COOLING PASSAGES FOR TURBINE ENGINE COMPONENTS

TECHNICAL FIELD

The present invention relates to turbine engines, and, more particularly, to cooling passages provided in a wall of a turbine engine component, such as in the sidewall of an airfoil.

BACKGROUND ART

In a turbomachine, such as a gas turbine engine, air is pressurized in a compressor then mixed with fuel and burned in a combustor to generate hot combustion gases. The hot combustion gases are expanded within a turbine of the engine where energy is extracted to power the compressor and to provide output power used to produce electricity. The hot combustion gases travel through a series of stages when passing through the turbine. A stage may include a row of stationary airfoils, i.e., vanes, followed by a row of rotating airfoils, i.e., blades, where the blades rotate to extract energy from the hot combustion gases for powering the compressor and providing output power.

Since the airfoils, i.e., vanes and blades, are directly exposed to the hot combustion gases as the gases pass through the turbine, the airfoils are typically provided with internal cooling circuits that channel a cooling fluid, such as compressor discharge air, through the airfoil and through various film cooling holes around the surface thereof. For example, film cooling holes are typically provided in the walls of the airfoils for channeling the cooling air through the walls for discharging the air to the outside of the airfoil to form a layer of film cooling air, which protects the airfoil from the hot combustion gases.

Film cooling effectiveness is related at least in part to the concentration of the film cooling air at the surface being cooled. In general, the greater the cooling effectiveness, the more efficiently the surface is cooled. A decrease in cooling effectiveness increases the amount of cooling air necessary to maintain a certain cooling capacity, which may cause a decrease in engine efficiency. SUMMARY OF INVENTION

In accordance with a first aspect of the present invention, a component wall is provided in a turbine engine. The component wall comprises a substrate having a first surface and a second surface opposed from the first surface, the substrate having a thickness defined between the first and second surfaces, and at least one cooling passage extending through the substrate for delivering cooling fluid from a chamber associated with the first surface to the second surface. The at least one cooling passage includes an entrance portion at the first surface of the substrate; an exit portion at the second surface of the substrate; and a metering portion between the entrance portion and the exit portion. The entrance portion of the at least one cooling passage includes a larger cross sectional area than the metering portion of the at least one cooling passage to effect a reduction in pressure losses associated with cooling fluid entering the cooling passage. The at least one cooling passage is continuously curved extending through the substrate from the entrance portion to the exit portion.

The entrance and exit portions of the at least one cooling passage may have a cross section having one of a circular, ovular, and rectangular shape.

The at least one cooling passage may further comprise a branch portion dividing the at least one cooling passage into corresponding branch passages, each branch passage having a corresponding exit portion at the second surface of the substrate. The branch portion may be located closer to the first surface of the substrate than to the second surface of the substrate.

The at least one cooling passage may be formed at an angle through the substrate, the angle coinciding with a direction of hot gas flow over the second surface of the substrate such that cooling fluid discharged from the exit portion of the cooling passage includes a velocity component in the same direction as the direction of hot gas flow.

The exit portion of the at least one cooling passage may include an elongated dimension extending transverse to a direction of hot gas flow over the second surface of the substrate. The exit portion of the at least one cooling passage may be defined by opposed first and second elongated walls defining the elongated dimension of the exit portion and by first and second end walls defining a shortened dimension of the exit portion, and at least one of the first and second elongated walls may extend toward the opposed elongated wall in a first location such that the exit portion has a reduced profile in a direction extending between the first and second elongated walls at the first location.

The at least one cooling passage may be cast in the substrate.

The exit portion of the at least one cooling passage may include a larger cross sectional area than the metering portion of the at least one cooling passage.

