A device for guiding a stream of a cooling medium

Abstract

 The present invention provides a robust device for guiding a stream of a cooling medium (9, 55, 306). The device comprises a first shell (2, 10, 301) spaced from a second shell (3, 20, 302) to form a cooling channel (9, 30, 303). The second shell (3, 20, 302) is adapted to be exposed to a higher temperature than the first shell (2, 10, 301). The first shell (2, 10, 301) has at least one supporting means (7, 40, 304) extending from said first shell (2, 10, 301) and terminating at a point near the second shell (3, 20, 302) forming a gap (8, 50, 305).

Description

[0001] The present invention relates to devices for guiding a stream of a cooling medium and in particular to devices having a first shell spaced from a second shell.

[0002] Cooling systems are used industrially for various applications, e.g. for cooling the hot casing of combustion chambers. Cooling techniques presently used are convection, impingement or impingement/effusion cooling, among others. A double shell design is typically used for convective or impingement cooling, with the inner shell to be cooled and the cooling medium being guided between the inner and the outer shell, the inner and the outer shell forming a cooling channel. When using concentric cooling channels (e. g. in a combustor or a transition duct) having a height significantly smaller than the curvature of the cross section of the channels, the cooling device might be deformed over time as the material in the inner wall distorts. This in turn will deteriorate the cooling performance in the affected area leading to accelerating creep which might eventually make the structure collapse.

[0003] It is an object of the present invention to provide a robust device for guiding a stream of a cooling medium.

[0004] The above object is achieved by a device for guiding a stream of a cooling medium,

said device having a first shell spaced from a second shell to form a cooling channel wherein the second shell is adapted to be exposed to a higher temperature than the first shell; and

the first shell having at least one supporting means extending from said first shell towards the second shell forming a gap between the supporting means and the second shell.

[0005] The underlying idea of the present invention is to ensure an optimum distance between the shells of a cooling channel and at the same time to avoid any direct thermal connection between both shells. The device has a first shell which might be exposed to a cold environment and a second shell which might be exposed to a hot environment. The supporting means acts as a support for the second shell when it distorts down towards the first shell, e. g. due to heating of the second shell. The supporting means extends from the first shell to the interior of the cooling channel and extends just up to the second shell, without actually touching it, thereby forming a gap between the supporting means and the second shell. The gap helps in avoiding the formation of cracks and extremely high stresses that can develop due to thermal mismatch between the shells in case they were directly thermally connected to each other. The second shell might be unevenly heated with buckling, creep and Low Cycle Fatigue (LCF) deformations. The supporting means keeps the distance between the first and the second shell correct during long operation times. It is advantageous not to connect the first and the second shell rigidly, since this might result in high stresses and cracks due to thermal mismatch between the shells.

[0006] In a preferred embodiment of the invention, said supporting means comprises: at least one first opening to the exterior of the cooling channel; at least one second opening to the interior of the cooling channel; and at least one conduit connecting the first opening and the second opening. In a further preferred embodiment of the invention the first opening, second opening and the conduit are used for maintaining a flow of the cooling medium from the exterior of the cooling channel into the cooling channel. The openings and conduit enable the maintenance of a cooling mechanism by allowing the entry of the cooling medium into the cooling channel even when the second wall creeps in and touches the supporting means. Nevertheless the supporting means acts as a creep support for the second shell.

[0007] In an alternative embodiment of the invention, the supporting means is a bend in the first shell, wherein said bend is curved towards the second shell. The bend acts as a support for the hot second shell incase the shell creeps down to the first shell. This helps in maintaining an optimum distance between the shells for providing optimized cooling. These bends could be manufactured easily by pressing tools and they are smooth to keep the stress concentrations low. This is a cheap simple and reliable way to keep the distance for hot double shell designs.

[0008] In another alternative embodiment the supporting means are equidistantly spaced from one another. This facilitates the maintenance of minimum distance between the shells for optimum cooling as well as for enabling support for creep through out the length of the device.

[0009] The present invention is further described hereinafter with reference to illustrated embodiments shown in the accompanying drawings, in which:

FIG 1 is a cross sectional view of the device with the supporting means;

FIG 2 is a cross sectional view of a device for guiding a stream of a cooling medium having a supporting means adapted to provide internal cooling;

FIG 3 is a cross sectional view of the device with the supporting means when said device is used as a cooling means for an enclosed circular casing;

FIG 4 is a cross sectional view of the device with the bend as the supporting means in the outer shell; and

FIG 5 is a cross sectional view of the device with the bend as the supporting means when said device is used as a cooling means for an enclosed circular casing.

[0010] FIG 1 is a cross sectional view of a device 1 for guiding a stream of a cooling medium 9. The device 1 comprises of a first shell 2 spaced from a second shell 3 to form a cooling channel 4. The second shell 3 is adapted to be exposed to a higher temperature than the first shell 2. This is because the second shell 3 is generally exposed to a hot environment 5 and the first shell 2 to a cold environment 6, for example when the device 1 is used as a cooled combustor wall for a gas turbine. When used as a cooled combustor wall the first shell 2 acts as an outer shell and the second shell 3 acts as the inner wall exposed to the hot environment. The first shell 2 holds a supporting means 7 which extends from said first shell 2 towards the second shell 3 forming a gap 8 between the supporting means 7 and the second shell 3. The supporting means 7 extends just up to the second shell 3, but do not actually touch the second shell 3. The gap 8 allow for thermal displacements between the first shell 2 and the second shell 3. This supporting means 7 facilitates the maintenance of minimum distance between the shells as well as acts as a support for the second shell 3 if said second shell 3 distorts down towards the first shell.

