WO2019046006A1

WO2019046006A1 - Advanced geometry platforms for turbine blades

Info

Publication number: WO2019046006A1
Application number: PCT/US2018/046612
Authority: WO
Inventors: Nicholas F. MARTIN Jr.; David J. Wiebe
Original assignee: Siemens Aktiengesellschaft; Siemens Energy, Inc.
Priority date: 2017-08-28
Filing date: 2018-08-14
Publication date: 2019-03-07

Abstract

A blade assembly for a turbine includes an airfoil (10), a root (62) and a platform (52). The platform (52) is positioned radially between the airfoil (10) and the root (62). An airfoil fillet (16) joins the airfoil (10) to an upper surface (56) of the platform (52). A suction side mate face (22) of the platform (52) mates with a pressure side mate face (24) of a similar adjacent platform (52) along a platform mate face angle (26) that substantially aligns with a camber line (68) in relation to an axial direction (A). A method of attaching blades to a rotor assembly is also disclosed.

Description

ADVANCED GEOMETRY PLATFORMS FOR TURBINE BLADES

BACKGROUND

1. Field

[0001] The present invention relates to gas turbine engines, and more specifically to an advanced geometry platform for a turbine blade.

2. Description of the Related Art

[0002] In an industrial gas turbine engine, hot compressed gas is produced. The hot gas flow is passed through a turbine and expands to produce mechanical work used to drive an electric generator for power production. The turbine generally includes multiple stages of stator vanes and rotor blades to convert the energy from the hot gas flow into mechanical energy that drives the rotor shaft of the engine. Turbine inlet temperature is limited to the material properties and cooling capabilities of the turbine parts. This is especially important for upstream stage turbine vanes and blades since these airfoils are exposed to the hottest gas flow in the system.

[0003] A combustion system receives air from a compressor and raises it to a high energy level by mixing in fuel and burning the mixture, after which products of the combustor are expanded through the turbine.

[0004] The blades and vanes of the turbine section are typically shaped in the form of an airfoil and have further elements connected to it such as platforms that provide a boundary for the working fluid path. The blade may also have a root portion that may fix the blade to a turbine disc.

[0005] Gas turbines are becoming larger, more efficient, and more robust. Large blades and vanes are being produced, especially in the hot section of the engine system. In order to help with the improvement of these blades and vanes, the blades have an increased airfoil camber that provides a greater circumferential footprint along the platform. These extended airfoils make it difficult to fit the airfoil on a conventional platform (as is shown in FIG. 1).

SUMMARY

[0006] In one aspect of the present invention, a blade assembly arrangement for a turbine comprises: an airfoil having a first end; a root extending radially from the airfoil; a platform positioned radially between the airfoil and the root, the platform comprising a platform lower surface, a platform upper surface opposite to the lower surface, a suction side mate face and a pressure side mate face, and a pair of platform ends connecting the suction side mate face and the pressure side mate face; and an airfoil fillet having a root radius, the root radius identifying the length of the airfoil fillet, wherein the airfoil extends radially from the upper surface of the platform wherein the airfoil fillet joins the first end of the airfoil to the upper surface of the platform, and the root extends from the lower surface of the platform, wherein the suction side mate face mates with a pressure side mate face of a similar adjacent platform along a platform mate face angle that substantially aligns with a camber line of the airfoil in relation to an axial direction.

[0007] In another aspect of the present invention, a method for attaching blades to a rotor assembly using the blade assembly arrangement according to the blade assembly arrangement above, the method comprising: assembling a plurality of blades adjacent to each other including a first blade through a second-to-last blade from downstream of a rotor; installing the next- to-last blade from downstream of the rotor adjacent to the second-to-last blade; installing the last blade from upstream of the rotor adjacent to the first blade; and axially locking the next-to-last blade and the last blade to the rotor.

[0008] These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS [0009] The invention is shown in more detail by help of figures. The figures show preferred configurations and do not limit the scope of the invention.

[0010] FIG 1 is a top radial view of a prior art blade with platform.

[0011] FIG 2 is a top radial view of a blade and platform of an exemplary embodiment of the present invention overlaid over the prior art platform.

[0012] FIG 3 is a perspective view of an assembly of a plurality of blades and platforms of an exemplary embodiment of the present invention.

[0013] FIG 4 is a perspective view of another assembly point of a plurality of blades and platforms of an exemplary embodiment of the present invention.

[0014] FIG 5 is a perspective view of another assembly point of a plurality of blades and platforms of an exemplary embodiment of the present invention.

