WO2018144008A1

WO2018144008A1 - Combustor with three-dimensional lattice premixer

Info

Publication number: WO2018144008A1
Application number: PCT/US2017/016420
Authority: WO
Inventors: Gilles Bourque
Original assignee: Siemens Aktiengesellschaft
Priority date: 2017-02-03
Filing date: 2017-02-03
Publication date: 2018-08-09

Abstract

A combustor for a combustion turbine engine incorporates a fuel and air premixer, embodiments of which locally vary structure of one or more of air ducts, fuel delivery passages, fuel and air mixing ducts, and/or fuel and air discharge ducts, in order to normalize fuel-air ratio at any location about the premixer's three-dimensional volume, or in the combustion chamber, during steady-state operating conditions, and/or in order to stabilize fluctuations in compressed air supply to the premixer, and/or in order to stabilize fluctuations in combustion gas back pressure upstream into the premixer, or within the combustion chamber. The premixer is a monolithic, three-dimensional lattice structure of selectively oriented, asymmetrical- and serpentine-shaped metallic webs. The web structure defines locally varying passages, which form: the aforementioned air ducts and passages. In some embodiments, the premixer, or a casting mold for the premixer is formed by additive manufacture.

Description

COMBUSTOR WITH THREE-DIMENSIONAL LATTICE PREMIXER

[0001] The entire disclosure of the following patents are hereby incorporated by reference in their entirety: US Patent No. 6,698,206, issued on March 2, 2004, and entitled "Combustion Chamber"; US Patent No. 6,732,527, issued on May 11, 2004, and entitled "Combustion Chamber"; US Patent No.7,841, 181, issued on November 30, 2010, and entitled "Gas Turbine Engine Combustion Systems"; and US Patent No. 8,881,531, issued on November 11, 2014, and entitled "Gas Turbine Engine Premix Injectors".

TECHNICAL FIELD

[0002] The invention relates to combustors for combustion or gas turbine engines. More particularly, the invention relates to combustors of combustion or gas turbine engines, which incorporate fuel-air premixers having a monolithic, three-dimensional lattice structure of selectively oriented, asymmetrical- and serpentine-shaped metallic webs and premixer passages formed therein.

BACKGROUND

[0003] Emission level requirements, established for industrial combustion or gas turbine engines, limit the quantity of oxide of nitrogen (NOx) produced during engine operation. A known way to reduce emissions of nitrogen oxides is to reduce the combustion reaction temperature, and this requires premixing of the fuel and a large proportion, preferably all, of the combustion air before combustion occurs. The oxides of nitrogen (NOx) are commonly reduced by use of multi-stage fuel injection. In multi-staged combustion, all the stages of combustion seek to provide lean combustion and hence the low combustion temperatures required to minimize NOx. The term "lean combustion" means combustion of fuel in air where the fuel to air ratio ("FAR") is low, i.e. less than the stoichiometric ratio. Uniform mixing of fuel and air throughout the combustor achieves consistently low emissions of NOx and CO. [0004] Many, but not all, known industrial combustion or gas turbine engines use a plurality of combustors with combustion chambers, whose axes are arranged in generally radial directions. The inlets of the combustors are at their radially outer ends, and transition ducts connect the outlets of the combustion chambers of the combustor with a row of nozzle guide vanes to discharge the hot gases axially into the turbine sections of the gas turbine engine. Each of the combustors has a premixer, which receives compressed air from an air intake plenum that is in communication with the engine's compressor, and fuel from a fuel delivery system. The premixer has a fuel and air mixing duct, which mixes the fuel and air at a desired fuel-air ratio and transfers the mixture, via a fuel and air discharge duct, into a combustion zone of the combustion chamber. In multi-stage combustors, a secondary fuel and air mixing duct supplies a mixture of fuel and air into a secondary combustion zone, via a secondary fuel and air discharge duct. Some combustors incorporate a tertiary fuel and air mixing duct, a tertiary fuel and air discharge duct, and a tertiary combustion zone.

[0005] One problem associated with gas turbine engines is caused by pressure and flow rate temporal fluctuations in either one or both of the compressed air source feeding the combustor premixer, or combustion gas generated within the combustion chamber and flowing down stream into the turbine section of the engine. Pressure fluctuations in the compressed air supply and/or combustion gas flow through the engine locally disrupt at different times the fuel-air ratio, which adversely influences engine emissions. In one example, a pressure fluctuation in the air intake plenum propagates through the air duct and disrupts the mixture ratio within the fuel and air mixing duct. In another example, pressure fluctuations in the combustion gas within the combustion chamber may propagate upstream, via the fuel and air discharge duct, and produce fluctuations in the fuel-air ratio at the exit of the fuel and air mixing ducts. In such cases, the fuel-air ratio in both the premixer' s fuel and air mixing ducts and the combustion chamber are disrupted by the combustion gas-pressure fluctuation. In an extreme example, frequency fluctuations in the compressed air supplied by the compressor coincides or couples with frequency fluctuations in the combustion gas. Such coupling effectively disrupts fuel-air ratio stability within the fuel and air mixing ducts, from both the inlet and exhaust portions of those ducts. Extreme, temporal pressure and flow fluctuations, whether coupled or uncoupled, may lead to severe damage, or failure, of components if the frequency of the pressure fluctuations coincides with the natural frequency of a vibration mode of one or more of the components.

[0006] Existing premixer designs, such as those shown and described in the aforementioned US Patent No. 6,732,527, issued on May 11, 2004, and entitled "Combustion Chamber", maintain temporally stable fuel-air ratios by attempting to normalize temporal fluctuations in compressed gas airflow into the fuel and air mixing ducts, and by shielding those ducts from backpressure temporal fluctuations that are caused by combustion gas fluctuations. Referring to FIGS. 1 to 4 herein, an industrial gas turbine engine 20, shown in FIG. 1, comprises in axial flow series an inlet 22, a compressor section 24, a combustion section 26 (also sometimes referred to as a combustion chamber assembly), a turbine section 28, a power turbine section 30 and an exhaust 32. The turbine section 28 is arranged to drive the compressor section 24 via one or more shafts (not shown). The power turbine section 30 is arranged to drive an electrical generator 36 via a shaft 34. The combustion section 26 comprises a plurality of equally circumferentially spaced combustors 38. Longitudinal axes of the combustors 38 are arranged to extend in generally radial directions. The inlets of the combustors 38 are at their radially outermost ends and their outlets are at their radially innermost ends. The casing of the combustion section 26 incorporates an air intake plenum, which is in communication with the compressor section compressed air output, for providing compressed air to the inlets of the combustors 38. Combustion gas generated within the combustor 38 flows through a corresponding transition 39, and thereafter into the turbine section 28. Known combustor designs include, without limitation, so-called can, annular, and can-annular designs. [0007] An exemplary known, can-type, three-stage combustor 40 is shown in FIGS.

2, 3 and 4. The combustor 40 includes a combustor outer casing 42, which receives compressed air CP from the compressor section via an air intake 44. An annular air intake plenum 46 is defined between the interior of the combustor outer casing 42 and a fuel-air premixer assembly ("premixer assembly") 47. The premixer assembly 47 receives compressed air and fuel from separate sources, combines the fuel and air into a fuel and air mixture, and discharges the fuel and air mixture into a combustion chamber of the combustor 40. More specifically, the air intake plenum 46 is in fluid communication, through air duct passages in the outer walls that form the premixer assembly 47, with respective, separate and isolated primary fuel and air mixing duct ("FAMD") 48, secondary FAMD 50, and tertiary FAMD 52, via respective upper 54 and lower 56 primary air ducts, secondary air duct 58 and tertiary air duct 62. In this embodiment of FIGs. 2, 3 and 4, each of the air ducts 54, 56, 58 and 62, as well as each of the FAMDs 48, 50, and 52 is annular-shaped, arrayed about the full circumference of the premixer, with respect to a central axis of the combustor 40. Alternatively, in other embodiments, one or more of the aforementioned air ducts 54, 56, 58 and 62, and/or FAMDs 48, 50, and 52 comprise a plurality of equally circumferentially-spaced conduits or channels, analogous to spokes of a bicycle wheel. In other embodiments, one or more of the air ducts 54, 56, 58 and 62 are annular-shaped, while one or more of the FAMDs 48, 50, and 52 are separate conduits or channels, analogous to tentacles of an octopus. In further embodiments, a plurality of each of the respective air ducts 54, 56, 58, 62, and their corresponding FAMDs 48, 50 and 52 are unified conduit or channel structures that are equally arrayed about the circumference of the premixer assembly 47, analogous to spokes of a bicycle wheel.

