ring rotors 118a, 118b are rotated, a second stage turbine ring anti-backout retainer tab 141b which extends from each of the second stage blade clusters 119b is aligned with an associated anti-backout retainer tab 141 which extends from the diffuser surface 116. A multitude of anti-backout retainer tabs 141 are located about the diffuser surface 116 to correspond with each of the turbine blade clusters 119b. The turbine ring anti-backout retainer tabs 141b and the anti-backout retainer tabs 141 are locked together through a retainer R such as screws, peening, locking wires, pins, keys, and/or plates as generally known. The turbine ring rotors 118a, 118b are thereby locked radially together and mounted to the fan-turbine rotor assembly 24 (Figure 10C).

Referring to Figure HA, the diffuser 114 defines a multitude of diffuser passages 144 (also illustrated in Figures 1 IB-I ID) which turn and diffuse the airflow from the radial core airflow passage 80 toward an axial airflow direction. Each core airflow passage 80 communicates with one of the multiple of diffuse passages 144 to direct the core airflow from the radial direction to an axial airflow direction, here illustrated as toward the front of the engine 10. A multitude of diffuser aspiration ports 146a, 146b (Figures 1 IB-11C) provide communication from within the diffuser 114. The diffuser passage 144 aspirates a diffuser annulus 117 (Figure HD) that is formed between the diffuser surface 116 and turbine clusters 119a, 119b. That is, the diffuser annulus 117 is sealed by the turbine clusters 119a, 119b when mounted to the diffuser surface 116.

Inside the diffuser annulus 117, the airflow from each core airflow passage 80 from each blade section 72 commingle. The diffuser annulus 117 permits the airflow within the diffuser passages 144 to equalize the potentially unbalanced core airflow from each core airflow passage 80 from each blade section 72. A structural diffuser wall 115 may be located within the diffuser annulus 117 to provide support therefore. The structural diffuser wall 115 (Figures HB, HC) may alternatively be perforated to facilitate commingling of flow within the diffuser annulus 117.

The diffuser aspiration ports 146a, 146b communicate with a first stage turbine passages 150a (Figure 12A). It should be understood that although the ports 146a, 146b are illustrated as communicating with just the first stage passage 150a, the ports 146a, 146b may alternatively or additionally communicate with a second stage turbine passage 150b (Figure 12B) as well as other turbine stages and engine components which may require a relatively cool airflow.

Referring to Figure HB, the diffuser aspiration ports 146a, 146b are preferably located though an upper and lower surface of each of the diffuser passages 144. As the diffuser aspiration ports 146a, 146b are located through an outer diameter wall of the diffuser passages 144, the aspiration airflows need not commingle and may be partitioned from each core airflow passage 80 from each blade section 72 to provide a controlled flow into each turbine clusters 119a, 119b (Figures 12A, 12B). Referring to Figure HC, the diffuser aspiration passages 146b are preferably located though an inner surface of the diffusers passages 144. The aspirated airflow generally exits from the underside of the diffuser passages 144 and flows around the edge of the diffuser passages 144 (also illustrated as a dashed line in Figure 13 A, 13B). The aspiration airflows need not commingle. The geometry is such that the exit route for the aspirated airflow is over the top of an adjacent diffuser passage 144.

Preferably, the diffuser aspiration ports 146a, 146b communicate airflow from each of the diffuser passages 144 at a location which reduces separation of the airflow as the airflow is turned from the radial core airflow passage 80 toward an axial airflow direction. That is, the diffuser aspiration ports 146a, 146b minimize turbulence and flow separation of the airflow which is passing through the diffuser passages 144 through aspiration at potentially turbulent locations. That is, the diffuser aspiration ports 146a, 146b not only provide regenerative cooling airflow, but also improve the efficiency of the diffuser 114.

