WO2020050854A1

WO2020050854A1 - Angular cooling channels for improved mechanical life

Info

Publication number: WO2020050854A1
Application number: PCT/US2018/049952
Authority: WO
Inventors: Krishna C. Miduturi; Landon TULLY; Sachin TERDALKAR; Vaidyanathan KRISHNAN; Urmi B. DAVE; Heather Marie WHIPP
Original assignee: Siemens Aktiengesellschaft; Siemens Energy, Inc.
Priority date: 2018-09-07
Filing date: 2018-09-07
Publication date: 2020-03-12

Abstract

An angular cooling arrangement to provide increased mechanical life is presented. The cooling arrangement includes a cooling channel disposed in a combustor liner (28) adapted to provide a region of blocking flow within a combustor exit/transition inlet ring interface (22). The cooling arrangement includes a cooling channel (26) and a redirecting element (30) that guides cooling fluid exiting the cooling channels that substantially reduces the tendency of hot working fluids to flow upstream away from a recirculation zone (42) within the combustor exit/transition inlet ring interface (22). With the presented arrangement, the need for purge air in this region is reduced, cooling efficiency is increased, NOx emissions are controlled to acceptable levels, and component life targets are met.

Description

ANGULAR COOLING CHANNELS FOR IMPROVED MECHANICAL LIFE

TECHNICAL FIELD

The present invention relates generally to gas turbine engine cooling and, more particularly, to a cooling arrangement for improving mechanical life of a gas turbine com- bustion chamber.

BACKGROUND OF THE INVENTION

A gas turbine engine is one known machine that provides efficient power, and often has application for an electric generator in a power plant, or engines in an aircraft or a ship. A typically gas turbine engine includes a compressor section, a combustion section and a turbine section. The compressor section provides a compressed airflow to the com bustion section where the air is mixed with a fuel, such as natural gas. The combustion section includes a plurality of circumferentially-disposed combustors that receive and ig- nite the fuel-and-air mixture to generate a working gas.

The working gas leaves the combustors through contoured transition sections linked to downstream turbine sections. As the working gas moves through the various tur bine sections, it expands and is directed across rows of blades therein by associated vanes. As the working gas passes through the turbine section, it causes the blades to rotate, which in turn causes a shaft to rotate, thereby producing mechanical work. The mechanical work may be converted into electrical energy by connecting the rotating shaft to a generator. During engine operation, components in the path of the working gas, including combustor baskets, turbine sections, and the transitions that extend therebetween are ex posed to elevated temperatures and are typically cooled using compressor airflow. The air flow used for this cooling can increase unwanted emissions by directing air away from the head end of the combustor, leading to elevated combustion temperatures that, in turn, can lead to the unwanted production of oxides of nitrogen (“NOx”).

Regions such as the interface between a combustor downstream exit and the inlet region of an associated transition are particularly prone to localized, NOx-producing pockets of extreme temperatures, due to stagnation or recirculation zones that can develop in this portion of the hot gas path. This interface is characterized by a backward-facing step that produces a pressure drop in the flowpath, encouraging hot exhaust gasses to recirculate instead of continuing downstream. Known attempts to counter the effects of this recirculation tendency, include increased flows of spring clip leakage air, increased flows of combustor liner cooling ring leakage air, and the addition of transition inlet ring cooling holes. Each of these approaches introduces streams of cooling fluid in an orientation parallel to the transition inlet ring, along the flow of hot gasses. While these approaches may overcome the heating tendencies of local recirculation zones, they are not efficient, and often require large amounts of cool- ing fluid to effectively overcome the tendency for recirculation zones to elevate tempera- tures at combustor basket exits. In many cases, this results in unwanted reductions in com ponent life, as well as increases in overall NOx emissions.

What is needed is a cooling arrangement that reduces temperatures in the com- bustor basket/transition interface to meet emissions requirements and component life tar gets, while also improving engine efficiency.

SUMMARY OF INVENTION

Briefly described, aspects of the present invention relate to a cooling arrange- ment for a gas turbine engine combustor basket and, more particularly, to an angled ar rangement that disrupts the formation of high-temperature stagnation zones in the combus tor exit/transition inlet interface. The present arrangement includes compound cooling cir cuits that have primary regions to direct cooling fluid parallel to working gas (also referred to as working fluid) flow and exit regions that direct cooling flow in a direction substan- tially-perpendicular to the flow of working fluid, thereby producing a wall of cooling fluid near the cooling channel exits that inhibits upstream travel of hot gasses upstream within a combustor basket exit/transition inlet ring interface.