[0008] In the embodiments of FIGS. 2, 3 and 4, the primary FAMD 48 is in fluid communication with an annular manifold of a primary fuel delivery system 70. Similarly, the secondary FAMD 50 is in fluid communication with an annular manifold of a secondary fuel delivery system 72, and the tertiary FAMD 52 is in fluid communication with an annular manifold of a tertiary fuel delivery system 74. Within each of the FAMDs 48, 50 and 52, fuel supplied by each corresponding fuel delivery system 70, 72, 74 is entrained within the compressed air supplied by the respective corresponding air ducts 54, 56, 58 and 62, at a desired fuel-air ratio. The fuel and air mixture discharges from the primary FAMD 48 through primary fuel and air discharge duct 80 ("FADD"). In some embodiments, such as in FIG. 3, a flow directing swirler 48D is incorporated on the downstream end of the FAMD 48, or any of the other FAMDs, in order to direct the fuel-air mixture FA1 within the corresponding primary fuel and air discharge duct 80. Referring back to FIG. 2, the fuel and air mixture discharges from secondary FAMD 50 via secondary fuel and air discharge duct ("FADD") 82, and from the tertiary FAMD 52 via tertiary fuel and air discharge duct ("FADD") 84. In this embodiment of FIGs. 2, 3 and 4, each of the air ducts 54, 56, 58 and 62, each of the FAMDs 48, 50, and 52 and each of the FADDs 80, 82 and 84, is annular-shaped, arrayed about the full circumference of the premixer, with respect to a central axis of the combustor 40. Alternatively, in other embodiments, one or more of the aforementioned air ducts 54, 56, 58 and 62, and/or

FAMDs 48, 50, and 52, and/or FADDs 80, 82 and 84, comprise a plurality of equally circumferentially-spaced conduits or channels, analogous to spokes of a bicycle wheel. In other embodiments, one or more of the air ducts 54, 56, 58 and 62 are annular-shaped, while one or more of the FAMDs 48, 50, and 52 and/or FADDs 80, 82 and 84, are separate conduits or channels, analogous to tentacles of an octopus. In further embodiments, a plurality of each of the respective air ducts 54, 56, 58, and 62 corresponding adjoining FAMDs 48, 50 and 52, and corresponding adjoining FADDS 80, 82, and 84 are unified conduit or channel structures that are equally arrayed about the circumference of the premixer assembly 47, analogous to spokes of a bicycle wheel. Henceforth, only annular-shaped embodiments of air ducts 54, 56, 58 and 62,

FAMDs 48, 50, and 52, and FADDs 80, 82 and 84 are described, but the principles are equally applicable to conduit or channel structures, alone or in combination with annular structures. [0009] The combustor 40 has a stepped combustion chamber 90, the upper axial end of which is defined by an upstream wall 91. The upstream wall 91 defines an upstream axial limit of a primary combustion zone 92, and a primary annular wall 93 defines a circumferential axial limit of the primary combustion zone. The fuel and air mixture supplied by the primary, annular FAMD 48 (or in other embodiments by separate conduit FAMDs 48) enters the primary combustion zone 92 via the corresponding primary fuel and air discharge duct 80 (or in other embodiments by separate conduit FADDs 80), as indicated by the arrow FA1. The combustion chamber 90 has a secondary combustion zone 94, circumferentially defined by a secondary annular wall 95, downstream of the primary combustion zone 92. The fuel and air mixture supplied by the secondary FAMD 50 enters the secondary combustion zone 94 via the corresponding secondary fuel and air discharge ducts 82 (arrow FA2). A tertiary combustion zone 96 is circumferentially defined by a tertiary annular wall

97, downstream of the secondary combustion zone 94. The fuel and air mixture supplied by the tertiary FAMD 52 enters the tertiary combustion zone 96 via the tertiary fuel and air discharge duct 84 (arrow FA3). [0010] As fuel is delivered to each separate type of FAMD at relatively higher pressure than that of the supplied compressed air CP, fuel flow rate does not significantly fluctuate. However, the compressed air CP and combustion backpressure BP do fluctuate temporally denoted as ACP and ΔΒΡ in FIG. 2, leading to temporal fluctuations in the fuel-air ratio. As described in United States Patent No. 6,732,527 radially aligned, circumferentially symmetrical, air slots are formed between respective FAMDs 48, 50, 52, and their corresponding air ducts 54, 56, 58, 62, in order to normalize temporal pressure fluctuations within the FAMDs. As shown in FIG. 3, the primary FAMD 48 forms a primary fuel air mixing chamber 48A. Elongated, radially aligned and symmetrically oriented, upper primary air slots 48B, which are formed in the primary fuel air mixing chamber 48A, are in fluid communication with the upper primary air duct 54 (airflow arrow A). Similarly, elongated, radially aligned and symmetrically oriented, lower primary air slots 48C are in fluid communication with the lower primary air duct 56 (airflow arrow B). As described in United States Patent No. 6,732,527, entry of compressor air (arrows A and B) generally perpendicular to combustion gas backpressure pulsations ΔΒΡ dampens the pulsations. In some known embodiments, shown in FIG. 4, metal foam blocks 49, containing sponge-like, randomly distributed interstices or pores, cover the primary 48B and secondary 48C air slots, in order to normalize pulsations within the airflow A and B. Referring now to FIG. 2, elongated, radially aligned and symmetrically oriented, secondary air slots 60, which are formed in the secondary, generally tubular, FAMD 50, establish fluid communication with the secondary air duct 58 (airflow arrow C). Similarly, elongated, radially aligned and symmetrically oriented, tertiary air slots 66, which are formed in the generally tubular tertiary FAMD 52, establish fluid communication with the a tertiary air chamber 64 and its upstream air duct 62 (airflow arrow E). [0011] Thus, referring back to FIG. 2, each of the previously described the fuel and air mixing ducts ("FAMDs") 48, 50, 52, their respective air ducts 54, 56, 58 and 62, and respective fuel and air discharge ducts ("FADDs") 80, 82, 84 are symmetrically oriented about the circumference of the outer annular wall of the premixer assembly 47 and the symmetrical, annular intake plenum 46. Despite such annular or bicycle spoke-like, symmetrical structure of the aforementioned ducts within the premixer assembly 47 and the air intake plenum 46, localized compressed air CP flow rate and pressure is not inherently uniform; it varies radially and axially, in three dimensions, within the volume and about the circumference of the air intake plenum 46. Thus, localized air flow into any of the respective upper 54 and lower 56 primary air ducts, secondary air duct 58 and tertiary air duct 62 is not necessarily uniform about the entire external circumference of the premixer assembly 47 that is in fluid communication with the air intake plenum's volume, even in the absence of compressor 24 temporal, induced pressure and flow fluctuations ACP. Furthermore, airflow into FAMDs 48, 50 and 52 is not inherently uniform. Similarly, localized combustion gas flow rate and pressure varies radially and axially within the volume of the combustion chamber 90, which means that localized back pressure BP combustion gas flow, upstream into any of the respective primary FADD 80, secondary FADD 82, and tertiary FADD 84 is not necessarily uniform about the entire combustion chamber, even in the absence of temporal combustion fluctuations ΔΒΡ.

[0012] Localized, steady-state, variations in compressed airflow CP within the air intake plenum 46, or combustion backpressure BP in the combustion chamber 90, influence corresponding localized fuel-air ratio in one or more of the corresponding primary FAMDs 48, secondary FAMDs 50, and/or tertiary FAMDs 52 within the premixer assembly 47. Due to such localized variations in compressed airflow CP and combustion backpressure BP, corresponding FAMDs of the same type that are in different circumferential position within the premixer assembly 47 can generate different fuel-air ratio mixtures, notwithstanding the overall goal of equalizing fuel-air ratio mixtures in those FAMDs. Assuming that uniform fuel-air ratios are fed into the combustion chamber 90 by each of the respective outlets of the FADD discharge ducts 80, 82 and 84, combusted gasses within the combustion chamber also exhibit local variations in the combusted fuel and air mixture.

SUMMARY

[0013] Exemplary embodiments described herein locally vary structure of one or more of air ducts, fuel delivery passages, fuel and air mixing ducts, and/or fuel and air discharge ducts in the premixer of a combustor, in order to normalize fuel-air ratio at any location about the premixer' s three-dimensional volume, or in the combustion chamber, during steady-state operating conditions, and/or in order to stabilize fluctuations in compressed air supply to the premixer, and/or in order to stabilize fluctuations in combustion gas back pressure upstream into the premixer, and/or to stabilize mass flow and pressure fluctuations in combustion gas within the combustor' s combustion chamber. In these exemplary combustor embodiments, the premixer is a monolithic, three-dimensional lattice structure of selectively oriented, asymmetrical- and serpentine-shaped metallic webs, for normalizing fuel-air ratio of a fuel and air mixture that is entrained throughout the volume of the premixer. The web structure defines locally passages of varying profile and dimensions, which form: at least one air duct; and/or at least one fuel delivery passage, and/or at least one fuel and air mixing duct in fluid communication with the air ducts and the fuel delivery passage; and/or at least one fuel and air discharge duct, in fluid communication with the fuel and air mixing duct. In some embodiments, the premixer has a plurality of air ducts, and/or fuel delivery passages, and/or fuel and air mixing ducts, and/or fuel and air discharge ducts.

