|Publication number||US20050036890 A1|
|Application number||US 10/639,473|
|Publication date||Feb 17, 2005|
|Filing date||Aug 13, 2003|
|Priority date||Aug 13, 2003|
|Also published as||CN1580496A, CN100406680C, EP1507064A2, EP1507064A3, US6857853|
|Publication number||10639473, 639473, US 2005/0036890 A1, US 2005/036890 A1, US 20050036890 A1, US 20050036890A1, US 2005036890 A1, US 2005036890A1, US-A1-20050036890, US-A1-2005036890, US2005/0036890A1, US2005/036890A1, US20050036890 A1, US20050036890A1, US2005036890 A1, US2005036890A1|
|Inventors||Steven Tomberg, Marvin Neeley|
|Original Assignee||General Electric Company|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (6), Referenced by (4), Classifications (14), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present invention relates to a variable conical fillet between an airfoil tip of a turbine bucket and a bucket tip shroud and particularly relates to a conical fillet shaped and sized to improve part life, performance and manufacturing of the turbine bucket
Turbine buckets generally comprise an airfoil, a platform, shank and dovetail along a radial inner end portion of the bucket and often a tip shroud at the tip of the airfoil in mechanical engagement with tip shrouds of adjacent buckets. The tip shroud and airfoil of a conventional turbine bucket are typically provided with a simple fillet shape of a predetermined size and generally of a constant radius about the intersection of the tip shroud and the airfoil tip. That is, a generally uniform radius was applied to the shroud fillet as the fillet was applied about the intersection of the airfoil tip and tip shroud. The fillet lowered the stress concentration between the airfoil and tip shroud.
While the stresses were reduced by use of constant radius fillets, it was discovered that high stresses in the fillet region were localized at various locations or points in and about the fillet between the airfoil and tip shroud and that such localized stresses lead to significant decreases in bucket life. Thus, while stresses were reduced by the application of fillets of constant radius, the localized high stresses in critical areas were still present. These stresses reduced the creep life of the tip shroud which can lead to premature failure of the bucket. It will also be appreciated that the failure of a single bucket causes the turbine to be taken offline for repair. This is a time-consuming and costly outage, causing the customer as well as the turbine producer to incur higher costs due to unproductivity, labor, part repair, outage time and replacement. Consequently, there has developed a need for a customization of the fillet between the tip of the airfoil and the tip shroud of a bucket to provide a more uniform distribution of stress taking into account the high localized stresses about the fillet as well as reducing the mass of the fillet thereby to extend the creep life of the tip shroud.
In accordance with the preferred embodiment of the present invention, there is provided a variable conical fillet between the airfoil tip and the tip shroud which minimizes creep as well as the mass of the fillet by varying the fillet size and configuration as a function of the high localized stresses about the intersection of the airfoil tip and tip shroud. The variable conical fillet profile is a function of an offset 1, an offset 2, Rho and discrete X, Y apex locations about the intersection of the airfoil and tip shroud. Offset 1 is a distance normal to the airfoil surface at each apex location projected along the airfoil surface and offset 2 is a distance extending normal to the tip shroud undersurface at each apex location projected along the tip shroud undersurface. Normals projected onto the airfoil surface and tip shroud undersurface from the intersection of offsets 1 and 2 define edge points which, upon connection about the respective tip shroud and airfoil, form the edges of the fillet. The offsets are determined by finite element stress analysis to minimize stress. Rho is a shape parameter defining the shape of the fillet at each apex location. These factors are utilized at various X and Y locations about the intersection of the airfoil tip and tip shroud, enabling the fillet to take on a variably configured profile at each location to evenly distribute the stress about the fillet while simultaneously minimizing the mass added to the bucket fillet. The shape of the fillet is thus biased toward the tip shroud or to the airfoil as determined by the stress analysis at the particular location under consideration whereby the high local stresses are accommodated and the mass of the fillet is minimized.
Particularly, the optimized conical tip shroud fillet hereof is defined, in a preferred embodiment, by 15 locations or points about the intersection of the tip shroud and airfoil tip with each location having three parameters, i.e., offset 1, offset 2 and Rho, which define the extent and shape of the fillet at that location. By varying the fillet in accordance with these parameters about the intersection, tip shroud creep life can be maximized while minimizing the mass of the bucket at the fillet. Particular locations and parameters are set forth in Table I below for the tip shroud/airfoil fillet of a second stage of a three stage turbine having 92 buckets. It will be appreciated that the number of locations at which these parameters are applied may vary while maintaining the shape of the fillet within a robust envelope sufficient to achieve the objectives of maximizing creep life and reducing bucket mass.
