Rotor blade having a flared tip

A rotor blade includes an airfoil having a blade tip and a tip cavity formed at the blade tip. The tip cavity includes a tip cap that is recessed radially inwardly from the tip and surrounded continuously by pressure and suction side walls of the airfoil. The tip cap further includes an aperture that extends through the tip cap and provides for fluid communication between an internal cavity defined within the airfoil and the tip cavity. An exhaust port provides for fluid communication out the tip cavity through one of the pressure side wall, the suction side wall or the trailing edge. A portion of at least one of the suction side wall and the pressure side wall that defines the tip cavity extends obliquely outwardly from the tip cavity with respect to a radial direction.

FIELD OF THE INVENTION

The present invention generally relates to a rotor blade for a turbine. More particularly, this invention involves a rotor blade having a flared tip configured for cooling a trailing edge portion of the rotor blade.

BACKGROUND OF THE INVENTION

In an air-ingesting turbo machine (e.g., a gas turbine), air is pressurized by a compressor and then mixed with fuel and ignited within an annular array of combustors to generate combustion gases. The hot gases are routed through a liner and into a hot gas path defined within a turbine section of the turbo machine. Kinetic energy is extracted from the combustion gases via one or more rows of turbine rotor blades that are connected to a rotor shaft. The extracted kinetic energy causes the rotor shaft to rotate, thus producing work.

The turbine rotor blades or blades generally operate in extremely high temperature environments. In order to achieve adequate service life, the blades typically include various internal cooling passages or cavities. During operation of the gas turbine, a cooling medium such as compressed air is routed through the internal cooling passages. A portion of the cooling medium may be routed out of the internal cooling passages through various cooling holes defined along the blade surface, thereby reducing high surface temperatures. An area that is generally challenging to cool effectively via the cooling medium is a blade tip portion of the turbine rotor blade, more particularly a trailing edge region of the blade tip.

The blade tip is generally defined at a radial extremity of the turbine rotor blade and is positioned radially inward from a turbine shroud that circumscribes the row of blades. The turbine shroud defines a radially outward boundary of the hot gas path. The proximity of the blade tip to the turbine shroud makes the blade tip difficult to cool. The contiguity of the shroud and the blade tip minimizes the leakage of hot operating fluid past the tip which correspondingly improves turbine efficiency.

In particular blade designs, a tip cavity formed by a recessed tip cap and a pressure side wall and a suction side wall provides a means for achieving minimal tip clearance while at the same time assuring adequate blade tip cooling. The pressure side wall and the suction side wall extend radially outwardly from the tip cap. At least a portion of at least one of the suction side wall and the pressure side wall is flared or inclined outward with respect to a radial centerline of the blade. The pressure side wall intersects with the suction side wall at a leading edge portion of the blade. However, the pressure side wall does not intersect with the suction side wall at the trailing edge, thus forming an opening therebetween. This configuration is generally due to the lack of an appropriate wall thickness of the blade along the trialing edge.

In operation, the cooling medium is exhausted from the internal passages through holes in the tip cap into the tip cavity, thus effectively cooling the pressure and suction side walls as well as the tip cap surface. However, it may also be desirable to effectively cool the leading and trailing edges of the airfoil. Therefore there is a need for a blade tip design having improved blade tip trailing edge cooling.

BRIEF DESCRIPTION OF THE INVENTION

One embodiment of the present invention is a rotor blade. The rotor blade includes an airfoil having a an airfoil having a leading edge and a trailing edge, a pressure side wall and a suction side wall connected at the leading and trailing edges, a blade tip having a radially outer surface that extends along the pressure and suction side walls between the leading and trailing edges, and an internal cavity for receiving a cooling medium. The airfoil further comprises a tip cavity that is formed at the blade tip. The tip cavity includes a tip cap that is recessed radially inwardly from the radially outer surface of the blade tip and that is surrounded continuously by the pressure and suction side walls. The tip cap further includes an aperture that extends through an inner surface and a radially opposed top surface of the tip cap. The aperture provides for fluid communication between the internal cavity and the tip cavity. An exhaust port provides for fluid communication from the tip cavity through the trailing edge, the pressure side wall or the suction side wall. A portion of at least one of the suction side wall or the pressure side wall that defines the tip cavity extends obliquely outwardly from the tip cavity with respect to a radial direction.

