US20160201918A1 - Small arrayed swirler system for reduced emissions and noise - Google Patents
Small arrayed swirler system for reduced emissions and noise Download PDFInfo
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- US20160201918A1 US20160201918A1 US14/857,439 US201514857439A US2016201918A1 US 20160201918 A1 US20160201918 A1 US 20160201918A1 US 201514857439 A US201514857439 A US 201514857439A US 2016201918 A1 US2016201918 A1 US 2016201918A1
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- combustion
- swirler
- fuel
- injector
- combustion apparatus
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23R—GENERATING COMBUSTION PRODUCTS OF HIGH PRESSURE OR HIGH VELOCITY, e.g. GAS-TURBINE COMBUSTION CHAMBERS
- F23R3/00—Continuous combustion chambers using liquid or gaseous fuel
- F23R3/28—Continuous combustion chambers using liquid or gaseous fuel characterised by the fuel supply
- F23R3/286—Continuous combustion chambers using liquid or gaseous fuel characterised by the fuel supply having fuel-air premixing devices
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23R—GENERATING COMBUSTION PRODUCTS OF HIGH PRESSURE OR HIGH VELOCITY, e.g. GAS-TURBINE COMBUSTION CHAMBERS
- F23R3/00—Continuous combustion chambers using liquid or gaseous fuel
- F23R3/002—Wall structures
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23R—GENERATING COMBUSTION PRODUCTS OF HIGH PRESSURE OR HIGH VELOCITY, e.g. GAS-TURBINE COMBUSTION CHAMBERS
- F23R3/00—Continuous combustion chambers using liquid or gaseous fuel
- F23R3/02—Continuous combustion chambers using liquid or gaseous fuel characterised by the air-flow or gas-flow configuration
- F23R3/04—Air inlet arrangements
- F23R3/10—Air inlet arrangements for primary air
- F23R3/12—Air inlet arrangements for primary air inducing a vortex
- F23R3/14—Air inlet arrangements for primary air inducing a vortex by using swirl vanes
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23R—GENERATING COMBUSTION PRODUCTS OF HIGH PRESSURE OR HIGH VELOCITY, e.g. GAS-TURBINE COMBUSTION CHAMBERS
- F23R3/00—Continuous combustion chambers using liquid or gaseous fuel
- F23R3/28—Continuous combustion chambers using liquid or gaseous fuel characterised by the fuel supply
- F23R3/34—Feeding into different combustion zones
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23R—GENERATING COMBUSTION PRODUCTS OF HIGH PRESSURE OR HIGH VELOCITY, e.g. GAS-TURBINE COMBUSTION CHAMBERS
- F23R2900/00—Special features of, or arrangements for continuous combustion chambers; Combustion processes therefor
- F23R2900/00014—Reducing thermo-acoustic vibrations by passive means, e.g. by Helmholtz resonators
Definitions
- the present disclosure relates to gas turbine engines, and more particularly, to an improved combustor assembly employing an array of swirlers to influence the flow field and enhance flame stabilization within a combustion chamber.
- Gas turbine engines are known to include a compressor for compressing air, a combustor for producing a hot gas by burning fuel in the presence of the compressed air produced by the compressor, and a turbine for expanding the hot gas to extract power.
- Gas turbine engines using annular combustion systems typically include a plurality of individual burners disposed in a ring about an axial centerline for providing a mixture of fuel and air to an annular combustion chamber disposed upstream of the annular turbine inlet vanes.
- Other gas turbines use can-annular combustors wherein individual burner cans feed hot combustion gas into respective individual portions of the arc of the turbine inlet vanes.
- combustion oscillations also known as combustion dynamics.
- Combustion oscillations in general are acoustic oscillations which are excited by the combustion itself.
- the frequency of the combustion oscillations may be influenced by an interaction of the combustion flame with the structure surrounding the combustion flame. Since the structure of the combustor surrounding the combustion flame is often complicated, and varies from one combustor to another, and because the combustion flame itself may vary over time, it is difficult to predict the frequency at which combustion oscillations occur.
- combustion oscillations may be monitored during operation and parameters may be adjusted in order to influence the interaction of the combustion flame with its environment.
- a combustion flame emits sound energy during combustion.
- a more uniform flame will generate more uniform acoustics, but perhaps with higher peak amplitude at a particular frequency than a less uniform flame.
- the system may operate in resonance, and the resulting combustion dynamics may damage the gas turbine components, or at least reduce their lifespan.
- One known way to reduce the interaction of the combustion flame with the combustion acoustics is to reduce the coherence of the flame, i.e. reduce the spatio-temporal uniformity of the flame.