[0015] FIG 6 is a perspective view of another assembly point of a plurality of blades and platforms of an exemplary embodiment of the present invention.

[0016] FIG 7 is a side view of a blade and platform of an exemplary embodiment of the present invention.

[0017] FIG 8 is a detailed side view of a contact point of a second-to-last blade and a last blade being assembled in an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

[0018] In the following detailed description of the preferred embodiment, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, and not by way of limitation, a specific embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and that changes may be made without departing from the spirit and scope of the present invention. [0019] Broadly, an embodiment of the present invention provides a blade assembly for a turbine that includes an airfoil, a root and a platform. The platform is positioned radially between the airfoil and the root. An airfoil fillet joins the airfoil to an upper surface of the platform. A suction side mate face of the platform mates with a pressure side mate face of a similar adjacent platform along a platform mate face angle that substantially aligns with a camber line angle in relation to an axial direction.

[0020] A gas turbine engine may comprise a compressor section, a combustor and a turbine section. The compressor section compresses ambient air. The combustor combines the compressed air with a fuel and ignites the mixture creating combustion products comprising hot gases that form a working fluid. The working fluid travels to the turbine section. Within the turbine section are circumferential rows of vanes and blades, the blades being coupled to a rotor. Each pair of rows of vanes and blades forms a stage in the turbine section. The turbine section comprises a fixed turbine casing, which houses the vanes, blades and rotor. A blade of a gas turbine receives high temperature gases from a combustion system in order to produce mechanical work of a shaft rotation.

[0021] A conventional blade is attached to a conventional platform along an attachment centerline 12. An airfoil 10 is placed on the conventional platform, the conventional platform having a conventional suction side mate face 18 and a conventional pressure side mate face 20. The airfoil 10 has a smooth transition to the conventional platform. The smooth transition portion can be called an airfoil fillet 16. The airfoil fillet 16 extends the airfoil out by a root radius 14.

[0022] With the advancement of turbine blades, there has been an increase in the airfoil camber in the airfoil that makes it have a greater circumferential footprint on the platform extending out beyond the platform along the sides of the conventional platform. The camber being the asymmetry between a top and bottom surfaces of an airfoil. As is seen in FIG. 1, an extended section 50 of the airfoil filet 16 extends out beyond the conventional platform. One of the reasons for the difficulty of fitting the airfoil on a conventional platform is that the conventional platform has edges that are parallel to a broach angle. The broach angle is the insertion angle of the blade, and in turn, the platform.

[0023] Axial retention of blades is a requirement and improved aerodynamics is desirable. Embodiments of the present invention provide an advanced geometry platform that may allow for a simplified axial retention for blades and improved aerodynamics through the advanced geometry of the platform.

[0024] As is shown in Figures 2 through 6, a turbine blade has an airfoil 10 with a first end 66. The airfoil 10 includes a pressure side 58 and a suction side 60. The airfoil 10 is joined to a platform 52 by an airfoil fillet 16. The airfoil fillet having a root radius 14 that identifies the length of the airfoil fillet 16. The platform 52 is positioned radially inward from the airfoil 10. The platform 52 includes a platform lower surface 54, a platform upper surface 56 opposite to the lower surface 54, a suction side mate face 22 and a pressure side mate face 24, and a pair of platform ends 64 connecting the suction side mate face 22 and the pressure side mate face 24.

[0025] Below is described several embodiments of a blade assembly arrangement and method for installing blades that provide different ways to provide an advanced geometry platform. Each embodiment provides a way to address the greater circumferential footprint of increased camber airfoils.

[0026] An embodiment is shown mainly in FIGS. 2 through 4. The platform 52 suction side mate face 22 and pressure side mate face 24 have been modified based on a notched shifted platform section 28. In order to be able to cover the full airfoil fillet 16, root radius 14, and airfoil 10, a section of the platform 52 is shifted so that the airfoil is fully covered by the platform 52. The notched shifted platform section 28 is shifted in a circumferential direction C. A platform mate face angle 26 is formed as the notched shifted platform section 28 shifts. FIG. 2 shows this shift in an individual platform. As is illustrated, the notched shifted platform section 28 shifts a portion of the platform 52 in a way that substantially aligns the platform mate face angle 26 with an angle of the camber line 68 of the airfoil 10 in relation to an axial direction A. [0027] The magnitude of the offset, or shift, and the platform mate face angle 26 can depend on a number of variables such as, blade stagger angle, number of blades, fillet size, and under-platform damper configuration. Additionally, the surface of the notched shifted platform section 28 along the circumferential direction C may be straight edges as shown or rounded edges, etc. based on the configuration of the turbine. The shape of the surface of the notched shifted platform section 28 is not limited to the straight edges shown.

