EP4680897A1

EP4680897A1 - Burner for gas turbine engine

Info

Publication number: EP4680897A1
Application number: EP24719021.8A
Authority: EP
Inventors: Daniel Moell; Nicklas Johansson; Josefine TENSELIUS; Michael Nyberg
Original assignee: Siemens Energy Global GmbH and Co KG
Current assignee: Siemens Energy Global GmbH and Co KG
Priority date: 2023-04-28
Filing date: 2024-03-26
Publication date: 2026-01-21
Also published as: WO2024226209A1; GB2629431A; GB202306306D0

Abstract

A burner (200) includes a mixing zone (206) including an inner wall (308), a mixing zone interior defined by the inner wall, and a plurality of film cooling holes (316) extending through the inner wall. Each film cooling hole has an inlet portion (402) extending from an inlet to an interface (406) and an outlet portion (404) extending from the interface (406) to an outlet. The inlet portion defines an inlet cross section area, and the outlet portion defines an outlet cross section area. The outlet cross section area is larger than the inlet cross section area.

Description

BURNER FOR GAS TURBINE ENGINE

BACKGROUND

[0001] A gas turbine engine typically includes a compressor section, a turbine section, and a combustion section disposed therebetween. The compressor section includes multiple stages of rotating compressor blades and stationary compressor vanes. The combustion section typically includes a plurality of combustors. The turbine section includes multiple stages of rotating turbine blades and stationary turbine vanes. Turbine blades and vanes often operate in a high temperature environment and are internally cooled.

[0002] The combustor may include a burner in which fuel is provided to a combustion zone. Compressed air from the compressor section is also provided to the combustion zone to mix with the fuel. The mixture of fuel and air is ignited by an ignitor to form hot exhaust gas for the turbine section.

BRIEF SUMMARY

[0003] In one aspect, a burner is provided. The burner includes a mixing zone including an inner wall, a mixing zone interior defined by the inner wall, and a plurality of film cooling holes extending through the inner wall, each film cooling hole having an inlet portion extending from an inlet to an interface and an outlet portion extending from the interface to an outlet, the inlet portion defining an inlet cross section area and the outlet portion defining an outlet cross section area, the outlet cross section area being larger than the inlet cross section area.

[0004] In one aspect, a method for manufacturing a burner is provided. The method includes positioning a base member to place a base surface in a preferred orientation, and adding a plurality of layers to the base surface to define a tube region, a first layer applied directly to the base surface, and each subsequent layer applied to a prior subsequent layer, the plurality of layers cooperating to define a plurality of film cooling holes, each film cooling hole having an inlet portion extending from an inlet to an interface and an outlet portion extending from the interface to an outlet, the inlet portion defining an inlet cross section area and the outlet portion defining an outlet cross section area, the outlet cross section area being larger than the inlet cross section area.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced.

[0006] FIG. l is a longitudinal cross-sectional view of a gas turbine engine taken along a plane that contains a longitudinal axis or central axis.

[0007] FIG. 2 is a perspective view of a burner suitable for use in the gas turbine engine of FIG. 1.

[0008] FIG. 3 is a cross section view of the burner of FIG. 2 including a plurality of film cooling holes.

[0009] FIG. 4 is a perspective view of a film cooling hole of the plurality of film cooling holes of FIG. 3.

[0010] FIG. 5 is a cross section view of a portion of the burner showing the film cooling hole of FIG. 4.

[0011] FIG. 6 is a flowchart of a method for manufacturing the burner of FIG. 2. DETAILED DESCRIPTION

[0012] Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in this description or illustrated in the following drawings. 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 terminology used herein is for the purpose of description and should not be regarded as limiting.

[0013] Various technologies that pertain to systems and methods will now be described with reference to the drawings, where like reference numerals represent like elements throughout. The drawings discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged apparatus. It is to be understood that functionality that is described as being carried out by certain system elements may be performed by multiple elements. Similarly, for instance, an element may be configured to perform functionality that is described as being carried out by multiple elements. The numerous innovative teachings of the present application will be described with reference to exemplary non-limiting embodiments.

[0014] Also, it should be understood that the words or phrases used herein should be construed broadly, unless expressly limited in some examples. For example, the terms “including”, “having”, and “comprising”, as well as derivatives thereof, mean inclusion without limitation. The singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Further, the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. The term “or” is inclusive, meaning and/or, unless the context clearly indicates otherwise. The phrases “associated with” and “associated therewith” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like. Furthermore, while multiple embodiments or constructions may be described herein, any features, methods, steps, components, etc. described with regard to one embodiment are equally applicable to other embodiments absent a specific statement to the contrary.

