EP2657609A1

EP2657609A1 - Combustor cap mounting structure for a turbine engine

Info

Publication number: EP2657609A1
Application number: EP13164743.0A
Authority: EP
Inventors: Christopher Paul Keener; Jason Stewart
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 2012-04-23
Filing date: 2013-04-22
Publication date: 2013-10-30
Also published as: JP2013224659A; RU2013118438A; CN103375802A; US20130276449A1

Abstract

A mounting structure for mounting a combustor cap 110 in a combustor of a turbine engine includes support struts 160 that are connected between the combustor cap 110 and a concentric combustor cap barrel flange 150. The support struts 160 may have an airfoil shape to minimize wakes created in a flow of compressed air that is passing over the support struts. Also, the support struts 160 may have an interior passageway that allows a portion of the compressed air to flow though the support strut 160. The flow of air passing through the support struts 160 may also pass through corresponding vent apertures in the combustor cap barrel flange 150 so that the flow of air passing through the support struts 160 is delivered into a space between the exterior of the combustor cap barrel flange 150 and a forward casing of the combustor.

Description

A combustor for a turbine engine used in the power generation industry can include a combustor cap that is mounted adjacent a forward end of the combustor. A plurality of fuel nozzles are typically mounted to an end cover and pass through the combustor cap. Compressed air flows around the exterior periphery of the combustor cap, makes a 180° turn, and then flows through the fuel nozzles, where the air is mixed with fuel. The air-fuel mixture is then ignited downstream from the combustor cap.
Figures 1 and 2 illustrate a typical background art combustor cap assembly mounted in a combustor. As illustrated in these Figures, a combustor cap 110 having openings 112 to receive a plurality of fuel nozzles is mounted to a combustor cap barrel flange 118 by a plurality of A-frame spacers 116. The A-frame spacers 116 are typically formed from flat metal strips. Center portions of the A-frame spacers are mounted to the inner circumference of the combustor cap barrel flange 118, and ends of the A-frame spacers 116 are attached to the outer circumference 114 of the combustor cap 110. The combustor cap barrel flange 118 includes a protruding flange 120. The protruding flange 120 is mounted between a flange 106 of an outer casing 105 and a flange 132 of a forward casing 130.
A flow sleeve 102 is positioned inside the outer casing 106. A combustor liner 104 is mounted concentrically inside the flow sleeve 102. A forward end of the combustor liner 104 engages a hula seal 117 on the exterior circumference 114 of the combustor cap 110. A flow of compressed air from the compressor section of the turbine engine flows through the annular space 103 between the flow sleeve 102 and the combustor liner 104, as illustrated by the arrows appearing in Figure 1. This flow of compressed air also flows through the annular space between the outer circumference 114 of the combustor cap 110 and the inner circumference of the combustor cap barrel flange 118. Because the A-frame spacers 116 are positioned between the outer circumference 114 of the combustor cap 110 and the inner circumference of the combustor cap barrel flange 118, the A-frame spacers 116 tend to impede and/or disrupt the flow of compressed air, resulting in flow losses and separation.
In addition, the combustor cap design illustrated in Figure 1 can result in a step located between the outer circumferential surface of the combustor cap barrel flange 118 and the inner circumferential surface of the forward casing 130. This step can cause disturbances in the flow of compressed air and a low pressure cavity 133 in the volume between the outer circumferential surface of the combustor cap barrel flange 118 and the inner circumferential surface of the forward casing 130. In designs where fuel is introduced through a fuel peg 135 located downstream from the combustor cap, such as with a quaternary fuel circuit, the disturbances caused by this step can provide a path for fuel to migrate upstream from the fuel peg 135. Other obstacles in the compressed air flow path, such as cross fire tubes, can also cause fuel to migrate upstream. If the fuel enters the low pressure cavity 133 in the volume between the outer circumferential surface of the combustor cap barrel flange 118 and the inner circumferential surface of the forward casing 130, it can lead to a flame holding event. All of which is undesirable.
In one aspect, the invention may be embodied in a combustor cap assembly for a turbine engine that includes a generally cylindrical combustor cap configured to receive at least one fuel nozzle, a generally cylindrical combustor cap barrel flange that surrounds an outer circumference of the combustor cap, and a plurality of support struts that mount the combustor cap to the combustor cap barrel flange. The support struts extend between the outer circumference of the combustor cap and an inner circumference of the combustor cap barrel flange. An interior passageway extends through an interior of each support strut.
In another aspect, the invention may be embodied in a support strut that is configured to mount a combustor cap to a combustor cap barrel flange of a combustor of a turbine engine. The support strut includes a main body having an inner end that is configured to be attached to the outer circumference of a combustor cap and an outer end that is configured to be attached to an inner circumference of a combustor cap barrel flange. Also, an interior passageway extends through the main body between an entrance aperture and an exit aperture.

