Converging duct with elongated and hexagonal cooling features

A gas turbine engine has a converging duct that has combustion products flow at low mach speeds through a first portion and a high mach speeds through a second portion. The converging duct has two types of cooling schemes formed. One type of cooling scheme is beneficial for the low mach speed combustion product flow and one type of cooling scheme is beneficial for the high mach speed combustion product flow. The two cooling schemes are blended together in order increase the efficiency of the cooling of the converging duct.

BACKGROUND

Disclosed embodiments are generally related to gas turbine engines and, more particularly to gas turbine engines producing low and high mach combustion products.

2. Description of the Related Art

Gas turbine engines comprise a casing or cylinder for housing a compressor section, a combustion section, and a turbine section. A supply of air is compressed in the compressor section and directed into the combustion section. The compressed air enters the combustion inlet and is mixed with fuel. The air/fuel mixture is then combusted to produce high temperature and high pressure gas. This working gas then travels past the combustor transition and into the turbine section of the turbine.

Generally, the turbine section comprises rows of vanes which direct the working gas to airfoil portions of the turbine blades. The working gas travels through the turbine section, causing the turbine blades to rotate, thereby turning the rotor. The rotor is attached to the compressor section, thereby turning the compressor and also an electrical generator for producing electricity. A high efficiency of a combustion turbine is achieved by heating the gas flowing through the combustion section to as high a temperature as is practical. The hot gas, however, may degrade the various metal turbine components, such as the combustor, transition ducts, vanes, ring segments and turbine blades that it passes when flowing through the turbine.

For this reason, strategies have been developed to protect turbine components from extreme temperatures such as the development of cooling features on components. Providing heat management features to improve the efficiency and life span of components and the gas turbine engines is further needed. Of course, the cooling features described herein are not limited to use in context of gas turbine engines, but are also applicable to other heat impacted devices, structures or environments.

SUMMARY

Briefly described, aspects of the present disclosure relate to cooling features in gas turbine engines.

An aspect of the disclosure may be a gas turbine engine comprising a combustor; a converging duct connected to the combustor, wherein the converging duct comprises; a first portion having a first portion layer, wherein the first portion has a first diameter, wherein the first portion layer has formed thereon cooling channels for cooling the first portion, wherein the cooling channels extend axially from upstream to downstream; a second portion having a second portion layer, wherein the second portion has a second diameter smaller than the first diameter, wherein the second portion layer has formed thereon high mach cooling features for cooling the second portion; and wherein effusion holes are formed in the cooling channels at a location proximate to the second portion layer.

Another aspect of the present disclosure may be a converging duct comprising a first portion having a first portion layer, wherein the first portion has a first diameter, wherein the first portion layer has formed thereon cooling channels for cooling the first portion, wherein the cooling channels extend axially from upstream to downstream; a second portion having a second portion layer, wherein the second portion has a second diameter smaller than the first diameter, wherein the second portion layer has formed thereon high mach cooling features for cooling the second portion; and wherein effusion holes are formed in the cooling channels at a location proximate to the second portion layer.

DETAILED DESCRIPTION

To facilitate an understanding of embodiments, principles, and features of the present disclosure, they are explained hereinafter with reference to implementation in illustrative embodiments. Embodiments of the present disclosure, however, are not limited to use in the described systems or methods.

In order to accelerate the combustion products to a high mach speed, a gas turbine engine may employ a converging duct.FIG. 1shows a converging duct10located within a gas turbine engine5. The converging duct is located downstream of a combustor6. The combustor6produces combustions products that move downstream through the converging duct10in an axial direction. As the combustion products move downstream through the converging duct10they move from a low mach speed to a high mach speed in some instances.

Combustion products will flow through the converging duct10at speeds between 0.2 to 0.85 mach. Low mach speed is when the flow speed of the combustion products is between 0.2 to 0.45 mach. High mach speed is when the flow speed of the combustion products is between 0.45 to 0.7 mach. It should be understood that flows speeds between 0.4-0.5 mach could be considered either low mach speed or high mach speed.

