EP3379033A1

EP3379033A1 - Systems and methods for minimizing an incidence angle between a number of streamlines in a not disturbed flow field by varying an inclination angle of a chord line of a snubber

Info

Publication number: EP3379033A1
Application number: EP17161833.3A
Authority: EP
Inventors: Roland SIGG; Thomas Lutz
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 2017-03-20
Filing date: 2017-03-20
Publication date: 2018-09-26

Abstract

A turbomachine is disclosed including a first blade (102), a second blade (104), and a snubber (100) disposed between a pressure side (106) of the first blade (102) and a suction side (108) of the second blade (104). An inclination angle of a chord line (112) of the snubber (100) may be varied from the pressure side (106) of the first blade (102) to the suction side (108) of the second blade (104) to minimize an incidence angle between a number of streamlines (110) in a not disturbed flow field and the inclination angle of the chord line (112).

Description

TECHNICAL FIELD

The disclosure relates generally to gas and/or steam turbine engines and more particularly relate to systems and methods for minimizing an incidence angle between a number of streamlines in a not disturbed flow field by varying an inclination angle of a chord line of a snubber.

BACKGROUND

The incidence angle between the streamlines of a not disturbed flow field between adjacent blades and the snubber radial inclination angle (snubber chord line or principal axis stagger angle) and also the snubber surface are generally aerodynamic loss amplifiers. Snubbers that are not aligned are prone to thickened boundary layers and/or flow separation downstream thereof at the snubber trailing edge and on the surrounding blade surfaces. Secondary flow may be formed in the separation and wake zones. The above discussed incidence angle on the snubber may generate an undesirable lift on the snubber and lift related secondary flow.
To reduce the incidence over the whole pitch-wise length of the snubber, the flow yaw angle variation from the pressure to suction side of the adjacent blades needs to be considered and the geometry accordingly adapted in the pitch-wise direction.

BRIEF DESCRIPTION

According to an embodiment, there is disclosed a system including a first blade, a second blade, and a snubber disposed between a pressure side of the first blade and a suction side of the second blade. An inclination angle of a chord line of the snubber may be varied from the pressure side of the first blade to the suction side of the second blade to minimize an incidence angle between a number of streamlines in a not disturbed flow field and the inclination angle of the chord line.
According to another embodiment, there is disclosed a snubber disposed between a pressure side of a first blade and a suction side of a second blade. The snubber includes a leading edge, a trailing edge, and a chord line. An inclination angle of a chord line of the snubber may be varied from the pressure side of the first blade to the suction side of the second blade to minimize an incidence angle between a number of streamlines in a not disturbed flow field and the inclination angle of the chord line.
Further, according to another embodiment, there is disclosed a method. The method includes positioning a snubber between a pressure side of a first blade and a suction side of a second blade. The method also includes varying an inclination angle of a chord line of the snubber from the pressure side of the first blade to the suction side of the second blade to minimize an incidence angle between a plurality of streamlines in a not disturbed flow field and the inclination angle of the chord line.
Other embodiments, aspects, and features of the disclosure will become apparent to those skilled in the art from the following detailed description, the accompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made to the accompanying drawings, which are not necessarily drawn to scale.

FIG. 1 depicts of an example gas turbine engine according to an embodiment.
FIG. 2 depicts a snubber disposed between two adjacent blades according to an embodiment.
FIG. 3 depicts a snubber disposed between two adjacent blades according to an embodiment.
FIG. 4 depicts a three-dimensional flow vector and projection to the meridional plane according to an embodiment.
FIG. 5 depicts a cross-section of a snubber according to an embodiment.