In accordance with a second aspect of the present invention, a component wall is provided in a turbine engine. The component wall comprises a substrate having a first surface and a second surface opposed from the first surface, the substrate having a thickness defined between the first and second surfaces, and at least one cooling passage extending through the substrate for delivering cooling fluid from a chamber associated with the first surface to the second surface. The at least one cooling passage includes an entrance portion at the first surface of the substrate; at least one branch portion located downstream from the entrance portion and dividing the at least one cooling passage into corresponding branch passages; an exit portion for each branch portion, each exit portion being located at the second surface of the substrate; and a metering portion between the entrance portion and the exit portion. The entrance portion of the at least one cooling passage includes a larger cross sectional area than the metering portion of the at least one cooling passage to effect a reduction in pressure losses associated with cooling fluid entering the cooling passage.

The entrance portion and the exit portions of the at least one cooling passage each may have a cross section having one of a circular, ovular, and rectangular shape.

The branch portion may be located closer to the first surface of the substrate than to the second surface of the substrate and between the metering portion and the exit portions of the at least one cooling passage. The at least one cooling passage may be formed at an angle through the substrate, the angle coinciding with a direction of hot gas flow over the second surface of the substrate such that cooling fluid discharged from the exit portions of the cooling passage includes a velocity component in the same direction as the direction of hot gas flow.

The exit portions of the at least one cooling passage may include an elongated dimension extending transverse to a direction of hot gas flow over the second surface of the substrate. The exit portions of the at least one cooling passage may be defined by opposed first and second elongated walls defining the elongated dimension of each exit portion and by first and second end walls defining a shortened dimension of each exit portion, and at least one of the first and second elongated walls of each exit portion may extend toward the opposed elongated wall in a first location such that each exit portion has a reduced profile in a direction extending between the first and second elongated walls at the first location.

In accordance with a third aspect of the present invention, a component wall is provided in a turbine engine. The component wall comprises a substrate having a first surface and a second surface opposed from the first surface, the substrate having a thickness defined between the first and second surfaces, and at least one cooling passage extending through the substrate for delivering cooling fluid from a chamber associated with the first surface to the second surface. The at least one cooling passage includes an entrance portion at the first surface of the substrate; at least one branch portion located downstream from the entrance portion and dividing the at least one cooling passage into corresponding branch passages; and an exit portion for each branch portion, each exit portion being located at the second surface of the substrate. The at least one cooling passage, including the entrance portion, the at least one branch portion, and the corresponding exit portions, is continuously curved extending through the substrate from the first surface to the second surface.

The entrance portion and the exit portions of the at least one cooling passage may each have a cross section having one of a circular, ovular, and rectangular shape. The branch portion may be located closer to the first surface of the substrate than to the second surface of the substrate.

The at least one cooling passage may be formed at an angle through the substrate, the angle coinciding with a direction of hot gas flow over the second surface of the substrate such that cooling fluid discharged from the exit portions of the cooling passage includes a velocity component in the same direction as the direction of hot gas flow.

The exit portions of the at least one cooling passage may include an elongated dimension extending transverse to a direction of hot gas flow over the second surface of the substrate. The exit portions of the at least one cooling passage may be defined by opposed first and second elongated walls defining the elongated dimension of each exit portion and by first and second end walls defining a shortened dimension of each exit portion, and at least one of the first and second elongated walls of each exit portion may extend toward the opposed elongated wall in a first location such that each exit portion has a reduced profile in a direction extending between the first and second elongated walls at the first location.

BRIEF DESCRIPTION OF DRAWINGS

While the specification concludes with claims particularly pointing out and distinctly claiming the present invention, it is believed that the present invention will be better understood from the following description in conjunction with the accompanying Drawing Figures, in which like reference numerals identify like elements, and wherein:

Fig. 1 is a side cross sectional view of a portion of a film cooled component wall according to an embodiment of the invention;

Fig. 2 is a plan view of the film cooled component wall shown in Fig. 1 ;

Figs. 2A-2C are plan views of other cooling passage configurations for the film cooled component wall shown in Fig. 1 ;

Fig. 3 is a side cross sectional view of a portion of a film cooled component wall according to another embodiment of the invention;

Fig. 4 is a plan view of the film cooled component wall shown in Fig. 3; Figs. 4A-4E are plan views of other cooling passage configurations for the film cooled component wall shown in Fig. 3.