[0014] Cavity profiles of any one, or more, or all of the respective air ducts, fuel delivery passages, fuel and air mixing ducts, and fuel and air discharge ducts vary locally within the volume occupied by the premixer' s three-dimensional lattice structure, in order to normalize temporally, despite compressed air or combustion gas pressure fluctuations, more uniform fuel-air ratio mixture at any location about or within the premixer's internal volume. Moreover, local variation in the cavity profiles of any or all of the respective air ducts, fuel delivery passages, fuel and air mixing ducts, and fuel and air discharge ducts provide for selective local discharge of selectively varied fuel and air mixtures out of one or more of the fuel and air discharge ducts, in order to compensate for localized variations in the fuel-air ratio within the combustion chamber volume. Thus local variations in the premixer cavity profiles contributes to more uniform combustion gas mass flow within the combustion chamber volume of the combustor. Any of location, angular orientation, cross- sectional area, and profile of any compressed air inlet passage, air duct, FAMD,

FADD, and/or fuel/air mixture discharge passage within the premixer structure is selectively varied, in order to achieve more uniform fuel-air ratio within the combustor. [0015] Some exemplary embodiments are utilized in premixers for combustors of combustion or gas turbine engines. These premixer embodiments locally vary structure of one or more of air ducts, fuel delivery passages, fuel and air mixing ducts, and/or fuel and air discharge ducts, in order to normalize fuel-air ratio at any location about the premixer's three-dimensional volume or in the combustion chamber, in response to any one or more of the following operational conditions: (a) during steady-state operation without temporal fluctuations in (i) compressed air supply to the premixer, or (ii) combustion gas back pressure upstream into the premixer, or (iii) combustion mass flow within the combustor; and/or (b) in order to stabilize fluctuations in compressed air supply to the premixer, and/or (c) in order to stabilize fluctuations in combustion gas back pressure upstream into the premixer; and/or (d) in order to stabilize combustion mass flow within the combustor. The premixer is a monolithic, three-dimensional lattice structure of selectively oriented, asymmetrical- and serpentine-shaped metallic webs. The web structure defines locally varying passages, which form: the aforementioned air ducts, fuel ducts, fuel delivery passages, fuel and air mixing ducts, and fuel and air discharge ducts. In some embodiments, the premixer, or a casting mold for the premixer is formed by additive manufacture. Additive manufacture processes facilitate formation of complex web and passages within the premixer that are not possible to manufacture by traditional solid metal fabrication, metal cutting, or metal casting methods.

[0016] Exemplary embodiments of the invention feature a combustor apparatus for a combustion turbine engine, which comprises a combustion chamber; an air intake plenum, for providing compressed air to the combustion chamber; a fuel delivery system, for delivering fuel to the combustion chamber; and a fuel-air premixer ("premixer"). In some embodiments, the premixer has a monolithic, three- dimensional lattice structure of selectively oriented, asymmetrical- and serpentine- shaped metallic webs and premixer passages formed therein, for normalizing fuel-air ratio of a fuel and air mixture that is entrained throughout the volume of the premixer. The premixer passages, in the monolithic, three-dimensional lattice structure form any one or more of: an air duct, in fluid communication with the air intake plenum; and/or a fuel delivery passage, in fluid communication with the fuel delivery system; and/or a fuel and air mixing duct, in fluid communication with the air duct and the fuel delivery passage; and/or a fuel and air discharge duct, in fluid communication with the fuel and air mixing duct and the combustion chamber.

[0017] Other exemplary embodiments of the invention feature a combustor apparatus for a combustion turbine engine, comprising: an annular-shaped combustion chamber wall, defining a cylindrical-shaped combustion chamber, the combustion chamber wall having a combustion chamber axial centerline, and an upstream axial combustion chamber wall, defining an upstream axial end of the combustion chamber; a combustor outer casing, which envelops the combustion chamber; an air intake plenum, interposed between the combustor outer casing and the combustion chamber, for providing compressed air to the combustion chamber; a fuel delivery system, for delivering fuel to the combustion chamber; and an annular-shaped fuel-air premixer ("premixer"), which circumscribes the cylindrical-shaped combustion chamber in nested fashion. The premixer has a premixer axial centerline, an inner annular wall proximate the combustion chamber and an outer annular wall in fluid communication with the air intake plenum. The premixer has a monolithic, three-dimensional lattice structure of selectively oriented, asymmetrical- and serpentine-shaped metallic webs and premixer passages formed therein, for normalizing fuel-air ratio of a fuel and air mixture that is entrained throughout the volume of the premixer. The premixer passages form any one or more of: a plurality of air ducts; and/or a fuel delivery passage; and/or a fuel and air mixing duct; and/or a fuel and air discharge duct. The plurality of air ducts of the premixer are oriented asymmetrically about the outer annular wall thereof, in fluid communication with the air intake plenum, for selectively directing compressed air radially inwardly with respect to the premixer axial centerline, at selectively varying flow rates and pressures at different locations about the outer annular wall of the fuel-air premixer, for equalizing and stabilizing over time air fuel mixture within the fuel-air premixer. The fuel delivery passage is in fluid communication with the fuel delivery system. The fuel and air mixing duct is in fluid communication with the air ducts and the fuel delivery passage, and is oriented intermediate the inner and outer annular walls of the annular-shaped fuel-air premixer. The fuel and air discharge duct is in fluid communication with the fuel and air mixing duct and the combustion chamber.

[0018] Additional exemplary embodiments of the invention feature a combustor apparatus for a combustion turbine engine, comprising an annular-shaped combustion chamber wall, defining a cylindrical-shaped combustion chamber. The combustion chamber wall has a combustion chamber axial centerline, and an upstream axial, combustion chamber wall, defining an upstream axial end of the combustion chamber. The combustor apparatus has an air intake plenum, for providing compressed air to the combustion chamber; a fuel delivery system, for delivering fuel to the combustion chamber; and an annular-shaped fuel-air premixer ("premixer"). The premixer has: an upper axial end; a lower axial end proximate the upstream axial wall of the combustion chamber; a premixer axial centerline, concentric with the axial centerline of the combustion chamber; an inner annular wall in fluid communication with the upstream axial wall of the combustion chamber; and an outer annular wall in fluid communication with the air intake plenum. The premixer has a monolithic, three- dimensional lattice structure of selectively oriented, asymmetrical- and serpentine- shaped metallic webs and premixer passages formed therein. The premixer passages form a first plurality of air ducts, oriented asymmetrically about the outer annular wall of the premixer, in fluid communication with the air intake plenum, for selectively directing compressed air radially inwardly with respect to the premixer axial centerline and axially toward the lower axial end thereof, at selectively varying flow rates and pressures at different locations about the outer annular wall of the fuel-air premixer, for equalizing and stabilizing over time air fuel mixture within the fuel-air premixer. In some embodiments, the premixer passages form a fuel delivery passage, in fluid communication with the fuel delivery system. In some embodiments, the premixer passages form a fuel and air mixing duct, in fluid communication with the first plurality of air ducts and the fuel delivery passage, with the fuel and air mixing duct oriented intermediate the inner and outer annular walls of the annular-shaped fuel-air premixer. In some embodiments, the premixer passages form a fuel and air discharge duct, in fluid communication with the fuel and air mixing duct and in fluid communication with the combustion through the lower axial end of the premixer.

[0019] The respective features of the exemplary embodiments of the invention that are described herein may be applied jointly or severally in any combination or subcombination.