[0015] Also, although the terms “first”, “second”, “third” and so forth may be used herein to refer to various elements, information, functions, or acts, these elements, information, functions, or acts should not be limited by these terms. Rather these numeral adjectives are used to distinguish different elements, information, functions or acts from each other. For example, a first element, information, function, or act could be termed a second element, information, function, or act, and, similarly, a second element, information, function, or act could be termed a first element, information, function, or act, without departing from the scope of the present disclosure.

[0016] Also, in the description, the terms “axial” or “axially” refer to a direction along a longitudinal axis of a gas turbine engine. The terms “radial” or “radially” refer to a direction perpendicular to the longitudinal axis of the gas turbine engine. The terms “downstream” or “aft” refer to a direction along a flow direction. The terms “upstream” or “forward” refer to a direction against the flow direction.

[0017] In addition, the term “adjacent to" may mean that an element is relatively near to but not in contact with a further element or that the element is in contact with the further portion, unless the context clearly indicates otherwise. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise. Terms “about” or “substantially” or like terms are intended to cover variations in a value that are within normal industry manufacturing tolerances for that dimension. If no industry standard is available, a variation of twenty percent would fall within the meaning of these terms unless otherwise stated.

[0018] FIG. 1 illustrates an example of a gas turbine engine 100 including a compressor section 102, a combustion section 104, and a turbine section 106 arranged along a central axis 1 12. The compressor section 102 includes a plurality of compressor stages 1 14 with each compressor stage 114 including a set of stationary compressor vanes 116 or adjustable guide vanes and a set of rotating compressor blades 118. A rotor 134 supports the rotating compressor blades 118 for rotation about the central axis 112 during operation. In some constructions, a single one-piece rotor 134 extends the length of the gas turbine engine 100 and is supported for rotation by a bearing at either end. In other constructions, the rotor 134 is assembled from several separate spools that are attached to one another or may include multiple disk sections that are attached via a bolt or plurality of bolts.

[0019] The compressor section 102 is in fluid communication with an inlet section 108 to allow the gas turbine engine 100 to draw atmospheric air into the compressor section 102. During operation of the gas turbine engine 100, the compressor section 102 draws in atmospheric air and compresses that air for delivery to the combustion section 104. The illustrated compressor section 102 is an example of one compressor section 102 with other arrangements and designs being possible.

[0020] In the illustrated construction, the combustion section 104 is an annular combustor 120 including a plurality of separate burners that each operate to mix a flow of fuel with the compressed air from the compressor section 102 and to combust that fuel-air mixture to produce a flow of high temperature, high pressure combustion gases or exhaust gas 122. Of course, many other arrangements of the combustion section 104 are possible.

[0021] The turbine section 106 includes a plurality of turbine stages 124 with each turbine stage 124 including a number of stationary turbine vanes 126 and a number of rotating turbine blades 128. The turbine stages 124 are arranged to receive the exhaust gas 122 from the combustion section 104 at a turbine inlet 130 and expand that gas to convert thermal and pressure energy into rotating or mechanical work. The turbine section 106 is connected to the compressor section 102 to drive the compressor section 102. For gas turbine engines 100 used for power generation or as prime movers, the turbine section 106 is also connected to a generator, pump, or other device to be driven. As with the compressor section 102, other designs and arrangements of the turbine section 106 are possible. [0022] An exhaust portion 1 10 is positioned downstream of the turbine section 106 and is arranged to receive the expanded flow of exhaust gas 122 from the final turbine stage 124 in the turbine section 106. The exhaust portion 110 is arranged to efficiently direct the exhaust gas 122 away from the turbine section 106 to assure efficient operation of the turbine section 106. Many variations and design differences are possible in the exhaust portion 110. As such, the illustrated exhaust portion 110 is but one example of those variations.

[0023] A control system 132 is coupled to the gas turbine engine 100 and operates to monitor various operating parameters and to control various operations of the gas turbine engine 100. In preferred constructions the control system 132 is typically micro-processor based and includes memory devices and data storage devices for collecting, analyzing, and storing data. In addition, the control system 132 provides output data to various devices including monitors, printers, indicators, and the like that allow users to interface with the control system 132 to provide inputs or adjustments. In the example of a power generation system, a user may input a power output set point and the control system 132 may adjust the various control inputs to achieve that power output in an efficient manner.