DESCRIPTION OF EMBODIMENTS

In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, and not by way of limitation, specific preferred embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and that changes may be made without departing from the spirit and scope of the present invention.

Referring to Figs. 1 and 2, a film cooled component wall 10 according to an embodiment of the invention is shown. The component wall 10 may comprise a wall of a component in turbine engine, such as, for example, an airfoil, i.e., a rotating blade or a stationary vane, a combustion liner, an exhaust nozzle, and the like.

The component wall 10 comprises a substrate 12 having a first surface 14 and a second surface 16, see Figs. 1 and 2. The first surface 14 may be referred to as the "cool" surface, as the first surface 14 defines a chamber 15 containing cooling fluid (see Fig. 1 ), while the second surface 16 may be referred to as the "hot" surface, as the second surface 16 may be exposed to hot combustion gases H _G during operation. Such combustion gases H _G may have temperatures of up to about 2,000° C during operation of the engine. In the embodiment shown, the first surface 14 and the second surface 16 are opposed and substantially parallel to each other.

The material forming the substrate 12 may vary depending on the application of the component wall 10. For example, the substrate 12 preferably comprises a material capable of withstanding typical operating conditions that occur within the respective portion of the engine, such as, for example, ceramics and metal-based materials, e.g., a steel, nickel, cobalt, or iron based superalloy, etc.

As shown in Fig. 1 , the substrate 12 may comprise one or more layers, and in the embodiment shown comprises an inner layer 18A, an outer layer 18B, and an intermediate layer 18C between the inner and outer layers 18A, 18B. The inner layer 18A in the embodiment shown comprises, for example, a steel, nickel, cobalt, or iron based superalloy, and, in one embodiment, may have a thickness T _A of about 1 .2 mm to about 2.0 mm, see Fig. 1 . The outer layer 18B in the embodiment shown comprises a thermal barrier coating that is used to provide a high heat resistance for the component wall 10, and, in one embodiment, may have a thickness T _B of about 0.5 mm to about 1 .0 mm. The intermediate layer 18C in the embodiment shown comprises a bond coat that is used to bond the outer layer 18B to the inner layer 18A, and, in one embodiment, may have a thickness T _c of about 0.1 mm to about 0.2 mm. The inner, outer, and intermediate layers 18A-C thus define a total thickness T _T of the substrate 12 between the first and second surfaces 14, 16, which total thickness T _T in the embodiment shown may be about 1 .8 mm to about 3.2 mm.

While the substrate 12 in the embodiment shown comprises the inner, outer, and intermediate layers 18A-C, it is understood that substrates having additional or fewer layers could be used without departing from the spirit and scope of the invention. For example, the thermal barrier coating, i.e., the outer layer 18B, may comprise a single layer or may comprise more than one layer. In a multi-layer thermal barrier coating application, each layer may comprise a similar or a different composition and may comprise a similar or a different thickness.

The component wall 10 includes at least one, and preferably a series of cooling passages 20 that extend through the substrate 12 from the first surface 14 of the substrate 12 to the second surface 16 of the substrate 12, i.e., the cooling passages 20 extend through the first, second, and third layers 18A, 18B, 18C in the embodiment shown. The cooling passages 20 deliver cooling fluid C _F , such as, for example, compressor discharge air, from the chamber 15 defined by the first surface 14 to the second surface 16. If multiple cooling passages 20 are present in the component wall 10, the cooling passages 20 may be spaced apart from each other across a dimension D _s of the substrate 12, see Fig. 2, or the cooling passages 20 may be arranged in other patterns, including a random pattern or a pattern dictated by cooling requirements of the substrate 12.

Assuming multiple cooling passages 20 are present in the component wall

10, a single one of the cooling passages 20 will now be described, it being understood that the remaining cooling passages 20 of the component wall 10 may be substantially identical to the described cooling passage 20.