BRIEF DESCRIPTION OF DRAWINGS

[0020] The exemplary embodiments of the invention are further described in the following detailed description in conjunction with the accompanying drawings, in which:

[0021] FIG. 1 is a fragmentary, side elevational view of a known gas turbine engine;

[0022] FIG. 2 is a fragmentary, axial cross-sectional view through a known, can-type combustion chamber;

[0023] FIG. 3 is a cross- sectional view of part of the known primary fuel and air mixing duct ("FAMD") shown in FIG. 2; [0024] FIG. 4 is a cross-sectional view of an alternative embodiment of a known primary fuel and air mixing duct ("FAMD");

[0025] FIG. 5 is a fragmentary, axial cross-sectional view through an embodiment of a can-type combustion chamber, which is constructed in accordance with the present invention;

[0026] FIG. 6 is a perspective view of another embodiment of a premixer that is constructed in accordance with an embodiment of the present invention, which has a monolithic, three-dimensional lattice structure of selectively oriented, asymmetrical - and serpentine-shaped metallic webs that define locally-varying passages;

[0027] FIG. 7 is a schematic, fragmentary cross-sectional view of a premixer that is constructed in accordance with another embodiment of the present invention;

[0028] FIG. 8 is a schematic, fragmentary cross-sectional view of a premixer that is constructed in accordance with another embodiment of the present invention;

[0029] FIG. 9 is a schematic, fragmentary cross-sectional view of a premixer that is constructed in accordance with another embodiment of the present invention;

[0030] FIG. 10 is a schematic, fragmentary cross-sectional view of a premixer that is constructed in accordance with another embodiment of the present invention; [0031] FIG. 11 is an axial cross-sectional view through an embodiment of an annular- type combustion chamber of the present invention;

[0032] FIG. 12 is an axial cross-sectional view through another embodiment of an annular-type combustion chamber of the present invention ; and

[0033] FIG. 13 is a flowchart showing an embodiment of a method for normalizing fuel-air mixture within a combustor, by designing and manufacturing a premixer, in accordance with the present invention, which has a monolithic, three-dimensional lattice structure of selectively oriented, asymmetrical- and serpentine-shaped metallic webs that define locally varying passages. [0034] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The figures are not drawn to scale.

DESCRIPTION OF EMBODIMENTS

[0035] Exemplary embodiments of the invention are utilized in premixers for combustors of combustion or gas turbine engines. Premixer embodiments described herein locally vary structure of one or more of air ducts, fuel delivery passages, fuel and air mixing ducts, and/or fuel and air discharge ducts, in order to normalize fuel-air ratio at any location about the premixer' s three-dimensional volume, or in the combustion chamber, during steady-state operating conditions, and/or in order to stabilize fluctuations in compressed air supply to the premixer, and/or in order to stabilize fluctuations in combustion gas back pressure upstream into the premixer, and/or in order to stabilize combustion mass flow within the combustor. The premixer is a monolithic, three-dimensional lattice structure of selectively oriented, asymmetrical- and serpentine-shaped metallic webs. The web structure defines locally varying passages, which form: the aforementioned air ducts, fuel ducts, fuel delivery passages, fuel and air mixing duct, and fuel and air discharge duct. In some embodiments, the premixer, or a casting mold for the premixer is formed by additive manufacture. Additive manufacture processes facilitate formation of complex web and passages within the premixer that are not possible to manufacture by traditional solid metal fabrication, metal cutting or metal casting methods.

[0036] FIG. 5 shows an exemplary embodiment of a three-stage, can-type combustor 100 for a combustion turbine engine, which incorporates features of the present invention. The combustor 100 is substituted for the prior art combustor 38 of the combustion turbine engine 20, shown in FIG. 1 or the combustor 40 of FIGs. 2-4. Features of the invention described herein are incorporated into other types of combustors, including annular and can-annular construction combustors, and other types of can combustors, for stationary power generation engines or aero-type engines. While the combustor 100 is a three-stage combustor, features of the invention described herein are incorporated into single-, two- or greater than three- stage combustors.

[0037] Referring to FIGs. 5 and 6, the combustor 100 is a can-type, three-stage combustor, enveloped by a combustor outer casing 102, which receives compressed air CP from the compressor of the engine section via an air intake 104. An annular air intake plenum 106 is defined between the interior of the combustor outer casing 102 and a fuel-air premixer ("premixer") 150. The exemplary embodiment premixer 150 is a monolithic, three-dimensional lattice structure of selectively oriented, asymmetrical- and serpentine-shaped metallic webs. As shown in greater detail in the embodiment of FIG. 6, the premixer 150 has a generally annular shape, with an outer circumferential surface 152 that is in fluid communication with the air intake plenum 106, an inner circumferential surface 154 that abuts and is in fluid communication with a stepped, annular combustion chamber 120, an upper axial surface 156 that abuts the combustor outer casing 102, and a lower axial surface 158 that is in communication with the air intake 104 and the air intake plenum 106. The metallic web forms a three-dimensional, lattice-like mesh 160 that defines locally apertures and passages 162 of varying profile and dimensions along one or more of its outer circumferential surface 152 (e.g., about the axial length L and about varying angular positions Θ along its outer circumferential surface), its inner circumferential surface 154, and optionally on its upper 156 and lower 158 axial surfaces, of the lattice structure of the premixer 150. The lattice-like mesh 160 defines locally apertures and passages 162, within the interior volume of the premixer 150. While the premixer 150 is shown as having an annular structure, in other embodiments, the premixer has different structural shapes, such as the hour glass-like external profile of the premixer 210 of FIG. 9. In other embodiments, the premixer has an asymmetrical structural profile. [0038] The locally varying structure of the lattice-like mesh 160 with its integral passages 162 within the volume occupied by the premixer 150 (bounded within the envelope of dimensions L and Θ), form a plurality of locally varying profile, orientation, and dimension air ducts; fuel delivery passages; fuel and air mixing ducts ("FAMDs"), in fluid communication corresponding air ducts and the fuel delivery passages; and fuel and air discharge ducts (FADDs"), in fluid communication with their corresponding FAMDs. In some embodiments, the premixer has a single fuel delivery passage in communication with a fuel and air mixing duct, with the FAME) in communication with a corresponding fuel and air discharge duct. In some embodiments, the premixer is constructed with one or more of locally varying, annular- shaped air ducts, and/or fuel delivery passages, and/or FAMDs and/or FADDs. In other embodiments, the premixer is constructed with one or more of locally varying, channel- or conduit-like air ducts, and/or fuel delivery passages, and/or FAMDs and/or FADDs. In yet other embodiments, the premixer is constructed with one or more of locally varying combinations of annular-, channel- and/or conduit like air ducts, and/or fuel delivery passages, and/or FAMDs and/or FADDs.

[0039] In some embodiments, profiles and/or spatial orientation of the various ducts and/or fuel passages is selectively altered locally within the lattice-like mesh 160 of the premixer 150, in order to achieve uniform fuel-air ratio within the premixed fuel and air mixture, throughout the premixer. In other embodiments, profiles and/or spatial orientation of the various ducts and/or fuel passages is selectively altered locally within the lattice-like mesh 160 of the premixer 150, in order to deliver uniform fuel and air mixture to the combustion chamber 120. In yet other embodiments, profiles and/or spatial orientation of the various ducts and/or fuel passages is selectively altered locally within the lattice-like mesh 160 of the premixer 150, in order to normalize mass flow of combustion gasses within the volume of the combustion chamber 120. Construction of the various ducts and fuel delivery passages is now described in detail.

[0040] As shown in FIG. 5, the air intake plenum 106 is in fluid communication with the interior volume of the premixer 150, through passages 162 formed in the outer circumferential surface 152 and in some embodiments, the lower axial surface 158. The passages 162 formed in outer circumferential surface 152 and/or the a lower axial surface 158 function as air duct passages (comparable to the air duct passages 54, 56, 58 and 62 of FIG. 2), which are in turn in fluid communication with respective, separate and isolated primary fuel and air mixing duct ("FAMD") 108 (see exemplary airflow arrows A and B), secondary FAMD 110 (see exemplary airflow arrows C and D), and tertiary FAMD 112 (see exemplary airflow arrows E). In some embodiments, one or more of the FAMDs 108, 110 and 112 has an annular construction, fully circumscribing the combustion chamber 120. In other embodiments one or more of the FAMDs 108, 110 and 112, comprises a plurality of circumferentially-spaced and arrayed discrete and separate conduits (with symmetrical, radially-oriented, angular spacing Θ, or alternatively, with asymmetrical angular spacing Θ or skewed or twisted, non-radial, spatial orientation). [0041] The primary FAMD 108 is in fluid communication with an annular manifold of a primary fuel delivery system 114. Similarly, the secondary FAMD 110 is in fluid communication with an annular manifold of a secondary fuel delivery system 116, and the tertiary FAMD 112 is in fluid communication with an annular manifold of a tertiary fuel delivery system 118. Within each of the FAMDs 108, 110 and 112, fuel F, supplied by each corresponding fuel delivery system 114, 116, 118 is entrained within the compressed air CP, at a desired fuel-air ratio. The compressed air CP is supplied to the corresponding FAMDs 108, 110 and 112 through the respective corresponding air ducts that are formed within the passages 162, along the paths indicated by the flow arrows A, B, C, D and E. In some embodiments, one or more of the fuel delivery systems 114, 116 or 118 comprise pressurized fuel rails obtained from a pressurized fuel source, which in turn are coupled to fuel injection nozzles, orifices or the like that introduce fuel into its corresponding FAMD. The fuel and air are mixed in each FAMD 108, 110, and 112. [0042] The fuel and air mixture discharges from the primary FAMD 108 through primary fuel and air discharge duct ("FADD") 130 and primary FADD outlet 131. In some embodiments, a flow directing swirler is incorporated on the downstream end of the FAMD 108, or any of the other FAMDs 110 or 112, in order to direct the fuel-air mixture within the corresponding primary fuel and air discharge duct. The fuel and air mixture discharges from secondary FAMD 110 via secondary fuel and air discharge duct 132, and from the tertiary FAMD 112 via tertiary fuel and air discharge duct 134. In some embodiments, one or more of the fuel and air discharge ducts 130, 132 or 134 has an annular construction, fully circumscribing the combustion chamber 120. In other embodiments one or more of the fuel and air discharge ducts 130, 132 or 134 comprises a plurality of circumferentially- spaced and arrayed discrete and separate conduits (with symmetrical, radially-oriented, angular spacing Θ, similar to the FAMDs of the combustor 40 of FIG. 2, or alternatively, with asymmetrical angular spacing Θ or skewed or twisted, non-radial orientation). In some embodiments, one or more of the FADDs 130, and/or 132, and/or 134 have locally varying profiles, cross-sectional area, and orientation. One or more of such FADDs have locally varying discharge orientation or outlet shape relative to the combustion chamber 120. The respective fuel and air discharge ducts 130, 132, 134 are in fluid communication with, and discharge their respective fuel and air mixtures FA1, FA2 and FA3 into the combustion chamber 120. In some embodiments, discharge location of the FADDs 130, 132, 134 varies locally about the combustion chamber 120, for example to resist local variations in combustion back pressure BP, or backpressure pulsation ΔΒΡ.