[0024] The control system 132 can control various operating parameters including, but not limited to variable inlet guide vane positions, fuel flow rates and pressures, engine speed, valve positions, generator load, and generator excitation. Of course, other applications may have fewer or more controllable devices. The control system 132 also monitors various parameters to assure that the gas turbine engine 100 is operating properly. Some parameters that are monitored may include inlet air temperature, compressor outlet temperature and pressure, combustor outlet temperature, fuel flow rate, generator power output, bearing temperature, and the like. Many of these measurements are displayed for the user and are logged for later review should such a review be necessary.

[0025] FIG. 2 illustrates a perspective view of a burner 200 suitable for use in the gas turbine engine 100 of FIG. 1. The burner 200 is a part of the combustor 120 that produces the exhaust gas 122. A plurality of burners 200 are arranged circumferentially around the central axis 108 of the gas turbine engine 100 and are spaced apart from each other to define an annular combustor 120, with other arrangements being possible. The burner 200 may be operated with different kinds of fuel, for example, gaseous fuel, or liquid fuel, or dual fuel including both gaseous fuel and liquid fuel.

[0026] The burner 200 includes an entry zone 202, a swirl zone 204 downstream of the entry zone 202, a mixing zone 206 downstream of the swirl zone 204, and an exit zone 208 downstream of the mixing zone 206. Upstream and downstream are defined with respect to a flow direction 224. The entry zone 202 has a general cylindrical shape, with other geometries possible.

[0027] The swirl zone 204 includes a plurality of swirlers 212 that extend between the entry zone 202 and the mixing zone 206. The plurality of swirlers 212 are circumferentially arranged around a burner central axis 214 and are spaced apart from each other. Each swirler 212 has a curved surface, with other geometries possible.

[0028] The mixing zone 206 includes an outer wall 210 that extends between the swirl zone 204 and the exit zone 208. The outer wall 210 defines a mixing zone interior 216 that receives the mixture of fuel and air from the swirl zone 204 for further mixing. A plurality of air exit holes 222 are defined on the outer wall 210. The plurality of air exit holes 222 are circumferentially arranged around the outer wall 210 and are spaced apart from each other. The mixing zone 206 has a general cylindrical shape, with other geometries possible.

[0029] The exit zone 208 includes an exit surface 218. A plurality of pilot fuel exit holes 220 are defined on the exit surface 218. The plurality of pilot fuel exit holes 220 are circumferentially arranged around the exit surface 218 and are spaced apart from each other. The exit zone 208 has a general truncated conic shape, with other geometries possible.

[0030] FIG. 3 illustrates a cross section view of the burner 200. The entry zone 202 includes a main fuel supply channel 302, a pilot fuel supply channel 304, and a fuel lance 324. The fuel lance 324 provides either liquid fuel or central pilot fuel to the burner 200. The main fuel supply channel 302 receives main fuel and guides the main fuel to the swirlers 212. Each swirler 212 includes a plurality of main fuel nozzles 306 to inject the main fuel into the swirl zone 204. The swirlers 212 swirl compressed air provided from the compressor section 102. The compressed air is mixed with the main fuel injected by the swirlers 212 to produce a mixture of fuel and air. The pilot fuel supply channel 304 receives pilot fuel and guides the pilot fuel to the swirler 212.

[0031] The mixing zone 206 includes an inner wall 308 and an intermediate wall 310 that is disposed between the outer wall 210 and the inner wall 308. A pilot fuel passage 312 is defined between the outer wall 210 and the intermediate wall 310. The pilot fuel passage 312 extends along a length of the mixing zone 206. The pilot fuel passage 312 receives the pilot fuel from the pilot fuel supply channel 304 via the swirlers 212 and injects the pilot fuel to the exit surface 218 through the pilot fuel exit holes 220.

[0032] A cooling flow passage 314 is defined between the intermediate wall 310 and the inner wall 308. The cooling flow passage 314 extends along the length of the mixing zone 206. The cooling flow passage 314 receives cooling air and guides a portion of the cooling air flowing along the inner wall 308 before exiting the burner 200 through the air exit holes 222. The cooling air may be provided from the compressor section 102 or other sources exterior of the burner 200.