In a preferred embodiment according to the present invention, there is provided a turbine bucket having an airfoil, an airfoil tip, a tip shroud, and a fillet about an intersection of said airfoil tip and the tip shroud, the fillet having a fillet profile variable about the intersection as a function of localized stresses about the intersection.
In a further preferred embodiment according to the present invention, there is provided a turbine bucket having an airfoil, an airfoil tip, a tip shroud and a fillet about an intersection of the airfoil tip and the tip shroud, the fillet having a nominal profile substantially in accordance with coordinate values of X and Y, offset 1, offset 2 and Rho set forth in Table 1 wherein X and Y define in inches discrete apex locations about the intersection of the airfoil tip and tip shroud, offset 1 and offset 2 are distances in inches perpendicular to the airfoil surface and tip shroud undersurface, respectively, at each respective X, Y location projected along the airfoil surface and tip shroud undersurface and which offsets intersect with one another such that normal projections from the intersection of the offsets onto the tip shroud undersurface and airfoil surface, respectively, define edge points which, upon connection about the respective tip shroud and airfoil, define edges of the fillet, and Rho is a non-dimensional shape parameter ratio of
at each apex location, wherein D1 is a distance between a midpoint along a chord between the fillet edge points and a shoulder point on a surface of the fillet and D2 is a distance between the shoulder point and the apex location, the fillet edge points on the tip shroud and the airfoil at each X, Y location being connected by a smooth continuing arc passing through the shoulder point in accordance with the shape parameter Rho to define a profile section at each apex location, the profile sections at each apex location being joined smoothly with one another to form the nominal fillet profile.
Referring now to the drawings, particularly to
Each bucket 20 of the second stage is provided with a platform 30, a shank 32 and a substantially or near axial entry dovetail 34 for connection with a complementary-shaped mating dovetail, not shown, on the rotor wheel 21. It will also be appreciated that each bucket 20 has a bucket airfoil 36, for example, as illustrated in
Referring now to
In a preferred embodiment of the present invention, the tip shroud fillet 40 is defined by fifteen points P1-P15 (
Particularly, and referring to
The configuration of the conical fillet 40 is dependent at each X, Y location upon three parameters: offset 1, offset 2 and Rho. Offset 1 as illustrated in
Rho is a non-dimensional shape parameter ratio at each location P. Rho is the ratio of
wherein, as illustrated in
The X, Y coordinate values, as well as the parameters offset 1 (O1), offset 2 (02), D1, D2 and Rho are given in Table I as follows:
TABLE I Offset 2 Offset 1 from the Z′ From the tip Point X Y Z Centerline Airfloil Shroud A B D1 D2 Rho P1 −0.793 1.272 10.669 34.769 0.070 0.070 0.085 0.083 0.031 0.031 0.50 P2 −0.548 1.101 10.725 34.825 0.150 0.100 0.191 0.133 0.063 0.063 0.50 P3 −0.349 0.907 10.769 34.869 0.200 0.175 0.238 0.220 0.088 0.088 0.50 P4 −0.089 0.527 10.831 34.931 0.310 0.325 0.368 0.371 0.113 0.169 0.40 P5 0.135 0.157 10.882 34.982 0.575 0.375 0.640 0.465 0.170 0.255 0.40 P6 0.334 −0.178 10.924 35.024 0.475 0.340 0.522 0.411 0.160 0.195 0.45 P7 0.459 −0.387 10.949 35.049 0.325 0.285 0.357 0.331 0.130 0.130 0.50 P8 0.546 −0.522 10.965 35.065 0.225 0.230 0.243 0.250 0.095 0.095 0.50 P9 0.717 −0.721 10.998 35.098 0.070 0.070 0.068 0.066 0.025 0.025 0.50 P10 −0.595 1.346 10.705 34.805 0.400 0.275 0.370 0.225 0.090 0.110 0.45 P11 −0.312 1.179 10.769 34.869 0.600 0.450 0.527 0.349 0.115 0.170 0.40 P12 −0.074 0.875 10.828 34.928 0.500 0.400 0.448 0.330 0.103 0.155 0.40 P13 0.140 0.541 10.880 34.980 0.250 0.300 0.213 0.267 0.070 0.085 0.45 P14 0.345 0.164 10.927 35.027 0.150 0.175 0.122 0.157 0.045 0.045 0.50 P15 0.646 −0.466 10.990 35.090 0.100 0.100 0.085 0.091 0.028 0.028 0.50
The values of A and B in Table I are the distances in inches of the edge points to the intersection of offsets O1 and O2. The Z value in Table I is the height of the airfoil and Z′ is the distance between the axis of rotation and the airfoil tip. The location of the radial Z axis extending perpendicular to the X-Y plane, is determined relative to predetermined reference surfaces in the shank 34 of the bucket. With specific reference to
It will also be appreciated that the values determining the surface configuration of the fillet 40 given in Table I are for a nominal fillet. Thus, ±typical manufacturing tolerances, i.e., ±values, including any coating thicknesses, are additive to the fillet surface configuration 64 as determined from the Table I. Accordingly, a distance of ±0.160 inches in a direction normal to any surface location along the fillet 40 defines a fillet profile envelope for this particular fillet 40, i.e., a range of variation between an ideal configuration of the fillet as given by the Table I above and a range of variations in the fillet configuration at nominal cold or room temperature. The fillet configuration is robust to this range of variation without impairment of mechanical and aerodynamic functions, while retaining the desired even distribution of stresses about the fillet region.