[0043] The combustion chamber 120 has an upper axial end that is defined by an upstream wall 121. The upstream wall 121 defines an upstream axial limit of a primary combustion zone 122. A primary annular wall 123 defines a circumferential axial limit of the primary combustion zone 122. The fuel and air mixture supplied by the primary FAMDs 108 enters the primary combustion zone 122 via the corresponding, coupled array of primary fuel and air discharge ducts 130 (arrow FA1). The combustion chamber 120 has a secondary combustion zone 124, circumferentially defined by a secondary annular wall 125, downstream of the primary combustion zone 122. The fuel and air mixture supplied by the secondary

FAMDs 110 enters the secondary combustion zone 124 via the corresponding, coupled array of secondary fuel and air discharge ducts 132 (arrow FA2). A tertiary combustion zone 126 is circumferentially defined by a tertiary annular wall 127, downstream of the secondary combustion zone 124. The fuel and air mixture supplied by the tertiary FAMDs 112 enters the tertiary combustion zone 126 via the tertiary fuel and air discharge ducts 134 (arrow FA3). In the embodiment of FIG. 5, the combustion chamber walls 121, 123, 125, and 127 are integrally formed as part of the inner circumferential surface 154 of the premixer 150. In other embodiments, the combustion chamber walls are formed in a separate sleeve or interlocking sleeves, which are subsequently circumscribed by the premixer inner circumferential surface 154.

[0044] During steady state operation of combustor 100, fuel F delivery to each separate type of FAMD 108, 110 and 112 does not significantly fluctuate. However, as previously noted the localized compressed air flow CP varies about the premixer 150 outer circumferential surface 152 and/or the lower axial surface 158. In the present invention, variations in localized compressed air flow CP is normalized by selectively varying at locations within the volume of the three-dimensional lattice web structure 160 of the premixer 150, altering the size, shape and density of the apertures or passages 162 that form the FAMDs 108, 110, 112 and/or the fuel and air discharge ducts 130, 132, 134. Compressed air flow CP and combustion backpressure BP do fluctuate temporally denoted as ACP and ΔΒΡ in FIG. 5, leading to temporal fluctuations in the fuel-air ratio. The temporal fluctuations ACP and ΔΒΡ are also normalized by selectively varying at locations within the volume of the three- dimensional lattice web structure 160 of the premixer 150, altering the size, shape and density of the apertures or passages 162, and or the wall surfaces that form the FAMDs 108, 110, 112 and/or the fuel and air discharge ducts 130, 132, 134. For example, to alter flow and/or pressure characteristics of compressed air CP or back pressure BP entering any portion of a particular FAMD, to dissipate localized fluctuations of ACP or ΔΒΡ. United States Patent No. 6,732,527 describes ways to counteract such fluctuations through preconditioning airflow into FAMDs, dimensioning of FAMDs and fuel and air discharge ducts. Gradual introduction of compressed air into the premixer, by incorporation of flow conditioning structures within the apertures or passages 162 within the lattice web structure 160 of the premixer 150 (comparable to the upper 48B or lower 48C primary air slots of FIG. 3, with or without the metal foam blocks 49 of FIG. 4) normalizes temporal pressure fluctuations, ACP and ΔΒΡ within the FAMDs. [0045] FIGs. 7-10 show embodiments of premixer three-dimensional lattice monolithic structures with localized variations of the webs, apertures, channels and cavity surfaces that form air ducts, FAMDs, and fuel and air discharge ducts. In FIG. 7, fragmentary view of a premixer 170 shows a lattice-like structure of generally vertically oriented webs 172, 174, 176, and generally horizontally oriented webs 178, 180, 182, 184, 186. In this example, the horizontally oriented webs 178, 180, 182,

184, 186 have varying density or pitch Pi, P₂, P₃, and thickness Ti, T₂. Aperture or passage 188 has a constant height Y, while passage 190 has a varying width X. The passage 192 is of generally circular cross section, while the passage 194 has an irregularly shaped cross section. In FIG. 8, the lattice structure of the premixer 200 comprises vertically aligned webs 202, oriented along axis Y, axially aligned webs

204, oriented along axis Z, and horizontally aligned webs 206, oriented along axis X. In this embodiment, the webs 204 and 206 are selectively oriented at a skew angle Θ relative to each other. The webs 202 and 204 extend vertically along axis Y to a length L.

[0046] In FIG. 9, the three dimensional, hour glass-like, lattice structure of the annular premixer 210 comprises nested, generally circular webs 212, 214, 216, 218, 222, having respective radii Ri, R₂, R₃, R4, and vertically aligned webs 220, which collectively define apertures or passages 224. Web 226 defines a generally circular passage 228. In this embodiment, the premixer 210 is formed from a stack of separate, three-dimensional, monolithic lattice structures, labeled I, II, III, IV and V. Those monolithic structures are coupled to form the completed premixer 210. In other embodiments, a premixer structure similar to premixer 210 is formed by coupling nested, concentric annular hoops (e.g., the hoop bounded by R₁-R₂, or R₂-R₃, or R₃-R4). In other embodiments, sector-shaped wedges of three-dimensional, monolithic lattice structures are coupled to form a completed premixer. In some embodiments, separate, discrete, three-dimensional, monolithic lattice structures are coupled by welding, brazing, fasteners, and mating or interlocking web portions.

[0047] FIG. 10 shows exemplary localized variations in the web portions of another embodiment of a three-dimensional, monolithic lattice structure of a premixer 230.

Cavities of an asymmetrical, serpentine-like fuel and air mixing duct ("FAMD") 231, fuel delivery system 232, and fuel and air discharge duct 233 are formed by three- dimensional walls 236, 238 and 240. Walls 242, 244, 246, 248, 250, 252, 254, and 256 form air ducts to direct air (AIR or A) into the FAMD 231, via apertures 258, 260, 262, 264, 268, 270, 272, 274, and 276. The fuel delivery system 232 introduces

(FUEL F) into the FAMD 231, where it is mixed with the incoming air to generate a fuel and air mixture. The wall structure of the cavity forming the FAMD 231, along with the orientation of the apertures and air ducts that feed air into the FAMD, induces swirling vortices V, for homogenization of the fuel and air mixture FA4 to a desired fuel-air ratio. The FAMD 231 and fuel and air discharge duct 233 collectively orient flow and cross section of the fuel and air mixture FA4, for normalizing backpressure fluctuations ΔΒΡ.