[0033] A plurality of film cooling holes 316 are arranged on the inner wall 308. The film cooling holes 316 are arranged in a plurality of rows 318. The rows 318 extend between a mixing zone upstream end 320 and a mixing zone downstream end 322. The mixing zone upstream end 320 is where the fuel starts to interact with the inner wall 308.

[0034] The rows 318 are spaced apart from and parallel to each other along the burner central axis 214. The rows 318 are evenly distributed between the mixing zone upstream end 320 and the mixing zone downstream end 322 with the same distance between adjacent rows 318. Each row 318 includes more than one fdm cooling holes 316 that are arranged circumferentially around the inner wall 308 and are spaced apart from each other. The film cooling holes 316 in adjacent rows 318 are arranged staggered in the circumferential direction, that means the film cooling holes 316 in two directly adjacent rows 318 are positioned offset in the circumferential direction. The film cooling holes 316 are manufactured by additive manufacturing, or other suitable manufacturing methods. In one construction, a selective laser melting process is used to manufacture the film cooling hole 316 in a layer-by-layer process. [0035] In the arrangement shown in FIG. 3, the plurality of film cooling holes 316 have the same configuration and geometry. Each row 318 includes the same number of film cooling holes 316. In other arrangements, the film cooling holes 316 may have different configurations, such as different geometries, different orientations, different numbers of film cooling holes 316 in each row 318, rows 318 are not evenly distributed between the mixing zone upstream end 320 and the mixing zone downstream end 322 along the burner central axis 214, and/or film cooling holes 316 in adjacent rows 318 may be arranged aligned to each other in the circumferential direction, etc.

[0036] FIG. 4 illustrates a perspective view of one of the film cooling holes 316 with the other film cooling holes 316 being substantially the same. The film cooling hole 316 includes an inlet portion 402 and an outlet portion 404 connected to the inlet portion 402 at an interface 406. The inlet portion 402 extends from an inlet 408 to the interface 406 having an inlet cross section area 412. The outlet portion 404 extends from the interface 406 to an outlet 410 having an outlet cross section area 414. The inlet cross section area 412 has a circular shape with a constant diameter along the inlet portion 402. The outlet cross section area 414 transitions from the circular shaped inlet cross section area 412 to a rectangular shape having a first surface 416, a second surface 418 that is opposite to the first surface 416, a third surface 420 that extends between the first surface 416 and the second surface 418 at one side, and a fourth surface 422 that extends between the first surface 416 and the second surface 418 at the other side.

[0037] The outlet cross section area 414 is larger than the inlet cross section area 412. The outlet cross section area 414 continuously increases from the interface 406 to the outlet 410 along the outlet portion 404. The outlet portion 404 forms a fan shaped film cooling hole 316 that diverges along the outlet portion 404. In other arrangements, the inlet portion 402 and the outlet portion 404 may have different geometries. For example, the inlet cross section area 412 may have a circular shape with increasing diameter along the inlet portion 402, or other shapes than a circular shape. The outlet portion 404 may have fewer than four surfaces or more than four surfaces as may be desired. In one construction, the outlet portion 404 has an increasing circular, elliptical, or oval shape. [0038] FIG. 5 illustrates a cross section view of a portion of the burner 200 showing the film cooling hole 316. The film cooling hole 316 extends through the inner wall 308. The inlet 408 faces the cooling flow passage 314. The outlet 410 faces the mixing zone interior 216. The inlet portion 402 defines an inlet central axis 502. The inlet central axis 502 is arranged at an oblique angle with respect to the inner wall 308. A length of the inlet portion 402 measured from the inlet 408 to the interface 406 along the inlet central axis 502 is shorter than a length of the outlet portion 404 measured from the interface 406 to the 410 along the inlet central axis 502. In other embodiments, the length of the inlet portion 402 may be longer than or equal to the length of the outlet portion 404. The first surface 416 is disposed closer to the mixing zone interior 216 than the second surface 418, the third surface 420, and the fourth surface 422. The first surface 416 extends parallel to the inlet central axis 502. The second surface 418, the third surface 420, and the fourth surface 422 diverge from the inlet central axis 502 from the interface 406 to the outlet 410.