Further, Table I defines the fillet profile about the intersection of the airfoil tip and the tip shroud. Any number of X, Y locations may be used to define this profile. Thus, the profiles defined by the values of Table I embrace fillet profiles intermediate the given X, Y locations as well as profiles defined using fewer X, Y locations when the profiles defined by Table I are connected by smooth curves extending between the given locations of Table I.
Also, it will be appreciated that the fillet disclosed in the above table may be scaled up or scaled down geometrically for use in other similar fillet designs in other turbines. For example, the offsets O1 and O2, as well as the X and Y coordinate values may be scaled upwardly or downwardly by multiplying or dividing those values by a constant number to produce a scaled-up or scaled-down version of the fillet 40. The Rho value would not be multiplied or divided by the constant number since it is a non-dimensional value.
It will also be appreciated that the fillet may be defined in relation to the airfoil since the Cartesian coordinate system used to define the fillet and to define the airfoil identified above are common. Thus, the fillet may be defined in relation to the airfoil shape of each second stage bucket airfoil 36 at 92% span just radially inwardly of the fillet. A Cartesian coordinate system of X, Y and Z values wherein the X, Y coordinate values are given in Table II below define the profile of the bucket airfoil at 92% span. The Z coordinate value at 92% span is preferably 10.410 inches, the Z=0 value being preferably at 24.1 inches along the radial Z axis from the rotor centerline. The coordinate values for the X and Y coordinates are set forth in inches in Table II although other units of dimensions may be used when the values are appropriately converted. The Cartesian coordinate system has orthogonally-related X, Y and Z axes and the X axis lies parallel to the turbine rotor centerline, i.e., the rotary axis and a positive X coordinate value is axial toward the aft, i.e., exhaust end of the turbine. The positive Y coordinate value looking aft extends tangentially in the direction of rotation of the rotor and the positive Z coordinate value is radially outwardly toward the bucket tip.
By connecting the X and Y values with smooth continuing arcs, the profile section 39 at 92% span is fixed. By using a common Z-axis origin for the X, Y coordinate systems for the fillet points and the points defining the airfoil profile at 92% span, the fillet surface configuration is defined in relation to the airfoil profile at 92% span. Other percentage spans could be used to define this relationship and the 92% span as used is exemplary only. These values represent the fillet and the airfoil profile at 92% span are at ambient, non-operating or non-hot conditions and are for an uncoated surface.
Like fillet 40, there are typical manufacturing tolerances as well as coatings which must be accounted for in the actual profile of the airfoil. Accordingly, the values for the profile at 92% span given in Table II are for a nominal airfoil. It will therefore be appreciated that ±typical manufacturing tolerances, i.e., ±values, including any coating thicknesses, are additive to the X and Y values given in Table II below. Accordingly, a distance of ±0.160 inches in a direction normal to any surface location along the airfoil profile at 92% span defines an airfoil profile envelope, i.e., a range of variation between measured points on the actual airfoil surface at nominal cold or room temperature and the ideal position of those points as given in Table II below at the same temperature. The bucket airfoil at 92% span is robust to this range of variation without impairment of mechanical and aerodynamic functions.