DETAILED DESCRIPTION

Referring now to the drawings, in which like numerals refer to like elements throughout the several views, FIG. 1 depicts a schematic view of gas turbine engine 10 as may be used herein. The gas turbine engine 10 may include a compressor 15. The compressor 15 compresses an incoming flow of air 20. The compressor 15 delivers the compressed flow of air 20 to a combustor 25. The combustor 25 mixes the compressed flow of air 20 with a compressed flow of fuel 30 and ignites the mixture to create a flow of combustion gases 35. Although only a single combustor 25 is shown, the gas turbine engine 10 may include any number of combustors 25. The flow of combustion gases 35 is in turn delivered to a turbine 40. The flow of combustion gases 35 drives the turbine 40 so as to produce mechanical work. The mechanical work produced in the turbine 40 drives the compressor 15 via a shaft 45 and an external load 50 such as an electrical generator and the like.
The gas turbine engine 10 may use natural gas, various types of syngas, and/or other types of fuels. The gas turbine engine 10 may be any one of a number of different gas turbine engines offered by General Electric Company of Schenectady, New York, including, but not limited to, those such as a 7 or a 9 series heavy duty gas turbine engine and the like. The gas turbine engine 10 may have different configurations and may use other types of components. Other types of gas turbine engines also may be used herein. Multiple gas turbine engines, other types of turbines, and other types of power generation equipment also may be used herein together.
A steam or vapor turbine may also be used herein in addition to or in lieu of the gas turbine engine. The steam/vapor turbine may be fed by any vapor generator (boiler, heat exchanger, or any suitable device for this purpose). The turbine may use any liquid in a vapor state, but is not restricted thereto. Any liquid-vapor mixtures, gases, or liquids are similarly applicable. Other types of steam/vapor turbine engines also may be used herein. Multiple steam/vapor turbine engines, other types of turbines, and other types of power generation equipment also may be used herein together. In some instances, a heating device may replace the compressor 15 and the combustor 25.
FIGS. 2 and 3 depict a snubber 100 disposed between a first blade 102 and a second blade 104 in a gas turbine engine. The second blade 104 has been omitted in FIG. 3 for clarity. The snubber 100 may be disposed between blades in a compressor or turbine. The snubber 100 may be referred to as a part span connector. The snubber 100 may be attached to the pressure side 106 of the first blade 102 and the suction side 108 of the second blade 104. In some instances, the snubber 100 may be attached to the pressure side 106 of the first blade 102 and/or the suction side 108 of the second blade 104 by fillets 109. The snubber 100 may include a leading edge 111 and a trailing edge 113. In some instances, the snubber 100 may be an airfoil or the like. The snubber 100 may be any size, shape, or configuration.
A number of streamlines 110 are depicted in FIGS. 2 and 3. The streamlines 110 represent streamlines in a not disturbed flow field (i.e., streamlines between the first blade 102 and the second blade 104 if the snubber 100 was omitted). In order to avoid or minimize aerodynamic loss amplifiers associated with the inclusion of the snubber 100, an incidence angle between the streamlines 110 in the not disturbed flow field may be minimized by varying an inclination angle (γ) of a chord line 112 of the snubber 100 from the pressure side 106 of the first blade 102 to the suction side 108 of the second blade 104. That is, the inclination angle of chord line 112 may be varied between the pressure side 106 of the first blade 102 and the suction side 108 of the second blade 104. The incidence angle includes a region about the fillets 109.
For example, γss depicts the inclination angle of the snubber 100 at the suction side 108 of the second blade 104, and yps depicts the inclination angle of the snubber 100 at the pressure side 106 of the first blade 102. γk depicts the inclination angle of the snubber 100 at the center of the snubber 100 and/or any intermediate position between the pressure 106 side of the first blade 102 and suction 108 side of the second blade 104 . γss, γps, and/or γk may be the same or may vary depending on the respective local streamlines 110. In this manner, the inclination angle of the chord line 112 may vary at any point across the width of the snubber 100 in order to minimize the incidence angle between the chord line 112 and the streamlines 110 across the width of the snubber 100.
In some instances, the inclination angle of chord line 112 may be varied such that the incidence angle may be less than about 20 degrees along the span of the snubber 100. In other instances, the incidence angle may be about 15 degrees. When the chord line 112 is curved, the inclination angle may be calculated between a slope of a local streamline 100 and a relevant local slope of the chord line 112.
FIG. 4 is a three dimensional flow vector and projection to the meridional plane. In FIG. 4:

γ3D: yaw angle 3D = arc sin(Cr/W)
γ_m: yaw angle in the meridional x-r-plane = atan(Cr/Cx)
Cx: axial velocity
Cr: radial velocity
Wu: circumferential velocity component in relative frame of rotating blade
W: velocity vector in relative frame of rotating blade

FIG. 5 depicts a cross section of the snubber 100. In FIG. 5, S is the curve length along the boundary of the snubber's cross section starting at the leading edge 111 (e.g., minimum x-coordinate). In this manner, the leading edge 111 is the minimum x-coordinate and the trailing edge 113 is the maximum x-coordinate. Δγ_i is the delta of the flow yaw angle and the snubber surface inclination at any selected position "i."
In some instances, a deviation of a local chord line 112 to a local radial flow angle of a local streamline 110 may be equal to or less than about 20 degrees for all positions (i) along the snubber surface S. In other instances, a deviation of a local surface S of the snubber to a local radial flow angle of a local streamline 110 may be equal to or less than about 15 degrees for all positions (i) along a first 20% of the snubber surface S from the leading edge 111. In addition, a deviation of a local surface of the snubber to a local radial flow angle of a local streamline 110 may be equal to or less than about 10 degrees for all positions (i) along a remaining 80% of the snubber surface S.
The pitch-wise flow aligned snubber/winglet design disclosed herein achieves minimum flow incidence and allows 20-60% loss reduction compared to typical prior art designs. Customers expect safe and endurable machine operation with maximum achievable performance (power output) for a given turbine size. The size of a turbine is often characterized by exit area of rotating blade of the last turbine stage. Based on the blade design (and especially for very long blades), part-span-connectors (snubbers) are commonly use. The flow aligned part-span-connector (snubber) design disclosed herein reduces the related performance losses for stiff snubbers (mainly used for mechanical stiffening) but is also applicable for winglet designs targeting to introduce additional damping on any blade movement/vibration. This application can be applied to new designs and/or to retrofit previous geometries. The mentioned performance improvement is not restricted to turbine blades but also applies to compressor blades and any devices of similar intent.
It should be apparent that the foregoing relates only to certain embodiments of the present application and the resultant patent. Numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof. Although embodiments have been described in language specific to structural features and/or methodological acts, it is to be understood that the disclosure is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as illustrative forms of implementing the embodiments. For completeness, various aspects of the invention are set out in the following numbered clauses:

1. A system, comprising:
- a first blade;
- a second blade; and
- a snubber disposed between a pressure side of the first blade and a suction side of the second blade,
- wherein an inclination angle of a chord line of the snubber varies from the pressure side of the first blade to the suction side of the second blade to minimize an incidence angle between a plurality of streamlines in a not disturbed flow field and the inclination angle of the chord line.
2. The system of clause 1, wherein the incidence angle is less than about 20 degrees.
3. The system of clause 2, wherein the incidence angle is about 15 degrees.
4. The system of clause 1, wherein a deviation of a local chord line to a local radial flow angle of a local streamline of the plurality of streamlines is equal to or less than about 20 degrees for all positions (i) along a snubber surface.
5. The system of clause 1, wherein a deviation of a local surface of the snubber to a local radial flow angle of a local streamline of the plurality of streamlines is equal to or less than about 15 degrees for all positions (i) along a first 20% of a snubber surface from a leading edge.
6. The system of clause 5, wherein a deviation of a local surface of the snubber to a local radial flow angle of a local streamline of the plurality of streamlines is equal to or less than about 10 degrees for all positions (i) along a remaining 80% of the snubber surface.
7. The system of clause 1, wherein the snubber is attached to the first blade and the second blade by fillets, wherein the incidence angle includes a region about fillets.
8. The system of clause 1, wherein when the chord line is curved, the inclination angle is calculated between a slope of a local streamline and local slope of the chord line.
9. A snubber disposed between a pressure side of a first blade and a suction side of a second blade, the snubber comprising:
- a leading edge;
- a trailing edge; and
- a chord line,
- wherein an inclination angle of the chord line varies from the pressure side of the first blade to the suction side of the second blade to minimize an incidence angle between a plurality of streamlines in a not disturbed flow field and the inclination angle of the chord line.
10. The snubber of clause 9, wherein the incidence angle is less than about 20 degrees.
11. The snubber of clause 10, wherein the incidence angle is about 15 degrees.
12. The snubber of clause 9, wherein a deviation of a local chord line to a local radial flow angle of a local streamline of the plurality of streamlines is equal to or less than about 20 degrees for all positions (i) along a snubber surface.
13. The snubber of clause 9, wherein a deviation of a local surface of the snubber to a local radial flow angle of a local streamline of the plurality of streamlines is equal to or less than about 15 degrees for all positions (i) along a first 20% of a snubber surface from a leading edge.
14. The snubber of clause 13, wherein a deviation of a local surface of the snubber to a local radial flow angle of a local streamline of the plurality of streamlines is equal to or less than about 10 degrees for all positions (i) along a remaining 80% of the snubber surface.
15. The snubber of clause 9, wherein the snubber is attached to the first blade and the second blade by fillets, wherein the incidence angle includes a region about fillets.
16. The snubber of clause 9, wherein when the chord line is curved, the inclination angle is calculated between a slope of a local streamline and local slope of the chord line.
17. A snubber disposed between a pressure side of a first blade and a suction side of a second blade, the snubber comprising:
- a leading edge;
- a trailing edge; and
- a chord line,
- wherein a deviation of a local surface of the snubber to a local radial flow angle of a local streamline of a plurality of streamlines in a not disturbed flow field is equal to or less than about 15 degrees for all positions (i) along a first 20% of a snubber surface from a leading edge.
18. The snubber of clause 17, wherein a deviation of a local surface of the snubber to a local radial flow angle of a local streamline of the plurality of streamlines is equal to or less than about 10 degrees for all positions (i) along a remaining 80% of the snubber surface.

Claims

A snubber (100) disposed between a pressure side (106) of a first blade (102) and a suction side (108) of a second blade (104), the snubber (100) comprising:
a leading edge (111);

a trailing edge (113); and

a chord line (112),

wherein an inclination angle of the chord line (112) varies from the pressure side (106) of the first blade (102) to the suction side (108) of the second blade (104) to minimize an incidence angle between a plurality of streamlines (110) in a not disturbed flow field and the inclination angle of the chord line (112).
The snubber of claim 1, wherein the incidence angle is less than about 20 degrees.
The snubber of claim 2, wherein the incidence angle is about 15 degrees.
The snubber of claim 1, wherein a deviation of a local chord line to a local radial flow angle of a local streamline of the plurality of streamlines is equal to or less than about 20 degrees for all positions (i) along a snubber surface.
The snubber of claim 1, wherein a deviation of a local surface of the snubber to a local radial flow angle of a local streamline of the plurality of streamlines is equal to or less than about 15 degrees for all positions (i) along a first 20% of a snubber surface from a leading edge.
The snubber of claim 5, wherein a deviation of a local surface of the snubber to a local radial flow angle of a local streamline of the plurality of streamlines is equal to or less than about 10 degrees for all positions (i) along a remaining 80% of the snubber surface.
The snubber of claim 1, wherein the snubber (100) is attached to the first blade (102) and the second blade (104) by fillets (109), wherein the incidence angle includes a region about fillets.
The snubber of claim 1, wherein when the chord line (112) is curved, the inclination angle is calculated between a slope of a local streamline and local slope of the chord line.
A snubber (100) disposed between a pressure side (106) of a first blade (102) and a suction side (108) of a second blade (104), the snubber (100) comprising:
a leading edge (111);

a trailing edge (113); and

a chord line (112),

wherein a deviation of a local surface of the snubber to a local radial flow angle of a local streamline of a plurality of streamlines (110) in a not disturbed flow field is equal to or less than about 15 degrees for all positions (i) along a first 20% of a snubber surface from a leading edge.
The snubber of claim 9, wherein a deviation of a local surface of the snubber to a local radial flow angle of a local streamline of the plurality of streamlines is equal to or less than about 10 degrees for all positions (i) along a remaining 80% of the snubber surface.