阅读说明：本技术 包含端壁挡板的涡轮 (Turbine comprising endwall baffles ) 是由 杰弗里·唐纳德·克莱门茨 保罗·哈德利·维特 莱尔·D·戴利 艾斯彼·拉斯托姆·瓦迪亚 弗朗 于 2019-08-08 设计创作，主要内容包括：一种涡轮转子,包括：涡轮,涡轮包括：涡轮部件,其限定弧形流路表面(40,70,76)；从流路表面(40,70,76)延伸的一组轴流式涡轮翼型件(46,64),涡轮翼型件(46,64)在它们之间限定空间(60,93)；在空间(60,93)中,从流路面(40,70,76)延伸的多个挡板(146,164,264),每个挡板具有在前缘和后缘之间延伸的相对的凹侧和凸侧,其中挡板(146,164,264)具有非零曲面和恒定厚度,轴向地位于相邻涡轮翼型件(46,64)的前缘附近,并且其中挡板(146,164,264)的翼弦尺寸和挡板(146,164,264)的翼展尺寸中的至少一个小于涡轮翼型件(46,64)的相应尺寸。(A turbine rotor, comprising: a turbine, the turbine comprising: a turbine component defining an arcuate flowpath surface (40,70, 76); a set of axial flow turbine airfoils (46,64) extending from a flow path surface (40,70,76), the turbine airfoils (46,64) defining a space (60,93) therebetween; a plurality of baffles (146,164,264) extending from the flowpath face (40,70,76) in the space (60,93), each baffle having opposite concave and convex sides extending between a leading edge and a trailing edge, wherein the baffle (146,164,264) has a non-zero camber and a constant thickness, located axially near the leading edge of an adjacent turbine airfoil (46,64), and wherein at least one of a chord dimension of the baffle (146,164,264) and a span dimension of the baffle (146,164,264) is less than a corresponding dimension of the turbine airfoil (46, 64).)

1. A turbine apparatus, comprising:

a turbine, the turbine comprising:

a turbine component defining an arcuate flowpath surface (40,70, 76);

a set of axial flow turbine airfoils (46,64) extending from the flow path surface (40,70,76), the turbine airfoils (46,64) defining a space (60,93) therebetween; and

a plurality of baffles (146,164,264), the plurality of baffles (146,164,264) extending from the flowpath surface (40,70,76) in the space (60,93) between the turbine airfoils (46,64), each baffle having opposite concave and convex sides extending between a leading edge and a trailing edge, wherein the baffle (146,164,264) has a non-zero camber and a constant thickness axially adjacent the leading edge of an adjacent turbine airfoil (46,64), and wherein at least one of a chord dimension of the baffle (146,164,264) and a span dimension of the baffle (146,164,264) is less than a corresponding dimension of the turbine airfoil (46, 64).

2. The apparatus of claim 1, wherein the leading edge of each baffle (146,164,264) is positioned tangentially in a range of 25% to 75% of a distance between two adjacent turbine airfoils (46, 64).

3. The apparatus of claim 1, wherein the leading edge of each baffle (146,164,264) is positioned tangentially in a range of 40% to 60% of a distance between two adjacent turbine airfoils (46, 64).

4. The apparatus of claim 1, wherein the leading edge of each of the baffles (146,164,264) is positioned axially relative to the leading edge of an adjacent one of the turbine airfoils (46,64) in a range of-30% to 30% of the chord dimension of the adjacent one of the turbine airfoils (46, 64).

5. The apparatus of claim 1, wherein the leading edge of each of the baffles (146,164,264) is positioned axially relative to the leading edge of an adjacent one of the turbine airfoils (46,64) in a range of 0% to 10% of the chord dimension of the adjacent one of the turbine airfoils (46, 64).

6. The apparatus of claim 1, wherein the spanwise dimension of the baffle (146,164,264) is 30% or less of the spanwise dimension of the turbine airfoil (46, 64).

7. The apparatus of claim 1, wherein the spanwise dimension of the baffle (146,164,264) is 2.5% to 10% of the spanwise dimension of the turbine airfoil (46, 64).

8. The apparatus of claim 1, wherein the chord dimension of the baffle (146,164,264) adjacent the flowpath surface (40,70,76) is 30% to 70% of the chord dimension of the turbine airfoil (46,64) adjacent the flowpath surface (40,70, 76).