Referring to Figure 13 A, the regenerative cooling airflow is communicated from the radial core airflow passage 80 through the diffuser passages 144, through the diffuser aspiration ports 146a, 146b and into the turbine blade passage 150a. For further clarity, it should be noted that what appears in the cross section of Figure 13A to be two aspiration chambers is one continuous chamber. The continuous chamber is at an angle and the cross-section of Figure 13A shows the respective parts of two chambers that are continuous with each other and all other chambers which is the diffuser annulus 117. The turbine blade passage 150a receives airflow from the diffuser aspiration ports 146a, 146b to provide for regenerative cooling airflow. Each of the multitude of turbine blades 34a defines respective turbine blade passage 150a, which extend through the arcuate tip shroud 120a and the arcuate base 122a, respectively. The regenerative cooling airflow receives thermal energy from each of the turbine blades 34a and exits through the arcuate tip shroud 120a. The regenerative cooling airflow also increases the centrifugal compression within the turbine 32 while transferring the increased temperature cooling airflow into the annular combustor 30 to increase the efficiency thereof through regeneration. The regenerative cooling airflow which exits through the arcuate tip shroud

120a communicates the received thermal energy from the turbine blades 34a through an axial static passage 155 within the static outer support structure 14. From the axial static passage 155, the airflow utilized to receive thermal energy from the turbine blades 34a is communicated through a forward turbine stator 36a and into the annular combustor 30 with the relatively cooler airflow which is directly exiting the core diffuser passage 144. It should be understood that the ports 146a, 146b, and the axial static passage 155 are peripherally located at a multitude of locations about the engine centerline A. Furthermore, it should be noted that various paths to the combustor 30 may also be utilized with the present invention. Referring to Figure 13B, the regenerative cooling airflow is alternatively communicated from the axial static passage 155, directly into the annular combustor 30 with the relatively cooler airflow from the core diffuser passage 144. That is, the regenerative cooling airflow is not first directed through the forward turbine stator 36a. The received thermal energy is recovered at the highest temperature in the cycle. The engine 10 is thereby benefited twice. Once by the cooling that allows elevated temperatures on the turbine blades 34a and a second time by the regeneration of the thermal energy in the annular combustor 30 which would otherwise lost downstream as per conventional application. It should be understood that various regenerative cooling flow paths may be utilized with the present invention.

It should be understood that relative positional terms such as "forward," "aft," "upper," "lower," "above," "below," and the like are with reference to the normal operational attitude of the vehicle and should not be considered otherwise limiting.

The foregoing description is exemplary rather than defined by the limitations within. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention.

Claims

CLAIMSWhat is claimed is:

1. A fan blade assembly comprising: a fan blade section which defines a core airflow passage therethrough; a diffuser section mounted to said fan blade section, said diffuser section defining a diffuser airflow passage, said diffuser airflow passage in communication with said core airflow passage to receive airflow from said core airflow passage; and a turbine blade which extends from said diffuser section, said turbine blade defining a turbine blade passage therethrough, said turbine blade passage in communication with said diffuser airflow passage to receive airflow from said diffuser airflow passage.

2. The tip turbine engine as recited in claim 1, wherein said turbine blade is located within a first row of a multi-stage turbine.

3. The tip turbine engine as recited in claim 1, wherein said turbine blade is located adjacent an annular combustor discharge.

4. The tip turbine engine as recited in claim 1, further comprising a seal adjacent said turbine blade to seal said turbine blade passage.

5. The tip turbine engine as recited in claim 1, further comprising an aspiration passage in communication with said diffuser airflow passages to aspirate a portion of said airflow from said diffuser airflow passage to said turbine blade passage.

6. A method of regenerative cooling of a tip turbine engine comprising the steps of:

(1) directing an airflow through a core airflow passage within a fan blade; (2) turning the airflow within a diffuser passage in communication with the core airflow passage to an axial airflow direction; and

(3) communicating the airflow from the diffuser passage through a turbine blade passage in a turbine blade;

(4) communicating the airflow from the turbine blade passage into an annular combustor; and

(5) locating the turbine blade downstream of a discharge flow from the annular combustor.

7. A method as recited in claim 6, further comprising the step of: aspirating the diffuser passage through an aspiration passage to reduce separation of the airflow through the diffuser passage, aspirated airflow within the aspiration passage communicated to the turbine blade passage.

8. A tip turbine engine comprising: a compressor for compressing a core airflow; a fan for accelerating bypass airflow, said fan having a core airflow passage that receives said core airflow from said compressor; a combustor for introducing fuel and combusting said core airflow from said fan; and a turbine for extracting energy from said core airflow exiting said combustor, said turbine having a turbine blade with a turbine passage that receives a portion of said core airflow from said fan, said portion of said core airflow exiting said turbine passage upstream of said fan.