Turbine bucket having a radial cooling hole

A turbine bucket is provided and includes a shank interconnectable with a rotor and formed to accommodate coolant therein and an airfoil blade coupled to a radially outward portion of the shank and including a body formed to define a substantially radially extending cooling hole therein, which is disposed to be solely receptive of the coolant accommodated within the shank for removing heat from the body, the cooling hole being further defined as having a substantially non-circular cross-sectional shape at a predefined radial position of the body.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to a turbine bucket having a radial cooling hole.

In turbine engines, such as gas turbine engines or steam turbine engines, fluids at relatively high temperatures contact blades that are configured to extract mechanical energy from the fluids to thereby facilitate a production of power and/or electricity. While this process may be highly efficient for a given period, over an extended time, the high temperature fluids tend to cause damage that can degrade performance and increase operating costs.

Accordingly, it is often necessary and advisable to cool the blades in order to at least prevent or delay premature failures. This can be accomplished by delivering relatively cool compressed air to the blades to be cooled. In many traditional gas turbines, in particular, this compressed air enters the bottom of each of the blades to be cooled and flows through one or more round machined passages in the radial direction to cool the blade through a combination of convection and conduction.

In these traditional gas turbines, as the temperature of the fluids increases, it becomes necessary to increase the amount of cooling flow through the blades. This increased flow can be accomplished by an increase in a size of the cooling holes. However, as the cooling holes increase in size, the wall thickness of each hole to the external surface of the blade decreases and eventually challenging manufacturability and structural integrity of the blade.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, a turbine bucket is provided and includes a shank interconnectable with a rotor and formed to accommodate coolant therein and an airfoil blade coupled to a radially outward portion of the shank and including a body formed to define a substantially radially extending cooling hole therein, which is disposed to be solely receptive of the coolant accommodated within the shank for removing heat from the body, the cooling hole being further defined as having a substantially non-circular cross-sectional shape at a predefined radial position of the body.

According to another aspect of the invention, a turbine bucket is provided and includes a shank interconnectable with a rotor and formed to accommodate coolant therein and an airfoil blade coupled to a radially outward portion of the shank and including a body formed to define a plurality of substantially radially extending cooling holes therein, which are each disposed to be solely and independently receptive of the coolant accommodated within the shank for removing heat from the body, each cooling hole in a subset of the plurality of cooling holes being further defined as having a substantially non-circular cross-sectional shape at a predefined radial position of the body.

According to yet another aspect of the invention, a turbine bucket is provided and includes a shank interconnectable with a rotor and formed to accommodate coolant therein and an airfoil blade coupled to a radially outward portion of the shank and including a body having opposing pressure and suction surfaces extending between opposing leading and trailing edge, the body being formed to define a substantially radially extending cooling hole therein, which is disposed to be solely receptive of the coolant accommodated within the shank for removing heat from the body, the cooling hole being further defined with elongated sidewalls having profiles that are substantially parallel with those of the pressure and suction surfaces.

DETAILED DESCRIPTION OF THE INVENTION

With reference toFIG. 1, a turbine bucket10is provided and includes a shank20and an airfoil blade40. The shank20is interconnectable with and rotatable about a rotor of a turbine engine, such as a gas turbine engine, and includes a shank body21that is formed to define a cavity or a plurality of passages22therein. The cavity may be cast into the shank body21and the plurality of passages22may be machined. While both the cavity and the plurality of passages22may be employed, for purposes of clarity and brevity, the shank body21will hereinafter be described as being formed to define only the plurality of passages22. The plurality of passages22may accommodate coolant, such as compressed air extracted from a compressor.

The shank body21may be formed with a fir-tree shape that, when installed within a dovetail seal assembly of the rotor, secures the shank20in a position relative to the rotor. In that position, each of the plurality of passages22is fluidly communicable with a supply of the coolant through, for example, a radially inward end of the turbine bucket10.

The airfoil blade40may be coupled to a platform23at a radially outward portion of the shank20and may include an airfoil body41formed to define a substantially radially extending cooling hole42therein. The cooling hole42may be machined by way of electro-chemical machining processes (ECM), for example, and is disposed to be solely receptive of the coolant accommodated within the shank20. That is, the cooling hole42does not communicate with any other cooling hole or cooling circuit and, therefore, does not receive coolant from any other source beside the shank20.

The coolant is made to flow in a radial direction along a length of the cooling hole42by fluid pressure and/or by centrifugal force. As the coolant flows, heat transfer occurs between the airfoil body41and the coolant. In particular, the coolant removes heat from the airfoil body41and, in addition, tends to cause conductive heat transfer within solid portions43of the airfoil body41. The conductive heat transfer may be facilitated by the airfoil body41being formed of metallic material, such as metal and/or a metal alloy that is able to withstand relatively high temperature conditions. The overall heat transfer decreases a temperature of the airfoil blade40from what it would otherwise be as a result of contact between the airfoil blade40with, for example, relatively high temperature fluids flowing through a gas turbine engine.

