Patent Application
20090097979
The exemplary embodiments relate generally to gas turbine engine components and more specifically to rotor blades having tip shrouds.
Gas turbine engines typically include a compressor, a combustor, and at least one turbine. The compressor may compress air, which may be mixed with fuel and channeled to the combustor. The mixture may then be ignited for generating hot combustion gases, and the combustion gases may be channeled to the turbine. The turbine may extract energy from the combustion gases for powering the compressor, as well as producing useful work to propel an aircraft in flight or to power a load, such as an electrical generator.
The turbine may include a rotor assembly and a stator assembly. The rotor assembly may include a plurality of rotor blades extending radially outward from a disk. Each rotor blade may include an airfoil, which may extend between a platform and a tip. Each rotor blade may also include a root that may extend below the platform and be received in a corresponding slot in the disk. Alternatively, the disk may be a blisk or bladed disk, which may alleviate the need for a root and the airfoil may extend directly from the disk. A combustion gas flowpath through the rotor assembly may be bound radially inward by the rotor blade platforms, and radially outward by a plurality of tip shrouds, wherein each tip shroud may include at least one seal tooth.
Typically, the at least one seal tooth may cooperate with a radially adjacent honeycomb to seal the flowpath. The at least one seal tooth may have at least one portion that is larger in cross section than the rest of the seal tooth. During forward motion of the blade relative to the honeycomb, this larger portion may engage with the honeycomb prior to the remainder of the seal tooth, and cut a wear track into the honeycomb. This may require the seal tooth to be non-axisymmetric.
Rotor blades can be made from a variety of materials. Some of these materials may allow the non-axisymmetric seal tooth to be cast into the final shape with little if any necessary machining. Other lower weight, lower cost or longer life materials, however, do not have the capability to be cast to a final shape and need to be machined. Machining of non-axisymmetric features with these materials can be time consuming and cause wasted material leading to longer production cycles.
One exemplary embodiment may be directed to a rotor blade having a tip shroud having at least one seal tooth disposed at an angle relative to an engine centerline when in an assembled condition. In another exemplary embodiment, the seal tooth may be disposed at an angle relative to the leading and/or trailing edge.
In operation, air flows through the fan assembly 12 and compressed air is supplied to the high pressure compressor 16 through the booster 14. The highly compressed air is delivered to the combustor 18, where it is mixed with a fuel and ignited to generate combustion gases. The combustion gases are channeled from the combustor 18 to drive the turbines 20 and 22. The turbine 22 drives the fan assembly 12 and booster 14 by way of shaft 32. The turbine 20 drives the compressor 16 by way of shaft 34.
Rotor blades 50 each include a leading edge 52, a trailing edge 54, and an airfoil 56 extending therebetween. Each airfoil 56 includes a suction side 58 and a circumferentially opposite pressure side 60. Suction and pressure sides 58 and 60, respectively, extend between axially spaced apart leading and trailing edges 52 and 54, respectively, and extend in radial span between a rotor blade tip shroud 62 and a rotor blade platform 64. A blade chord is measured between rotor blade leading and trailing edges 52 and 54, respectively. The radially outer surfaces 66 of the platforms 64 define a radially inner flowpath surface of rotor assembly 36 and the radially inner surfaces 68 of the blade tip shrouds 62 define a radially outer flowpath surface of rotor assembly 36.
As shown in
The rotor blades and/or tip shrouds may be made of any material known in the art. In one exemplary embodiment, the blades and/or tip shrouds may be made from a nickel or cobalt-based superalloy. In another exemplary embodiment, the blades and/or tip shrouds may be made from a titanium alloy, such as, but not limited to titanium aluminide. In addition, the blade, tip shroud and/or seal teeth may be coated with any coating known in the art. In one exemplary embodiment, the blade and/or tip shroud may be coated with an environmental coating. The seal teeth may be coated with an abrasive coating, such as, but not limited to, aluminum oxide.
The blades and/or tip shrouds may be formed to their final shape or they may be formed and then machined to their final shape. In the event that the outer surface of the tip shroud needs to be machined, the use of an angled seal tooth may facilitate an axisymmetric form for ease of machining, while allowing a feature to ‘cut’ the honeycomb. Typically, the tip shrouds may be machined on an arcuate path with the axis of rotation being the engine centerline. When the outer surface of the tip shroud is generally cylindrical (i.e. substantially parallel to the engine centerline in cross-section) then the axis of rotation of the arcuate path to create the outer surface may be the engine centerline rotated sufficiently to achieve the offset between adjacent seal teeth. If the outer surface is generally conical, the axis of rotation may need to be offset as well as angled relative to engine centerline. This may be required to ensure that the thickness at the edges of the tip shroud do not become undesirably thin or thick.
While this application has described various specific exemplary embodiments, those skilled in the art will recognize that those exemplary embodiments can be practiced with modification within the spirit and scope of the claims.