[0048] FIG. 1 1 is a two-stage annular combustor of the general type shown in U. S. Patent No. 7,841, 181. Here, the combustor 300 incorporates a premixer having a monolithic, three-dimensional lattice structure in accordance with another embodiment of the invention. In this particular embodiment of FIG. 11, the combustor 300 has a combustion chamber 302. An upstream axial, combustion chamber wall 304 has an annular-shape, with an outer peripheral edge conjoined with a cylindrical outer wall 306, and an inner peripheral edge with an inner wall 312. The inner 312 and outer 306 cylindrical walls of the combustion chamber 302 are concentrically aligned with the combustion chamber axial centerline. The axial centerline of the combustion chamber 302 is coextensive with the combustor 300 axial centerline. The combustion chamber 302 defines, sequentially from the axial, upstream, combustion chamber wall 304, a primary combustion zone 310 (sometimes also referred to as a main combustion zone or a main 1 combustion zone), between the inner wall 312 and the outer cylindrical wall 306 of the combustion chamber, and a secondary combustion zone 308 (sometimes also referred to as a pilot combustion zone or a main 2 combustion zone), downstream of the lower axial end wall 348 of the inner wall 312 of the combustion chamber. [0049] An air intake plenum 314 provides compressed air CP to the combustion chamber 302, through the annular-shaped premixer 320. The premixer 320 has a centerline that is coextensive with centerlines of the combustor 300 and the combustion chamber 302. The premixer 320 has an upper axial end; a lower axial end proximate the upstream axial wall 304 of the combustion chamber 302; an inner annular wall 340 in fluid communication with the upstream axial wall of the combustion chamber; and an outer annular wall 322 in fluid communication with the air intake plenum 314.

[0050] The premixer 320 has a monolithic, three-dimensional lattice structure of selectively oriented, asymmetrical- and serpentine- shaped metallic webs and premixer passages formed therein. The premixer passages form a first plurality of air ducts 324, oriented asymmetrically about the outer annular wall 322 of the premixer, in fluid communication with the air intake plenum 314, for selectively directing compressed air radially inwardly with respect to the premixer axial centerline and axially toward the lower axial end thereof, at selectively varying flow rates and pressures at different locations about the outer annular wall of the fuel-air premixer, for equalizing and stabilizing over time air fuel mixture within the fuel-air premixer. Primary 332 and secondary 346 fuel delivery passages are respectively in fluid communication with a primary fuel delivery system 330 and a secondary fuel delivery system 344.

[0051] A primary fuel and air mixing duct 326 is, in fluid communication with the first plurality of air ducts 324 and the primary fuel delivery passage 332, oriented intermediate the inner 340 and outer 322 annular walls of the annular-shaped fuel-air premixer 320. A primary fuel and air discharge duct 328 is in fluid communication with the primary fuel and air mixing duct 326 and is in fluid communication with the primary combustion zone 310 of the combustion chamber 302, where its fuel and air mixture FA5 is discharged through the lower axial end of the premixer 320. A secondary fuel and air mixing duct 345 is in fluid communication with a secondary air mixing duct 342, the secondary fuel delivery passage 346 and a secondary fuel and air discharge duct 350. The secondary fuel and air discharge duct 350 is coupled to lower axial end wall 348 of the inner wall 312 of the combustion chamber 302. The secondary fuel and air discharge duct 350 is in fluid communication with the secondary combustion zone 308, where its fuel and air mixture FA6 is discharged. The three-dimensional lattice structure of the premixer 320 forms the webs and passages therein to equalize and normalize fuel-air ratio in the premixer, and optionally within the combustion chamber 302, as is done in the combustors and premixers of FIGs. 5-10. While the combustor 300 is a two-stage annular combustor, its features are also applicable to single-stage annular combustors, as well as annular combustors having more than two stages. [0052] FIG. 12 is another embodiment of a two-stage annular combustor 400 of the general type shown in U.S. Patent No. 8,881,531, with compressed air CP from the air intake plenum 414 entering the combustor radially around the circumferential outer periphery of the premixer 420 (similarly to the premixer 320 of FIG. 11) and additionally, axially through its upper axial end. Similar to the previously described embodiments of FIGs. 5-11, the combustor 400 incorporates a premixer 420 having a monolithic, three-dimensional lattice structure in accordance with another embodiment of the invention. The combustor 400 has a combustion chamber 402, similar to the combustion chamber 302 of FIG. 11. In the embodiment of FIG. 12, the upstream axial, combustion chamber wall 404 has an annular-shape, with an outer peripheral edge conjoined with a cylindrical outer wall 406, and an inner peripheral edge with an inner wall 412. The inner 412 and outer 406 cylindrical walls of the combustion chamber 402 are concentrically aligned with the combustion chamber axial centerline. The axial centerline of the combustion chamber 402 is coextensive with the combustor 400 axial centerline. The combustion chamber 402 defines, sequentially from the axial, upstream, combustion chamber wall 404, a primary combustion zone 410 (sometimes also referred to as a main combustion zone or a main 1 combustion zone), between the inner wall 412 and the outer cylindrical wall 406 of the combustion chamber, and a secondary combustion zone 408 (sometimes also referred to as a pilot combustion zone or a main 2 combustion zone), downstream of the lower axial end wall 448 of the inner wall 412 of the combustion chamber. [0053] The air intake plenum 414 provides compressed air CP to the combustion chamber 402, through the annular-shaped premixer 420. The premixer 420 has a centerline that is coextensive with centerlines of the combustor 400 and the combustion chamber 402. The premixer 420 has an open, upper axial end, in communication with the air intake plenum 414, through axial air duct 425 that is formed in the lattice structure, which receives compressed air CP. The premixer 420 also has a lower axial end proximate the upstream axial wall 404 of the combustion chamber 402; an inner annular wall 440 in fluid communication with the upstream axial wall 404 of the combustion chamber and the air intake plenum 414; and an outer annular wall 422 in fluid communication with the air intake plenum 414.

[0054] The premixer 420 has a monolithic, three-dimensional lattice structure of selectively oriented, asymmetrical- and serpentine- shaped metallic webs and premixer passages formed therein. The premixer passages form a first plurality of air ducts 424, oriented asymmetrically about the outer annular wall 422 of the premixer, in fluid communication with the air intake plenum 414, for selectively directing compressed air radially inwardly with respect to the premixer axial centerline and axially toward the lower axial end thereof, at selectively varying flow rates and pressures at different locations about the outer annular wall of the premixer, for equalizing and stabilizing over time air fuel mixture within the fuel-air premixer. Primary 432 and secondary 446 fuel delivery passages are respectively in fluid communication with a primary fuel delivery system 430 and a secondary fuel delivery system 444.

[0055] A primary fuel and air mixing duct 426 is, in fluid communication with the first plurality of air ducts 424 and the primary fuel delivery passage 432, oriented intermediate the inner 440 and outer 422 annular walls of the annular-shaped fuel-air premixer 420. A primary fuel and air discharge duct 428 is in fluid communication with the primary fuel and air mixing duct 426 and is in fluid communication with the primary combustion zone 410 of the combustion chamber 402, through the lower axial end of the premixer 420, where its fuel and air mixture FA7 is discharged through the lower axial end of the premixer 420. A secondary fuel and air mixing duct 445 is in fluid communication with the axial air duct 425, via a secondary air duct 442, the secondary fuel delivery passage 446 and a secondary fuel and air discharge duct 450. The secondary fuel and air discharge duct 450 is coupled to the lower axial end wall 448 of the inner wall 412 of the combustion chamber 402. The secondary fuel and air discharge duct 450 is in fluid communication with the secondary combustion zone 408, where its fuel and air mixture FA8 is discharged.

The three-dimensional lattice structure of the premixer 420 forms the webs and passages therein to equalize and normalize fuel-air ratio in the premixer, and optionally within the combustion chamber 402, as is done in the combustors and premixers of FIGs. 5-11. While the combustor 400 is a two-stage annular combustor, its features are also applicable to single-stage annular combustors, as well as annular combustors having more than two stages.

[0056] FIG. 13 illustrates a method for fabricating a premixer, having a monolithic, three-dimensional lattice structure of selectively oriented, asymmetrical- and serpentine- shaped metallic webs and premixer passages, such as the premixer 150 in

FIG. 5, in order to achieve uniform fuel-air ratio within the premixed fuel and air mixture, throughout the premixer, during steady state operation in the absence of temporal fluctuations in fuel delivery or compressor airflow, or combustion backpressure. The method is also useful for fabricating a premixer, such as the premixer 150 in FIG. 5, where profiles of the various ducts and/or fuel passages is selectively altered locally within the lattice-like mesh 160, in order to deliver uniform fuel and air mixture to the combustion chamber of the combustor. In yet other embodiments, profiles of the various ducts and/or fuel passages is selectively altered locally within the lattice-like mesh 160 of the premixer 150, in order to normalize mass flow of combustion gasses within the volume of the combustion chamber 120. [0057] Methods for determining profiles and orientations of the various ducts and fuel delivery passages throughout the premixer volume, such as in the premixer 150 of FIGs. 5 and 6, and the structure of the webs in the lattice-like mesh 160 that defines those passages, is now described in greater detail, with reference to the exemplary method 500 shown in FIG. 13. In the exemplary method 500, at modeling step 502, combustor 100 structure, as well as desired intake air CP, fuel F, fuel and air mixture FA in the premixer 150 and combustion gas flow dynamics within the combustion chamber 120, including combustion backpressure BP dynamics within the combustion chamber and upstream into the premixer, are modeled, in a computer work station, running commercially available structural and fluid dynamics software.