- a flame with less uniform combustion throughout its volume is likely to perturb the gas turbine less than a uniform flame because the energy released is spatially distributed and therefore decreases its coupling to the system resonant frequencies or acoustic modes.
- combustion dynamics of flames with less uniform combustion throughout its volume are less likely to be exacerbated than by a more uniform flame. Creating a less uniform fuel-air mixture would be helpful.
- pollutants such as, but not limited to, carbon monoxide (“CO 2 ”), unburned hydrocarbons (“UHC”), and nitrogen oxides (“NO x ”) may be formed and emitted into an ambient atmosphere.
- CO 2 carbon monoxide
- UHC unburned hydrocarbons
- NO x nitrogen oxides
- the flame stabilizer to include these considerations into its design and be able to function in a robust manner in engine architectures of reasonable variation.
- symmetric systems are the goal for reasons of ease of operation and lowered costs but rarely achieved in real-life.
- Still another tradeoff lies in ensuring that the mixture in the premixer is expelled before it auto-ignites.
- the compressed air can reach over 800K and pressures in excess of 500 psi.
- simple fuels like CH4 can ignite within 40 milliseconds while more reactive fuels such as diesel can ignite in less than 2 milliseconds.
- Premixer design should ensure that adequate uniformity of mixing is achieved within a timescale that is lower than the ignition delay of the range of fuels required. With safety factors that can range from a tenth to twentieth of the timescales, it is difficult to achieve a uniformity of mixture unless the premixer design employs high turbulence intensities.
- Fuel injection into a continuous burning combustion chamber as, for example, in a gas turbine engine has posed continuing design problems. Difficulties have been encountered in injecting fuel in a highly dispersed manner so as to achieve complete and efficient combustion of the fuel, and at the same time minimize the occurrence of fuel-rich pockets which upon combustion produce carbon, smoke, or unburned hydrocarbon pollutants. Fuel injection difficulties have been further complicated by the introduction of gas turbine engines having increased combustor pressure levels.
- High fuel pressure spray atomizers also have not proved entirely satisfactory because of the present limitations on fuel pump pressure.
- Systems for vaporizing fuel upon injection into the combustor have also proved to be severely limited due to the dependence of the vaporization process on the temperature of the fuel and air entering the combustor.
- the system may be tunable and include a plurality of swirlers that results in a heat release that is designed to be out of phase with each other so as to ensure that thermo-acoustic couplings are dampened.
- FIG. 1 illustrates a schematic view of a gas turbine engine employing the improvements discussed herein;
- FIG. 2 illustrates a partial perspective view of combustor for a gas turbine engine employing an exemplary swirler assembly for use with a combustor;
- FIG. 3 illustrates a perspective view of a swirler ring assembly having a plurality of swirlers disposed circumferentially around a ring structure
- FIG. 4 is a side elevational view of the FIG. 3 swirler ring assembly
- FIG. 5 is a front elevational view of the FIG. 3 swirler ring assembly
- FIG. 6 is a front elevational view of an alternative swirler ring assembly, employing an array of swirlers and slots;
- FIG. 7 is a front elevational view of another alternative swirler ring assembly, employing ports located adjacent to the swirlers.
- FIG. 8 is a schematic view of a section of a combustor, showing a primary section and a secondary section, and fluid flow within the combustion chamber.
- An exemplary embodiment discloses an improved combustor assembly and method that overcomes traditional combustor challenges by employing a tunable flame stabilizer assembly in the injector section of an engine, such as, but not limited to, a gas turbine.
- the stabilizer assembly includes an array of swirlers located downstream of a premixing section that are designed to correct bias of fuel residence times in the combustion chamber.
- the flame stabilizer could employ an ejector like ring having a plurality of circumferentially spaced swirlers that induce a premixed air/fuel mixture to the combustion chamber.
- the stabilizer may be tuned by varying the swirl number in order to produce recirculation zones that ensure out of phase nature of the heat release within the combustion chamber.
- Individual premixing channels receive fuel and pre-heated air which rely on turbulent mixing set up by vortices generated within the premixer channel and expels the mixed material through each swirler and into the combustion chamber where it is burned to provide energy for the turbine section.
- An alternative embodiment provides a flame stabilizer assembly featuring a hybrid arrangement of swirlers and jet nozzles for passing the air/fuel mixture through an injector. This allows a compensation of more drastic combustion chamber residence time biases.
