FIELD OF THE INVENTION

This invention is directed generally to turbine airfoils, and more particularly to cooling systems in hollow turbine airfoils.

BACKGROUND

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. Serpentine cooling channels sometimes suffer from regions of higher temperature and poor flow distribution. Radial serpentine cooling passages are commonly used in turbine engines for cooling the airfoil in the mid- chord of the blades. Coriolis force causes cooling fluids flowing within the serpentine cooling channels to form a secondary flow within the serpentine cooling channels. The secondary flow can cause elevated temperature hot spots within the radial serpentine cooling passages. Thus, a need exists for cooling channels that eliminate the elevated temperature hot spots in internal cooling systems of turbine airfoils.

SUMMARY OF THE INVENTION

A turbine airfoil with an internal cooling system including features, such as, but not limited to, turbulators, mini-grooves and mini-ribs, taking advantage of cooling fluid flow characteristics due to rotating Coriolis force is disclosed. The cooling system may include one or more generally spanwise extending cooling channels including at least one turbulator positioned on a surface of an internal rib and extending between outer walls forming suction and pressure sides of the airfoil. The internal cooling system may also include a plurality of turbulators extending from an inner surface of the suction side of the airfoil and one or more mini-grooves positioned between adjacent turbulators on the inner surface of the suction side. Such cooling features of the internal cooling system may increase heat transfer by nearly 80 percent. The internal cooling system with turbulators on cold internal ribs extending between suction and pressure sides and mini-grooves positioned between adjacent turbulators on the inner surface of the suction side take advantage of the rotating Coriolis forced induced secondary flow within the generally spanwise extending cooling channels to greatly enhance the heat transfer within the internal cooling system and reduce localized hot spots within the turbine airfoil.

In at least one embodiment, the turbine airfoil may be formed from a generally elongated, hollow airfoil having a leading edge, a trailing edge, a pressure side, a suction side on an opposite side of the airfoil from the pressure side, a tip section at a first end, a root coupled to the airfoil at an end generally opposite the first end for supporting the airfoil and for coupling the airfoil to a disc, and a cooling system formed from at least one cavity in the elongated, hollow airfoil. The cooling system may include one or more generally spanwise extending cooling channels defined at least in part by an inner surface of an outer wall forming the pressure side of the generally elongated, hollow airfoil, an inner surface of an outer wall forming the suction side of the generally elongated, hollow airfoil, a first inner surface of a first internal rib extending between the outer walls forming the pressure and suction side and a second inner surface of a second internal rib extending between the outer walls forming the pressure and suction side. The cooling system may include one or more turbulators positioned on the first inner surface of the first internal rib and extending from the first inner surface of the first internal rib toward the second internal rib.

In at least one embodiment, the turbulator positioned on the first inner surface of the first internal rib may be positioned inline with a core die opening direction. The cooling system may also include one or more turbulators positioned on the second inner surface of the second internal rib. In at least one embodiment, the turbulator positioned on the first inner surface of the first internal rib may be a plurality of turbulators positioned on the first inner surface of the first internal rib, whereby each plurality of turbulators positioned on the first inner surface are separated from each other. Similarly, the turbulator positioned on the second inner surface of the second internal rib may be a plurality of turbulators positioned on the second inner surface of the second internal rib, whereby each plurality of turbulators positioned on the second inner surface are separated from each other.

The cooling system may also include a plurality of turbulators extending from the inner surface of an outer wall forming the suction side of the generally elongated, hollow airfoil within the at least one generally spanwise extending cooling channel and one or more mini-grooves positioned in the inner surface of an outer wall forming the suction side between adjacent turbulators. The mini-grooves may be aligned with the adjacent turbulators. The mini-groove and the adjacent turbulators may be nonparallel and nonorthogonal with a longitudinal axis of the at least one generally spanwise extending cooling channel.

In at least one embodiment, the cooling system may include a plurality of mini-grooves positioned between adjacent turbulators. The plurality of mini-grooves are aligned with each other and with the plurality of turbulators extending from the inner surface of an outer wall. The mini-groove may be defined by mini-ribs extending less than 40 percent of a height of adjacent turbulators from the inner surface of an outer wall forming the suction side of the generally elongated, hollow airfoil. The mini-groove may also be misaligned with the adjacent turbulators. The mini-groove may be generally aligned with a longitudinal axis of the generally spanwise extending cooling channel. The mini-groove may be generally orthogonal to a longitudinal axis of the at least one generally spanwise extending cooling channel. In at least one embodiment, the mini-groove may be positioned between 30 percent distance and 60 percent distance from a radially inner end of the at least one generally spanwise extending cooling channel towards a radially outer end of the at least one generally spanwise extending cooling channel.

The plurality of turbulators extending from the inner surface of an outer wall forming the suction side of the generally elongated, hollow airfoil may be positioned nonparallel and nonorthogonal with a longitudinal axis of the at least one generally spanwise extending cooling channel. The plurality of turbulators extending from the inner surface of an outer wall forming the suction side of the generally elongated, hollow airfoil may be positioned in a repetitive V shaped configuration with turbulators forming a V shape being offset from each other along longitudinal axis of the at least one generally spanwise extending cooling channel.

An advantage of the internal cooling system is that the internal cooling system includes enhanced heat transfer coefficients due to use of turbulators on cold internal ribs extending between pressure and suction sides and mini-grooves on the inner surfaces of the outerwalls forming the pressure and suction sides of the airfoil, which are castable features.

Another advantage of the internal cooling system is that the Coriolis force carries the turbulence generated from the turbulators on the cold internal rib extending between the pressure and suction side outer walls to the suction side of the outbound spanwise expending cooling channels where the surface may be enhanced with mini-grooves.

Yet another advantage of the internal cooling system is that the Coriolis force carries the turbulence generated from the turbulators on the cold internal rib extending between the pressure and suction side outer walls to the pressure side of the inbound spanwise expending cooling channels where the surface may be enhanced with mini-grooves.

These and other embodiments are described in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

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.

Figure 1 is a perspective view of a turbine airfoil with an internal cooling system including turbulators, mini-grooves and mini-ribs.

Figure 2 is a cross-sectional filleted view of the turbine airfoil of Figure 1 taken at Section line 2-2.

Figure 3 is a cross-sectional filleted view of a first outbound leg and second inbound leg of a serpentine cooling channel of the internal cooling system shown in Figure 2. Figure 4 is a cross-sectional view of the first outbound leg of the serpentine cooling channel taken at section line 4-4 in Figure 3.

Figure 5 is a cross-sectional view of the turbine airfoil with an internal cooling system taken at section line 5-5 in Figure 1 .

Figure 6 is a suction side view of the turbine airfoil with metal temperatures represented and localized hot spots shown in the midchord region.

Figure 7 is a cross-sectional filleted view of a first outbound leg and second inbound leg of a serpentine cooling channel of the internal cooling system shown in Figure 2.

Figure 8 is a detail view of the first outbound leg of the serpentine cooling channel taken from Figure 7 and showing a baseline configuration with turbulators on an inner surface of an outer wall forming the suction side.

Figure 9 is a detail view of the first outbound leg of the serpentine cooling channel taken from Figure 7 and including turbulators on an inner surface of an outer wall forming the suction side and turbulators extending from the first inner surface of the first internal rib and extending from the second inner surface of the second internal rib.

Figure 10 is a detail view of the first outbound leg of the serpentine cooling channel taken from Figure 7 and including turbulators on an inner surface of an outer wall forming the suction side and mini-grooves and mini-ribs aligned with a longitudinal axis of the spanwise extending cooling channel, which may be referred to as radial mini-grooves and mini-ribs.

Figure 1 1 is a detail view of the first outbound leg of the serpentine cooling channel taken from Figure 7 and including turbulators on an inner surface of an outer wall forming the suction side and mini-grooves and mini-ribs orthogonal to a longitudinal axis of the spanwise extending cooling channel, which may be referred to as axial mini-grooves and mini-ribs.

Figure 12 is a detail view of the first outbound leg of the serpentine cooling channel taken from Figure 7 and including turbulators on an inner surface of an outer wall forming the suction side and mini-grooves and mini-ribs nonparallel and nonorthogonal with a longitudinal axis of the spanwise extending cooling channel, which may be referred to as angled mini-grooves and mini-ribs. Figure 13 is a cross-sectional filleted view of a first outbound leg and second inbound leg of a serpentine cooling channel of the internal cooling system shown in Figure 2 including mini-grooves and mini-ribs aligned with a longitudinal axis of the spanwise extending cooling channel, which may be referred to as radial mini- grooves and mini-ribs.

Figure 14 is a set of tables showing the increase in heat transfer coefficient relative to each configuration.

Figure 15 is a cross-sectional filleted view of a first outbound leg and second inbound leg of a serpentine cooling channel of the internal cooling system shown in Figure 2.

Figure 16 is a set of tables showing the change in pressure loss from baseline configuration shown in Figure 8 and the percent loss difference from the baseline shown in Figure 8.

Figure 17 is a cross-sectional, pressure side filleted view of a first outbound leg and second inbound leg of a serpentine cooling channel of the internal cooling system shown in Figure 2 including mini-grooves and mini-ribs orthogonal to a longitudinal axis of the spanwise extending cooling channel, which may be referred to as axial mini-grooves and mini-ribs, and positioned on an inner surface of the outer wall forming the suction side.

Figure 18 is an alternative view of the serpentine cooling channel of Figure 17 taken at section line 18-18 in Figure 17.

Figure 19 is another view of the serpentine cooling channel of Figure 17 looking at the suction side of the airfoil.

Figure 20 is a perspective view of the serpentine cooling channel of Figure 17. Figure 21 is a detail view of the mini-grooves and mini-ribs on the inner surface of the outer wall forming the suction side in Figure 20.

Figure 22 is a partial cross-sectional side view of the mini-grooves and mini- ribs on the inner surface of the outer wall forming the suction side taken at section line 22-22 in Figure 21 .

Figure 23 is a cross-sectional, suction side filleted view of a first outbound leg and second inbound leg of a serpentine cooling channel of the internal cooling system shown in Figure 2 including mini-grooves and mini-ribs orthogonal to a longitudinal axis of the spanwise extending cooling channel, which may be referred to as axial mini-grooves and mini-ribs, and positioned on an inner surface of the outer wall forming the suction side.

Figure 24 is a detail view of the mini-grooves and mini-ribs of the spanwise extending cooling channel on the inner surface of an outer wall forming a suction side of the airfoil.

Figure 25 is a set of graphs showing the area average heat transfer coefficient (HTC) versus airfoil span location.

Figure 26 is a cross-sectional filleted view of a first outbound leg and second inbound leg of a serpentine cooling channel of the internal cooling system shown in Figure 2.

Figure 27 is a table of the predicted metal temperature at different locations on the airfoil of the different configurations the internal cooling system shown in Figure 2.

DETAILED DESCRIPTION OF THE INVENTION

As shown in Figures 1-27, a turbine airfoil 10 with an internal cooling system 12 including features 14, such as, but not limited to, turbulators 16, mini-grooves 18 and mini-ribs 20, taking advantage of cooling fluid flow characteristics due to rotating Coriolis force is disclosed. The cooling system 12 may include one or more generally spanwise extending cooling channels 22 including at least one turbulator 16 positioned on a surface 24 of an internal rib 26 and extending between outer walls 28, 30 forming suction and pressure sides 32, 34 of the airfoil 10. The internal cooling system 12 may also include a plurality of turbulators 16 extending from an inner surface 36 of the suction side 32 of the airfoil 10 and one or more mini-grooves 18 positioned between adjacent turbulators 16 on the inner surface 36 of the suction side 32. Such cooling features of the internal cooling system 12 may increase heat transfer by nearly 80 percent. The internal cooling system 12 with turbulators 16 on cold internal ribs 26 extending between suction and pressure sides 32, 34 and mini- grooves 18 positioned between adjacent turbulators 16 on the inner surface 36 of the suction side 32 take advantage of the rotating Coriolis forced induced secondary flow within the generally spanwise extending cooling channels 22 to greatly enhance the heat transfer within the internal cooling system 12 and reduce localized hot spots within the turbine airfoil 10.

In at least one embodiment, as shown in Figures 1 and 2, the turbine airfoil 10 may be formed from a generally elongated, hollow airfoil 40 having a leading edge 42, a trailing edge 44, a pressure side 34, a suction side 32 on an opposite side of the airfoil 40 from the pressure side 34, a tip section 46 at a first end 48, a root 50 coupled to the airfoil 40 at a second end 52 generally opposite the first end 48 for supporting the airfoil 40 and for coupling the airfoil 1 0 to a disc, and the internal cooling system 12 formed from at least one cavity 54 in the elongated, hollow airfoil 40. The cooling system 12 may include one or more generally spanwise extending cooling channels 22 defined at least in part by an inner surface 38 of an outer wall 30 forming the pressure side 34 of the generally elongated, hollow airfoil 40, an inner surface 36 of an outer wall 28 forming the suction side 32 of the generally elongated, hollow airfoil 40, a first inner surface 58 of a first internal rib 60 extending between the outer walls 30, 28 forming the pressure and suction side 34, 32 and a second inner surface 62 of a second internal rib 64 extending between the outer walls 30, 28 forming the pressure and suction side 34, 32. The cooling system 12 may include one or more turbulators 16 positioned on the first inner surface 58 of the first internal rib 60 and extending from the first inner surface 58 of the first internal rib 60 toward the second internal rib 64. In at least one embodiment, the generally spanwise extending cooling channel 22 may form one leg of a serpentine cooling channel 66. In at least one embodiment, the serpentine cooling channel 66 may include a plurality of legs extending in a generally spanwise direction 68 within the generally elongated, hollow airfoil 40. In at least one embodiment, the generally spanwise extending cooling channel 22 may be a first outbound leg 78 of a serpentine cooling channel 66. As shown in Figure 2, 3, 7, 13, 15, 17 and 23, the generally spanwise extending cooling channel 22 may be a first outbound leg 78 of a serpentine cooling channel 66 and may be the third cooling channel aft of the leading edge 42 of the airfoil 40. In at least one embodiment, the turbulator 16 positioned on the first inner surface 58 of the first internal rib 60 may be positioned inline with a core die opening direction 70. In at least one embodiment, the generally spanwise extending cooling channel 22 may form an inbound leg 80 of a serpentine cooling channel 66. In such an inbound leg 80 of a serpentine cooling channel 66, the Coriolis force may have an opposite effect on the flow of cooling fluid through the generally spanwise extending cooling channel 22 than in the outbound leg 78 of a serpentine cooling channel 66. As such, cooling fluid striking turbulators 16 on internal ribs 26 extending between the pressure and suction side walls 30, 28 may be deflected toward the inner surface 38 of the outer wall 30 forming the pressure side 34. The inner surface 38 of the outer wall 30 forming the pressure side 34 may include one or more mini-grooves 18 such as between turbulators 16. The mini-groves 18 may be positioned and oriented as described herein.

The internal cooling system 12 may also include one or more turbulators 16 positioned on the second inner surface 62 of the second internal rib 64. In at least one embodiment, the turbulator 16 positioned on the first inner surface 58 of the first internal rib 60 may include a plurality of turbulators 16 positioned on the first inner surface 58 of the first internal rib 60, whereby the turbulators 16 positioned on the first inner surface 58 may be separated from each other. The turbulator 16 positioned on the second inner surface 62 of the second internal rib 64 may include a plurality of turbulators 16 positioned on the second inner surface 62 of the second internal rib 64, whereby the turbulators 16 positioned on the second inner surface 62 may be separated from each other. In at least one embodiment, the turbulator 16 positioned on the second inner surface 62 of the second internal rib 64 may be positioned inline with a core die opening direction 70.

The internal cooling system 12 may also include a plurality of turbulators 16 extending from the inner surface 36 of an outer wall 28 forming the suction side 32 of the generally elongated, hollow airfoil 40 within the generally spanwise extending cooling channel 22 and one or more mini-grooves 18 positioned in the inner surface 36 of an outer wall 28 forming the suction side 32 between adjacent turbulators 16. In at least one embodiment, as shown in Figure 12, one or more mini-grooves 18 may be aligned with the adjacent turbulators 16. The mini-groove 18 and the adjacent turbulators 16 may be nonparallel and nonorthogonal with a longitudinal axis 72 of the at least one generally spanwise extending cooling channel 22. In at least one embodiment, as shown in Figure 12, the cooling system 12 may include a plurality of mini-grooves 18 positioned between adjacent turbulators 16. Each of the groups of plurality of mini-grooves 18 may be aligned with each other and with the plurality of turbulators 16 extending from the inner surface 36 of an outer wall 28 forming the suction side 32 of the generally elongated, hollow airfoil 40. The mini-groove 18, as shown in Figure 22, may be defined by mini-ribs 20 extending less than 40 percent of a height of adjacent turbulators 16 from the inner surface 36 of an outer wall 28 forming the suction side 32 of the generally elongated, hollow airfoil 40.

In at least one embodiment, as shown in Figure 10, the mini-groove 18 may be misaligned with the adjacent turbulators 16. The mini-groove 18 may be generally aligned with a longitudinal axis 72 of the generally spanwise extending cooling channel 22. In at least one embodiment, as shown in Figures 1 1 , 18-21 , 23 and 24, the mini-groove 18 may be generally orthogonal to a longitudinal axis 72 of the generally spanwise extending cooling channel 22.

The mini-groove 18 may be positioned between 30 percent distance and 60 percent distance from a radially inner end 74 of the generally spanwise extending cooling channel 22 towards a radially outer end 76 of the generally spanwise extending cooling channel 22. The plurality of turbulators 16 extending from the inner surface 36 of an outer wall 28 forming the suction side 32 of the generally elongated, hollow airfoil 40 may be positioned nonparallel and nonorthogonal with a longitudinal axis 72 of the generally spanwise extending cooling channel 22.

In at least one embodiment, the plurality of turbulators 16 extending from the inner surface 36 of an outer wall 28 forming the suction side 32 of the generally elongated, hollow airfoil 40 may be positioned in a repetitive V shaped configuration with turbulators 16 forming a V shape being offset from each other along longitudinal axis 72 of the generally spanwise extending cooling channel 22.

As shown in Figures 13 and 14, a summary of heat transfer coefficients on the inner surface 36 of the outer wall 28 of the suction side 32 and the inner surface 38 of the outer wall 30 of the pressure side 34 is displayed for the features 14, including the turbulators 16 on the cold internal ribs 26 extending between suction and pressure sides 32, 34 and mini-grooves 18 positioned between adjacent turbulators 16 on the inner surface 36 of the suction side 32 and on the inner surface 38 of the pressure side 34. There are two conditions shown on the cold internal ribs 26 extending between suction and pressure sides 32, 34, including with turbulators 16 and without turbulators 16. The baseline has smooth cold internal ribs 26 without turbulators 16 and turbulators 16 on the inner surface 36 of the suction side 32 and on the inner surface 38 of the pressure side 34 without mini-grooves 18. The results indicated that the mini-groove 18 alone has small heat transfer improvement, such as between four percent and thirteen percent when compared with the baseline. The turbulators 16 on the cold internal ribs 26 extending between suction and pressure sides 32, 34 alone has moderate heat transfer improvement, such as about twenty percent when compared with the baseline. The combination of turbulators 16 and mini-grooves 18 on the inner surface 36 of the outer wall 28 of the suction side 32 and turbulators 16 on the cold internal ribs 26 extending between suction and pressure sides 32, 34 may result in significant heat transfer improvement of between about 40 percent and about 80 percent compared with the baseline. The most significant improvement of heat transfer is the turbulators 16 on the cold internal ribs 26 extending between suction and pressure sides 32, 34 and the axial mini-grooves 18 in the inner surface 36 of the outer wall 28 of the suction side 32. Figures 17-22 further display the best combination of cold internal ribs 26 extending between suction and pressure sides 32, 34 and axial mini-grooves 18 on the inner surface 36 of the outer wall 28 of the suction side 32. The combination of turbulators 16 on the cold internal ribs 26 extending between suction and pressure sides 32, 34 and the axial mini-grooves 18 in the inner surface 36 of the outer wall 28 of the suction side 32 and axial mini-grooves 18 in the inner surface 38 of the outer wall 30 of the pressure side 34 may reduce metal temperature by up to about 85 degrees Celsius.

During the engine rotating condition, the radially flowing cooling air in the generally spanwise extending cooling channel 22 interacts with the rotating force and results in Coriolis force to generate a secondary flow that is perpendicular to the radial flow direction, as shown in Figure 4. In the radially outward flowing generally spanwise extending cooling channel 22, the Coriolis force brings the core cooling air toward the trailing or pressure sides with increased heat transfer. This phenomenon is more pronounced in the first leg 78 of outward flowing generally spanwise extending cooling channel 22 and results in significant differences in heat transfer on pressure and suction side surfaces of the cooling passage. The turbulators 16 on the cold internal ribs 26 extending between suction and pressure sides 32, 34 and the axial mini-grooves 18 in the inner surface 36 of the outer wall 28 of the suction side 32 utilize the existence of the Coriolis force in the rotating outward flowing generally spanwise extending cooling channel 22 to improve the heat transfer on the inner surface 36 of the outer wall 28 of the suction side 32 or leading surface forming the first inner surface 62 of the first internal rib 60. The Coriolis force has a reverse direction in the radially inward legs 80 of the serpentine cooling channel 66.

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.