Figure 1 is a diagram of a background art mounting structure for mounting a combustor cap in a combustor of a turbine engine;
Figure 2 is a diagram illustrating how a background art combustor cap is mounted to a combustor cap barrel flange;
Figure 3 is a perspective view of a first embodiment of a support strut that is used to mount a combustor cap to a combustor cap barrel flange;
Figure 4 is a cross-sectional view of a support strut mounted to a combustor cap barrel flange;
Figure 5 is a diagram illustrating how support struts as illustrated in Figures 3 and 4 are used to mount a combustor cap to a combustor cap barrel flange;
Figure 6 is a diagram, illustrating how a combustor cap and combustor cap barrel flange assembly that includes support struts as illustrated in Figures 3 and 4 is mounted to a combustor of a turbine engine;
Figure 7 is a cross-sectional view of an alternate embodiment of a support strut that can be used to mount a combustor cap to a combustor cap barrel flange; and
Figure 8 is a diagram, illustrating how another embodiment of a combustor cap and combustor cap barrel flange assembly that includes support struts as illustrated in Figures 3 and 4 is mounted to a combustor of a turbine engine.

Figures 3 and 4 illustrate a support strut 160 which can be used to mount a combustor cap to a combustor cap barrel flange. The support strut 160 replaces the A-frame spacers 116 used for this purpose in the background art combustor cap assembly illustrated in Figures 1 and 2. The support strut 160 has an airfoil shape, with a rounded leading edge 161 and a tapered trailing edge 163. In addition, an interior passageway extends through the interior of the support strut 160 between an entrance aperture 162 and an exit aperture 164.
Figure 4, which is a cross-sectional view of a support strut 160 attached to a combustor cap barrel flange 150, illustrates that the inner end 166 and outer end 168 of the support strut 160 are substantially parallel to one another. In alternate embodiment, however, the inner and outer ends could be angled relative to one another. In some embodiments, the leading edge 161 and trailing edge 163 of each support strut 160 may be angled with respect to the inner end 166 and outer end 168. Figure 4 also illustrates that an interior passageway 165 passes between an entrance aperture 162 and an exit aperture 164 of the support strut. The exit aperture 164 is in communication with a vent aperture 152 in the combustor cap barrel flange 150. As a result, air entering the entrance aperture 162, flowing through the interior passageway 165 and exiting the exit aperture 164 can pass through the vent aperture 164 of the combustor cap barrel flange 150.
Figure 5 illustrates how a plurality of support struts 160 are used to mount a combustor cap 110 to a combustor cap barrel flange 150. Inner ends 166 of each support strut 160 are mounted to an exterior circumference 114 of the combustor cap 110. Outer ends 168 of each support strut 160 are mounted to an interior circumferential surface 154 of the combustor cap barrel flange 150. In some embodiments, the inner and outer ends of the support struts 160 may be integral to the combustor cap 110 and combustor cap barrel flange 150, respectively. In alternate embodiments, additional structure may be provided to help attach the support struts 160 to one or both of the combustor cap 110 and combustor cap barrel flange 150. Figure 5 presents a view which shows the leading edges of the support struts 160. As a result, one can see the entrance apertures 162 on the leading edges of the support struts 160.
Figure 6 illustrates a side view of the combustor assembly, which shows how the support struts 160 are mounted between the combustor cap 110 and the combustor cap barrel flange 150. Figure 6 also illustrates that the leading edge 161 of the support struts are positioned so that the flow of compressed air exiting the annular space 103 between the flow sleeve 102 and the combustor liner 104 impinges directly on the leading edges 161 of the support struts 160. As a result, a portion of the compressed air flows into the entrance aperture 162, through the interior passageway 165, out the exit aperture 164 of the support strut 160, and then through the vent aperture 152 in the combustor cap barrel flange 150, as illustrated by the arrows in Figure 6. The flow of air passing through the interior of the support struts 160 is delivered into the low pressure cavity 133 between the outer circumferential surface of the combustor cap barrel flange 150 and the inner circumferential surface of the forward casing 130. Thus, the flow of air continuously purges the low pressure cavity 133 that existed in the background art design.
