Patent Application
20110038709
This invention is directed generally to gas turbine engines, and more particularly to turbine vanes for gas turbine engines.
Typically, gas turbine engines include a compressor for compressing air, a combustor for mixing the compressed air with fuel and igniting the mixture, and a turbine blade assembly for producing power. Combustors often operate at high temperatures that may exceed 2,500 degrees Fahrenheit. Typical turbine combustor configurations expose turbine vane and blade assemblies to high temperatures. As a result, turbine vanes and blades must be made of materials capable of withstanding such high temperatures, or must include cooling features to enable the component to survive in an environment which exceeds the capability of the material. Turbine engines typically include a plurality of rows of stationary turbine vanes extending radially inward from a shell and include a plurality of rows of rotatable turbine blades attached to a rotor assembly for turning the rotor.
Typically, the turbine vanes are exposed to high temperature combustor gases that heat the airfoil. The airfoils include an internal cooling system for reducing the temperature of the airfoils. While there exist many configurations of cooling systems, there exists a need for improved cooling of gas turbine airfoils.
This invention is directed to a turbine vane for a gas turbine engine. The turbine vane may be configured to better accommodate high combustion gas temperatures than conventional vanes. In particular, the turbine vane may include an internal cooling system positioned within internal aspects of the vane. The internal cooling system may be formed from one or more serpentine cooling channels that may extend from an inner endwall (ID) to an outer endwall (OD) and from a leading edge to a trailing edge. The serpentine cooling channel may include a first turn manifold positioned at least partially in the inner endwall and may include one or more purge rim orifices for exhausting cooling fluids into a rim cavity for cooling. The first turn manifold may also include a plurality of trip strips on suction and pressure sidewalls to enhance the efficiency of the cooling system. The increased efficiency reduces the thermal degradation of the turbine vane.
The turbine vane may be formed from a generally elongated airfoil formed from an outer wall, and having a leading edge, a trailing edge, a pressure side, a suction side generally opposite to the pressure side, a first endwall at a first end, a second endwall at a second end opposite the first end, and an internal cooling system positioned within the generally elongated airfoil. The internal cooling system may include at least one serpentine cooling channel that extends from proximate to the leading edge to proximate to the trailing edge. The serpentine cooling channel may include a first turn manifold in communication with a first pass and positioned at least partially in the first endwall at the first end and includes a plurality of trip strips protruding inwardly from an inner surface of a suction sidewall forming the suction side toward the pressure side and includes a plurality of trip strips protruding inwardly from an inner surface of a pressure sidewall forming the pressure side toward the suction side. The trip strips on the suction sidewall may be offset from the trip strips on the pressure sidewall. In at least one embodiment, the serpentine cooling channel may be a triple pass serpentine cooling channel. The trip strips may be positioned throughout first, second and third passes of the serpentine cooling channel.
The cooling system may also include a forward purge rim orifice in the first turn manifold at the suction sidewall and aligned with the first pass. The cooling system may also include a forward purge rim orifice in the first turn manifold at the pressure sidewall and aligned with the first pass. The forward purge rim orifices enable cooling fluids that have been used to cool the leading edge of the airfoil to also be used to purge the rim cavity.
The cooling system may include one or more trailing edge exhaust orifices in communication with the a serpentine cooling channel. The trailing edge exhaust orifices may also include one or more aft purge rim orifices proximate to an intersection of the trailing edge and the first endwall and proximate to the trailing edge exhaust orifices. The aft purge rim orifices may be positioned to provide cooling fluids to the rim cavities.
During use, cooling fluids are supplied from a compressor or other such source to the first pass at the outer endwall. Cooling fluids may be passed along the leading edge to cool the material forming the leading edge. A portion of the cooling fluids may be exhausted from the first pass through one or more forward purge rim orifices. The cooling fluids flowing out of the forward purge rim orifices accomplish two purposes. In particular, those cooling fluids cool the leading edge and purge the rim cavity. The remaining cooling fluids flow into the first turn manifold where the cooling fluids encounter the offset trip strips. The offset trip strips on the suction and pressure sidewalls cause turbulence in the cooling fluids that increase the heat transfer versus conventional configurations. The pressure side walls increase skin friction coefficient for the turn side walls thereby eliminating flow separation within the manifold. The cooling fluids are then passed through the second and third passes where the cooling fluids cool aspects of the turbine vane in the midchord region. The cooling fluids may be exhausted through the trailing edge exhaust orifices positioned along the trailing edge. A portion of the cooling fluids may also be exhausted through the aft purge rim orifices.