9. The apparatus of claim 1, wherein the chord dimension of the baffle (146,164,264) adjacent the flowpath surface (40,70,76) is about 50% of the chord dimension of the turbine airfoil (46,64) adjacent the flowpath surface (40,70, 76).

10. The apparatus of claim 1, wherein the baffle (146,164,264) has a thickness in a range of one-half a trailing edge diameter of the turbine airfoil (46,64) to three times the trailing edge diameter of the turbine airfoil (46, 64).

Technical Field

The present invention relates generally to turbines in gas turbine engines, and more particularly to rotor and stator airfoils for such turbines.

Background

The gas turbine engine includes, in serial flow communication, a compressor, a combustor, and a turbine. The turbine is mechanically connected to the compressor, and the three components define a turbomachinery core. The core is operable in a known manner to generate a flow of hot pressurized combustion gases to operate the engine and perform useful work, such as providing propulsive thrust or mechanical work. One common type of turbine is an axial flow turbine having one or more stages, each stage comprising a rotating disk with a row of axial flow airfoils, known as turbine blades. Typically, this type of turbine also includes stationary airfoils, referred to as turbine buckets, alternating with rotating airfoils. Turbine buckets are generally defined at their inner and outer ends by curved end wall structures.

During engine operation, the locus of stagnation points of incident combustion gases extends along the leading edge of each airfoil in the turbine and forms respective boundary layers along the pressure and suction sides of each airfoil and along each of the radially outer and inner endwalls that collectively define the four sides of each flow passage. In the boundary layer, the local velocity of the combustion gases changes from zero along the endwall and airfoil surfaces to an unconstrained velocity in the combustion gases at which the boundary layer terminates.

One common source of turbine pressure loss is the formation of horseshoe vortices that are generated when the traveling combustion gases split near the junction of the endwall and the leading edge of the blade. The static pressure increases along streamlines from upstream to the leading edge of the blade. Since the free-flow velocity is higher than the velocity in the boundary layer of the end wall, the static pressure increases more in the free-flow region than in the vicinity of the end wall. As a result, a pressure gradient perpendicular to the endwall is generated in the boundary layer at the junction of the blade leading edge and the endwall. This spanwise pressure gradient causes the vortex to wind up and create a pair of counter-rotating horseshoe vortices that travel downstream on opposite sides of each airfoil near the end walls.

The two vortices travel aft along opposite pressure and suction sides of each airfoil and behave differently due to different pressure and velocity distributions therealong. The interaction of the pressure side and suction side vortices occurs near the mid-chord region of the airfoil and produces an overall pressure loss and a corresponding reduction in turbine efficiency. These vortices also create turbulence and increase undesirable heating of the end walls.

As a result of the formation of the horseshoe vortices at the points of attachment of the turbine rotor blades to their integral root platforms, and at the points of attachment of the nozzle stator blades to their outer and inner bands, a corresponding loss of turbine efficiency, as well as a corresponding additional heating of the endwall components, occurs.

Accordingly, there remains a need for an improved turbine stage for reducing the horseshoe vortex effect.

Disclosure of Invention

This need is addressed by a turbine that incorporates leading edge endwall baffles in the blade and/or bucket rows to disrupt the movement of the horseshoe vortices towards adjacent airfoils.

According to one aspect of the technology described herein, a turbine apparatus comprises: a turbine, the turbine comprising: a turbine component defining an arcuate flowpath surface; a set of axial flow turbine airfoils extending from a flow path surface, the turbine airfoils defining a space therebetween; a plurality of baffles extending from the flow path surface in a space between the turbine airfoils (46,64), each baffle having opposite concave and convex sides extending between a leading edge and a trailing edge, wherein the baffle has a non-zero camber and a constant thickness, is positioned axially near the leading edge of an adjacent turbine airfoil, and wherein at least one of a chord dimension of the baffle and a span dimension of the baffle is less than a corresponding dimension of the turbine airfoil.