The airfoil shape of the support struts 160 also help to minimize any flow losses that result from the flow of compressed air impinging on the structure used to attach the combustor cap 110 to the combustor cap barrel flange 150. Another benefit of the airfoil shape is that it helps to minimize wakes if the flow of compressed air has a tangential component (swirl). If the air coming from the annular space 103 is swirling, the background art A-frames tended to cause a large wake, as they essentially act like flat plates with an angle of attack. In contrast, when airfoil shapes are used for the support struts the air will tend to stay attached to the airfoil in moderate angles of attack (swirl) thereby minimizing wakes or flow deficits from the structure.
Figure 7 illustrates an alternate embodiment of a support strut 190 that can be used to attach a combustor cap 110 to a combustor cap barrel flange 150. In this embodiment, the interior passageway 175 makes a smooth curve between the entrance aperture 162 on the leading edge 161 of the support strut and the exit aperture 164 that is in communication with the vent aperture 152 in the combustor cap barrel flange 150. The smoothly curved interior passageway 175 also serves to minimize flow losses and maximize the flow of air that is used to purge the dead cavity.
In alternate embodiments, the entrance aperture of a support strut could be located on portions of the sidewall of the support strut other than the leading edge. For example, the entrance aperture could be located on a portion of the sidewall between the leading and trailing edges.
In still other embodiments, multiple entrance apertures could be provided on multiple portions of the sidewall of the support strut. For example, multiple entrance apertures could be formed on the leading edge 161 of a support strut. In some embodiments, all of the entrance apertures would lead to the same interior passageway. In alternate embodiments, each entrance aperture could lead to a separate interior passageway.
Also, in the embodiments described above, the exit aperture is located on the outer end of the support struts. In alternate embodiments, the exit aperture could be located in different locations. Also, multiple exit apertures could be provided.
In an embodiment of a support strut having multiple entrance apertures and/or multiple exit apertures, multiple interior passageways may be provided.
In the embodiments described above, the support struts have a cross-sectional shape with a rounded leading edge and a tapered trailing edge. In alternate embodiments, the support strut could have alternate cross-sectional shapes. For example, the support struts could have a rectangular cross-sectional shape, with or without rounded edges. Alternatively, the support struts could have a circular or oval cross-sectional shape. Still other cross-sectional shapes are also possible, depending on design considerations.
In the embodiments described above, the leading and trailing edges of the support struts were angled with respect to the inner and outer ends. In alternate embodiments, the inner and outer ends could form right angles with the leading and trailing edges of the support struts. Also, in alternate embodiments, the leading and trailing edges may be angled such that the inner ends of the support struts extend further rearward than the outer ends.
Figure 8 illustrates another embodiment of a combustor assembly where support struts 160 are mounted between a combustor cap 110 and a combustor cap barrel flange 150. In this embodiment, a slot 137 is cut in the forward casing 130, and the combustor cap barrel flange 150 is mounted in the slot 137. A cavity 139 is formed between the inner circumference of the slot 137 and the outer circumference of the combustor cap barrel flange 150. A portion of the compressed air exiting the annular space 103 flows into the entrance aperture of the support strut 160, through the interior passageway, out the exit aperture of the support strut 160, and then through a vent aperture in the combustor cap barrel flange 150 and into the cavity 139, as illustrated by the arrows in Figure 6. Thus, a flow of air continuously purges the cavity 139. The flow of air exiting the cavity 139 through the gap 151 prevents fuel delivered from a downstream fuel peg 135 from migrating upstream into the location adjacent the trailing edges of the support struts 160.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements which are encompassed within the spirit and scope of the appended claims.