TABLE II X Y Z′ X Y Z′ X Y Z′ −0.815 1.203 10.410 0.308 −0.119 10.410 0.367 0.129 10.410 −0.812 1.158 10.410 0.331 −0.157 10.410 0.346 0.168 10.410 −0.783 1.126 10.410 0.354 −0.196 10.410 0.325 0.208 10.410 −0.740 1.112 10.410 0.377 −0.234 10.410 0.304 0.247 10.410 −0.697 1.100 10.410 0.400 −0.273 10.410 0.282 0.287 10.410 −0.655 1.086 10.410 0.424 −0.311 10.410 0.260 0.326 10.410 −0.613 1.070 10.410 0.447 −0.349 10.410 0.239 0.365 10.410 −0.573 1.050 10.410 0.470 −0.387 10.410 0.216 0.404 10.410 −0.534 1.028 10.410 0.494 −0.425 10.410 0.194 0.442 10.410 −0.497 1.003 10.410 0.517 −0.463 10.410 0.171 0.481 10.410 −0.462 0.975 10.410 0.541 −0.501 10.410 0.148 0.519 10.410 −0.428 0.946 10.410 0.565 −0.539 10.410 0.125 0.558 10.410 −0.396 0.915 10.410 0.589 −0.577 10.410 0.101 0.596 10.410 −0.365 0.883 10.410 0.613 −0.614 10.410 0.077 0.633 10.410 −0.335 0.849 10.410 0.637 −0.652 10.410 0.053 0.671 10.410 −0.305 0.815 10.410 0.661 −0.690 10.410 0.028 0.708 10.410 −0.277 0.781 10.410 0.685 −0.728 10.410 0.003 0.745 10.410 −0.249 0.746 10.410 0.715 −0.761 10.410 −0.022 0.782 10.410 −0.222 0.710 10.410 0.757 −0.757 10.410 −0.048 0.819 10.410 −0.195 0.674 10.410 0.774 −0.718 10.410 −0.075 0.855 10.410 −0.169 0.638 10.410 0.758 −0.676 10.410 −0.102 0.891 10.410 −0.143 0.602 10.410 0.739 −0.636 10.410 −0.129 0.926 10.410 −0.118 0.565 10.410 0.720 −0.595 10.410 −0.157 0.961 10.410 −0.093 0.528 10.410 0.701 −0.554 10.410 −0.186 0.995 10.410 −0.068 0.490 10.410 0.683 −0.514 10.410 −0.216 1.028 10.410 −0.044 0.453 10.410 0.664 −0.473 10.410 −0.247 1.061 10.410 −0.019 0.415 10.410 0.645 −0.433 10.410 −0.278 1.092 10.410 0.005 0.377 10.410 0.626 −0.392 10.410 −0.311 1.123 10.410 0.029 0.340 10.410 0.607 −0.352 10.410 −0.345 1.152 10.410 0.052 0.302 10.410 0.587 −0.311 10.410 −0.380 1.179 10.410 0.076 0.264 10.410 0.568 −0.271 10.410 −0.417 1.204 10.410 0.099 0.226 10.410 0.548 −0.231 10.410 −0.456 1.227 10.410 0.123 0.187 10.410 0.529 −0.191 10.410 −0.496 1.247 10.410 0.146 0.149 10.410 0.509 −0.151 10.410 −0.538 1.263 10.410 0.169 0.111 10.410 0.489 −0.110 10.410 −0.581 1.276 10.410 0.193 0.073 10.410 0.469 −0.070 10.410 −0.625 1.284 10.410 0.216 0.034 10.410 0.449 −0.030 10.410 −0.669 1.286 10.410 0.239 −0.004 10.410 0.428 0.010 10.410 −0.714 1.281 10.410 0.262 −0.042 10.410 0.408 0.049 10.410 −0.756 1.266 10.410 0.285 −0.081 10.410 0.387 0.089 10.410 −0.792 1.240 10.410
Thus, by defining the airfoil profile at 92% span, the same Cartesian coordinate system as used to define the fillet 40, the relationship between the fillet and airfoil is established.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
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|Citing Patent||Filing date||Publication date||Applicant||Title|
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|International Classification||F01D11/08, F01D5/14, F01D5/16|
|Cooperative Classification||F05D2250/17, F05D2250/16, F05D2250/14, F05D2250/70, Y10S415/914, F05D2260/94, F01D5/147, F01D5/225|
|European Classification||F01D5/14C, F01D5/22B|
|Aug 13, 2003||AS||Assignment|
|Aug 18, 2008||FPAY||Fee payment|
Year of fee payment: 4
|Aug 22, 2012||FPAY||Fee payment|
Year of fee payment: 8