Another embodiment of the present invention is a gas turbine. The gas turbine includes, in serial flow order, a compressor section, a combustion section and a turbine section. The turbine section includes a rotor shaft and a plurality of rotor blades that are coupled to the rotor blade. Each rotor blade includes an airfoil having a leading edge and a trailing edge, a pressure side wall and a suction side wall connected at the leading and trailing edges, a blade tip having a radially outer surface that extends along the pressure and suction side walls between the leading and trailing edges, and an internal cavity for receiving a cooling medium. The airfoil further includes a tip cavity that is formed at the blade tip. The tip cavity includes a tip cap that is recessed radially inwardly from the radially outer surface and that is surrounded continuously by the pressure and suction side walls. The tip cap further includes an aperture that extends through an inner surface and a radially opposed top surface of the tip cap and that provides for fluid communication between the internal cavity and the tip cavity. An exhaust port provides for fluid communication from the tip cavity through the trailing edge, the pressure side wall or the suction side wall. A portion of at least one of the suction side wall or the pressure side wall that defines the tip cavity extends obliquely outwardly from the tip cavity with respect to a radial direction.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention. As used herein, the terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. The terms “upstream” and “downstream” refer to the relative direction with respect to fluid flow in a fluid pathway. For example, “upstream” refers to the direction from which the fluid flows, and “downstream” refers to the direction to which the fluid flows. The term “radially” refers to the relative direction that is substantially perpendicular to an axial centerline of a particular component and/or substantially perpendicular to an axial centerline of the turbomachine, and the term “axially” refers to the relative direction that is substantially parallel and/or coaxially aligned to an axial centerline of a particular component and/or to an axial centerline of the turbomachine.

Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. Although an industrial or land based gas turbine is shown and described herein, the present invention as shown and described herein is not limited to a land based and/or industrial gas turbine unless otherwise specified in the claims. For example, the invention as described herein may be used in any type of turbine including but not limited to a steam turbine or marine gas turbine.

Referring now to the drawings,FIG. 1illustrates a schematic diagram of one embodiment of a gas turbine10. The gas turbine10generally includes an inlet section12, a compressor section14disposed downstream of the inlet section12, a plurality of combustors (not shown) within a combustor section16disposed downstream of the compressor section14, a turbine section18disposed downstream of the combustor section16and an exhaust section20disposed downstream of the turbine section18. Additionally, the gas turbine10may include one or more shafts22coupled between the compressor section14and the turbine section18.

The turbine section18may generally include a rotor shaft24having a plurality of rotor disks26(one of which is shown) and a plurality of rotor blades28extending radially outwardly from and being interconnected to the rotor disk26. Each rotor disk26may, in turn, be coupled to a portion of the rotor shaft24that extends through the turbine section18. The turbine section18further includes an outer casing30that circumferentially surrounds the rotor shaft24and the rotor blades28, thereby at least partially defining a hot gas path32through the turbine section18.

During operation, a working fluid such as air flows through the inlet section12and into the compressor section14where the air is progressively compressed, thus providing pressurized air to the combustors of the combustion section16. The pressurized air is mixed with fuel and burned within each combustor to produce combustion gases34. The combustion gases34flow through the hot gas path32from the combustor section16into the turbine section18, wherein energy (kinetic and/or thermal) is transferred from the combustion gases34to the rotor blades28, thus causing the rotor shaft24to rotate. The mechanical rotational energy may then be used to power the compressor section14and/or to generate electricity. The combustion gases34exiting the turbine section18may then be exhausted from the gas turbine10via the exhaust section20.

FIG. 2is a perspective view of an exemplary rotor blade100as may incorporate one or more embodiments of the present invention and as may be incorporated into the turbine section18of the gas turbine10in place of rotor blade28as shown inFIG. 1. As shown inFIG. 2, the rotor blade100generally includes a mounting or shank portion102having a mounting body104and an airfoil106that extends outwardly in a radial direction108from a platform portion110of the rotor blade100. The platform110generally serves as a radially inward boundary for the combustion gases34flowing through the hot gas path32of the turbine section18(FIG. 1). As shown inFIG. 2, the mounting body104of the mounting or shank portion102may extend radially inwardly from the platform110and may include a root structure, such as a dovetail, configured to interconnect or secure the rotor blade100to the rotor disk26(FIG. 1).

The airfoil106includes an outer surface112that surrounds the airfoil106. The outer surface112is at least partially defined by a pressure side wall114and an opposing suction side wall116. The pressure side wall114and the suction side wall116extend substantially radially outwardly from the platform110in span from a root118of the airfoil106to a blade tip or tip120of the airfoil106. The root118of the airfoil106may be defined at an intersection between the airfoil106and the platform110. The blade tip120is disposed radially opposite the root118. As such, a radially outer surface122of the blade the tip120may generally define the radially outermost portion of the rotor blade100.

The pressure side wall114and the suction side wall116are joined together or interconnected at a leading edge124of the airfoil106which is oriented into the flow of combustion gases34. The pressure side wall114and the suction side wall116are also joined together or interconnected at a trailing edge126of the airfoil106which is spaced downstream from the leading edge124. The pressure side wall114and the suction side wall116are continuous about the trailing edge126. The pressure side wall114is generally concave and the suction side wall116is generally convex. The chord of the airfoil106is the length of a straight line connecting the leading edge114and the trailing edge116and the direction from the leading edge114to the trailing edge116is typically described as the chordwise direction. A chordwise line bisecting the pressure side wall114and the suction side wall116is typically referred to as the mean-line or camber-line128of the airfoil106.

Internal cooling of turbine rotor blades is well known and typically utilizes a cooling medium, as indicated by solid and dashed arrows130, such as a relatively cool compressed air bled from the compressor section14(FIG. 1) of the gas turbine engine10which is suitably channeled through the mounting or shank portion102of the rotor blade100and into an internal cavity or passage132that is at least partially defined within the airfoil106between the pressure side wall114and the suction side wall116.

The internal cavity132may take any conventional form and is typically in the form of a serpentine passage. The cooling medium130enters the internal cavity132from the mounting or shank portion102and passes through the internal cavity132for suitably cooling the airfoil106from the heating effect of the combustion gases34flowing over the outer surface112thereof. Film cooling holes (not shown) may be disposed on the pressure side wall114and/or the suction side wall116for conventionally film cooling the outer surface112of the airfoil106.

In various embodiments, a tip cavity or plenum134is formed at or within the blade tip120. The tip cavity134is at least partially formed by a tip cap136. As shown inFIG. 2, the tip cap136is recessed radially inwardly from the blade tip120and/or the top surface122of the blade tip120and forms a floor portion of the tip cavity134. The tip cap136is surrounded continuously by the pressure side wall114and the suction side wall116.

The tip cap136is connected to and/or forms a seal against an inner surface or side138of the pressure side wall114and an inner surface or side140of the suction side wall116along a periphery142of the tip cap136between the leading and trailing edges124,126of the airfoil106. The tip cap136further includes a plurality of holes or apertures144that extend through an inner surface or side146and a top surface or side148of the tip cap136and that provide for fluid communication between the internal cavity132and the tip cavity134.

FIG. 3provides a perspective view of a portion the airfoil106which includes the blade tip120according to at least one embodiment of the present invention.FIG. 4provides a perspective view of a portion the airfoil106which includes the blade tip120according to at least one embodiment of the present invention.FIG. 5provides a cross sectioned side view of a portion of the airfoil106taken along section lines A-A as shown inFIG. 4, according to at least one embodiment.

In particular embodiments, as shown inFIG. 3, a portion of at least one of the suction side wall116or the pressure side wall114that defines the tip cavity134extends obliquely outwardly from the tip cavity134with respect to radial direction108and/or with respect to the outer surface112of the airfoil106. Radial direction108may be substantially perpendicular to the top surface148of the tip cap136.

In various embodiments, as shown inFIG. 3, a portion of the suction side wall116that defines the tip cavity134and a portion of the pressure side wall114that defines the tip cavity134extends obliquely outwardly from the tip cavity134with respect to radial direction108and/or with respect to the outer surface112of the airfoil106. In various embodiments, a portion of the suction side wall116that defines the tip cavity134extends obliquely outwardly from the tip cavity134with respect to radial direction108and/or with respect to the outer surface112of the airfoil106. In various embodiments, a portion of the pressure side wall114that defines the tip cavity134extends obliquely outwardly from the tip cavity134with respect to radial direction108and/or with respect to the outer surface112of the airfoil106.

A portion of the inner surface or side140of the suction side wall116that defines the tip cavity134may extend obliquely outwardly from the tip cavity134with respect to radial direction108, thus increasing an overall volume of the tip cavity134. In addition or in the alternative, as shown inFIG. 3, a portion of the inner surface or side138of the pressure side wall114that defines the tip cavity134may extend obliquely outwardly from the tip cavity134with respect to radial direction108, thus increasing an overall volume of the tip cavity134.

In various embodiments, as shown inFIG. 3, at least one exhaust port provides for fluid communication of a cooling medium from the tip cavity through the trailing edge126, the pressure side wall114or the suction side wall116. The airfoil106may include any number of exhaust ports and is not limited to a particular number of exhaust ports or to particular locations of exhaust ports shown in the figures provided and described herein unless specifically provided in the claims.

In various embodiments, as shown inFIG. 3, the airfoil106includes an exhaust port150that extends through the trailing edge126. The exhaust port150may be generally defined and/or positioned between the top surface146of the tip cap136and the radially outer surface122of the blade tip120. In one embodiment, the exhaust port150extends through the trailing edge126along or aligned with the camber line128(FIG. 2) of the airfoil106. The exhaust port150may be circular or oblong or have any suitable cross sectional shape.

As shown inFIG. 3, at least one aperture152of the plurality of apertures144may extend through the inner surface146and the top surface148of the tip cap136proximate and/or adjacent to the exhaust port150. The aperture152provides for fluid communication between the internal cavity132and the tip cavity134in an area that is upstream from the exhaust port150.

In various embodiments, as shown inFIG. 4, the airfoil106may include one or more exhaust ports154that extend through the suction side wall116between the top surface148of the tip cap136and the radially outer surface122of the blade tip120proximate and/or adjacent to the trailing edge126. In addition or in the alternative, the airfoil106may include one or more exhaust ports156that extend through the pressure side wall114between the top surface122of the tip cap136and the radially outer surface122of the blade tip120proximate and/or adjacent to the trailing edge126.

In particular embodiments, as shown inFIGS. 4 and 5, aperture152is angled towards the trailing edge126of the airfoil106. In particular embodiments, one or more holes158are defined along the trailing edge126of the airfoil106radially below the tip cap136and/or radially below exhaust port150. The one or more holes158may be in fluid communication with the internal cavity132. In various embodiments, as shown inFIG. 5, exhaust port150may be tapered or shaped such that an inlet160of exhaust port150is smaller or has a smaller cross sectional area than an outlet162of exhaust port150.

FIG. 6provides a perspective view of a portion the airfoil106which includes the blade tip120according to at least one embodiment of the present invention.FIG. 7provides a cross sectioned side view of a portion of the airfoil106taken along section lines B-B as shown inFIG. 6, according to at least one embodiment.FIG. 8provides a cross sectioned view of a portion of the airfoil taken along lines C-C shown inFIG. 6according to at least one embodiment of the present invention.

In particular embodiments, as shown inFIGS. 6-8collectively, a surface indentation such as a trench, slot or groove164is defined within the top surface148of the tip cap136. The trench164may be defined proximate to exhaust port150. In particular embodiments, the trench164extends from the trailing edge126towards the leading edge124of the airfoil106. In particular embodiments, the trench164extends along the camber line128(FIG. 2) of the airfoil106. In particular embodiments, the trench164may at least partially define exhaust port150.

FIG. 9provides a perspective view of a portion the airfoil106which includes the blade tip120according to at least one embodiment of the present invention.FIG. 10provides a cross sectioned side view of a portion of the airfoil106taken along section lines D-D as shown inFIG. 9, according to at least one embodiment. In particular embodiments, as shown inFIGS. 9 and 10collectively, the airfoil106may include exhaust ports154positioned along the suction side wall116proximate to the trailing edge126that provide for fluid communication out of the tip cavity134. In addition or in the alternative, the airfoil106may include exhaust ports156positioned along the pressure side wall114proximate to the trailing edge126that provide for fluid communication out of the tip cavity134. In particular embodiments, as shown inFIGS. 9 and 10, the airfoil106may include hole(s)158defined along the trialing edge126.

FIG. 11provides a perspective view of a portion the airfoil106which includes the blade tip120according to at least one embodiment of the present invention.FIG. 12provides a cross sectioned side view of a portion of the airfoil106taken along section lines E-E as shown inFIG. 11, according to at least one embodiment. In particular embodiments, as shown inFIGS. 11 and 12collectively, the airfoil106may include an exhaust port166that extends through the radially outer surface122of the blade tip120at the trailing edge126of the airfoil106. As shown inFIG. 12, a portion of exhaust port166may extend chordwise before turning radially upwardly and penetrating the radially outer surface122. In this manner, exhaust port166may direct a portion of the cooling medium radially outwards from the blade tip120towards a shroud (not shown) of the gas turbine10. As shown inFIG. 12, exhaust port166is in fluid communication with the tip cavity134.