Patent Application
20130287556
The subject matter disclosed herein relates to turbine engines and, more particularly, to rotor assemblies for turbine engines.
Turbine blades or buckets are often designed for installation on a turbine rotor wheel in a circumferential direction. The buckets are typically attached to the turbine wheel using external circumferential dovetails, with a receiving dovetail in a circumferential groove or slot on the wheel periphery and a complimentary dovetail in the base or root of the bucket. In order to load these buckets onto the wheel, a notch which locally removes the receiving dovetail portion is cut on the periphery of the wheel, leaving a generally rectangular opening in the slot on the rotor wheel. Each bucket is then initially placed in the notch opening and then moved circumferentially around the wheel. The opening in the circumferential groove causes a discontinuity in the relatively uniform rotor wheel design. Thus, the notch opening can be a source of stress concentration in the rotor wheel and can lead to reduced rotor life.
According to one aspect of the invention, a turbine assembly includes a rotor wheel and a circumferential slot formed in the rotor wheel, the circumferential slot including a uniform cross-section shape for a circumference of the rotor wheel. The assembly also includes a first ring member positioned in the circumferential slot, the first ring member being configured to prevent radial movement of a dovetail attachment when positioned in the circumferential slot, wherein the dovetail attachment is part of a turbine blade.
According to another aspect of the invention, a turbine assembly includes a rotor wheel, a circumferential slot formed in the rotor wheel configured to receive blades, and first and second ring members positioned in the circumferential slot, the first and second ring members located on each side of a portion of a blade to prevent radial movement of the blade when positioned in the circumferential slot.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
In an embodiment, when the blade 104 is installed in the rotor wheel 102, the first ring member 110 is positioned between a first side wall 114 of the circumferential slot 108 and a first side 116 of the dovetail attachment 106. Similarly, the second ring member 112 is positioned between a second side wall 118 of the circumferential slot 108 and a second side 120 of the dovetail attachment 106 when the blade 104 is located in the circumferential slot 108. In an embodiment, the first ring member 110 and second ring member 112 conform to the first side wall 114 and second side wall 118, respectively, of the circumferential slot 108. As depicted, the circumferential slot 108 has a substantially uniform cross section shape for the entire circumference of the rotor wheel 102. The cross section shape of the circumferential slot 108 may be any suitable shape to receive one or more blades and one or more ring members. The depicted embodiment of the circumferential slot 108 has a substantially dovetail shape that is larger than the dovetail attachment 106.
In an embodiment the sidewalls on the dovetail and the rotor wheel 102 may be of different inclination or profile, where the ring member sidewalls having complementary profiles to the mating wheel or dovetail attachment profile.
The substantially uniform cross section shape of the circumferential slot 108 reduces stress concentration points in the relatively uniform wheel that may occur in other rotor wheel embodiments. Specifically, the opening 122 and retaining characteristics provided by the first ring member 110 and second ring member 112 enable blade retention in the substantially uniform circumferential slot 108. In an embodiment, the first ring member 110 and second ring member 112 are not attached, fixed or coupled to the rotor wheel 102. In other embodiments, one or more of the ring members 110, 112 are attached to the rotor wheel. In addition, the first ring member 110 and second ring member 112 may be each comprised of or more ring members that form the rings 110 and 112. In one exemplary embodiment, the first ring member 110 comprises a plurality of member portions, such as member portion 124. Exemplary ring members may be formed from 2, 3, 5, 50 up to any suitable number of ring portions as determined application specific criteria. In another embodiment, each of the ring members 110 and 112 are formed from a single ring member. Further, embodiments of the first ring member 110 and second ring member 112 may be identical in shape or geometry or may be shaped differently to meet desired blade loading patterns depending upon the application. An embodiment reduces stress concentration associated with blade load slots on rotor wheels and facilitates use of alternative lower cost materials, thus reducing costs.
The dovetail circumferential slot 108 is typically termed a “circumferential entry” slot in that the dovetail attachment 106 of the blade 104 is inserted into the slot in a generally circumferential direction. The features described herein are generally applicable to any airfoil and disk interface. The structure depicted in
As used herein, “downstream” and “upstream” are terms that indicate a direction relative to the flow of working fluid through the turbine. As such, the term “downstream” refers to a direction that generally corresponds to the direction of the flow of working fluid, and the term “upstream” generally refers to the direction that is opposite of the direction of flow of working fluid. The term “radial” refers to movement or position perpendicular to an axis or center line. It may be useful to describe parts that are at differing radial positions with regard to an axis. In this case, if a first component resides closer to the axis than a second component, it may be stated herein that the first component is “radially inward” of the second component. If, on the other hand, the first component resides further from the axis than the second component, it can be stated herein that the first component is “radially outward” or “outboard” of the second component. The term “axial” refers to movement or position parallel to an axis. Finally, the term “circumferential” refers to movement or position around an axis. Although the following discussion primarily focuses on gas turbines, the concepts discussed are not limited to gas turbines and may apply to any suitable machinery, including steam turbines, oil and gas machinery and aviation engines. Accordingly, the discussion herein is directed to gas turbine embodiments, but may apply to other turbine systems.
Referring now to
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