[0039] FIG. 6 illustrates a flowchart of a method 600 for manufacturing the burner 200. The method 600 uses an additive manufacturing process such as or similar to a selective laser melting process. In step 602, the method 600 positions a base member to place a base surface in a preferred orientation. In step 604, the method 600 adds a plurality of layers to the base surface to define a tube region, a first layer applied directly to the base surface, and each subsequent layer applied to a prior subsequent layer, the plurality of layers cooperating to define a plurality of film cooling holes, each film cooling hole having an inlet portion extending from an inlet to an interface and an outlet portion extending from the interface to an outlet, the inlet portion defining an inlet cross section area and the outlet portion defining an outlet cross section area, the outlet cross section area being larger than the inlet cross section area.

[0040] During operation, the main fuel supply channel 302 receives the main fuel and the pilot fuel supply channel 304 receives the pilot fuel. The main fuel is guided by the main fuel supply channel 302 to the swirlers 212 and is injected into the swirl zone 204 through the main fuel nozzles 306. The swirlers 212 swirl the compressed air from the compressor section 102 that is mixed with the injected main fuel. The mixture of fuel and air enters the mixing zone 206 for further mixing. The pilot fuel is guided to the swirlers 212 and enters the pilot fuel passage 312 from the swirlers 212. The pilot fuel is injected into the exit surface 218 through the pilot fuel exit holes 220 and is ignited. The ignited pilot fuel is mixed with the mixture of fuel and air flows at the exit surface 218 to produce the exhaust gas 122. The exhaust gas 122 exits the exit surface 218 and enters a combustion chamber (not shown) for further combustion. The exhaust gas 122 is guided to the turbine section 106 from the combustion chamber via a transition duct (not shown).

[0041] The cooling flow passage 314 receives cooling air from the compressor section 102 or other cooling air sources. The cooling air flows through the cooling flow passage 314 to cool the inner wall 308. A portion of the cooling air exits the cooling flow passage 314 through the air exit holes 222 and is mixed into the exhaust gas 122. Another portion of the cooling air enters the mixing zone interior 216 through the film cooling holes 316 along the inner wall 308 and is mixed with the mixture of fuel and air in the mixing zone interior 216. The inlet portion 402 has a constant inlet cross section area 412 that controls the flow rate of the cooling air passing through the film cooling hole 316. The flow rate is designed to meet a desired value between cooling air consumption and performance of the gas turbine engine 100.

[0042] The outlet portion 404 expends in three directions with respect to the inlet portion 402 that spreads the cooling air evenly across an inlet of the inner wall 308 to cover a large inlet area. The first surface 416 that is closest to the mixing zone interior 216 compared to the second surface 418, the third surface 420, and the fourth surface 422 and does not expand with respect to the inlet portion 402. Such design of the film cooling hole 316 reduces occurrence of flow separation when expanding the cooling flow.

[0043] When operating the burner 200 on liquid fuel, particles from the liquid fuel may be pushed towards the inner wall 308. These particles may contaminate the surface of the inner wall 308 and can increase over time. The buildup of deposits on the inner wall 308 may cause flashback if the buildup is large enough. The arrangement of the film cooling holes 316 along the entire inner wall 308 efficiently distributes the cooling air along the entire inner wall 308. Potential fuel rich regions along the inner wall 308 are diluted with the cooling air. The cooling air effectively cools the entire inner wall 308 to reduce the buildup of deposit on the inner wall 308 and reduce flashback.

[0044] Although an exemplary embodiment of the present disclosure has been described in detail, those skilled in the art will understand that various changes, substitutions, variations, and improvements disclosed herein may be made without departing from the spirit and scope of the disclosure in its broadest form.

[0045] None of the description in the present application should be read as implying that any particular element, step, act, or function is an essential element, which must be included in the claim scope: the scope of patented subject matter is defined only by the allowed claims. Moreover, none of these claims are intended to invoke a means plus function claim construction unless the exact words "means for" are followed by a participle.

LISTING OF DRAWING ELEMENTS

100 gas turbine engine

102 compressor section

104 combustion section

106 turbine section

108 inlet section

110 exhaust portion

112 central axis

114 compressor stage

116 stationary compressor vane

118 rotating compressor blade combustor exhaust gas turbine stage stationary turbine vane rotating turbine blade turbine inlet control system rotor burner entry zone swirl zone mixing zone exit zone outer wall swirler burner central axis mixing zone interior exit surface pilot fuel exit hole air exit hole flow direction main fuel supply channel pilot fuel supply channel main fuel nozzle inner wall intermediate wall pilot fuel passage cooling flow passage film cooling hole row mixing zone upstream end mixing zone downstream end fuel lance inlet portion outlet portion interface inlet outlet inlet cross section area outlet cross section area first surface second surface third surface fourth surface inlet central axis method step step