- Another embodiment features a premixer that injects non-uniform fuel flow through a series of ports that are located near the array of swirlers. It will be appreciated that a combination of the embodiments disclosed herein may be employed so as to include a variety of swirler, slot and injector configurations so as to accommodate a wide variety of combustion chambers typical of gas turbine engines
- a method of operating an injector for a combustor includes mixing air and fuel into a first primary mixing chamber, introducing the air/fuel mixture into a plurality of swirlers, directing the mixture into a combustion chamber, and then igniting the mixture.
- the method further includes mixing air and fuel into a secondary mixing chamber, introducing the mixed air and fuel into a common secondary swirler, directing the mixture into a secondary combustion zone within the combustion chamber, and igniting the mixture.
- the method may further include additional primary mixing chambers that are circumferentially spaced around the central axis 28 of the machine 10 .
- each primary mixing chamber has an associated swirler that is associated with it which operates in a manner similar to that discussed for the first primary mixing chamber.
- the resulting combustor assembly is an array of swirlers that generates a series of small recirculation zones in order to reduce the length of scales of coherent flame structures.
- the number of swirlers can be varied in order to produce recirculation zones that ensure out of phase nature of the heat released within the combustor.
- the swirl number is tuned to the asymmetry of the combustion chamber so that swirlers with a low swirl number are situated at locations which give rise to stream tubes of high residence time.
- swirlers with a high swirl number are situated at locations which rise to stream tubes of low residence time.
- the swirler may be used to correct bias of residence times in the combustion chamber. It will be appreciated that the number of swirlers may range from 0 to 18 (as shown), or more.
- FIG. 1 illustrates a gas turbine engine 10 , which includes a fan 12 , a low pressure compressor and a high pressure compressor, 14 and 16 , a combustor 18 , and a high pressure turbine and low pressure turbine, 20 and 22 , respectively.
- the high pressure compressor 16 is connected to a first rotor shaft 24 while the low pressure compressor 14 is connected to a second rotor shaft 26 .
- the shafts extend axially and are parallel to a longitudinal center line axis 28 .
- Ambient air 30 enters the fan 12 and is directed across a fan rotor 32 in an annular duct 34 , which in part is circumscribed by fan case 36 .
- the bypass airflow 38 provides engine thrust while the primary gas stream 40 is directed to the combustor 18 and the high pressure turbine 20 .
- the gas turbine engine 10 includes an improved combustor 18 having a unique flame stabilizer assembly 42 for improved heat release in the combustion chamber.
- FIG. 2 illustrates a perspective view of the inside of a combustor assembly 18 showing some of the components of the flame stabilizer assembly 42 . It will be appreciated that the outer liner wall has been removed so as to provide improved understanding of the components of the stabilizer assembly 42 .
- the stabilizer assembly includes an injector ring 44 , a primary mixing chamber or duct 46 , a secondary mixing chamber or duct 48 , a secondary swirler 50 , a plurality of primary swirlers 52 , and a liner 54 .
- a primary combustion zone 56 connotes the area in which the air/fuel mixture from an array primary swirlers 52 deposit atomized fuel particles or fuel-air mixtures that are ready to be combusted.
- a secondary combustion zone 58 connotes an area where the secondary swirler 50 deposits atomized fuel particles or fuel-air mixtures that are ready to be combusted.
- the secondary mixing chamber 48 receives air flow from air duct 74 and fuel flow from fuel supply 64 in which the air and fuel are mixed and exited at outlet 66 . Vanes 68 force the mixture from chamber 48 to exit through the outlet 66 , thereby directing the heated, pressurized fuel/air mixture or atomized fuel/air mixture to be stabilized prior to combustion.
- the inner liner 54 is made of conventional material and extends between the secondary swirler 50 and the array of swirlers 52 .
- the liner 54 extends axially from the injector ring 44 and terminates near a flange 70 that is formed near one end of a partition member 72 .
- An air duct 74 supplies cooling air to the inner liner 54 where ports 76 deliver the air to the primary combustion zone 56 .
- the secondary duct 48 receives secondary fuel 78 and secondary air 80 that collectively form the fuel/air mixture 64 . See FIG. 8 .
- the injector ring 44 can be, but is not limited to, an annularly shaped member that circumscribes the inner liner 54 .
- the ejector 44 has an inner diameter 82 and an outer diameter 84 that are concentric with axis 28 and is uniform in width and depth but variations thereof to accommodate non-circular jets are included as well.
- a plurality of passages 86 extend from the face 88 , through the body 90 of the ejector 44 , and extends to back 92 of the injector 44 . Each passage 86 receives a swirler 52 for advancing the mixed air/fuel 64 ′ that is generated from the primary duct 46 .
