BACKGROUND

1. Field [0001] Disclosed embodiments are generally related to combustors and, more particularly to cooling rings used with combustor baskets.

2. Description of the Related Art

[0002] Cooling rings used with combustor baskets typically require reduction of the outer diameter of the cooling ring just before an entrance into a cooling channel. The diameter of the cooling ring is reduced by reducing the material thickness of the cooling ring. The reduction of the outer diameter occurs due to manufacturing needs and to provide the cooling air with a smooth entrance to the combustor basket's cooling channels. [0003] Fig. 1 shows a standard combustor basket system 10 that uses a typical cooling ring 2. In Fig. 1 the cooling ring 2 is cylindrical shaped. The cooling ring 2 has an outer diameter Di throughout a majority of its length. Prior to a cooling channel entrance 4 of a cooling channel 6 is a transition zone 8, which begins at transition zone start 11 and ends at transition zone end 13. Transition zone end 13 is located at the cooling channel entrance 4. The transition zone 8 has a wall 3, which has an inner surface 5 and outer surface 7. The transition zone 8 has an outer diameter Di that is reduced to an outer diameter D2 as it approaches the transition zone end 13 and the cooling channel entrance 4. D2 is the outer diameter of the cooling ring 2 at a portion of the transition zone 8. This reduction to outer diameter D2 is due to reduction of the material thickness of the cooling ring 2 at the transition zone 8. This is done so that flow of air remains beneficial for the combustor basket system 10.

[0004] The reduction of the outer diameter Di to the outer diameter D2 of the cooling ring 2 prior to the entrance to the cooling channel 6 reduces the thickness T i of the cooling ring 2. The reduction of the thickness Ti of the cooling ring 102 results in reduction of the material strength in that area, leading to a reduction in low cycle fatigue life.

[0005] Figs. 2A and 2B illustrate the stresses that occur with the cooling ring 2. Fig. 2A depicts the temperatures that impact the cooling ring 2. Fig. 2B illustrates the Von Mises stresses that occur within the cooling ring 2 due to the effect of the temperatures. As shown in Fig. 2B, the Von Mises stresses are greater at the location of the cooling ring 2 where the outer diameter Di is reduced to the outer diameter D2 and where there is reduction of the thickness Ti of wall 3. [0006] In the past to address this problem the temperature of the cooling ring in the weakened area was reduced. Reducing the temperature limited the stresses that occur at the area to an acceptable value, however would require trade-offs to other aspects of the combustor basket system. SUMMARY

[0007] Briefly described, aspects of the present disclosure relate to cooling rings used in combustor basket systems.

[0008] A first aspect of the disclosure provides a combustor basket system having a cooling ring comprising a transition zone, wherein the transition zone extends from a transition zone start to a cooling channel entrance. The combustor basket system also comprises a transition zone that has a cross-section profile configured to provide a substantially uniform material strength.

[0009] A second aspect of the disclosure provides a cooling ring for use with a combustor basket system. The cooling ring comprises a wall having an outer surface and an inner surface. The wall forms a transition zone that extends to a cooling channel entrance of the basket cooling system. The wall has a thickness which is the distance between the outer surface and the inner surface and further wherein the material strength of the wall is substantially uniform throughout the transition zone. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Fig. 1 is cross-sectional side view of a combustor basket system that uses a prior art cooling ring. [0011] Fig. 2A shows a diagram illustrating the temperatures that affect the cooling ring shown in Fig. 1.

[0012] Fig. 2B shows a diagram illustrating the Von Mises stresses that occur with the cooling ring shown in Fig 1.

[0013] Fig. 3 is a cross-sectional side view of a combustor basket system that uses a cooling ring in accordance with an embodiment of the present disclosure.

[0014] Fig. 4A shows a diagram illustrating the temperatures that affect the cooling ring shown in Fig. 3.

[0015] Fig. 4B shows a diagram illustrating the Von Mises stresses that occur with the cooling ring show in Fig. 3.

DETAILED DESCRIPTION

[0016] 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.

[0017] The components and materials described hereinafter as making up the various embodiments are intended to be illustrative and not restrictive. Many suitable components and materials that would perform the same or a similar function as the materials described herein are intended to be embraced within the scope of embodiments of the present disclosure. [0018] To ameliorate the problems that occur due to the reduction in the thickness of the cooling ring 2 shown in Fig. 1, an embodiment of the present disclosure has the location of the entrance to cooling channels not at a cylindrical section of a combustor, but instead locates the entrance to the cooling channels at a conical section of a combustor basket system. By moving the transition zone and entrance to a conical section of the of the combustor basket system, the machined feature of the cooling ring 2 that results in a weakness is eliminated and the thickness of the cooling ring can be maintained throughout its length. This also provides the benefit of being able to use fewer liners than in previous combustor basket systems.

[0019] Referring to Fig. 3, wherein an embodiment of the present invention shown, a cooling ring 102 is shown used in combustor basket system 110. The combustor basket system 1 10 shown in Fig. 3 is colloquially referred to as a G-type basket style system. By "G-type basket style" it is meant the basket is used with a G-frame combustor. With a G-type basket style the active combustion length is split between 25% being the combustor basket and 75% the transition zone. In other words, the transition zone is longer than the combustor basket. In other types of combustor basket systems, the active combustion length is generally split between the combustor basket and the transition zone so that it is 50% combustor basket and 50% transition zone. While, the combustor basket system 110 shown in Fig. 3 is a G-type basket style, it is contemplated that other types of styles may be employed. For example, the cooling ring 102 may be employed with baskets colloquially referred to as "D-type," "E-type," "F-type", "H-type baskets" and "J-type baskets."