Drawings

The invention may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a cross-sectional schematic view of a gas turbine engine including a turbine having a baffle;

FIG. 2 is an elevation view of a portion of a turbine rotor suitable for inclusion in the engine of FIG. 1;

FIG. 3 is a top view of the rotor of FIG. 2;

FIG. 4 is a side view of the turbine blade shown in FIG. 2;

FIG. 5 is a side view of the baffle shown in FIG. 2;

FIG. 6 is an enlarged end view of the flapper shown in FIG. 3;

FIG. 7 is an elevation view of a portion of a turbine nozzle assembly suitable for inclusion in the engine of FIG. 1;

FIG. 8 is a view taken along line 7-7 in FIG. 7;

FIG. 9 is a side view of the stator vane shown in FIG. 7;

FIG. 10 is a side view of the baffle shown in FIG. 7; and

FIG. 11 is an elevation view of a portion of an alternative turbine nozzle assembly suitable for inclusion in the engine of FIG. 1.

Detailed Description

Referring to the drawings, wherein like reference numbers refer to like elements throughout the several views, FIG. 1 depicts an exemplary gas turbine engine 10. Although the illustrated example is a high bypass turbofan engine, the principles of the present invention are also applicable to other types of engines, such as low bypass turbofan engines, turbojet engines, turboprop engines, and the like. The engine 10 has a longitudinal centerline or axis 11 and a stationary core housing 12, the stationary core housing 12 being concentrically disposed about the axis 11 and coaxially along the axis 11.

It should be noted that as used herein, the terms "axial" and "longitudinal" both refer to directions parallel to the centerline axis 11, while "radial" refers to directions perpendicular to the axial direction, and "tangential" or "circumferential" refers to directions mutually perpendicular to the axial and radial directions. As used herein, the term "forward" or "front" refers to a location relatively upstream of the airflow through or around the component, and the term "rearward" or "rear" refers to a location relatively downstream of the airflow through or around the component. The direction of this flow is indicated by arrow "F" in fig. 1. 1. These directional terms are used merely for convenience of description and do not require a particular orientation of the structure described thereby.

The engine 10 has a fan 14, a booster 16, a compressor 18, a combustor 20, a high pressure turbine or "HPT" 22, and a low pressure turbine or "LPT" 24 arranged in serial flow relationship. In operation, pressurized air from the compressor 18 is mixed with fuel and ignited in the combustor 20 to generate combustion gases. The high pressure turbine 22 extracts some work from these gases, and the high pressure turbine 22 drives the compressor 18 via an outer shaft 26. The combustion gases then flow into the low pressure turbine 24, and the low pressure turbine 24 drives the fan 14 and booster 16 via the inner shaft 28. Inner shaft 28 and outer shaft 26 are rotatably mounted in bearings 30, which bearings 30 are themselves mounted in fan frame 32 and turbine aft frame 34.

2-6 illustrate a portion of an exemplary turbine rotor 36 suitable for inclusion in the HPT 22 or the LPT 24. While the concepts of the present invention will be described using the HPT 22 as an example, it should be understood that the concepts are applicable to any turbine in a gas turbine engine. As used herein, the term "turbine" refers to a turbomachine element in which the kinetic energy of a fluid flow is converted into rotational motion.

The rotor 36 includes a disk 38, and the disk 38 includes an annular flowpath surface 40 extending between a forward end 42 and an aft end 44. A set of turbine blades 46 extend from the flow path surface 40. The turbine blades 46 constitute "turbine airfoils" for the purposes of the present invention. Each turbine blade 46 extends from a root 48 at the flowpath surface 40 to a tip 50 and includes a concave pressure side 52 joined to a convex suction side 54 at a leading edge 56 and a trailing edge 58. Adjacent turbine blades 46 define a space 60 therebetween.

The turbine blades 46 are evenly spaced around the periphery of the flowpath surface 40. The average circumferential spacing "s" (see fig. 2) between adjacent turbine blades 46 is defined as s-2R/Z, where "R" is the specified radius of the turbine blades 46 (e.g., at the root 48), and "Z" is the number of turbine blades 46.

As best shown in FIG. 4, each turbine blade 46 has a span (or span dimension) "S1," which is defined as the radial distance from the root 48 to the tip 50. The span S1 may vary at different axial locations depending on the particular design of the turbine blade 46. For reference purposes, the relevant measurement is the span S1 at the leading edge 56. Each turbine blade 46 has a chord (or chord dimension) "C1" (fig. 3), which is defined as the length of an imaginary straight line connecting the leading edge 56 and the trailing edge. The chord C1 may be different at different locations along the span S1 depending on the particular design of the turbine blade 46. For the purposes of the present invention, the relevant measurement is the chord C1 at the root 48 (i.e., adjacent to the flowpath surface 40).

Each turbine blade 46 has a thickness "T1" defined as the distance between the pressure side 52 and the suction side 54 (see FIG. 3). The "thickness ratio" of the turbine blade 46 is defined as the maximum value of the thickness T1 divided by the chord length, expressed as a percentage.

An array of baffles 146 (fig. 2) extend from the flow path surface 40. One baffle is disposed in each space 60 between the turbine blades 46. Each baffle 146 extends from a root 148 at the flow path surface 40 to a tip 150 and includes a concave side 152 joined to a convex side 154 at a leading edge 156 and a trailing edge 158.

The tangential position of the baffle 146 relative to the turbine blade 46 may be described by reference to the tangential position of its leading edge 156. In one example, the leading edge 156 may be located in the range of 25% to 75% of the tangential distance "D2" measured between adjacent turbine blade leading edges 56, with the leading edge 56 of one turbine blade 46 representing 0% and the adjacent turbine blade representing 100%. In another example, the tangential position of the leading edge 156 may be located in the range of 40% to 60% of the tangential distance D between adjacent turbine blades 46.

The axial position of the baffle 146 relative to the turbine blade 46 may be described by reference to the axial position of its leading edge 156. The axial position of the baffle 146 may be varied to suit a particular application. In one example, the leading edge 156 of the baffle 146 may be located in the range of-30% to 30% of the chord C1 of the turbine blade 46 adjacent the flow path surface 40. In another example, the leading edge 156 of the baffle 146 may be located in a range of 0 to 10% of the chord dimension C1 of the turbine blade 46 adjacent the flow path surface 40. In this term, negative values indicate the position of the leading edge of the baffle axially forward of the leading edge 56 of the turbine blade 46, and positive values indicate the position of the leading edge of the baffle behind the leading edge 56 of the turbine blade 46. (0% in this notation means that the leading edges 156 and 52 are at the same axial position). In the example shown in fig. 2-6, the baffles 146 are positioned such that their leading edges 156 are at substantially the same axial position as the leading edges 56 of the turbine blades 46.

As best shown in FIG. 5, each baffle 146 has a span (or span dimension) "S2" defined as the radial distance from the root 148 to the tip 150. The span S2 may be different at different axial locations depending on the particular design of the baffle 146. For reference purposes, the relevant measurement is the span S2 at the leading edge 156. Each baffle 146 has a chord (or chord dimension) "C2," which is defined as the length of an imaginary straight line connecting leading edge 156 and trailing edge 158. Depending on the particular design of the baffle 146, its chord C2 may be different at different locations along the span S2. For the purposes of the present invention, the relevant measurement is chord C2 at root 148 (i.e., adjacent to flowpath surface 40).

The baffle 146 acts to reduce pressure loss by blocking or breaking the tendency of the Pressure Side (PS) horseshoe swirl leg to move toward the adjacent profile Suction Side (SS). The size of the baffle 146 and its location can be selected to control the secondary flow while minimizing its surface area.

Each baffle 146 has a thickness "T2" (fig. 3) defined as the distance between concave side 152 and convex side 154. The "thickness ratio" of the baffle 146 is defined as the maximum value of the thickness T2 divided by the chord C2, expressed as a percentage. In general, the thickness of the baffle 146 should be as small as possible, consistent with structural, thermal, and aeroelastic considerations. For optimum performance in breaking up the vortices, they should have a constant thickness from the leading edge 156 to the trailing edge 158. Generally, the thickness ratio of the baffle 146 should be significantly less than the thickness ratio of the turbine blade 46. As one example, the baffle 146 may have a constant thickness in the range of one-half the diameter "d 1" of the turbine blade trailing edge 58 to three times the diameter of the turbine blade trailing edge 58. This corresponds to a thickness ratio of about 0.1% to 0.6%. For comparison purposes, this is substantially less than the thickness of the turbine blade 46. For example, the thickness of the turbine blade 46 may be approximately 30% to 40% thick. Other turbine blades within engine 10 (e.g., in LPT 24) may be about 5% to 10% thick.