- FIG. 4 illustrates a side view of the injector ring 44 whereby the face 88 has an angle alpha that forms a relief from outer surface 94 .
- This configuration differs from the flat face 88 that is shown in the embodiment of FIG. 2 whereby the flat face 88 is basically normal to the axis 28 of the machine.
- each passage 86 is oriented to no longer be normal to the axis 28 , but instead is redirected to provide a path extending a flow of atomized fuel or fuel-air mixture into the combustion chamber 18 that is non-normal. This causes small pockets of recirculation zones that bleed over to adjacent recirculation zones from the adjacent swirler 52 .
- the angle alpha may be a variety of configurations including, but not limited to 21, 24 or 26 degrees.
- the injector ring 44 further has a first annular grove 96 and a second annular groove 98 .
- the grooves extend around the periphery of the ring 44 and form a fluid flow path.
- the ring 44 is made of suitable material to withstand the temperatures that are traditionally present in the combustor applications.
- FIG. 5 illustrates the injector ring 44 from the front elevational view.
- the ring 44 is shown in this exemplary embodiment having 18 swirlers 52 that are spaced apart around the circumference of the body 90 .
- Each swirler is positioned within a passage 86 for providing its own small recirculation zone within the primary combustion zone 56 . It will be appreciated that more or less swirlers may be provided. While 5 blades 100 are shown on each swirler 52 , it will be appreciated that the number of blades 100 on each swirler 52 may vary.
- the injector ring 44 may be tuned by varying the number of swirlers 52 and blades 100 that are employed.
- the alpha angle may be varied so as to change the pitch or trajectory 258 ( FIG. 8 ) of delivery of atomized fuel air mixture into the primary combustion zone 56 .
- FIG. 6 illustrates an alternative embodiment of an injector ring 150 having a blend of swirlers 52 and slots 152 .
- the swirler designs are similar to those mentioned above, and in this variation, 9 swirlers are presented in an array between the 6 o'clock to 12 o'clock positions.
- an array of slots 152 are aligned between the 1 o'clock and 5 o'clock positions. It will be appreciated that this mix of swirlers and slots may be positioned at other locations and they could even be mixed intermittently between one another.
- the slots 152 are shown as arcuate shaped rectangles and they have a space 154 of material separating each adjacent slot 152 .
- the slots 152 are ports or jets that extend through the body 90 and provide a passageway for the jet flames to enter the primary combustion zone 56 .
- the slots 152 may be fed with a fuel/air mixture at a different equivalence ratio compared to the swirlers 52 .
- the recirculation zone 202 ( FIG. 8 ) may be designed to have preferred performance characteristics that are based upon a combination of swirlers 52 and slots 152 .
- FIG. 7 depicts another alternative embodiment injector ring 200 that is designed to inject a non-uniform fuel flow into the primary combustor zone 56 .
- This intentional mixture of non-uniformity however is with small acceptable margins of non-uniformity so as to contain the NOx emissions within industry standards.
- This alternative embodiment 200 is a variant of the FIG. 5 assembly, whereby jets 204 and 206 are positioned adjacent to swirlers 52 at positions around the circumference of the body 90 .
- the jets 204 and 206 are shown in pairs in alternating patterns spaced adjacent to a pair of swirlers 52 . It will be appreciated that the jets may be positioned in between each swirler 52 .
- the jet 204 is shown larger in diameter than jet 206 and they could be reversed to have the smaller jet on the outside of the ring 200 with the larger jet 204 positioned near the inside diameter of the ring 200 .
- FIG. 8 illustrates a schematic fluid diagram 250 of the fuel/air mixtures entering the combustion zones within the combustor 18 .
- the primary mixer or duct 46 represents the fluid mixing channel where primary fuel 252 and primary air 254 are mixed to form the fuel/air mixture 64 ′.
- the mixed fuel 64 ′ is delivered to an injector ring of the styles shown at ejectors 44 , 150 , or 200 .
- the mixture 64 ′ is atomized in the process and passes through the injector ring 44 to the primary combustion zone 56 which is at a leading portion of the combustor 18 .
- the example shown has the injector outlet passage 86 configured at an angle alpha which results in the plume 256 of atomized fuel or fuel-air mixture to enter the primary combustion zone 56 along a trajectory 258 .
- a small pocket 260 of recirculation zone is induced into the primary combustion zone 56 .
- the small pockets 260 overlap with one another so as to enhance combustion and to maintain ignition within the combustor 18 .