Claims

A combustor cap assembly for a turbine engine, comprising:
a generally cylindrical combustor cap (110) configured to receive at least one fuel nozzle;

a generally cylindrical combustor cap barrel flange (150) that surrounds an outer circumference of the combustor cap; and

a plurality of support struts (160) that mount the combustor cap to the combustor cap barrel flange and which extend between the outer circumference of the combustor cap and an inner circumference of the combustor cap barrel flange, wherein an interior passageway extends through an interior of each support strut.
The combustor cap assembly of claim 1, wherein vent apertures are formed in the combustor cap barrel flange at locations corresponding to where the support struts are attached to the combustor cap barrel flange, and wherein each vent aperture operatively communicates with the interior passageway of a corresponding support strut.
The combustor cap assembly of claim 1 or claim 2, wherein the interior passageway in each support strut extends between an entrance aperture located on a side surface of the support strut and an exit aperture that is formed on a portion of the support strut that abuts the combustor cap barrel flange.
The combustor cap assembly of any preceding claim, wherein the entrance aperture of each support strut is located on a leading edge portion of the support strut which is impacted by a flow of compressed air.
The combustor cap assembly of any preceding claim, wherein the support struts are mounted to the combustor cap barrel flange such that a flow of air can pass from the entrance aperture of each support strut, through the interior passageway, out the exit aperture of the support strut and through a corresponding vent aperture of the combustor cap barrel flange to a location adjacent an exterior circumference of the combustor cap barrel flange.
The combustor cap assembly of any preceding claim, wherein each support strut has an airfoil shape with a rounded leading edge and a tapered trailing edge.
The combustor cap assembly of any preceding claim, wherein a leading edge of each support strut is angled with respect to the outer circumference of the combustor cap and the inner circumference of the combustor cap barrel flange such that the portion of the leading edge that is coupled to the combustor cap is located further forward than the portion of the leading edge that is coupled to the combustor cap barrel flange.
The combustor cap assembly of any preceding claim, wherein each support strut has an airfoil shape with a rounded leading edge and a tapered trailing edge.
A support strut configured to mount a combustor cap to a combustor cap barrel flange of a combustor of a turbine engine, comprising:
a main body having an inner end that is configured to be attached to the outer circumference of a combustor cap and an outer end that is configured to be attached to an inner circumference of a combustor cap barrel flange; and

an interior passageway that extends through the main body between an entrance aperture and an exit aperture.
The support strut of any preceding claim, wherein the entrance aperture is located on a sidewall of the main body and the exit aperture is located on the outer end of the support strut.
The support strut of any preceding claim, wherein the entrance aperture is located on a leading edge of the main body.
The support strut of any preceding claim, wherein the main body has an airfoil shape with a rounded leading edge and a tapered trailing edge.
The support strut of any preceding claim, wherein the inner and outer ends are substantially parallel to one another, wherein a leading edge of the main body forms an oblique angle with the inner end, and wherein a trailing edge of the main body forms an acute angle with the inner end.
The support strut of any preceding claim, wherein the main body has an airfoil shape with a rounded leading edge and a tapered trailing edge.
The support strut of any preceding claim, wherein the entrance aperture is located on the leading edge of the main body and the exit aperture is located on the outer end of the main body.