In one embodiment, the arrangement includes cooling fluid channels within the combustor liner and a flow re-orientation element at the exit of the channel that changes the direction of cooling fluid as it exits the channels into a path substantially-perpendicular to the transition inlet ring. The re-direction element may be a wall or other element, such as a channel bend or contour, that imparts a flow vector sufficient for the cooling fluid leav- ing the cooling channel to form a cross-flow blocking region within the interface gap be- tween the combustor exit and transition inlet. The blocking region to reduce temperatures in that gap by diminish the amount of working gasses traveling upstream into that region. With this arrangement, the need for purge air in this region is reduced, cooling efficiency is increased, NOx emissions are controlled to acceptable levels, and component life targets are met.

Various aspects and embodiments of the application as described above and hereinafter may not only be used in the combinations explicitly described, but also in other combinations. Modifications will occur to the skilled person upon reading and understand- ing of the description.

BRIEF DESCRIPTION OF DRAWINGS

Exemplary embodiments of the application are explained in further detail with respect to the accompanying drawings. In the drawings:

FIG. 1 illustrates a schematic partial cross section view of a gas turbine engine in which embodiments of the invention may be incorporated;

FIG. 2 illustrates a schematic partial view of a combustor liner and transition inlet ring interface incorporating elements of the present invention;

FIG. 3 illustrates a partial schematic view of a cooling arrangement in which embodiments of the invention may be incorporated, and FIG. 4 illustrates a schematic partial view of a cooling arrangement in a gas turbine combustor incorporating elements of the present invention. DET AILED DESCRIPTION OF INVENTION

A detailed description related to aspects of the present invention is described hereafter with respect to the accompanying figures. FIG. 1 illustrates a schematic view of a gas turbine engine in which the present invention may be incorporated. With continued reference to FIG.l, and as noted above, a gas turbine engine 10 includes a compressor section 12, a combustion section 14, and a turbine section 18. The compressor section 12 provides a compressed airflow to the com bustion section 14, where the air is mixed with a fuel (not shown), such as natural gas. The combustion section 12 includes a plurality of circumferentially disposed-combustors 16 (only one shown for clarity) that receive and ignite the fuel-and-air mixture to generate a working gas 19.

As shown in FIG. 2, the combustors 16 of the present arrangement include cooled combustor liners 28 that join transition elements 20 at a combustor/transition inter- face 22. At this interface, transition inlet rings 32 and combustor basket exits 36 are dy- namically linked by coupling elements, such as thermally-compliant spring clips 34. The interface 22 is characterized by a backwards-facing step 38 formed in the combustor exit 36.

During operation, most of the working gas 19 leaves the combustors 14 at ele- vated temperature, travels through the combustor exit 36 and passes into the transition 20 through the transition inlet ring 32 and moves downstream into the turbine section to pro- duce work. Not all working gas 19 passes into the transition, however. Due to the back ward-facing step 38 geometry in the combustor exit 36, a recirculation (or stagnation) zone 42 develops between the distal end of the exit and the transition inlet ring 32. An associat- ed drop in pressure at this recirculation zone 42 impedes downstream flow of hot gasses 19 from the combustor 16, and heat can be transferred from the relatively- hot working gas to the combustor/transition interface 22.

To keep temperature levels in the combustor 16 within acceptable limits, cool- ing channels 26 in the combustor liner 28 transmit cooling fluid to remove heat and lower combustor liner temperatures acceptably in most combustor exit 36 locations. However, as shown in FIG. 2 and FIG. 3, in the recirculation zone 42, hot gasses tend to linger and at- tempt to travel upstream through the basket/inlet ring interface 22. With the arrangement of the present invention, cooling fluid 40 is guided by a flow re-directing element 30 at the exit of the channels that changes the direction of cooling fluid as it exits the channels into a path substantially perpendicular to the transition inlet ring 32. Although the re-direction element 30 is shown as a wall, other elements such as a channel bend, may also suffice.

During operation, the re-direction element 30 imparts a flow vector to the cool- ing fluid 40 sufficient for the fluid leaving the cooling channel to form a cross-flow block ing region 44 to prevent upstream flow of hot working gasses 19 through the interface 22 and past the coupling elements 34. With this arrangement, the need for purge air in the interface region 22 is reduced, cooling efficiency is increased, NOx emissions are con trolled to acceptable levels, and component life targets are met.

With reference to FIG. 3 and FIG. 4, one embodiment of the re-directing ele ment 30 is a wall or similar barrier disposed near the free end of a given combustor 16, proximate an associated cooling channel exit 46; in the present embodiment, the wall 30 (or similar element) forms part of the cooling channel exit 46, but it could also be a parti tion strategically positioned with respect to the cooling channel exit.