- the performance of each small pocket 260 is controlled by, in part, the angle alpha, the number and design of each blade for each swirler 52 , and other controllable features. As such the ejector ring 44 is tunable to afford different performance characteristics which results in different fluid flow patterns within the primary combustion zones 56 and the secondary combustion zone 58 .
- the secondary duct 48 is a mixing channel that receives the secondary fuel 78 and the secondary air 80 which in turn is heated and mixed to form a mixture 64 within the flow path 60 .
- the mixture 64 is delivered to the jet or swirler 50 and exits into the secondary combustion zone 58 and forms a recirculation pattern 262 .
- the recirculation patterns 262 and 202 may combine within the trailing portion of the combustor 18 so as to enhance ignition of the fuel particles and create heat for rotating the turbines.
- Fuel and air mixtures are induced to the primary duct 46 and secondary duct 48 .
- the fuel mixtures 64 and 64 ′ advance to their associated jets, 50 and 52 , which in turn delivers atomized fuel particles to their respective combustion zones 58 and 56 . Ignition now occurs within the combustion zones which produced heat for driving the turbines 20 and 22 .
- the method of operation may be tuned by changing the injector ring 44 to have a variety of swirlers 52 and slots 152 and/or jets 204 and 206 , or any combination thereof.
- the recirculation zone characteristics 202 within the primary combustion zone 56 can be tuned to a desired performance. This results in part due to the individual recirculation zones 260 that are generated by each individual swirler 52 , slot 152 and or jets 204 and 206 .
- the user can influence the combustion, emission, and energy generated by the engine 10 .
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Abstract
Description
- The present disclosure relates to gas turbine engines, and more particularly, to an improved combustor assembly employing an array of swirlers to influence the flow field and enhance flame stabilization within a combustion chamber.
- Gas turbine engines are known to include a compressor for compressing air, a combustor for producing a hot gas by burning fuel in the presence of the compressed air produced by the compressor, and a turbine for expanding the hot gas to extract power. Gas turbine engines using annular combustion systems typically include a plurality of individual burners disposed in a ring about an axial centerline for providing a mixture of fuel and air to an annular combustion chamber disposed upstream of the annular turbine inlet vanes. Other gas turbines use can-annular combustors wherein individual burner cans feed hot combustion gas into respective individual portions of the arc of the turbine inlet vanes. Each can includes a plurality of main burners disposed in a ring around a central pilot burner.
- During operation, the combustion flame can generate combustion oscillations, also known as combustion dynamics. Combustion oscillations in general are acoustic oscillations which are excited by the combustion itself. The frequency of the combustion oscillations may be influenced by an interaction of the combustion flame with the structure surrounding the combustion flame. Since the structure of the combustor surrounding the combustion flame is often complicated, and varies from one combustor to another, and because the combustion flame itself may vary over time, it is difficult to predict the frequency at which combustion oscillations occur. As a result, combustion oscillations may be monitored during operation and parameters may be adjusted in order to influence the interaction of the combustion flame with its environment.
- A combustion flame emits sound energy during combustion. A more uniform flame will generate more uniform acoustics, but perhaps with higher peak amplitude at a particular frequency than a less uniform flame. When an emitted frequency of combustion coincides with a resonant frequency of the combustion chamber the system may operate in resonance, and the resulting combustion dynamics may damage the gas turbine components, or at least reduce their lifespan.
- One known way to reduce the interaction of the combustion flame with the combustion acoustics is to reduce the coherence of the flame, i.e. reduce the spatio-temporal uniformity of the flame. A flame with less uniform combustion throughout its volume is likely to perturb the gas turbine less than a uniform flame because the energy released is spatially distributed and therefore decreases its coupling to the system resonant frequencies or acoustic modes. As a result, combustion dynamics of flames with less uniform combustion throughout its volume are less likely to be exacerbated than by a more uniform flame. Creating a less uniform fuel-air mixture would be helpful.
- During the combustion of gas, pollutants such as, but not limited to, carbon monoxide (“CO2”), unburned hydrocarbons (“UHC”), and nitrogen oxides (“NOx”) may be formed and emitted into an ambient atmosphere. Because of stringent emission control standards, it is desirable to control emissions of such pollutants by the suppressing formation of such emissions. It would be helpful to reduce such emissions to target levels so as to meet government emission levels. This may be accomplished by minimizing the resident time unburnt fuel resides within the combustion chamber.