With reference toFIG. 2, the airfoil body41may extend in a radial direction from the platform23and may include opposing pressure and suction surfaces44,45extending between leading and trailing edges46,47to cooperatively define a camber line48. The camber line48defines a major axis50and a minor axis51, which is perpendicular to the major axis50.

The cooling hole42may be defined as having a substantially non-circular cross-sectional shape60at any one or more predefined radial positions of the airfoil body41. This non-circular shape60allows for an increased perimeter and larger cross-sectional area of the cooling hole42and leads to a greater degree of heat transfer without a thickness of the wall70having to be sacrificed beyond a wall thickness that is required to maintain manufacturability and structural integrity.

Where the cooling hole42is non-circular, the cooling hole42may have various alternative shapes including, but not limited to, elliptical or otherwise elongated shapes. The cooling hole42may be rounded or angled, regular or irregular. The cooling hole42may be symmetric about a predefined axis or non-symmetric about any predefined axis. The cooling hole42may be defined with elongate sidewalls71that have profiles mimicking local profiles of the pressure and suction surfaces44,45such that the wall70is elongated with a thickness that is equal to or greater than a wall thickness required for the maintenance of manufacturability and structural integrity. Similarly, the cooling hole42may be longer in an axial direction of the airfoil body41than a circumferential direction thereof and/or may have an aspect ratio that is less than or greater than 1, non-inclusively, with respect to the camber line48.

The substantial non-circularity of the cooling hole42may be localized, may extend along a partial radial length of the cooling hole42or may extend along an entire radial length of the cooling hole42. In this way, the increased heat transfer facilitated by the substantial non-circularity of the cooling hole42may be provided to only a portion of the length of the airfoil body41or to a portion along the entire length of the airfoil body41.

With reference toFIGS. 3-5and6-8, the turbine bucket10may further include a turbulator80positioned within the cooling hole42. The turbulator80and, more generally, the turbulated section of the cooling hole42where the turbulator80is located may act to increase the heat transfer in the airfoil body41. The turbulation acts to trip the flow of coolant through the cooling hole42, which results in a boundary restart layer with an increased localized heat transfer coefficient. The turbulation can be along the entire perimeter of the hole, or at partial sections and may allow for part life of the airfoil body41to be lengthened and a required amount of cooling flow to be decreased. The turbulator80may be formed by various processes, such as electro-chemical machining (ECM).

The turbulator80may be a single component within the cooling hole42or may be plural in number. Where the turbulator80is plural in number, a series of turbulators80may be arrayed in a radial direction along a length of the cooling hole42.

As shown inFIGS. 3 and 6, the turbulator80may be symmetric about any predefined axis. In this case, the turbulator80may be provided with a first configuration81in which the turbulator80extends around an entire perimeter of the cooling hole42. The turbulator80may be symmetric about the axial direction (i.e., the A direction), as shown inFIGS. 4 and 7, in which case the turbulator80may be provided with the second configuration82. The turbulator80may be symmetric about the circumferential direction (i.e., the B direction), as shown inFIGS. 5 and 8, in which case the turbulator80may be provided with the third configuration83. Still further, the turbulator80may be non-symmetric and/or irregular.

With reference back toFIGS. 1 and 2, the airfoil body41may be formed to define a plurality of substantially radially extending cooling holes42. Here, each cooling hole42is disposed to be solely and independently receptive of the coolant accommodated within the shank20for removing heat from the airfoil body41. As mentioned above, where multiple cooling holes42are defined, the cooling holes42are independent from one another and do not fluidly communicate.

Where multiple cooling holes42exist, all or only a subset may be further defined as having the substantially non-circular cross-sectional shape. This subset may include one or more of the cooling holes42. One or more turbulators80may be positioned within at least one of the cooling holes42in the subset. In this case, a position of each turbulator80within a cooling hole42is dependent or independent of a position of another turbulator80in another cooling hole42.

The plurality of cooling holes42may be arranged in one, two or more groups, such as groups90,91and92, depending on design considerations. Here, each group may include one or more cooling holes42. Of these, zero, one or more cooling holes42may be defined as having the substantially non-circular cross-sectional shape at the predefined radial position. Again, one or more turbulators80may be positioned within at least one of the cooling holes42in the subset. In this case, a position of each turbulator80within a cooling hole42is dependent or independent of a position of another turbulator80in another cooling hole42.