During operation, the wall re-directs cooling fluid from a flow-aligned direction within the cooling fluid channel 26 to a cross-flow-blocking direction substantially per pendicular to the transition inlet ring 32. It is noted that a preferred orientation for cooling fluid flow within the blocking region 44 is flow that moves substantially-perpendicular to the flow of working fluid 19 attempting to leave the recirculation zone 42 to flow upstream within the exit/inlet ring interface 22. In the embodiment shown in FIG. 2, this angle of orientation is approximately ninety degrees to the combustor liner walls 28. However, oth er angles of orientation 48, such as between 90 and 40 degrees, could also be used as need ed to overcome upstream flow properties of fluid leaving the recirculation zone 42, as dic tated by strength of fluid flow in the zone.

With continued reference to operation with this cooling arrangement 24, cross- flowing fluid in the blocking region 44 inhibits flow of hot gasses 19 attempting to leave the recirculation zone 42 to flow upstream within the interface 22, past the blocking region. This reduces the accumulation of heat in upstream regions of the interface 22, and cooling requirements for (and NOx levels produced by) this area are efficiently reduced. It is noted that the circular-shaped cooling fluid exits 46 are particularly effective at reducing the temperature within the interface 22, but other shapes could also be used.

Although various embodiments that incorporate the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readi- ly devise many other varied embodiments that still incorporate these teachings. The inven- tion is not limited in its application to the exemplary embodiment details of construction and the arrangement of components set forth in the description or illustrated in the draw- ings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminol- ogy used herein is for the purpose of description and should not be regarded as limiting. The use of“including,”“comprising,” or“having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms“mounted,”“connected,”“supported,” and “coupled” and variations thereof are used broadly and encompass direct and indirect mountings, connections, supports, and couplings. Further,“connected” and“coupled” are not restricted to physical or mechanical connections or couplings.

Claims

CLAIMS What claimed is:

1. A cooling channel arrangement for a gas turbine gas turbine engine comprising: a combustor adapted for burning fuel and air to produce a working fluid, said combustor including a peripheral boundary with at least one cooling channel disposed therein, said cooling channel having an entrance and an exit defining a major axis substantially aligned with a major axis of said combustor, said combustor having a downstream exit; a transition disposed downstream of said combustor, said transition having an upstream inlet in fluid communication with said combustor exit, thereby forming a combustor/transition interface section substantially defined by said combustor exit and said transition inlet; and a flow-redirecting element proximate said at least one cooling channel exit, said flow-redirecting element being constructed and arranged to define a cooling channel minor axis rotationally offset from said major axis by an angle of orientation adapted to direct flow along said minor axis, wherein said flow along said minor axis is effective to form a region of blocking flow extending between said combustor exit and said transition inlet; whereby said region of blocking flow is effective to substantially prevent upstream flow of a working fluid within said interface past said flow-redirecting element.

2. The cooling channel arrangement of Claim 1, wherein said angle of

orientation is from 40 to 90 degrees offset from said major axis.

3. The cooling channel arrangement of Claim 2, wherein said flow-redirecting element is a wall constructed and arranged within said disposed channel, in a manner effective to from said minor axis of flow.

4. The cooling channel arrangement of Claim 1, wherein said interface further includes a recirculation zone.

5. The cooling channel arrangement of Claim 4, wherein said combustor exit includes a backwards-facing step and wherein said recirculation zone is located proximate said backwards-facing step.

6. The cooling channel arrangement of Claim 4, wherein said at least one cooling channel exit has a circular cross section.

7. A gas turbine engine having angular cooling channels, comprising: a combustor adapted for burning fuel and air to produce a working fluid, said combustor including a peripheral boundary with at least one cooling channel disposed therein, said cooling channel having an entrance and an exit defining a major axis substantially aligned with a major axis of said combustor, said combustor having a downstream exit; a transition disposed downstream of said combustor, said transition having an upstream inlet in fluid communication with said combustor exit, thereby forming a combustor/transition interface section substantially defined by said combustor exit and said transition inlet; and a flow-redirecting element proximate said at least one cooling channel exit, said flow-redirecting element being constructed and arranged to define a cooling channel minor axis rotationally offset from said major axis by an angle of orientation adapted to direct flow along said minor axis, wherein said flow along said minor axis is effective to form a region of blocking flow extending between said combustor exit and said transition inlet; whereby said region of blocking flow is effective to substantially prevent upstream flow of a working fluid within said interface past said flow- redirecting element.

8. The cooling channel arrangement of Claim 7, wherein said angle of

orientation is from 40 to 90 degrees offset from said major axis.

9. The cooling channel arrangement of Claim 8, wherein said flow-redirecting element is a wall constructed and arranged within said disposed channel, in a manner effective to from said minor axis of flow.

10. The cooling channel arrangement of Claim 7, wherein said interface further includes a recirculation zone.

11. The cooling channel arrangement of Claim 10 wherein said combustor exit includes a backwards-facing step and wherein said recirculation zone is located proximate said backwards-facing step.

12. The cooling channel arrangement of Claim 7, wherein said at least one cooling channel exit has a circular cross section.