- In the case of industrial gas turbines which primarily burn gaseous fuels (e.g. for power generation purposes) several contradictory requirements with respect to premixer, flame stabilizer and combustion chamber design for lean partially-premixed systems require an achievement of tradeoffs between cost, complexity, robustness to operating conditions and lowered emissions. For example, a perfectly premixed system is more prone to thermo-acoustic oscillations leading to hardware damage while a less uniformly mixed system results in increase of pollutant formation, in particular, NOx. Another issue is that the orientation of the combustion chamber within any engine architecture can impose constraints on burner geometry, that result in unsymmetrical stream tubes within the combustion chamber, which in turn, lead to a variation of mixture residence times leading to lowered combustion efficiencies, increased risk of undesirable events such as poor flame stabilization, flashback, blow out and less than adequate mixing of post-flame gases which is required for the fast burnout of Carbon Monoxide to Carbon Dioxide. The time taken for the latter is a hard constraint in many systems as it is obtained—in a simple example—as the time taken for the mixture to travel from the flame front to the chamber exhaust, which is determined by the engine shaft length. However, overly long residence times (desirable for oxidation of CO) can increase the amount of NOx formation at high temperatures.
- For this reason, it is helpful that the flame stabilizer to include these considerations into its design and be able to function in a robust manner in engine architectures of reasonable variation. Typically, symmetric systems are the goal for reasons of ease of operation and lowered costs but rarely achieved in real-life. Still another tradeoff lies in ensuring that the mixture in the premixer is expelled before it auto-ignites. At typical engine operating conditions, the compressed air can reach over 800K and pressures in excess of 500 psi. At these conditions, simple fuels like CH4 can ignite within 40 milliseconds while more reactive fuels such as diesel can ignite in less than 2 milliseconds. Premixer design should ensure that adequate uniformity of mixing is achieved within a timescale that is lower than the ignition delay of the range of fuels required. With safety factors that can range from a tenth to twentieth of the timescales, it is difficult to achieve a uniformity of mixture unless the premixer design employs high turbulence intensities.
- Fuel injection into a continuous burning combustion chamber as, for example, in a gas turbine engine has posed continuing design problems. Difficulties have been encountered in injecting fuel in a highly dispersed manner so as to achieve complete and efficient combustion of the fuel, and at the same time minimize the occurrence of fuel-rich pockets which upon combustion produce carbon, smoke, or unburned hydrocarbon pollutants. Fuel injection difficulties have been further complicated by the introduction of gas turbine engines having increased combustor pressure levels. Existing fuel spray atomizer efficiency decreases as combustor pressure is increased, resulting in a more non-uniform dispersion of fuel, together with an increase in the fuel-rich zones within the combustion chamber which cause reduced burner efficiency, excessive exhaust smoke, and a non-uniform heating of the combustor shell, a condition commonly referred to as hot streaking, which can lead to rapid deterioration of the shell.
- High fuel pressure spray atomizers also have not proved entirely satisfactory because of the present limitations on fuel pump pressure. Systems for vaporizing fuel upon injection into the combustor have also proved to be severely limited due to the dependence of the vaporization process on the temperature of the fuel and air entering the combustor.
- In view of the aforementioned challenges, there is a need to provide an improved combustor assembly and method of operation that provides improved flame stabilization for reducing emissions and noise. The system may be tunable and include a plurality of swirlers that results in a heat release that is designed to be out of phase with each other so as to ensure that thermo-acoustic couplings are dampened.
- While the claims are not limited to a specific illustration, an appreciation of the various aspects is best gained through a discussion of various examples thereof. Referring now to the drawings, exemplary illustrations are shown in detail. Although the drawings represent the illustrations, the drawings are not necessarily to scale and certain features may be exaggerated to better illustrate and explain an innovative aspect of an example. Further, the exemplary illustrations described herein are not intended to be exhaustive or otherwise limiting or restricted to the precise form and configuration shown in the drawings and disclosed in the following detailed description. Exemplary illustrations are described in detail by referring to the drawings as follows:
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FIG. 1 illustrates a schematic view of a gas turbine engine employing the improvements discussed herein; -
FIG. 2 illustrates a partial perspective view of combustor for a gas turbine engine employing an exemplary swirler assembly for use with a combustor; -
FIG. 3 illustrates a perspective view of a swirler ring assembly having a plurality of swirlers disposed circumferentially around a ring structure; -
FIG. 4 is a side elevational view of theFIG. 3 swirler ring assembly; -
FIG. 5 is a front elevational view of theFIG. 3 swirler ring assembly; -
FIG. 6 is a front elevational view of an alternative swirler ring assembly, employing an array of swirlers and slots; -
FIG. 7 is a front elevational view of another alternative swirler ring assembly, employing ports located adjacent to the swirlers; and -
FIG. 8 is a schematic view of a section of a combustor, showing a primary section and a secondary section, and fluid flow within the combustion chamber. - An exemplary embodiment discloses an improved combustor assembly and method that overcomes traditional combustor challenges by employing a tunable flame stabilizer assembly in the injector section of an engine, such as, but not limited to, a gas turbine. The stabilizer assembly includes an array of swirlers located downstream of a premixing section that are designed to correct bias of fuel residence times in the combustion chamber. The flame stabilizer could employ an ejector like ring having a plurality of circumferentially spaced swirlers that induce a premixed air/fuel mixture to the combustion chamber. The stabilizer may be tuned by varying the swirl number in order to produce recirculation zones that ensure out of phase nature of the heat release within the combustion chamber. Individual premixing channels receive fuel and pre-heated air which rely on turbulent mixing set up by vortices generated within the premixer channel and expels the mixed material through each swirler and into the combustion chamber where it is burned to provide energy for the turbine section.