[0028] FIG. 5 shows another embodiment of the blade assembly arrangement. As mentioned above, the broach angle 38 of the platforms during installation is typically consistent with the angle of the platform. In this embodiment, the platform has a skewed platform angle 40 that is different than the broach angle 38. In certain embodiments, the skewed platform angle 40 is greater than the broach angle 38. The skewed platform angle 40, once again, takes into consideration the size of the airfoil circumferential length. The skewed platform angle 40 allows for the coverage of the airfoil 10 and airfoil fillet 16 with root radius 14.

[0029] During installation of the blades, each blade is assembled from downstream, or aft side 44, of a rotor 70 except for the last blade 32. The first blade 30 through until the second-to-last blade 36 is assembled from the aft side 44. The next-to-last blade 34 follows the second-to-last blade 36 in the installation, as is shown in FIG. 3 and FIG. 4. The next-to-last blade 34 installation direction 46 the same as the blades before. The last blade 32 is installed in the forward side 48 or upstream of the rotor 70. As can be seen in FIG. 4 through FIG. 5, the next-to-last blade 34 and the last blade 32 can be slightly different than the rest of the blades. The facing suction side mate face 22 and pressure side mate face 24 of the next-to-last blade 34 and the last blade 32 are modified and can be similar to the conventional suction side mate face 18 and conventional pressure side mate face 20 as these are the last blades placed into the assembly of the rotor 70. For certain embodiments, this modification removes the notched shifted platform section 28, and in other embodiments, a platform angle 72 and the broach angle 38 are the same S for the next-to-last blade 34 and the last blade 32. Further, the next-to-last blade 34 and the last blade 32 will be individually axially locked to the rotor 70. The first blade 30 through the second-to-last blade 36 do not have to be axially locked to the rotor 70. Due to the advanced geometry of these blades, the assembly provides stability and allows for simplified axial retention.

[0030] In certain embodiments, a buildup addition 42 is made for side mate faces that match up for the next-to-last blade 34 and the adjacent last blade 32 as is seen in FIG. 6. The next-to-last blade 34 and the last blade 32 can be modified with these buildup additions 42 in order to have improved aerodynamics by completing the cut-off fillet sections. The buildup addition 42 modifications can be only for the next-to-last blade 34 and the last blade 32 while the rest of the blades have the advanced geometry.

[0031] FIG. 7 illustrates how the airfoil 10, the airfoil fillet 16 along with the root radius 14 is presented along the platform 52. As can be seen in FIG. 7, all of these components of the blade are positioned and supported by the platform 52. FIG. 8 shows another view other than FIG. 6 of how the next-to-last blade 34 and the last blade 32 may have an overlap. The buildup addition 42 is shown from a side view in order to disclose how the platforms 52 mate. Since the last blade 32 and the next-to-last blade 34 do not have the interlocking notched shifted platform section 28 or the skewed platform angle 40, the last blade 32 and the next-to-last blade 34 provide for the overlapping of the components. Only the last blade 32 and the next-to-last blade 34 may need to have axial locking, typical of conventional blade/platform offerings, therefore not further discussed here.

[0032] A plurality of blades can be placed and installed on a wheel. The wheel may include a rotating disc. The disc may include a plurality of elongated channels provided therein and spaced along a disc periphery.

[0033] Having a notched shifted platform section 28 increases the overall mate face length of the platform 52. Increasing the overall mate face length of the platform 52 allows for more options under the platform for damping. Various damping configurations can be placed underneath the platform 52 with the additional space provided with either the notched shifted platform section 28 and/or with the skewed platform angle 40. Since there are no issues as to a blade airfoil fillet 16 overhanging the platform 52, there are smooth fillet transitions from the airfoil 10 to the platform 52. The smooth fillet transitions provide improved aerodynamics. The platforms 52 with the advanced geometry allow for the platforms 52 to have improved axial retention for the blades when using the interlocked mate faces that are created with the notched shifted platform section 28. By having a difference between the broach angle 38 and the skewed angle 40 of the platforms 52, the platforms 52 can stay in position without concern of retention. Only the next-to-last blade 34 and the last blade 32 need to have individual axial locking to the rotor 70 since the geometry of the other platforms 52 allow the blades to be fixed in position. The next-to-last blade 34 and the last blade 32 are locked to keep the full amount of blades in place. FIG. 7 shows a partial selection of the rotor 70.

[0034] While specific embodiments have been described in detail, those with ordinary skill in the art will appreciate that various modifications and alternative to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims, and any and all equivalents thereof.

