Patent Application
20100226790
This invention is directed generally to turbine blades, and more particularly to cooling systems in hollow turbine blades.
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.
Typically, turbine blades are formed from a root portion at one end and an elongated portion forming a blade that extends outwardly from a platform coupled to the root portion at an opposite end of the turbine blade. The blade is ordinarily composed of a tip opposite the root section, a leading edge, and a trailing edge. The inner aspects of most turbine blades typically contain an intricate maze of cooling channels forming a cooling system. The cooling channels in the blades receive air from the compressor of the turbine engine and pass the air through the blade. The cooling channels often include multiple flow paths that are designed to maintain all aspects of the turbine blade at a relatively uniform temperature. However, centrifugal forces and air flow at boundary layers often prevent some areas of the turbine blade from being adequately cooled, which results in the formation of localized hot spots. Localized hot spots, depending on their location, can reduce the useful life of a turbine blade and can damage a turbine blade to an extent necessitating replacement of the blade. Often times, localized hot spots form in the tip section of turbine blades. As shown in
This invention relates to a turbine blade cooling system for a turbine blade used in turbine engines. In particular, the turbine blade cooling system may be directed to a cooling system located in a cavity positioned between two or more walls forming a housing of the turbine blade. The cooling system may include one or more leading edge cooling chambers for cooling the leading edge and for exhausting cooling fluids through a tip exhaust outlet. Portions of the leading edge cooling channel proximate to the tip exhaust outlet may be narrower than the radially inward sections of the leading edge cooling channel and may direct cooling fluids to be exhausted from tip exhaust outlet at skewed angles towards the suction side of the blade. As such, the leading edge cooling channel and tip exhaust outlet cooperate to exhaust the cooling fluids from the blade without forming a separation zone at the upstream side of the intersection between the leading edge cooling channel and the tip exhaust outlet.
The turbine blade may be formed from a generally elongated blade having a leading edge, a trailing edge, a tip section at a first end, 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 cooling system may have any appropriate configuration. In one embodiment, the cooling system may include a leading edge cooling channel and a triple pass serpentine cooling channel extending from proximate the leading edge cooling channel to the trailing edge. The turbine blade may be formed from an outer wall forming a pressure side and suction side that is generally opposite to the pressure side. The pressure and suction sides may be coupled together with the leading and trailing edges. The pressure and suction sides at the tip section may be separated from each other by an outer tip surface having a generally concave shape forming a squealer tip. A tip exhaust outlet may be positioned proximate to a intersection between the tip section and the leading edge. In one embodiment, the tip exhaust outlet may be in contact with the outer wall forming the suction side, and a downstream side of the tip exhaust outlet may be positioned generally at a midpoint between the leading and trailing edges. At least a portion of the cooling system may exhaust cooling fluids from the tip exhaust outlet after passing through the leading edge cooling channel. The leading edge cooling channel in communication with the tip exhaust outlet may be curved proximate to the tip exhaust outlet such that an axis aligned with the cooling fluid flow at the tip exhaust outlet may be skewed towards the suction side of the blade to exhaust cooling fluids into the hot gas path to prevent formation of an efficiency destroying fluid separation zone.
The cooling system of the blade may include a leading edge cooling channel in communication with the tip exhaust outlet. The cooling channel may have a first section with generally linear side walls formed by the outerwalls forming the pressure and suction sides and may have a second section between the first section and the tip exhaust outlet that is formed by a generally convex shaped surface on the suction sidewall and a generally concave shaped surface on the pressure sidewall. The second section may have a cross-sectional area that is less than a cross-sectional area of the first section, which increases the velocity of the cooling fluids in the second section. In another embodiment, a longitudinal axis of the leading edge cooling channel may change direction twice in the second section of the leading edge cooling channel. In particular, the longitudinal axis of the leading edge cooling channel may be generally aligned with the pressure and suction sidewalls of the first section. When moving radially outwardly, the longitudinal axis may be skewed toward the pressure side between the intersection of the first and second sections and a point radially outward of the intersection. The longitudinal axis may then be skewed toward the suction side between the point radially outward of the intersection and the tip exhaust outlet.
An advantage of this invention is that the tip exhaust outlet and the leading edge cooling channel form a tip cooling and sealing device void of internal flow separation at the upstream side of the tip exhaust outlet, thereby eliminating over temperatures.
Another advantage of this invention is that the leading edge cooling channel immediately proximate to the tip exhaust outlet is skewed towards the suction side to prevent an internal separation zone from forming.
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
As shown in
In at least one embodiment, the cooling system 10 may include a leading edge cooling channel 18 positioned along the leading edge 20. The leading edge cooling channel 18 may extend from the root 28 to the tip 40 of the elongated blade 26. In other embodiments, the leading edge cooling channel 18 may have a shorter length. The leading edge cooling channel 18 may intersect with the tip exhaust outlet 22 at an outer tip surface 42 forming the tip 40. In at least one embodiment, as shown in
The leading edge cooling channel 18 may be in communication with the tip exhaust outlet 22 and may be curved proximate to the tip exhaust outlet 22 such that an axis 48 aligned with the cooling fluid flow at the tip exhaust outlet 22 is skewed towards the suction side 24 of the blade 12. In one embodiment, the leading edge cooling channel 18 may be formed from a first section 44 formed by the outerwalls 32 forming the pressure and suction sides 34, 24 and a second section 46 between the first section 44 and the tip exhaust outlet 22. In at least one embodiment, the first section 44 may be formed from generally linear side walls formed by the outerwalls 32 forming the pressure and suction sides 34, 24. The second section 46 may curved proximate to the tip exhaust outlet 22 such that the axis 48 aligned with the cooling fluid flow at the tip exhaust outlet 22 is skewed towards the suction side 24 of the blade 12. In one embodiment, the second section 46 may be formed by a generally convex shaped surface on the suction sidewall 24 and a generally concave shaped surface on the pressure sidewall 34. The second section 46 may have a cross-sectional area that is less than a cross-sectional area of the first section 44, which increases the velocity of the cooling fluids flowing through the second section 46. The second section 46 may also be configured such that the tip exhaust outlet 22 is in contact with the outer wall 32 forming the suction side 24, and a downstream side of the tip exhaust outlet 22 may be positioned generally at a midpoint 50 between the leading and trailing edges 20, 38.
In another embodiment, as shown in
During use, cooling fluids enter the cooling system 10 through chambers in the root 28 of the elongated airfoil 26. At least a portion of the cooling fluids are directed into the leading edge cooling channel 18. A portion of those cooling fluids may then be exhausted through orifices 36 and the remaining cooling fluids may be passed through the first and second sections 44, 46. As the cooling fluids enter the second section proximate to the tip 40, the velocity of the cooling fluids may increase. The direction of the cooling fluid flow may change and may be skewed relative to the longitudinal axis 48 in the first section 44 and toward the suction side 24 to prevent a separation zone from forming within the leading edge cooling channel 18 at the intersection of the leading edge cooling channel 18 and the tip exhaust outlet 22. By preventing the internal flow separation and formation of the separation zone, the cooling system 10 is able to operate more efficiently than conventional systems.
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.