- An alternative embodiment provides a flame stabilizer assembly featuring a hybrid arrangement of swirlers and jet nozzles for passing the air/fuel mixture through an injector. This allows a compensation of more drastic combustion chamber residence time biases. Another embodiment features a premixer that injects non-uniform fuel flow through a series of ports that are located near the array of swirlers. It will be appreciated that a combination of the embodiments disclosed herein may be employed so as to include a variety of swirler, slot and injector configurations so as to accommodate a wide variety of combustion chambers typical of gas turbine engines
- A method of operating an injector for a combustor includes mixing air and fuel into a first primary mixing chamber, introducing the air/fuel mixture into a plurality of swirlers, directing the mixture into a combustion chamber, and then igniting the mixture. The method further includes mixing air and fuel into a secondary mixing chamber, introducing the mixed air and fuel into a common secondary swirler, directing the mixture into a secondary combustion zone within the combustion chamber, and igniting the mixture. The method may further include additional primary mixing chambers that are circumferentially spaced around the
central axis 28 of themachine 10. Likewise, each primary mixing chamber has an associated swirler that is associated with it which operates in a manner similar to that discussed for the first primary mixing chamber. - The resulting combustor assembly is an array of swirlers that generates a series of small recirculation zones in order to reduce the length of scales of coherent flame structures. The number of swirlers can be varied in order to produce recirculation zones that ensure out of phase nature of the heat released within the combustor. The swirl number is tuned to the asymmetry of the combustion chamber so that swirlers with a low swirl number are situated at locations which give rise to stream tubes of high residence time. By contrast, swirlers with a high swirl number are situated at locations which rise to stream tubes of low residence time. As such, the swirler may be used to correct bias of residence times in the combustion chamber. It will be appreciated that the number of swirlers may range from 0 to 18 (as shown), or more.
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FIG. 1 illustrates agas turbine engine 10, which includes afan 12, a low pressure compressor and a high pressure compressor, 14 and 16, acombustor 18, and a high pressure turbine and low pressure turbine, 20 and 22, respectively. Thehigh pressure compressor 16 is connected to afirst rotor shaft 24 while thelow pressure compressor 14 is connected to asecond rotor shaft 26. The shafts extend axially and are parallel to a longitudinalcenter line axis 28. -
Ambient air 30 enters thefan 12 and is directed across afan rotor 32 in anannular duct 34, which in part is circumscribed byfan case 36. Thebypass airflow 38 provides engine thrust while theprimary gas stream 40 is directed to thecombustor 18 and thehigh pressure turbine 20. Thegas turbine engine 10 includes animproved combustor 18 having a uniqueflame stabilizer assembly 42 for improved heat release in the combustion chamber. -
FIG. 2 illustrates a perspective view of the inside of acombustor assembly 18 showing some of the components of theflame stabilizer assembly 42. It will be appreciated that the outer liner wall has been removed so as to provide improved understanding of the components of thestabilizer assembly 42. - The stabilizer assembly includes an
injector ring 44, a primary mixing chamber orduct 46, a secondary mixing chamber orduct 48, asecondary swirler 50, a plurality ofprimary swirlers 52, and aliner 54. Aprimary combustion zone 56 connotes the area in which the air/fuel mixture from an arrayprimary swirlers 52 deposit atomized fuel particles or fuel-air mixtures that are ready to be combusted. Asecondary combustion zone 58 connotes an area where thesecondary swirler 50 deposits atomized fuel particles or fuel-air mixtures that are ready to be combusted. - The
secondary mixing chamber 48 receives air flow fromair duct 74 and fuel flow fromfuel supply 64 in which the air and fuel are mixed and exited atoutlet 66.Vanes 68 force the mixture fromchamber 48 to exit through theoutlet 66, thereby directing the heated, pressurized fuel/air mixture or atomized fuel/air mixture to be stabilized prior to combustion. - The