For optimum performance in terms of breaking up the vortices, the baffles 146 should be aerodynamically "unloaded", i.e., configured such that they generate little or no aerodynamic lift. Therefore, they should be curved to follow the streamlines of the flow field around the turbine blades 46. A parameter called "camber" describes the curvature of the cross-sectional shape of the airfoil. Referring to FIG. 6, for each individual airfoil portion of the baffle 146, an imaginary straight line, referred to as a "chord line" 157, connects the leading edge 158 and the trailing edge 158. In addition, for each individual airfoil portion of the baffle 146, a curve referred to as an "arc" 159 represents the locus of points located halfway between the concave side 152 and the convex side 154. Camber is generally described in terms of the offset or distance of camber line 159 from chord line 157. The large distance between the two lines is a large curved surface; in contrast, a small distance is a small curved surface. The shape of the flow field streamlines can be determined via analysis or testing. For example, commercially available computational fluid dynamics ("CFD") solver software operates using a software representation (e.g., a solid model) of the physical structure exposed to fluid flow.

The span S2 and/or chord C2 of the baffle 146 is less uniform than the corresponding span S1 and chord C1 of the turbine blade 46. These may be referred to as "partial-span" and/or "partial-chord" baffles. For example, the span S2 may be equal to or less than the span S1. In one example, the span S2 of the baffle 146 is 30% or less of the span S2 of the turbine blade 46. In another example, the span S2 of the baffle 146 is 2.5% to 10% of the span S2 of the turbine blade 46. In one example, for example, the chord C2 may be 30% to 70% of the chord dimension of the turbine blade 46 adjacent to the flow path surface. In another example, chord C2 is approximately 50% of chord C1.

The disk 38, turbine blades 46, and baffles 146 may be constructed of any material capable of withstanding the stresses and environmental conditions expected in operation. Non-limiting examples of known suitable alloys include nickel-based and cobalt-based alloys.

In fig. 2-5, the disk 38, turbine blades 46, and the baffle 146 are depicted as an assembly of separate components. The principles of the present invention are equally applicable to rotors having airfoils that are constructed as a complete, unitary, or monolithic whole. This type of structure may be referred to as a "bladed disk" or "blisk".

The baffle concepts described above may also be incorporated into turbine stator components within engine 10. For example, FIGS. 7-10 illustrate a portion of a turbine nozzle 62 suitable for inclusion in the HPT 22 or the LPT 24.

Turbine nozzle 62 includes an exhaust-shaped turbine bucket 64 bounded at inboard and outboard ends by inner and outer bands 66,68, respectively. Turbine bucket 64 constitutes a "stator airfoil" for purposes of the present invention.

The inner band 66 defines an annular inner flowpath surface 70 extending between a forward end 72 and an aft end 74. Outer band 68 defines an annular outer flow path surface 76 extending between a forward end 78 and a rearward end 80. Each turbine bucket 64 extends from a root 82 at inner flowpath surface 70 to a tip 84 at outer flowpath surface 76 and includes a concave pressure side 86 joined to a convex suction side 88 at a leading edge 90 and a trailing edge 92. Adjacent turbine buckets 46 define spaces 93 therebetween.

The turbine buckets 64 are evenly spaced about the outer periphery of the inner flow path surface 70. Turbine buckets 64 have an average circumferential spacing "s" defined as described above (see FIG. 7).

As best shown in FIG. 9, each turbine bucket 64 has a span (or span dimension) "S3" defined as the radial distance from the root 82 to the tip 84. The span S3 may vary at different axial locations depending on the particular design of the turbine bucket 64. For reference purposes, the relevant measurement is the span S3 at the leading edge 90. Each turbine blade 64 has a chord (or chord dimension) "C3," which is defined as the length of an imaginary straight line connecting leading edge 90 and trailing edge 92. The chord C3 may be different at different locations along the span S3 depending on the particular design of the turbine blade 64. For purposes of the present invention, the relevant measurement would be the chord C3 at the root 82 or tip 84 (i.e., adjacent to the flow path surface 70 or 76).

Each turbine bucket 64 has a thickness "T3" defined as the distance between pressure side 86 and suction side 88. The "thickness ratio" of the turbine bucket 64 is defined as the maximum value of the thickness T3 divided by the chord length, expressed in percent.

One or both of the inner and outer flowpath surfaces 70,76 may be provided with a set of baffles. In the example shown in fig. 7, a set of baffles 164 extend radially inward from the outer flowpath surface 76. A baffle 164 is disposed between each pair of turbine buckets 64. In the circumferential direction, the baffles 164 may be evenly or unevenly spaced between two adjacent turbine buckets 64. Each baffle 164 extends from a tip 184 at the outer flow path surface 76 to a root 182 and includes a concave side 186 joined to a convex side 188 at a leading edge 190 and a trailing edge 192.

