Patent Application
20130302166
This invention is directed generally to turbine blades, and more particularly to airfoil tips for 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.
Typically, turbine blade is 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 tip of a turbine blade often has a tip feature to reduce the size of the gap between ring segments and blades in the gas path of the turbine to prevent tip flow leakage, which reduces the amount of torque generated by the turbine blades. The tip features are often referred to as squealer tips and are frequently incorporated onto the tips of blades to help reduce aerodynamic losses in turbine stages. These features are designed to minimize the leakage between the blade tip and the ring segment.
A squealer tip usable in repair systems and formed from a pressure side outer weld rib and a suction side outer weld rib extending radially outward from a tip of a turbine blade and resting upon pressure side and suction side weld members separated by a mid-chord member is disclosed. The pressure and suction side outer weld ribs may be positioned along the pressure side and the suction side of the turbine blade, respectively. The pressure side outer weld rib may include a chamfered pressure side with pressure side film cooling holes having exhaust outlets positioned therein. The pressure side film cooling holes may be configured to be diffusion cooling holes with one or more tapered sections for reducing the velocity of cooling fluids, increasing the convective surfaces, thereby increasing the efficiency of the cooling system. The pressure and suction side weld members may be configured to retain the mid-chord member in position with over extending side surfaces.
The turbine blade may be formed from a generally elongated blade having a leading edge, a trailing edge, a tip at a first end, a root coupled to the blade at a second end generally opposite the first end for supporting the blade and for coupling the blade to a disc, and an internal cooling system formed from at least one cavity positioned within the generally elongated blade. The squealer tip may be formed from a first tip cap member and a second tip cap member. The second tip cap member may be formed from a pressure side weld member and a suction side weld member, and the first tip cap member may be formed from a mid-chord member positioned between the pressure and suction side weld members. The mid-chord member may include an upstream contact surface that is nonorthogonal and nonparallel with a longitudinal axis of the generally elongated blade such that an innermost corner of the upstream contact surface extends further upstream than an outermost corner of the upstream contact surface and may include a downstream contact surface that is nonorthogonal and nonparallel with the longitudinal axis of the generally elongated blade such that an innermost corner of the downstream contact surface extends further downstream than an outermost corner of the downstream contact surface. The pressure side weld member may have a downstream contact surface that is nonorthogonal and nonparallel with the longitudinal axis of the generally elongated blade such that an outermost corner of downstream contact surface extends further downstream than an innermost corner of the downstream contact surface. The suction side weld member may have an upstream contact surface that is nonorthogonal and nonparallel with the longitudinal axis of the generally elongated blade such that an outermost corner of upstream contact surface extends further upstream than an innermost corner of the upstream contact surface. The mid-chord member may be welded on innermost corners to the generally elongated blade.
The pressure side outer weld rib may extend radially outward from the pressure side weld member such that the pressure side outer weld rib extends radially outward further than an outer surface of the suction side weld member. The pressure side outer weld rib may have a chamfered pressure side surface such that an outermost corner of the pressure side is positioned downstream from all other aspects of the pressure side surface of the pressure side outer weld rib. The chamfered pressure side surface may extend over an entire upstream side of the pressure side outer weld rib. The pressure side outer weld rib may be formed from a first material, and the pressure side weld member, the suction side weld member and the mid-chord member may be formed from a second material that is different from the first material. The pressure side outer weld rib may have an outer side surface that is aligned with an outer surface of the generally elongated blade forming a pressure side.
One or more pressure side film cooling holes may be positioned in the pressure side outer weld rib with an outlet in the chamfered pressure side surface in the pressure side outer weld rib and an inlet that couples the at least one pressure side film cooling hole with the cavity forming the internal cooling system. One or more mid-chord film cooling holes may be positioned in the mid-chord member with an outlet in an outer surface of the mid-chord member and an inlet that couples the at least one mid-chord film cooling hole with the at least one cavity forming the internal cooling system.
A suction side outer weld rib may extend radially outward from the suction side weld member such that the suction side outer weld rib extends radially outward further than an outer surface of the pressure side weld member. The suction side outer weld rib may have an outer side surface that is aligned with an outer surface of the generally elongated blade forming a suction side. The suction side outer weld rib may be formed from a first material, and the pressure side weld member, the suction side weld member and the mid-chord member may be formed from a second material that is different from the first material. A thermal barrier coating may be included on outer surfaces forming pressure and suction sides of the generally elongated blade and on outer surfaces of the pressure side weld member, the suction side weld member and the mid-chord member.
Turbine blades may be repaired by reworking the tip. In particular, a method of repairing a turbine blade may include preparing the tip of a blade by removing existing tip structure on the generally elongated blade. The tip may be prepared by grinding the surface flat. The existing tip structure may be removed by grinding or other appropriate method. A pre-weld overage heat treatment may be applied before the mid-chord member is placed on the tip. A squealer tip may be formed by positioning a mid-chord member on the tip covering the cavity forming the internal cooling system. The mid-chord member may be held in place by welding the mid-chord member on the blade tip.
A pressure side weld member may be formed on an upstream side of the mid-chord member and a suction side weld member on a downstream side of the mid-chord member by welding. In at least one embodiment, the radially outer surfaces of the pressure side weld member and suction side weld member may be ground flush with a radially outer surface of the mid-chord member.
A pressure side outer weld rib extending radially outward from the pressure side weld member may be formed. The pressure side outer weld rib may extend radially outward further than an outer surface of the suction side weld member. The pressure side outer weld rib may be formed by a weld buildup of material. A suction side outer weld rib may be formed that extends radially outward from the suction side weld member. The suction side outer weld rib may extend radially outward further than an outer surface of the pressure side weld member. The suction side outer weld rib may be formed by a weld buildup of material. A chamfered pressure side surface may be formed on the pressure side outer weld rib such that an outermost corner of the pressure side is positioned downstream from all other aspects of the pressure side surface of the pressure side outer weld rib.
The method may also include applying a thermal barrier coating on the outer surfaces forming pressure and suction sides of the generally elongated blade and on outer surfaces of the pressure side weld member, the suction side weld member and the mid-chord member. One or more pressure side film cooling holes may be established in the pressure side outer weld rib as described above through the thermal barrier coating via drilling or other appropriate method. One or more mid-chord film cooling holes may be established in the mid-chord member as described above through the thermal barrier coating via drilling or other appropriate method.
An advantage of this invention is that blades usable within turbine engines may be repaired with a squealer tip configured as described herein, thereby improving the operability of the blade when reinstalled in a gas turbine engine.
Another advantage of this invention is that squealer tip with the different materials forming the pressure and suction side outer weld ribs from the pressure and suction side weld members, the chamfered surface, the configuration of convective cooling holes realizes an increase in performance compared with blades with squealer tips without these elements.
Yet another advantage of this invention is that the tapered section of the compound angle diffuser film cooling hole increases the convection cooling surface and cooling coverage inside the squealer tip.
Another advantage of this invention is that the squealer tip has more reliable convective cooling in the squealer tip for better blade tip life and therefore lower tip leakage flow.
Still another advantage of this invention is that the chamfered surface enables cooling holes to be positioned on the surface at hot spots and for the cooling holes to have longer lengths for better cooling.
Another advantage of this invention is that the cooling holes also provide exit film cooling at the chamfered surface, thereby reducing the temperature of the airfoil at a location that is typically a hot spot, which is an area of material having an increased temperature.
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
As shown in
The pressure side weld member 17 may be formed in place around of the mid-chord member 21 between the pressure side 20 and the mid-chord member 21. For instance, in at least one embodiment, the pressure side weld member 17 may be formed as a weld from materials, such as, but not limited to, IN 738. The pressure side weld member 17 may have a downstream contact surface 39 that is nonorthogonal and nonparallel with the longitudinal axis 27 of the generally elongated blade 30 such that an outermost corner 41 of the downstream contact surface 39 extends further downstream than an innermost corner 43 of the downstream contact surface 39.
Similarly, the suction side weld member 19 may be formed in place around of the mid-chord member 21 between the suction side 22 and the mid-chord member 21. For instance, in at least one embodiment, the suction side weld member 19 may be formed as a weld from materials, such as, but not limited to, IN 738. The suction side weld member 19 may have an upstream contact surface 45 that is nonorthogonal and nonparallel with the longitudinal axis 27 of the generally elongated blade 30 such that an outermost corner 47 of upstream contact surface 45 extends further upstream than an innermost corner 49 of the upstream contact surface 45.
The pressure side outer weld rib 12 may extend radially from an outer surface 46 of the pressure side weld member 17. In one embodiment, the pressure side outer weld rib 12 may extend from the leading edge 32 and may terminate at the trailing edge 34, as shown in
As shown in
One or more pressure side film cooling holes 26 may be positioned in the pressure side outer weld rib 12 with an outlet 28 in an outer surface 50 in the pressure side outer weld rib 12 and an inlet 52 that couples the pressure side film cooling hole 26 with the cavity 44 forming the internal cooling system 42. In one embodiment, as shown in
As shown in
The pressure side outer weld rib 12 may be formed from a first material, and the pressure side weld member 17, the suction side weld member 19 and the mid-chord member 21 may be formed from a second material that is different from the first material. The suction side outer weld rib 14 may be formed from a first material, and the pressure side weld member 17, the suction side weld member 19 and the mid-chord member 21 may be formed from a second material that is different from the first material. The pressure and suction side outer weld ribs 12, 14 may be formed from the same material, such as, but not limited to, IN625. The pressure side weld member 17, the suction side weld member 19 and the mid-chord member 21 may be formed from a material, such as, but not limited to, IN738.
One or more mid-chord film cooling holes 53 positioned in the mid-chord member 21 with an outlet 28 in an outer surface 64 in the mid-chord member 21, and an inlet 66 that couples the film cooling hole 26 with the cavity 44 forming the internal cooling system 42. As shown in
As shown in
The pressure side film cooling holes 26 positioned in the pressure side ribs 12 or the mid-chord film cooling holes 53 may be formed from one or more diffusion cooling holes, as shown in
As shown in
Turbine blades 18 incur tip wear during normal warm startup conditions. Turbine blades 18 may be repaired by reworking the tip. In particular, a method of repairing a turbine blade may include preparing the tip 16 of a blade 18 by removing existing tip structure on the generally elongated blade 30, as shown in
As shown in
The method may also include applying a thermal barrier coating 70, as shown in
During use, cooling fluids are passed into the internal cooling system 42. The cooling fluids may be passed into the film cooling holes 26 in the tip 16 of the turbine blade 18. The cooling fluids may cool the tip 16 through convection and may cool aspects of the squealer tip 10 by being exhausted through the outlets 28. A portion of the cooling fluids may collect in the squealer tip downstream from the pressure side outer weld rib 12.
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.