[0020] Still referring to Fig. 3, the cooling ring 102 is formed by a wall 103 that has an inner surface 105 and an outer surface 107 and forms transition zone 108. In the embodiment shown in Fig. 3, the cooling ring 102 is conically shaped. However it should be understood that other shapes may be accommodated provided that the cooling ring 102 is able to maintain its material strength at the transition zone 108. By "material strength" it is meant that that the stresses that the material is able to withstand due to environmental factors, such as forces impacting the material or temperatures that the material can withstand without failure. The limiting factor of cooling rings is low cycle fatigue life which is impacted by material properties and the temperature. [0021] The transition zone 108 is the portion of the cooling ring 102 that begins at transition zone start 1 1 1 and ends at transition zone end 1 13. Transition zone start 1 1 1 may be the area where the cooling ring 102 begins, or alternatively an area proximate to where the cooling ring 102 begins. The transition zone start 1 1 1 may also begin prior to the hot section of the combustor basket system 1 10, however the transition zone start 1 1 1 may be located after another cooling feature of the combustor basket system 1 10. Transition zone end 1 13 is that area of the transition zone 108 where the cooling channel entrance 104 begins. The transition zone 108 may be 75% of the length of the active combustion length, which is defined as the length of the combustor in which combustion occurs.

[0022] The cooling ring 102 may be made of nickel alloys with high nickel concentrations, or other materials capable of withstanding temperatures found within combustor basket system 1 10. Generally speaking the temperatures that the cooling ring 102 can withstand in the transition zone 108 are temperatures within the range of 500 to 1000 °C, more preferably the cooling ring 102 can withstand temperatures greater than 700 °C.

[0023] The transition zone 108 of the cooling ring 102 is able to withstand temperatures greater than 750 °C without having to provide additional measures to cool the area in the transition zone 108, such as those required in typical combustor basket systems. In some embodiments this means that the number of air holes 1 17 located in the combustor basket system 1 10 may be reduced. For example the number of air holes used in previous combustor basket systems may be greater than 180. In combustor basket system 1 10 the number of air holes 1 17 may be less than 180 and may be as low as 90, or less. [0024] Still referring to Fig. 3, the combustor basket system 1 10 has a cooling channel entrance 104 that permits access of cooling air into a cooling channel 106. In an embodiment of the present invention, the outer diameter D3 of the cooling ring 102 gradually increases, to the diameter D ₄ as it approaches cooling channel entrance 104. The gradual increase may be accomplished by having an angle a that is less than about 10° but greater than 3°, and more preferably from between about 4-6°. The angle a is an angle that is formed between a point on the horizontal line formed by the central axis of the cooling basket system 110 and a point on the inner surface 105 of the wall 103 _.

[0025] While the outer diameter of the cooling ring 102 gradually increases, the thickness T2 of the cooling ring 102 may remain substantially constant, that is within appropriate manufacturing tolerances. The thickness T2 is the distance between the outer surface 107 and the inner surface 105 of the wall 103 of the cooling ring 102. Thus the transition zone 108 has substantially the same thickness T2 throughout. Preferably the thickness T2 is between 4 to 12 mm and more preferably between 5-8 mm, while it is contemplated that a uniform thickness extends throughout the transition zone 108, it should be understood that preferably the thickness is such that the integrity of the cooling ring 102 is not compromised during use due to material weaknesses, or that the Von Mises stresses that affect the cooling ring 102 are such that they do not adversely impact the cooling ring 102 in a particular location. In other words, maintaining the thickness T2 constant throughout the transition zone 108 is one way in which material weaknesses do not adversely impact one particular area of the cooling ring 102. Other features of the cooling ring 2, discussed herein, may also provide ways in which the material strength of the cooling ring 2 may remain constant throughout the transition zone 108.

[0026] In an embodiment of the present disclosure, the transition zone 108 is integrally formed as part of the cooling ring 102. However, the transition zone 108 may also be formed from sheet metal and welded to the cooling ring 102. By maintaining the thickness T2 substantially constant the weakness exhibited by typical cooling rings is avoided because there is no change in the material thickness of the transition zone 108 thereby maintaining a uniform material strength. [0027] Additionally, the transition zone 108 approaches the cooling channel entrance 104 with a step-like feature having a having a height of Hi. The height Hi is the distance the cooling channel entrance 104 is above the outer surface 103. Hi may be between the ranges of 3 to 15 mm. The height Hi plays a beneficial role in the flow of air through the combustor basket system 1 10. [0028] Figs. 4A and 4B illustrate representative stresses that may occur with the cooling ring 102. Fig. 4A depicts the temperatures that impact the cooling ring 102. Fig. 4B illustrates representative Von Mises stresses that occur within the cooling ring 102 due to the impact of the temperature on the cooling ring 102. As shown in Fig. 4B, the Von Mises stresses are reduced at the cooling channel entrance 104, as compared with the cylindrical cooling ring 2, because there is no reduction in the thickness T2 of the cooling ring 102 at the cooling channel entrance 104. Further, the angle and direction at which the transition zone 108 meets the cooling channel entrance 104 permits there to be smooth flow of air. Further, as opposed to typical combustor basket systems, the number of liners 1 19 used in the system may be reduced.

[0029] While embodiments of the present disclosure have been disclosed in exemplary forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the spirit and scope of the invention and its equivalents, as set forth in the following claims.