[0058] In step 504, operation of the modeled combustor 100, including the three- dimensional, lattice-like premixer 150, are simulated in computer workstation running commercially available computational fluid dynamics ("CFD") simulation software. During the simulated operation, intake air CP, fuel F, fuel and air mixture FA in the premixer 150 and combustion gas flow dynamics within the combustion chamber 120, including combustion backpressure BP dynamics within the combustion chamber and upstream into the premixer, are evaluated. Empirical, operational knowledge about such flow dynamics, based on past physical observation and simulations are utilized to evaluate the CFD simulations. Local deviations from a desired fuel-air ratio within the fuel and air mixture, throughout the premixer volume and the sources of such deviations are identified and evaluated.

[0059] In step 506, the premixer lattice structure, as well as structure of any other components in the combustor, are revised and altered, in order to equalize the fuel and air mixture ("F/A") throughout the combustor and normalize influence of transient fluctuations in CP and/or BP on the F/A. For example, localized variations in steady state airflow CP, or normalization of transient pulsations ACP within the air intake plenum 106 of FIG. 5 at different circumferential angular positions Θ or axial position L are compensated by altering the cross sectional dimensions or shape of air ducts leading to the locally associated fuel and air mixing ducts (FAMDs) 108, 110, 112. Localized airflow into any portion of a FAMD is similarly evaluated and compensated as necessary. For example, fuel and air mixing is normalized within a FAMD by altering its surface profile, to stimulate creation of vortices V. Dimensions and shape of FAMDs 108, 1 10, 1 12, and their associated fuel and air discharge ducts 130, 132, 134 are locally varied to resist backpressure BP and backpressure fluctuations ΔΒΡ. Dimensions and shape of fuel and air discharge ducts 130, 132, 134, are locally varied to normalize flow of the fuel and air mixture within the combustion chamber 120 volume, and/or to normalize combustion burning in various zones 122, 124, 126 of the combustion chamber. [0060] Upon achievement of satisfactory results, after revision of the combustor 100 structure of FIG. 5, such as any one or more of F/A equalization, A P or ΔΒΡ normalization in the premixer 150 and/or F/A equalization into the combustion chamber 120, and/or combustion normalization throughout the combustion chamber, the revised combustor 100 structural model is stored in step 508 of FIG. 13.

[0061] In step 510 of FIG. 13, the stored, revised structural model of step 508 is used to construct the premixer 150 of FIG. 5, and other combustor 100 components. In this embodiment, manufacture focus is on the premixer 150, which is constructed as a monolithic, three-dimensional lattice, metallic structure. Metal alloys used to form the premixer, as well as other components within the combustor, are typically nickel/cobalt/chromium-based so-called superalloys.

[0062] Profiles of the locally varying profile and dimension ducts and/or fuel passages of the various embodiments of the monolithic, three-dimensional lattice structure premixers of FIGs. 5-12 is not readily accomplished by traditional metal component fabrication and welding methods. While unistructural welded metal premixers have been formed in the past, traditional metal cutting methods, including electro -discharge machining ("EDM") cannot readily fabricate complex, internal duct passages within a premixer' s internal volume space. Traditional metal casting methods, using molds with mold cavities and mold cavity inserts, also cannot readily fabricate complex, internal duct passages within a premixer' s internal volume space. [0063] In performing step 510 of FIG. 13 of the method embodiments, monolithic, three-dimensional lattice structure premixers of FIGs. 5-12 are fabricated, using additive manufacture methods. In some embodiments, the premixer, such as the premixer 150 of FIGs. 5 and 6, is directly constructed, layer by layer, by fusing metallic powder, with a focused energy source such as a laser, into a monolithic, three-dimensional lattice structure of selectively oriented, asymmetrical- and serpentine- shaped metallic webs and premixer passages that replicate desired ultimate structure of the premixer. [0064] In other embodiments, the monolithic, three-dimensional lattice structure premixers of FIGs. 5-12 are fabricated by a sacrificial-pattern, mold-casting process. A pattern mold, which replicates the structure of the desired, monolithic, three- dimensional lattice structure of selectively oriented, asymmetrical- and serpentine- shaped metallic webs and premixer passages of the premixer, is formed by an additive manufacture process, by fusing powdered mold material with an energy source. The pattern mold is encased in a metal casting mold. The formed mold is filled with molten metal, which displaces the sacrificial mold pattern. After the molten metal hardens, the surrounding mold is removed. The completed cast-metal premixer replicates the desired, monolithic, three-dimensional lattice structure of selectively oriented, asymmetrical- and serpentine-shaped metallic webs and premixer passages.

[0065] The constructed premixer 150 of FIGs. 5 and 6 is assembled, with other components, into combustor 100. The combustor 100, or any other previously described combustor embodiment described in this portion of this document, is then installed in a combustion turbine engine, such as the engine 20 of FIG. 1, in place of the combustor 38.

[0066] Although various embodiments that incorporate the invention have been shown and described in detail herein, others can readily devise many other varied embodiments that still incorporate the claimed invention. The invention 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 drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. The phraseology and terminology 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 direct physical or mechanical connections or couplings.

Claims

What is claimed is: Claim 1. A combustor apparatus for a combustion turbine engine, comprising: a combustion chamber;

an air intake plenum, for providing compressed air to the combustion chamber;

a fuel delivery system, for delivering fuel to the combustion chamber; and a fuel-air premixer, having a monolithic, three-dimensional lattice structure of selectively oriented, asymmetrical- and serpentine- shaped metallic webs and premixer passages formed therein, for normalizing fuel-air ratio of a fuel and air mixture that is entrained throughout the volume of the premixer, the premixer passages, in the monolithic, three-dimensional lattice structure forming any one or more of:

an air duct, in fluid communication with the air intake plenum; and/or a fuel delivery passage, in fluid communication with the fuel delivery system; and/or

a fuel and air mixing duct, in fluid communication with the air duct and the fuel delivery passage; and/or

a fuel and air discharge duct, in fluid communication with the fuel and air mixing duct and the combustion chamber.

Claim 2. The apparatus of claim 1, the fuel-air premixer comprising a monolithic, three-dimensional lattice structure of selectively oriented, asymmetrical- and serpentine-shaped metallic webs and premixer passages formed by an additive manufacture process, by fusing metallic powder into the three-dimensional, monolithic lattice structure with an energy source.

Claim 3. The apparatus of claim 1, the fuel-air premixer comprising a monolithic, three-dimensional lattice structure of selectively oriented, asymmetrical- and serpentine-shaped metallic webs and premixer passages formed by a sacrificial- pattern, mold casting process, by: forming a sacrificial pattern mold, replicating the three-dimensional, monolithic lattice structure of the premixer, by an additive manufacture process, which fuses powdered mold material with an energy source;

encasing the sacrificial pattern mold in a metal casting mold;

filling the metal casting mold with molten metal, displacing the sacrificial pattern mold; and

removing the metal casting mold.

Claim 4. The apparatus of claim 1, the fuel-air premixer comprising a plurality of monolithic, three-dimensional lattice structures that are coupled to each other.

Claim 5. The apparatus of claim 1, further comprising portions of the air duct directly leading to the fuel and air mixing duct having shapes, which evenly distribute and stabilize over time, air flow and pressure into the fuel and air premixing duct.

Claim 6. The apparatus of claim 1, further comprising walls forming the fuel and air mixing duct defining profiles which induce swirling fuel and air mixture vortices within the fuel and air mixing duct.

Claim 7. The apparatus of claim 1, further comprising walls forming the fuel and air mixing duct defining asymmetric profiles at different locations within the fuel- air premixer, for equalizing and stabilizing over time, fuel and air mixture within the fuel-air premixer.

Claim 8. The apparatus of claim 1, the fuel-air premixer including solid wall portions, which form at least part of the combustion chamber.