An advantage of the internal cooling system is that a portion of the cooling fluids flowing through the first pass of the cooling system also flow through the forward purge rim orifices and thereby are used for two cooling purposes, which improves efficiency.
Another advantage of the internal cooling system is that the leading edge of the turbine vane is cooled with the entire flow of cooling fluids into the turbine vane, which maximizes the use of the cooling fluids at the highest heat load region of the vane and minimizes the over heating of cooling air delivery to the inter-stage housing.
Yet another advantage of the internal cooling system is that the forward purge rim orifices are positioned such that cooling fluids that pass through the orifices do so before the cooling fluids reach the first turn manifold and undergo a pressure reduction. Exhausting the cooling fluids through the forward purge rim orifices before the first turn manifold also minimizes rapid changing of the internal flow Mach number in the first turn manifold.
Another advantage of the internal cooling system is that the aft purge rim orifice not only exhausts cooling fluids during use of the turbine vane in a turbine engine but also can function as a conduit through which additional support for the ceramic core used to form the serpentine cooling channel may be inserted during casting.
Still another advantage of the internal cooling system is that use of the overlapping trip strips in the serpentine cooling channel yields higher heat transfer at the airfoil leading edge with the curved trip strips than conventional configurations and minimizes overheating of the purge cooling air.
Another advantage of the internal cooling system is that the offset trip strips in the first turn manifold increase the side wall surface skin friction coefficient, which eliminates the internal flow separation within the first turn manifold.
These and other embodiments are described in more detail below.
The accompanying drawings, which are incorporated in and form a part of the specification, illustrate embodiments of the presently disclosed invention and, together with the description, disclose the principles of the invention.
As shown in
The turbine vane 10 may have any appropriate configuration and, in at least one embodiment, may be formed from a generally elongated airfoil 34 formed from an outer wall 36, and having the leading edge 20, the trailing edge 22, a pressure side 42, a suction side 44 generally opposite to the pressure side 42, a first endwall 16, which is also referred to as the inner endwall, at a first end 48, a second endwall 18, which is also referred to as the outer endwall, at a second end 52 opposite the first end 48, and an internal cooling system 12 positioned within the generally elongated airfoil 34.
The internal cooling system 12 may include one or more serpentine cooling channels 14 that extend from proximate to the leading edge 20 to proximate to the trailing edge 22. The serpentine cooling channel 14 may include a first turn manifold 24 in communication with a first pass 54. The serpentine cooling channel 14 may be positioned at least partially in the first endwall 16 at the first end 48 and may include a plurality of trip strips 28 protruding inwardly from an inner surface 56 of a suction sidewall 30 forming the suction side 44 toward the pressure side 42.
The serpentine cooling channel 14 may include a plurality of trip strips 28 protruding inwardly from an inner surface 58 of a pressure sidewall 32 forming the pressure side 42 toward the suction side 44. As shown in
In at least one embodiment, as shown in
The trip strips 28, as shown in
The cooling system 12 may also include one or more purge rim orifices 26 for providing cooling fluids to the rim cavity. In particular, the cooling system 12 may include a forward purge rim orifice 64 in the first turn manifold 24 at the suction sidewall 30 and aligned with the first pass 54. As shown in
As shown in
During use, cooling fluids are supplied from a compressor or other such source to the first pass 54 at the outer endwall 18. Cooling fluids may be passed along the leading edge 20 to cool the material forming the leading edge 20. A portion of the cooling fluids may be exhausted from the first pass 54 through one or more forward purge rim orifices 64. The cooling fluids flowing out of the forward purge rim orifices 64 accomplish two purposes. In particular, those cooling fluids cool the leading edge and purge the rim cavity. The remaining cooling fluids flow into the first turn manifold 24 where the cooling fluids encounter the offset trip strips 28. The offset trip strips 28 on the suction and pressure sidewalls 30, 32, as shown in
The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of this invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of this invention.