Referring to Figs. 1 and 2, the cooling passage 20 includes an entrance portion 22 located at the first surface 14 of the substrate 12. The entrance portion 22 may have a circular shape as shown in Figs. 1 and 2, a rectangular shape, an ovular shape or any other suitable shape. The entrance portion 22 of the cooling passage 20 receives cooling fluid C _F from the chamber 15 via an inlet 24 of the entrance portion 22 comprising an opening formed in the first surface 14 of the substrate 12.

The entrance portion 22 extends from the inlet 24 to a metering portion 26, which is spaced from the entrance portion 22 in a direction extending between the first and second surfaces 14, 16 of the substrate 12. As shown in Fig. 1 , the metering portion 26 is positioned downstream from the entrance portion 22 with regard to a flow direction of the cooling fluid C _F passing through the cool ing passage 20, and in the embodiment shown is positioned closer to the first surface 14 of the substrate 12 than to the second surface 16 of the substrate 12. However, it is understood that the metering portion 26 could be positioned closer to the second surface 16 of the substrate 12 or about midway between the first and second surfaces 14, 16 of the substrate 12 as desired.

As shown in Figs. 1 and 2, the entrance portion 22 of the cooling passage 20 includes a larger cross sectional area A _E p than a cross sectional area A _M p of the metering portion 26. In the exemplary embodiment shown, the cross sectional area A _E p of the entrance portion 22 is gradually reduced to the cross sectional area A _M p of the metering portion 26. The gradual reduction of the flow cross sectional area near the entrance portion 22 effects a reduction in pressure losses associated with cooling fluid C _F entering the cooling passage 20, i.e., caused by the gradual reduction in cross sectional area as the cool ing fluid C _F flows from the entrance portion 22 to the metering portion 26.

The cooling passage 20 further comprises an exit portion 32 at the second surface 16 of the substrate 12, wherein the metering portion 26 of the cooling passage 20 is thus defined between the entrance and exit portions 22, 32. The exit portion 32 includes an outlet 34 at the second surface 16 of the substrate 12 for discharging the cooling fluid C _F from the cooling passage 20 to the second surface 16 of the substrate 12.

In the embodiment shown in Figs. 1 and 2, the entrance portion 22 of the cooling passage 20 is generally cone shaped from the inlet 24 to the metering portion 26, and thereafter the cooling passage 20 has a generally constant cross sectional area from the metering portion 26 to the exit portion 32, which comprises a generally circular shape as shown in Fig. 2. However, it is contemplated that the exit portion 32 may have other shapes, such as an ovular shape, shown in Fig. 2A, or a rectangular shape, shown in Fig. 2B. It is noted that while the outlet portion 32 shown in Fig. 2B has rounded corners, it could also have sharper corners without departing from the scope and spirit of the invention. As shown in Figs. 2A and 2B, elongated dimensions E _D of the exit portions 32 extend transverse to the direction of hot gas H _G flow over the second surface 16 of the substrate 12. Hence, in these two embodiments, cooling fluid C _F is distributed by the cooling passage 20 over a larger area of the second surface 16 transverse to the direction of hot gas H _G flow, thus increasing a cooled area of the second surface 16.

Another exemplary shape for the exit portion 32 is shown in Fig. 2C. As shown in Fig. 2C, the exit portion 32 is defined by opposed first and second elongated walls 36A, 36B defining an elongated dimension E _D of the exit portion 32, and by first and second end walls 38A, 38B defining a shortened dimension S _D of the exit portion 32. In the embodiment shown, the first elongated wall 36A extends toward the opposed second elongated wall 36B in a first location L-i generally midway between the first and second end walls 38A, 38B such that the exit portion 32 has a reduced profile in a direction extending between the first and second elongated walls 36A, 36B at the first location L-i . This exit portion shape effects a distribution of cooling fluid C _F shown in Fig. 2C to increase a cooled area of the second surface 16, wherein amounts of cooling fluid C _F distributed by the cooling passages 20 to the second surface 16 of the substrate 12 at the first and second end walls 38A, 38B is increased over the embodiment shown in Fig. 2B. In each of the three embodiments shown in Figs. 2A-2C, a cross sectional area A _XP of the exit portion 32 is larger than the cross sectional area A _M p of the metering portion 26. This effects a reduction in velocity of the cooling fluid C _F flowing out of the cooling passage 20, which is believed to effect an increase in adherence of the cooling fluid C _F to the second surface 16 of the substrate 12 to further enhance film cooling provided by the cooling fluid C _F .

Referring back to Fig. 1 , the cooling passage 20 according to this aspect of the invention is preferably continuously curved extending through the substrate 12 from the inlet 24 of the entrance portion 22 to the outlet 34 of the exit portion 32. Hence, cooling fluid C _F is able to enter the inlet 24 of the entrance portion 22 and then curve with the profile of the cooling passage 20 so as to be discharged from the outlet 34 of the cooling passage 20 at an angle β relative to the second surface 16 of the substrate 12. The angle β may be in a range of from about 5 degrees to about 45 degrees relative to the second surface 16 of the substrate 12, and preferably coincides with the direction of hot gas H _G flow over the second surface 16 of the substrate 12, see Fig. 1 . Hence, the cooling fluid C _F discharged from the exit portion 32 of the cooling passage 20 includes a velocity component in the same direction as the direction of hot gas H _G flow, so as to increase adherence of the cooling fluid C _F to the second surface 16 of the substrate 12.

Referring now to Figs. 3 and 4, a film cooled component wall 1 10 according to another embodiment of the invention is shown, where structure similar to that described above with reference to Figs. 1 and 2 includes the same reference number increased by 100. Structure similar in configuration and/or in function to that described above with reference to Figs. 1 and 2 may not be specifically discussed herein for Figs. 3 and 4.

In the embodiment shown in Figs. 3 and 4, the cooling passage 120 further comprises a branch portion 150 that divides the cooling passage 120 into

corresponding branch passages 152. Each branch passage 152 includes a corresponding exit portion 132 at the second surface 1 16 of the substrate 1 12.

As shown in Fig. 3, the branch portion 150 is located downstream from the entrance portion 122 and just downstream from the metering portion 126, i.e., between the metering portion 126 and the respective exit portions 132, and is located closer to the first surface 1 14 of the substrate 1 12 than to the second surface 1 16 of the substrate 1 12 such that a convectively cooled area effected by the cooling passage 120 is increased, i.e., due to longer branch passages 152.

As shown in Figs. 3 and 4, the entrance portion 122 of the cooling passage

120 includes a larger cross sectional area A _E p than a cross sectional area A _M p of the metering portion 126. In the exemplary embodiment shown, the cross sectional area A _E p of the entrance portion 122 is gradually reduced to the cross sectional area A _M p of the metering portion 126. The gradual reduction of flow cross sectional area near the entrance portion 122 effects a reduction in pressure losses associated with cooling fluid C _F entering the cooling passage 120, i.e., caused by the gradual reduction in cross sectional area as the cooling fluid C _F flows from the entrance portion 122 to the metering portion 126.

The branch passages 152 each receive a portion of the cooling fluid C _F from the entrance portion 122 and deliver the respective portions of cooling fluid C _F to the corresponding exit portions 132 to provide film cooling for the second surface 1 16 of the substrate 1 12 as described above. As shown in Fig. 4, the exit portions 132 of the cooling passage 120 are preferably spaced apart in a direction transverse to the direction of hot gas H _G flow over the second surface to increase a cooled area of the second surface 1 16.

In the embodiment shown in Figs. 3 and 4, the entrance portion 122 of the cooling passage 120 is generally cone shaped from the inlet 124 to the metering portion 126, and each branch passage 152 of the cooling passage 120 has a generally constant or diverging cross sectional area from the branch portion 150 to the corresponding exit portion 132, which comprise a generally circular shape as shown in Fig. 4. However, it is contemplated that the exit portions 132 may have other shapes, such as an ovular shape, shown in Fig. 4A, or a rectangular shape, shown in Fig. 4B. As shown in Figs. 4A and 4B, elongated dimensions E _D of the exit portions 132 extend transverse to the direction of hot gas H _G flow over the second surface 1 16 of the substrate 1 12. Hence, in these two embodiments, cooling fluid C _F is distributed by the cooling passage 120 over a larger area of the second surface 1 16 transverse to the direction of hot gas H _G flow, thus increasing a cooled area of the second surface 1 16.