Claims

CLAIMS What is claimed is:

1. A blade assembly arrangement for a turbine comprising:

an airfoil (10) having a first end (66);

a root (62) extending radially from the airfoil (10);

a platform (52) positioned radially between the airfoil (10) and the root (62), the platform comprising a platform lower surface (54), a platform upper surface (56) opposite to the lower surface (54), a suction side mate face (22) and a pressure side mate face (24), and a pair of platform ends (64) connecting the suction side mate face (22) and the pressure side mate face (24); and

an airfoil fillet (16) having a root radius (14), the root radius (14) identifying the length of the airfoil fillet (16),

wherein the airfoil (10) extends radially from the upper surface (56) of the platform (52) wherein the airfoil fillet (16) joins the first end (66) of the airfoil (10) to the upper surface (56) of the platform (52), and the root (62) extends from the lower surface (54) of the platform (52),

wherein the suction side mate face (22) mates with a pressure side mate face (24) of a similar adjacent platform (52) along a platform mate face angle (26) that substantially aligns with a camber line (68) of the airfoil (10) in relation to an axial direction (A).

2. The blade assembly arrangement according to claim 1, wherein the suction side mate face (22) interlocks with a pressure side mate face (24) of a similar adjacent platform (52) along a platform mate face angle (26) in relation to an axial direction (A).

3. The blade assembly arrangement according to claim 1 or 2, wherein the platform (52) further comprises a notched shifted section (28), the notched shifted section (28) of the platform (52) offsets a portion of the platform (52) towards one of the suction side mate face (22) and the pressure side mate face (24) so that the root radius (14) of the airfoil fillet (16) is fully covered by the platform (52), the notched shifted section (28) offset at a platform interlock face angle (26), from an axial direction (A).

4. The blade assembly arrangement according to one of claim 1 through 3, wherein the platform (52) comprises a skewed platform angle (40) that is different than that of a broach angle (38), wherein the skewed platform angle (40) is an angle that the platform (52) forms that is off from a 90 degree right angle, and the broach angle (34) is an insertion angle in relation to an axial direction (A).

5. The blade assembly arrangement according to claim 4, wherein the skewed platform angle (40) is greater than the broch angle (38).

6. The blade assembly arrangement according to one of claims 1 through 5, wherein a next-to-last blade (34) insertion and a last blade insertion (32) have the same platform angle (72) as the broach angle (38).

7. The blade assembly arrangement according to one of claims 1 through 3, wherein the notched shifted section (28) comprises straight edges.

8. The blade assembly arrangement according to one of claims 1 through 3, wherein the notched shifted section (28) comprises rounded edges.

9. The blade assembly arrangement according to one of claims 1 through 8, wherein a buildup addition (42) is along the pressure side mate face (24) and suction side mate face (22) of the next-to-last blade (32) insertion and last blade (30) insertion, wherein the buildup addition (42) provides support for the airfoil fillets (16) of the next- to-last blade (34) and the last blade (32).

10. A method for attaching blades to a rotor assembly using the blade assembly arrangement according to claim 1, the method comprising:

assembling a plurality of blades adjacent to each other including a first blade (30) through a second-to-last blade (36) from downstream of the rotor (70); installing the next-to-last blade (34) from downstream of the rotor (70) adjacent to the second-to-last blade (36);

installing the last blade (32) from upstream of the rotor (70) adjacent to the first blade (30); and

axially locking the next-to-last blade (34) and the last blade (32) to the rotor.

11. The method according to claim 10, wherein the suction side mate face (22) interlocks with a pressure side mate face (24) of a similar adjacent platform (52) along a platform mate face angle (26) in relation to an axial direction (A).

12. The method according to claim 10 or 11, wherein the platform (52) further comprises a notched shifted section (28), the notched shifted section (28) of the platform (52) offsets the platform (52) towards one of the suction side mate face (22) and the pressure side mate face (24) so that the root radius (14) of the airfoil fillet (16) is fully covered by the platform (52), the notched shifted section (28) offset at a platform interlock face angle (26), from an axial direction (A).

13. The method according to one of claims 10 through 12, wherein the platform (52) comprises a skewed platform angle (40) that is different than that of a broach angle (38), wherein the skewed platform angle (40) is an angle that the platform forms that is off from a 90 degree right angle, and the broach angle (38) is an insertion angle in relation to an axial direction (A).

14. The method according to claim 13, wherein the platform angle (72) is the same as the broach angle (38) for the next-to-last blade (34) and the last blade (32) during installing.