The tangential position of the baffle 164 relative to the turbine bucket 64 may be described by reference to the tangential position of its leading edge 190. In one embodiment, the leading edge 190 may be located in the range of 25% to 75% of the tangential distance "D2" measured between adjacent turbine bucket leading edges 90, where the leading edge 90 of one turbine bucket 64 represents 0% and the adjacent turbine bucket represents 100%. In another example, the tangential position of leading edge 190 may be located in a range of 40% to 60% of the tangential distance D2 between adjacent turbine buckets 64.

The axial position of the baffle 164 relative to the turbine bucket 64 may be described by reference to the axial position of its leading edge 190. The axial position of the baffle 164 may be varied to suit a particular application. In one example, leading edge 190 of baffle 164 may be located in the range of-30% to 30% of chord C3 of turbine bucket 64 adjacent to flow path surface 76. In another example, leading edge 190 of baffle 164 may be located in a range of 0 to 10% of chord dimension C3 of turbine bucket 64 adjacent to flow path surface 76. In this term, negative values indicate the baffle leading edge position axially forward of the leading edge 90 of the turbine bucket 64, and positive values indicate the baffle leading edge position aft of the leading edge 90 of the turbine bucket 64. (0% in this symbol indicates that leading edges 190 and 90 are at the same axial position 7-10 illustrate an example where baffles 164 are positioned such that their leading edges 190 are at substantially the same axial position as leading edge 90 of turbine bucket 64.

As best shown in FIG. 10, each baffle 164 has a span (or span dimension) "S4" defined as the radial distance from the root 182 to the tip 184 and a chord (or chord dimension) "C4" defined as the length of an imaginary straight line connecting the leading edge 190 and the trailing edge 192. The chord C4 may be different at different locations along the span S4 depending on the particular design of the baffle 164. For purposes of the present invention, the relevant measurement is chord C4 at tip 184 (i.e., adjacent to flow path surface 76).

The baffle 164 acts to reduce pressure losses by blocking or breaking the tendency of the Pressure Side (PS) horseshoe swirl legs to move toward the adjacent contoured Suction Side (SS). The size of the baffles 164 and their location may be selected to control the secondary flow while minimizing their surface area.

Each baffle 164 has a thickness "T4" (fig. 8) defined as the distance between concave side 186 and convex side 188. The "thickness ratio" of the baffle 146 is defined as the maximum value of the thickness T4 divided by the chord C4, expressed in percentage. In general, the thickness of the baffle 164 should be as small as possible, consistent with structural, thermal, and aeroelastic considerations. For optimum performance in breaking up the vortices, they should have a constant thickness from the leading edge 190 to the trailing edge 192. Generally, the thickness ratio of the baffle 194 should be significantly less than the thickness ratio of the turbine bucket 64. As one example, the baffle 164 may have a constant thickness in the range of one-half the diameter "d 2" of the turbine bucket trailing edge 92 to three times the diameter of the turbine bucket trailing edge 92. This corresponds to a thickness ratio of about 0.1% to 0.6%. For comparison purposes, this is substantially less than the thickness of turbine bucket 64.

For optimal performance in terms of breaking up the vortices, the baffles 164 should be aerodynamically "unloaded", i.e., configured such that they generate little or no aerodynamic lift. Therefore, they should be curved to follow the streamlines of the flow field around the turbine buckets 64, as described above for the baffle 46.

The span S4 and/or chord C4 of the baffle 146 is less uniform than the corresponding span S3 and chord C3 of the turbine vane 64. These may be referred to as "partial-span" and/or "partial-chord" baffles. For example, the span S4 may be equal to or less than the span S3. In one example, the span S4 of the baffle 164 is 30% or less of the span S3 of the turbine bucket 64. In another example, the span S4 of the baffle 164 is 2.5% to 10% of the span S3 of the turbine bucket 64. In one example, chord C4 may be 30% to 70% of chord C3 of turbine bucket 64 adjacent flow path surface 76. In another example, the chord C4 is about 50% of the chord C3 adjacent the flow path surface 76.

Fig. 11 shows a set of baffles 264 extending radially outward from the inner flowpath surface 70. The baffles 264 may be identical to the baffles 164 described above in terms of their shape, axial and circumferential position relative to the stator vanes 64, their thickness, span and chord dimensions, and their material composition, except for the fact that they extend from the inner flowpath surface 70. As noted above, baffles may optionally be incorporated at the inner flowpath surface 70 or the outer flowpath surface 76, or both.

The combined turbine apparatus described herein has the technical effects and benefits of reducing losses associated with horseshoe vortices and flow turning deviations, improving turbine performance, as compared to the prior art.

It should be noted that, as used herein, when describing numerical values, the relative term "about" is intended to include sources of variation of the stated values, including, but not limited to, measurement errors and/or manufacturing variability. Thus, the relative term "about" includes the stated value, plus or minus 5% of the stated value, unless otherwise stated.

The turbine endwall baffle apparatus has been described hereinbefore. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the embodiment(s) described above. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Further aspects of the invention are provided by the subject matter of the following clauses:

1. a turbine arrangement, comprising: a turbine, the turbine comprising: a turbine component defining an arcuate flowpath surface (40,70, 76); a set of axial flow turbine airfoils (46,64) extending from the flow path surface (40,70,76), the turbine airfoils (46,64) defining a space (60,93) therebetween; and a plurality of baffles (146,164,264), the plurality of baffles (146,164,264) extending from the flowpath surface (40,70,76) in the space (60,93) between the turbine airfoils (46,64), each baffle having opposite concave and convex sides extending between a leading edge and a trailing edge, wherein the baffle (146,164,264) has a non-zero camber and a constant thickness, located axially adjacent the leading edge of an adjacent turbine airfoil (46,64), and wherein at least one of a chord dimension of the baffle (146,164,264) and a span dimension of the baffle (146,164,264) is less than a corresponding dimension of the turbine airfoil (46, 64).

2. The apparatus of any preceding claim, the leading edge of each baffle (146,164,264) being positioned tangentially in a range of 25% to 75% of a distance between two adjacent turbine airfoils (46, 64).

3. The apparatus of any preceding claim, the leading edge of each baffle (146,164,264) being positioned tangentially in the range of 40% to 60% of the distance between two adjacent turbine airfoils (46, 64).

4. The apparatus of any preceding claim, the leading edge of each said baffle (146,164,264) being positioned axially relative to the leading edge of an adjacent one of the turbine airfoils (46,64) in a range of-30% to 30% of the chord dimension of the adjacent one of the turbine airfoils (46, 64).

5. The apparatus of any preceding claim, the leading edge of each said baffle (146,164,264) being positioned axially relative to the leading edge of an adjacent one of the turbine airfoils (46,64) in a range of 0% to 10% of the chord dimension of the adjacent one of the turbine airfoils (46, 64).

6. The apparatus of any preceding clause, wherein the spanwise dimension of the baffle (146,164,264) is 30% or less of the spanwise dimension of the turbine airfoil (46, 64).

7. The apparatus of any preceding clause, wherein the spanwise dimension of the baffle (146,164,264) is 2.5% to 10% of the spanwise dimension of the turbine airfoil (46, 64).

8. The apparatus of any preceding claim, the chord dimension of the baffle (146,164,264) adjacent the flowpath surface (40,70,76) being 30% to 70% of the chord dimension of the turbine airfoil (46,64) adjacent the flowpath surface (40,70, 76).

9. The apparatus of any preceding claim, the chord dimension of the baffle (146,164,264) adjacent the flowpath surface (40,70,76) being about 50% of the chord dimension of the turbine airfoil (46,64) adjacent the flowpath surface (40,70, 76).

10. The apparatus of any preceding item, the baffle (146,164,264) having a thickness in a range of one-half a trailing edge diameter of the turbine airfoil (46,64) to three times the trailing edge diameter of the turbine airfoil (46, 64).

11. The apparatus of any preceding claim, the turbine including a turbine rotor stage comprising a disk (38) rotatable about a centerline axis; the flow path surface (40) is defined by the disc (38); and the turbine airfoils are a set of axial flow turbine blades (46) extending outwardly from the rotor surface.

12. The apparatus of any preceding item, said turbine comprising a turbine nozzle stage (62), said turbine nozzle stage (62) comprising at least one wall (66, 68); said flow path surface (70,76) being defined by one or both of said walls (66, 68); the turbine airfoil is a set of axial turbine buckets (64) extending between the flow path surfaces (70, 76); and the baffles (164,264) extend from one or both of the flow path surfaces (70, 76).