Claims

CLAIMS What is claimed is:

1. A burner comprising: a mixing zone including an inner wall; a mixing zone interior defined by the inner wall; and a plurality of film cooling holes extending through the inner wall, each film cooling hole having an inlet portion extending from an inlet to an interface and an outlet portion extending from the interface to an outlet, the inlet portion defining an inlet cross section area and the outlet portion defining an outlet cross section area, the outlet cross section area being larger than the inlet cross section area, wherein the inlet cross section area has a circular shape with a constant diameter along the inlet portion, and wherein the outlet cross section area has a rectangular shape.

2. The burner of claim 1, wherein the outlet cross section area continuously increases from the interface to the outlet along the outlet portion.

3. The burner of claim 1, wherein the inlet portion defines an inlet central axis that is arranged at an oblique angle with respect to the inner wall.

4. The burner of claim 5, wherein a length of the inlet portion measured from the inlet to the interface along the inlet central axis is shorter than a length of the outlet portion measured from the interface to the outlet along the inlet central axis.

5. The burner of claim 5, wherein the outlet cross section area comprises a first surface, a second surface opposite to the first surface, a third surface and a fourth surface extending between the first surface and the second surface, wherein the first surface is disposed closer to the mixing zone interior and extends parallel to the inlet central axis, and wherein the second surface, the third surface, and the fourth surface diverge from the inlet central axis from the interface to the outlet.

6. The burner of claim 1, wherein the plurality of the film cooling holes are arranged in a plurality of rows that extend between a mixing zone upstream end and a mixing zone downstream end and are parallel to each other.

7. The burner of claim 8, wherein the plurality of rows are evenly distributed between the mixing zone upstream end and the mixing zone downstream end with the same distance between adjacent rows.

8. The burner of claim 8, wherein each row of the plurality of rows comprises more than one film cooling holes that are arranged around the inner wall in a circumferential direction and are spaced apart from each other, and wherein the film cooling holes in adjacent rows are arranged staggered in the circumferential direction.

9. A method for manufacturing a burner, the method comprising: positioning a base member to place a base surface in a preferred orientation; adding a plurality of layers to the base surface to define a tube region, a first layer applied directly to the base surface, and each subsequent layer applied to a prior subsequent layer, the plurality of layers cooperating to define a plurality of film cooling holes, each film cooling hole having an inlet portion extending from an inlet to an interface and an outlet portion extending from the interface to an outlet, the inlet portion defining an inlet cross section area and the outlet portion defining an outlet cross section area, the outlet cross section area being larger than the inlet cross section area; and forming the inlet cross section area having a circular shape with a constant diameter along the inlet portion and the outlet cross section area having a rectangular shape.

10. The method of claim 11, further comprising forming the outlet cross section area continuously increasing from the interface to the outlet along the outlet portion.

11. The method of claim 11, further comprising forming the inlet portion defining an inlet central axis that is arranged at an oblique angle with respect to the inner wall.

12. The burner of claim 14, further comprising forming a length of the inlet portion measured from the inlet to the interface along the inlet central axis shorter than a length of the outlet portion measured from the interface to the outlet along the inlet central axis.

13. The method of claim 14, further comprising forming the outlet cross section area comprising a first surface, a second surface opposite to the first surface, a third surface and a fourth surface extending between the first surface and the second surface, wherein the first surface is disposed closer to the mixing zone interior and extends parallel to the inlet central axis, and wherein the second surface, the third surface, and the fourth surface diverge from the inlet central axis from the interface to the outlet.

14. The method of claim 11, further comprising forming the plurality of the film cooling holes in a plurality of rows that extend between a mixing zone upstream end of the burner and a mixing zone downstream end of the burner and parallel to each other.

15. The method of claim 17, further comprising evenly distributing the plurality of rows between the mixing zone upstream end and the mixing zone downstream end with the same distance between adjacent rows.

16. The method of claim 17, further comprising forming each row of the plurality of rows comprising more than one film cooling holes that are arranged around the inner wall in a circumferential direction and are spaced apart from each other, and further comprising forming the film cooling holes in adjacent rows staggered in the circumferential direction.

17. The method of claim 11, wherein the preferred orientation comprises a direction to place the base surface in a horizontal direction.