[0011] FIG 2 is a cross sectional view of a device 100 for guiding a stream of a cooling medium 55 having a supporting means 40 adapted to provide internal cooling. The device 100 comprises of a first shell 10 spaced from a second shell 20 to form a cooling channel 30. When used as cooling systems in gas turbines the second shell 20 is generally exposed to a hot environment 25, where the second shell 20 acts typically as a combustor wall. The first shell 10 holds a supporting means 40 which extends from said first shell 10 towards the second shell 20 forming a gap 50 between the supporting means 40 and the second shell 20. The gap 50 allow for thermal displacements between the first shell 10 and the second shell 20. The supporting mean 40 is designed to provide internal cooling. The cooling medium 55 is allowed to enter into the cooling channel 30 through a first opening 60 in the supporting means 40. The cooling medium 55 entering the supporting means 40 from the cold environment 66 is allowed to come in contact with the hot second shell 20 to facilitate the cooling process. The supporting means 40 further comprises of a second set of openings 70, 80, 90 which allows the flow of the cooling medium which has entered said supporting means 40 into the cooling channel 30. The supporting means 40 further comprises of a conduit 65 connecting the first opening 60 and the second set of openings 70, 80, 90. Even if the inner second shell 20 distorts down towards the first shell 10, it can rest on the supporting means 40, still maintaining the minimum distance between the shells for optimum cooling. When the inner second shell 20 distorts down to the outer first shell 10, there is a high probability that the opening 90 may get closed. Even if the second opening 90 gets closed, the cooling medium entering the supporting means 40 can pass through the other second openings 70 ,80 from the inside of the supporting means 40 into the cooling channel 30. The design helps in maintaining the cooling of the second shell 20 as well as maintaining an optimum distance between the shells by acting as a support. In practical industrial application scenarios, there might be a pressure difference between within and outside of the device 100. The pressure outside the first shell 10 at the cold environment 66 is comparatively higher than that inside the cooling channel 30. The pressure difference drives the cooling medium 55 from the cold environment 66 into the cooling channel 30. These supporting means could be mounted in any stage of the manufacturing process of the device.

[0012] FIG 3 is a cross sectional view of the device 200 when used as a cooling apparatus for an enclosed circular casing 201. The inner shell of the device 200 is the enclosed hot casing 201. In practical operation, the inner shell 201 will be at a much higher temperature than the outer shell 202. The inner shell 201 and the outer shell 202 form a cooling channel 203 between them. The device 200 comprises a plurality of supporting means 204 equidistantly spaced along the entire circumference of the outer shell 202. The supporting means 204 helps in maintaining a minimum distance between the shells if the inner shell 201 distorts towards the outer shell 202. The device also allows for internal cooling even when the casing 201 distorts down towards the outer shell 202.

[0013] FIG 4 shows a cross sectional view of the device 300 with a bend 304 of the first shell as a supporting means. The device 300 comprises of a first shell 301 and a second shell 302 forming a cooling channel 303.The cooling channel 303 enables the flow of a cooling medium 306. A bend 304 formed in the first shell 301 acts as a support which helps in maintaining a minimum distance between the first shell 301 and the second shell 302 in case the second shell 302 distorts down towards the first shell 301. The bend 304 is made in the first shell 301 and is positioned so as to be curved towards the second shell 302 but terminates at a point near the second shell 302 forming a gap 305 to allow for thermal displacements between the first shell 301 and the second shell 302. These bends could be manufactured easily by pressing tools and they are smooth to keep the stress concentrations low.

[0014] FIG 5 illustrates the device 400 with the bend as the supporting means when used in an enclosed circular casing 401. The inner shell 401 of the device 400 will act as the enclosed hot casing. The casing 401 and the outer shell 402 form a cooling channel 403 between them. The device comprises a plurality of bends 404 equidistantly spaced along the entire circumference of the outer shell 402. The bends 404 help in maintaining a minimum space between the shells when the casing 401 creeps down towards the outer shell 402.

[0015] Summarizing, the present invention provides a robust device for guiding a stream of a cooling medium. The device comprises a first shell spaced from a second shell to form a cooling channel. The second shell is adapted to be exposed to a higher temperature than the first shell. The first shell has at least one supporting means extending from said first shell and terminating at a point near the second shell forming a gap.

[0016] Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the present invention as defined.

Claims

1. A device (1, 100, 300) for guiding a stream of a cooling medium (9, 55, 306),

said device (1, 100, 300) having a first shell (2, 10, 301) spaced from a second shell (3, 20, 302) to form a cooling channel (4, 30, 303) wherein the second shell (20, 302) is adapted to be exposed to a higher temperature than the first shell (2, 10, 301); and

the first shell (2, 10, 301) having at least one supporting means (7, 40, 304) extending from said first shell (2, 10, 301) towards the second shell (3, 20, 302) forming a gap (8, 50, 305) between the supporting means (7, 40, 304) and the second shell (3, 20, 302).

2. The device according to claim 1 wherein said supporting means (40) comprises:

at least one first opening (60) to the exterior of the cooling channel (30);

at least one second opening (70, 80, 90) to the interior of the cooling channel (30); and

at least one conduit (65) connecting the first opening (60) and the second opening (70, 80, 90).

3. The device according to claim 2 wherein the first opening (60), second opening (70, 80, 90) and the conduit (65) are used for maintaining a flow of the cooling medium (55) from the exterior of the cooling channel (30) into the cooling channel (30).

4. The device according to any of the preceding claims wherein the supporting means is a bend (304) in the first shell (301), wherein said bend (304) is curved towards the second shell (302).

5. The device according to any of the preceding claims wherein the supporting means (40, 304) are equidistantly spaced from one another.

Drawing