Claim 9. A combustor apparatus for a combustion turbine engine, comprising: an annular- shaped combustion chamber wall, defining a cylindrical-shaped combustion chamber, the combustion chamber wall having a combustion chamber axial centerline, and an upstream axial combustion chamber wall, defining an upstream axial end of the combustion chamber; a combustor outer casing, which envelops the combustion chamber;

an air intake plenum, interposed between the combustor outer casing and the combustion chamber, for providing compressed air to the combustion chamber;

a fuel delivery system, for delivering fuel to the combustion chamber;

an annular-shaped fuel-air premixer circumscribing the cylindrical- shaped combustion chamber in nested fashion, having a premixer axial centerline, an inner annular wall proximate the combustion chamber and an outer annular wall in fluid communication with the air intake plenum, said premixer having a monolithic, three- dimensional lattice structure of selectively oriented, asymmetrical- and serpentine- shaped metallic webs and premixer passages formed therein, for normalizing fuel-air ratio of a fuel and air mixture that is entrained throughout the volume of the premixer, the premixer passages forming any one or more of:

a plurality of air ducts, the plurality of air ducts of said fuel-air premixer oriented asymmetrically about the outer annular wall thereof, in fluid communication with the air intake plenum, for selectively directing compressed air radially inwardly with respect to the premixer axial centerline, at selectively varying flow rates and pressures at different locations about the outer annular wall of the fuel-air premixer, for equalizing and stabilizing over time air fuel mixture within the fuel-air premixer; and/or

a fuel delivery passage, in fluid communication with the fuel delivery system; a fuel and air mixing duct, in fluid communication with the air ducts and the fuel delivery passage, oriented intermediate the inner and outer annular walls of the annular- shaped fuel-air premixer; and/or

Claim 10. The apparatus of claim 9, further comprising the fuel and air discharge duct of said fuel-air premixer oriented about the inner annular wall thereof, in fluid communication with the combustion chamber.

Claim 11. The apparatus of claim 9, further comprising the plurality of fuel and air discharge ducts within said fuel-air premixer, oriented asymmetrically about the inner annular wall thereof, in fluid communication with the combustion chamber, for selectively directing premixed fuel and air into the combustion chamber at selectively varying flow rates and pressures at different locations about inner annular wall of the fuel-air premixer, for equalizing and stabilizing over time combustion pressure and temperature within the combustion chamber.

Claim 12. The apparatus of claim 9, further comprising:

an annular- shaped combustion chamber wall, defining a cylindrical-shaped combustion chamber, the combustion chamber wall having an axial centerline, and an upstream axial combustion chamber wall, defining an upstream axial end of the combustion chamber; the combustion chamber defining sequentially from the upstream combustion chamber wall:

a primary combustion zone, having a first axial length and a first diameter; and a secondary combustion zone, having a second axial length and a second diameter greater than the first diameter;

the fuel-air premixer having a monolithic, three-dimensional lattice structure of selectively oriented, asymmetrical- and serpentine-shaped metallic webs and premixer passages formed therein, the premixer passages forming:

a primary fuel and air mixing duct, in fluid communication with a primary fuel delivery passage and a primary fuel and air discharge duct, the primary fuel and air discharge duct in fluid communication with the primary combustion zone; and

a secondary fuel and air mixing duct, in fluid communication with a secondary fuel delivery passage and a secondary fuel and air discharge duct, the secondary fuel and air discharge duct in fluid communication with the secondary combustion zone.

Claim 13. The apparatus of claim 9, further comprising:

a primary combustion zone, having a first axial length and a first diameter; a secondary combustion zone, having a second axial length and a second diameter greater than the first diameter; and

a tertiary combustion zone, having a third axial length and a third diameter greater than the second diameter;

a primary fuel and air mixing duct, in fluid communication with a primary fuel delivery passage and a primary fuel and air discharge duct, the primary fuel and air discharge duct in fluid communication with the primary combustion zone;

a secondary fuel and air mixing duct, in fluid communication with a secondary fuel delivery passage and a secondary fuel and air discharge duct, the secondary fuel and air discharge duct in fluid communication with the secondary combustion zone; and

a tertiary mixing duct, in fluid communication with a tertiary fuel delivery passage and a tertiary fuel and air discharge duct, the tertiary fuel and air discharge duct in fluid communication with the tertiary combustion zone.

Claim 14. A combustor apparatus for a combustion turbine engine, comprising: an annular- shaped combustion chamber wall, defining a cylindrical-shaped combustion chamber, the combustion chamber wall having a combustion chamber axial centerline, and an upstream axial, combustion chamber wall, defining an upstream axial end of the combustion chamber;

an air intake plenum, for providing compressed air to the combustion chamber;

a fuel delivery system, for delivering fuel to the combustion chamber;

an annular-shaped fuel-air premixer, having: an upper axial end;

a lower axial end proximate the upstream axial wall of the combustion chamber;

a premixer axial centerline, concentric with the axial centerline of the combustion chamber;

an inner annular wall in fluid communication with the upstream axial wall of the combustion chamber; and an outer annular wall in fluid communication with the air intake plenum;

said premixer having a monolithic, three-dimensional lattice structure of selectively oriented, asymmetrical- and serpentine- shaped metallic webs and premixer passages formed therein, the premixer passages forming:

a first plurality of air ducts, oriented asymmetrically about the outer annular wall of the premixer, in fluid communication with the air intake plenum, for selectively directing compressed air radially inwardly with respect to the premixer axial centerline and axially toward the lower axial end thereof, at selectively varying flow rates and pressures at different locations about the outer annular wall of the fuel- air premixer, for equalizing and stabilizing over time air fuel mixture within the fuel- air premixer;

a fuel delivery passage, in fluid communication with the fuel delivery system; a fuel and air mixing duct, in fluid communication with the first plurality of air ducts and the fuel delivery passage, oriented intermediate the inner and outer annular walls of the annular-shaped fuel-air premixer; and

a fuel and air discharge duct, in fluid communication with the fuel and air mixing duct and in fluid communication with the combustion through the lower axial end of the premixer.

Claim 15. The apparatus of claim 14, further comprising a second plurality of air ducts, oriented asymmetrically about the upper axial end of the premixer, in fluid communication with the air intake plenum and the fuel and air mixing duct, for selectively directing compressed air radially inwardly with respect to the premixer axial centerline and axially toward the lower axial end thereof, at selectively varying flow rates and pressures at different locations about the upper axial end of the fuel-air premixer, for equalizing and stabilizing over time air fuel mixture within the fuel-air premixer.

Claim 16. The apparatus of claim 14, further comprising:

the axial, upstream, wall of the combustion chamber having an annular-shape, with an outer peripheral edge thereof conjoined with a cylindrical outer wall that forms the annular-shaped combustion chamber, and an inner peripheral edge thereof conjoined with an inner cylindrical wall, the inner and outer cylindrical walls of the combustion chamber concentrically aligned with the combustion chamber axial centerline, the combustion chamber defining sequentially from the axial, upstream, combustion chamber wall:

a primary combustion zone, between the inner and outer cylindrical walls of the combustion chamber;

a secondary combustion zone, downstream of the inner cylindrical wall of combustion chamber; and

the fuel-air premixer having a monolithic, three-dimensional lattice structure of selectively oriented, asymmetrical- and serpentine-shaped metallic webs and premixer passages formed therein, for normalizing fuel-air ratio of a fuel and air mixture that is entrained throughout the volume of the premixer, forming:

a primary, fuel and air mixing duct, in fluid communication with a primary fuel delivery passage and a primary fuel and air discharge duct, the primary fuel and air discharge duct coupled to the axial, upstream, wall of the combustion chamber, in fluid communication with the primary combustion zone;

a secondary fuel and air mixing duct, in fluid communication with a secondary fuel delivery passage and a secondary fuel and air discharge duct, the secondary fuel and air discharge duct circumscribed by the inner cylindrical wall of the combustion chamber, and in fluid communication with the secondary combustion zone.

Claim 17. The apparatus of claim 16, further comprising a second plurality of air ducts, oriented asymmetrically about the upper axial end of the premixer, in fluid communication with the air intake plenum and the primary and secondary fuel and air mixing ducts, for selectively directing compressed air radially inwardly with respect to the premixer axial centerline and axially toward the lower axial end thereof, at selectively varying flow rates and pressures at different locations about the upper axial end of the fuel-air premixer, for equalizing and stabilizing over time air fuel mixture within the primary and secondary mixing ducts.

Claim 18. A combustion turbine engine including the combustor apparatus of claim 1, further comprising:

a combustion section, including the combustor apparatus of claim 1, and a transition coupled to an exhaust end of the combustion chamber;

a compressor section, coupled to and in fluid communication with the air intake plenum, for feeding compressed air to the combustion chamber, through intake plenum and the fuel-air premixer; and

a turbine section coupled to and in fluid communication with the transition of the combustion section, for feeding combustion gas to the turbine section.

Claim 19. A combustion turbine engine including the combustor apparatus of claim 9, further comprising:

Claim 20. A combustion turbine engine including the combustor apparatus of claim 14, further comprising: