Patent Application
20130230408
The present application and the resultant patent relate generally to gas turbine engines and more particularly relate to a gas turbine engine with a turbine bucket having an airfoil with a contoured internal rib about a leading edge thereof so as to reduce stress therein due to thermal expansion.
Known gas turbine engines generally include rows of circumferentially spaced nozzles and buckets. A turbine bucket generally includes an airfoil having a pressure side and a suction side and extending radially upward from a platform. A hollow shank portion may extend radially downward from the platform and may include a dovetail and the like so as to secure the turbine bucket to a turbine wheel. The platform generally defines an inner boundary for the hot combustion gasses flowing through a gas path.
Various types of cooling schemes have been used to keep the components of the turbine bucket within operational ranges so as to promote component lifetime. These cooling schemes, however, may promote localized regions of temperature differentials that may lead to thermally induced strain. For example, an airfoil may have a number of internal ribs with internal cooling holes therethrough for the passage of a cooling medium. One such rib may be positioned about the leading edge of the airfoil so as to provide the cooling medium via the internal cooling holes for impingement cooling. The internal rib thus may be highly cooled by the cooling medium but connected to the relatively hot airfoil walls. Such a high temperature differential therein may cause a thermal strain to develop in the internal rib. This strain may be amplified by stress concentration factors associated with the internal cooling holes such that the stress may impact on component lifetime. Although attempts have been made to control the temperature differentials, temperature control techniques generally require additional cooling flows at the expense of engine efficiency.
There is thus a desire for an improved turbine bucket for use with a gas turbine engine. Preferably such a turbine bucket may have an airfoil that may limit the internal stresses caused by a temperature differential therein without excessive manufacturing and operating costs and without excessive cooling medium losses for efficient operation and an extended component lifetime.
The present application and the resultant patent thus provide an example of a turbine bucket. The turbine bucket may include a platform and an airfoil extending from the platform. The airfoil may include an internal rib with a number of through holes positioned along a number of hole spaces and a number of in-between spaces. The in-between spaces may include a first depth, the hole spaces may include a second depth, and wherein the first depth is less than the second depth.
The present application and the resultant patent further provide an example of a turbine bucket with a cooling medium flowing therethrough. The turbine bucket may include a platform and an airfoil extending from the platform. The airfoil may include an internal rib positioned about a leading edge thereof. The airfoil may include an internal rib with a number of through holes positioned along a number of hole spaces and a number of in-between spaces. The in-between spaces may include a first depth, the hole spaces may include a second depth, and wherein the first depth is less than the second depth.
The present application and the resultant patent further provide an example of a turbine bucket with a cooling medium flowing therethrough. The turbine bucket may include a platform and an airfoil extending from the platform. The airfoil may include an internal rib positioned about a leading edge thereof. The internal rib may include a number of through holes. The internal rib also may include a number of thick hole spaces with the through holes and a number of thin in-between spaces without the through holes.
These and other features and improvements of the present application and the resultant patent will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawings and the appended claims.
Referring now to the drawings, in which like numerals refer to like elements throughout the several views,
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, N.Y., 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.
The turbine bucket 55 may include one or more cooling circuits 95 extending therethrough for flowing a cooling medium 96 such as air from the compressor 15 or from another source. The cooling circuits 95 and the cooling medium 96 may circulate at least through portions of the airfoil 60, the shank portion 65, and the platform 70 in any order, direction, or route. Many different types of cooling circuits 95 and cooling mediums 96 may be used herein. Specifically, impingement cooling and other types of cooling techniques may be used herein. Other components and other configurations also may be used herein.
The airfoil 110 of the turbine bucket 100 may have one or more a contoured internal ribs 160 therein. Specifically, the internal rib 160 may be a leading edge rib 170 positioned about a leading edge surface 180 of the airfoil 110. Other positions also may be used herein. The internal rib 160 may have a number of through holes 190 extending therethrough. Any number of the through holes 190 may be used herein with any size, shape, or orientation. The through holes 190 may extend along on one side of the internal rib 160 and may extend therethrough in whole or in part towards the opposite side. The through holes 190 may be in communication with a number of cooling cavities 185 for a flow of a cooling medium 195 therethrough.
The internal rib 160 may be in the form of an elongated plate 210. The through holes 190 may be separated from one another along the elongated plate 210 by an in-between space 220. The in-between spaces 220 may vary in number, size, shape, and configuration. Likewise, the through holes 190 may be positioned on the plate 210 in a hole space 230. Likewise, the hole spaces 230 may vary in number, size, shape, and configuration. The in-between spaces 220 may have a first depth 240 while the hole spaces 230 may have a second depth 250. The first depths 240 and the second depths 250 may vary along the length of the elongated plates 210. The first depth 240 is less than the second depth 250, i.e., the in-between space 220 without the through holes 190 has less material along the elongated plate 210 than the hole space 230 with the through holes 190. Other components and other configurations may be used herein.
By having the in-between spaces 220 without the through holes 190 being thinner or having less material than the hole spaces 230 with the through holes 190, the contoured internal rib 160 may have increased strain in the in-between spaces 220 and hence reduced strain in the hole spaces 230. Reducing the strain in the hole spaces 230 may reduce the peak stresses about the through holes 190 so as to improve component lifetime. Improved component lifetime may reduce overall maintenance costs without reducing overall efficiency through requiring an increased cooling flow. The strain caused by thermal gradients thus may be reduced. Moreover, the in-between spaces 220 generally do not have a stress concentration factor (“KT”) associated with the through holes 190. Specifically, the strain may be concentrated in the in-between spaces 220 by reducing the thickness and stiffness therein.
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.