Another exemplary shape for the exit portion 132 is shown in Fig. 4C. As shown in Fig. 4C, each exit portion 132 is defined by opposed first and second elongated walls 136A, 136B defining an elongated dimension E _D of the respective exit portion 132, and by first and second end walls 138A, 138B defining a shortened dimension S _D of the respective exit portion 132. In the embodiment shown, each first elongated wall 136A extends toward the opposed second elongated wall 136B in a first location L-i generally midway between the respective first and second end walls 138A, 138B such that each exit portion 132 has a reduced profile in a direction extending between the respective first and second elongated walls 136A, 136B at the first location L-i . This exit portion shape effects a distribution of cooling fluid C _F shown in Fig. 4C to increase a cooled area of the second surface 1 16, wherein amounts of cooling fluid C _F distributed by the cooling passages 120 to the second surface 1 16 of the substrate 1 12 at the respective first and second end walls 138A, 138B is increased over the embodiment shown in Fig. 4B.

In each of the three embodiments shown in Figs. 4A-4C, a cross sectional area A _XP of the exit portions 132 is larger than the cross sectional area A _M p of the metering portion 126. This effects a reduction in velocity of the cooling fluid C _F flowing out of the cooling passage 120, which is believed to effect an increase in adherence of the cooling fluid C _F to the second surface 1 16 of the substrate 1 12 to further enhance film cooling provided by the cooling fluid C _F .

Two more exemplary embodiments of the cooling passage 120 according to this aspect of the invention are shown in Figs. 4D and 4E. In these embodiments, the branch portion 150 divides the cooling passages 120 into three branch passages 152, wherein in Fig. 4D, each branch passage exit portion 132 includes the same size outlet 134, while in Fig. 4E, the center branch passage exit portion 132 includes a smaller outlet 134 than the two laterally outer outlets 134. The cooling passage 120 may include even more branch passages 152 than as shown in Figs. 4D and 4E, depending on the total thickness T _T of the substrate 1 12. Referring back to Fig. 3, the cooling passage 120 according to this aspect of the invention is preferably continuously curved extending through the substrate 1 12 from the entrance portion 122 to the exit portion 132, including the entrance portion 122, the branch portion 150, the branch passages 152, and the corresponding exit portions 132. Hence, cooling fluid C _F is able to enter the inlet 124 of the entrance portion 122 and then curve with the profile of the cooling passage 120 so as to be discharged from the cooling passage 120 at an angle β relative to the second surface 1 16 of the substrate 1 12. The angle β may be in a range of from about 5 degrees to about 45 degrees relative to the second surface 1 16 of the substrate 1 12, and preferably coincides with the direction of hot gas H _G flow over the second surface 1 16 of the substrate 1 12, as shown in Fig. 3. Hence, the cooling fluid C _F discharged from the exit portions 132 of the cooling passage 120 includes a velocity component in the same direction as the direction of hot gas H _G flow.

It is noted that traditional drilling procedures are not believed to be capable of forming the cooling passages 20, 120 disclosed herein, at least in part due to the continuous curve of the cooling passages 20, 120 through the substrate 12, 1 12. Hence, according to an embodiment of the invention, the cooling passage 20, 120 may be cast into the substrate 12, 1 12. For example, a sacrificial member (not shown), such as a ceramic core, may be formed into the shape of a cooling passage 20, 120 to be formed, and the substrate 12, 1 12 may be molded or otherwise disposed over the core. Thereafter, the core can be removed, such as in a burn-off procedure or with an acidic solution, thereby leaving an empty space so as to create the cooling passage 20, 120. If multiple cooling passages 20, 120 are to be formed, multiple ceramic cores could be used, which cores may be joined together outside of the substrate 12, 1 12 in an integral structure as desired.

While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.