A converging duct10, made in accordance with an embodiment of the present disclosure, is shown inFIG. 2. The converging duct10needs to be cooled in order to maintain the durability of the component and to increase the life span of the converging duct10. The passage of the combustion products through the converging duct go from the low mach range to the high mach range. The transition of the flow speed of the combustion productions from low mach to high mach speeds complicates the way in which cooling features are employed in the converging duct10. Some cooling schemes are not effective for flows that are in the high mach range and some cooling schemes would waste air if cooling structures in regions subject to low mach speed flows. This occurs due to an increasing pressure drop across cooling schemes associated with higher mach flows.

In order to fully take advantage of the different mach ranges of combustion products passing through the converging duct10a blended combination of effective cooling schemes for the low mach and the high mach ranges are employed in order to reduce the consumption of cooling air in the converging duct10.

The cooling scheme shown inFIG. 1may be able to reduce consumption of cooling air by the converging duct10by up to 50%. By employing bonded panel technology this can be accomplished. Bonded panel technology is when layers can be bonded together to form a component. This permits more complicated geometries to be formed than when a component is cast as a single piece. The bonded panel technology employed in forming the converging duct10enables multiple cooling features to be employed by using a single bonded sheet to form both the low speed and high speed mach cooling features and then bonding these sheets to form additional layers of the component.

While bonded panel technology is discussed herein in forming the converging duct10, it should be understood that other techniques may be employed as well, such as casting, welding and brazing pieces together. However, the resulting products may not have the same structural integrity as when bonded panel technology is employed.

FIG. 2shows a view of a converging duct10made in accordance with an embodiment of the present disclosure. Connected to the converging duct10is an inlet ring8having support struts9. The inlet ring8is connected to a combustor6which is located upstream from the converging duct10. Located at the opposite end of the converging duct10is an outlet ring12. The outlet ring12is connected to an inlet extension piece (IEP). It should be understood that the outlet ring12and IEP may be unitary piece. It should further be understood that while a converging duct10is shown and described herein it is possible to implement aspects of the present invention in other components of the gas turbine engine5in which there low mach and high mach combustion products flowing through them.

The converging duct10may be made of a metal material and has a first portion14and second portion15. The first portion14forms the shape of a conical section and has combustion products flow through it at low mach speeds. As the combustion products flow through the first portion14their speeds increase. The diameter D1of the first portion14at the location of the inlet ring8is substantially the same as the inlet ring8. The diameter D1of the converging duct10decreases as it extends downstream from the inlet ring8to the second portion15.

The second portion15has a diameter D2that is less than the diameter D1of the first portion14. The diameter D2also decreases as the second portion15extends downstream to the outlet ring12. Combustion products flow at high mach speeds through the second portion15. The combustion products increase in speed as they flow through the converging duct10.

Referring toFIG. 3, first portion14has a first portion layer16. In the embodiment shown, the first portion layer16forms one of the bonded layers used in forming the converging duct10. The second portion15has a second portion layer17, which forms one of the bonded layers used in forming the converging duct10. In particular both the first portion layer16and the second portion layer17may be formed as a single bonded layer. In particular the first portion layer16and the second portion layer17form the middle bonded layer23of the three bonded layers used in forming the converging duct10, these layers are the top bonded layer22, middle bonded layer23and bottom bonded layer24, shown inFIGS. 4 and 5.

Formed in the first portion layer16are a plurality cooling channels18. The cooling channels18extend in an axial direction downstream from the location where the first portion14is connected to the inlet ring8to the location where the first portion14meets the second portion15. The cooling channels18extend axially down the first portion18without intersecting any of the other cooling channels18. The cooling channels18may extend over 50% of the axial length of the converging duct10.

