Patent Application
20120076653
This invention is directed generally to turbine blades for gas turbine engines, and more particularly to turbine blade tips.
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 blade assemblies to these high temperatures. As a result, turbine blades must be made of materials capable of withstanding such high temperatures. In addition, turbine blades often contain cooling systems for prolonging the life of the blades and reducing the likelihood of failure as a result of excessive temperatures.
The hot combustion gases flow from the combustor and past the blades of the rotor assembly. The combustion gases cause the rotor assembly to rotate. Some of the combustion gases flow between the tips of the blades and the outer casing. Such fluids flowing between the tips of the blades and the outer casing result in losses and inefficiencies in the system.
This invention relates to a turbine blade tip leakage prevention system for turbine blades used in turbine engines to reduce tip leakage during operation of the turbine engines. In particular, the blade tip leakage prevention system may include one or more vortex generators on a tip wall of the turbine blade. The vortex generators may extend radially outward from the tip wall but not a distance sufficient to contact a stationary outer wall during turbine engine operation. In at least one embodiment, the vortex generators may extend a distance from the tip wall generally equal to a rib forming a squealer tip. The vortex generators may be positioned in a number of different positions to limit leakage of gas path gases between the tip of the turbine blade and a stationary outer wall.
The turbine blade may be formed from a generally elongated blade having a leading edge, a trailing edge, a pressure side, a suction side, a tip wall at a first end, wherein the tip wall has a radially outer surface, a root coupled to the blade at an end generally opposite the first end for supporting the blade and for coupling the blade to a disc, and at least one cavity forming a cooling system in the blade. The turbine blade may include one or more ribs extending radially outward from the radially outer surface of the tip wall. The rib may be aligned with an outer surface of the suction side of an outer wall forming the generally elongated blade.
The turbine blade may also include one or more vortex generators positioned at the tip wall. The vortex generator may extend radially outward from the radially outer surface of the tip wall. The vortex generator may be positioned between the rib extending radially outward from the radially outer surface of the tip wall and an intersection between the outer surface of the tip wall and an outer surface on the pressure side. The vortex generator may include a base and three sides forming a triangular point with a first side having a larger surface are than second and third sides. The vortex generator may be formed from a plurality of vortex generators and the plurality of vortex generators may be positioned such that the first side faces into the flow of hot gases, which is generally toward the leading edge. In another embodiment, one or more of the plurality of vortex generators may be positioned such that the first side faces into the flow of hot gases, which is generally toward the leading edge of the generally elongated blade and one or more of the plurality of vortex generators may be positioned such that the first side faces away from the flow of hot gases, which is generally away from the leading edge of the generally elongated blade. In another embodiment, one or more of the plurality of vortex generators are positioned such that the first side faces away from the flow of hot gases, which is generally away from the leading edge.
One or more film cooling holes may be positioned in the tip wall such that the film cooling hole is positioned between the suction side and the pressure side. In another embodiment, the film cooling hole may be positioned on one or more of the three sides of the at least one vortex generator. The film cooling hole may be positioned in a side other than the first side. The tip wall and the vortex generator may be coated with a thermal barrier coating.
In another embodiment, the vortex generator may be formed from a groove cut into the tip wall at an intersection between the tip wall and the pressure side. The groove may be formed from first and second sides.
During turbine engine operation, the turbine blades are attached to a rotor assembly that rotates as hot gases flow past the blades from the combustor. The rib and the vortex generators reduce the leakage of the hot gases past the tip of the blades. In particular, the vortex generators create vortices. The vortices assist in reducing the hot gas leakage at the tip.
An advantage of this invention is that the vortex generators form geometric blockages that reduce leakage in addition to the rib forming the squealer tip.
Another advantage of this invention is that the vortex generators create additional turbulence at the tip in the tip flow, thereby creating additional resistance to air flow passing over the tip.
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 blade 12 may be formed from a generally elongated blade 18 coupled to the root 20 at the platform 22. Blade 18 may have an outer wall 24 adapted for use, for example, in a first stage of an axial flow turbine engine. Outer wall 24 may form a generally concave shaped portion forming pressure side 26 and may have a generally convex shaped portion forming suction side 28. The generally elongated blade 18 may have a leading edge 30 and a trailing edge 32. The turbine blade 12 may include an internal cooling system 34 for directing one or more gases, which may include air received from a compressor (not shown), through the blade 18 to reduce the temperature of the blade 18, including film cooling at the tip wall 16. The internal cooling system 34 may be arranged in various configurations and is not limited to a particular flow path.
As shown in
As shown in
As shown in
The vortex generators 14 are oriented on the outer surface 40 of the tip wall 16 in concert with the overall flow field create by the airfoil shape and is thus dependent upon the specific airfoil design. Computational fluid dynamics and experimental testing may be used to determine where to position the vortex generators 14. The vortex generators 14 may shed vortices off the sidewalls and downstream surfaces, thus highly mixing and creating turbulence in the local field flow. The turbulence creates aero-dynamic resistance to the tip leakage flow.
The turbine blade tip leakage prevention system 10 may also include film cooling holes 58 in the tip wall 16, as shown in
In another embodiment, as shown in
During turbine engine operation, the turbine blades 12 are attached to a rotor assembly that rotates as hot gases flow past the blades 12 from the combustor. The rib 17 and the vortex generators 14 reduce the leakage of the hot gases past the tip 36 of the blades 12. In particular, the vortex generators 14 create vortices, 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.