Each of the cooling channels18may have the same width. The conical shape of the converging duct10and the first portion14on which the cooling channels18extend leads to a reduction in pitch between each of the cooling channels18as they extend axially downstream. This can best be seen inFIG. 6where the width W1between two cooling channels18is greater than a width W2between the same two cooling channels18at a location further downstream of the converging duct10. The reduction in pitch between two cooling channels18offsets the increase in coolant temperature and increase in hot side transfer that occurs as it flows through the cooling channels18. At the location where the coolant is no longer providing a significant cooling benefit to the first portion14the coolant will be expelled. The expelled coolant will still be able to provide film cooling of the converging duct10.

Additional modifications may be made to the cooling channels18in order to further increase heat transfer. For example, the cooling channels18may be formed with jogs, so as to promote pressure loss and heat transfer increase. Cooling channels18may also be formed that have additional circumferential components. Additionally, zig-zags may be incorporated into the cooling channels18.

InFIG. 4, a close up view of the area where the cooling channels18approach the second portion layer17and the high mach cooling features19is shown. As the cooling channels18approach the second portion layers17they may begin to curve in the circumferential direction. The curvature of the cooling channels18is represented by the angle α. The angle α may be between 30° and 45°. The formed angle helps in controlling the film cooling of the converging duct10.

Additionally formed at the distal end of the cooling channels18inFIG. 4may be a plurality of effusion holes21. The effusion holes21are formed at an angle through the bottom bonded layer24. The formed angle slants in the downstream direction.

In the embodiment shown inFIG. 5the effusion holes21may be staggered in the in the location proximate to the second portion15. By staggered it is meant that the effusion holes21in adjacent channels18may be located at different positions as one extends along the circumferential direction.

Impingement holes26may be formed on the top bonded layer22at locations further upstream. The impingement holes26are formed so as to expel cooling air into the converging duct10prior to entering the second portion15. These impingement holes26allow there to be no film starter rows. This is a benefit in that air consumption in previous film starter rows has been costly in consumption.

As shown inFIG. 5, when impingement holes26are used with the channels18a reservoir27is formed in the layer in which the channels18are formed. The impingement holes26extend through the top bonded layer22at the location of the reservoirs27.

In the embodiment tshown inFIG. 5, the reservoir27may be formed in the middle bonded layer23. The reservoir27is a widening of the channel18in middle bonded layer23. Reservoirs27are formed as circles in which the impingement holes26or effusion holes21may open into. The reservoirs27aid in the manufacturing of the converging duct10by facilitating the ease with which channels18can be connected during construction. The reservoirs27also create more area with which to take advantage of cooling air.

As shown inFIG. 5, the high mach cooling features19formed in the second portion layer17are shown as being hexagonal in shape. However, it should be understood that other shapes may be employed, such as circular, pentagonal, octagonal, etc.

FIG. 6shows a close up view of the high mach cooling features19formed in the second portion surface17. The hexagonal features are formed in the middle bonded layer23. Also shown are impingement holes26and effusion holes21which are formed in the top bonded layer22and the bottom bonded layer24, respectively. The effusion hole21is angled with and slants in the downstream direction.

FIGS. 7 and 8show top down views of the first surface16and second surface17. From this viewpoint it can be seen how the cooling channels18can extend into the second surface19. While the cooling channels18extend in the axial direction without intersecting each other, some of the cooling channels18extend further into the second surface17than other cooling channels18. The extension of the cooling channels18into the second surface17maximizes the cooling air that flows over the first portion14and the second portion15, by maximizing the surface area that the cooling features cover. Furthermore, as discussed above, the pitch between the cooling channels decreases as the cooling channels extend downstream in the axial direction.

The high mach cooling features19also vary slightly in their nature as they are located further downstream on the converging duct10. InFIGS. 7 and 8, the dimensions of the hexagons formed decrease as one moves further downstream on the converging duct10and as it approaches the outlet ring12. For instance, the overall size of the hexagon decreases. The decreasing dimensional nature of the hexagonal high mach cooling features19permits retention of the spacing between the high mach cooling features19. Maintaining the spacing of the high mach cooling features19permits the cooling features to effectively cool structures in regions subject to the high mach combustion product flow.