inner liner 54 is made of conventional material and extends between thesecondary swirler 50 and the array ofswirlers 52. Theliner 54 extends axially from theinjector ring 44 and terminates near aflange 70 that is formed near one end of apartition member 72. Anair duct 74 supplies cooling air to theinner liner 54 whereports 76 deliver the air to theprimary combustion zone 56. Thesecondary duct 48 receivessecondary fuel 78 andsecondary air 80 that collectively form the fuel/air mixture 64. SeeFIG. 8 . - With reference to
FIGS. 2 and 3 , theinjector ring 44 can be, but is not limited to, an annularly shaped member that circumscribes theinner liner 54. Theejector 44 has aninner diameter 82 and anouter diameter 84 that are concentric withaxis 28 and is uniform in width and depth but variations thereof to accommodate non-circular jets are included as well. A plurality ofpassages 86 extend from theface 88, through thebody 90 of theejector 44, and extends to back 92 of theinjector 44. Eachpassage 86 receives aswirler 52 for advancing the mixed air/fuel 64′ that is generated from theprimary duct 46. -
FIG. 4 illustrates a side view of theinjector ring 44 whereby theface 88 has an angle alpha that forms a relief fromouter surface 94. This configuration differs from theflat face 88 that is shown in the embodiment ofFIG. 2 whereby theflat face 88 is basically normal to theaxis 28 of the machine. However, by locating theface 88 at an angle alpha as is shown inFIG. 4 , eachpassage 86 is oriented to no longer be normal to theaxis 28, but instead is redirected to provide a path extending a flow of atomized fuel or fuel-air mixture into thecombustion chamber 18 that is non-normal. This causes small pockets of recirculation zones that bleed over to adjacent recirculation zones from theadjacent swirler 52. The angle alpha may be a variety of configurations including, but not limited to 21, 24 or 26 degrees. - The
injector ring 44 further has a firstannular grove 96 and a secondannular groove 98. The grooves extend around the periphery of thering 44 and form a fluid flow path. Thering 44 is made of suitable material to withstand the temperatures that are traditionally present in the combustor applications. -
FIG. 5 illustrates theinjector ring 44 from the front elevational view. Thering 44 is shown in this exemplary embodiment having 18swirlers 52 that are spaced apart around the circumference of thebody 90. Each swirler is positioned within apassage 86 for providing its own small recirculation zone within theprimary combustion zone 56. It will be appreciated that more or less swirlers may be provided. While 5blades 100 are shown on eachswirler 52, it will be appreciated that the number ofblades 100 on eachswirler 52 may vary. Thus, theinjector ring 44 may be tuned by varying the number ofswirlers 52 andblades 100 that are employed. Also, the alpha angle may be varied so as to change the pitch or trajectory 258 (FIG. 8 ) of delivery of atomized fuel air mixture into theprimary combustion zone 56. -
FIG. 6 illustrates an alternative embodiment of aninjector ring 150 having a blend ofswirlers 52 andslots 152. The swirler designs are similar to those mentioned above, and in this variation, 9 swirlers are presented in an array between the 6 o'clock to 12 o'clock positions. By contrast, an array ofslots 152 are aligned between the 1 o'clock and 5 o'clock positions. It will be appreciated that this mix of swirlers and slots may be positioned at other locations and they could even be mixed intermittently between one another. Theslots 152 are shown as arcuate shaped rectangles and they have aspace 154 of material separating eachadjacent slot 152. Theslots 152 are ports or jets that extend through thebody 90 and provide a passageway for the jet flames to enter theprimary combustion zone 56. Theslots 152 may be fed with a fuel/air mixture at a different equivalence ratio compared to theswirlers 52. The recirculation zone 202 (FIG. 8 ) may be designed to have preferred performance characteristics that are based upon a combination ofswirlers 52 andslots 152. -
FIG. 7 depicts another alternativeembodiment injector ring 200 that is designed to inject a non-uniform fuel flow into theprimary combustor zone 56. This intentional mixture of non-uniformity however is with small acceptable margins of non-uniformity so as to contain the NOx emissions within industry standards. Thisalternative embodiment 200 is a variant of theFIG. 5 assembly, wherebyjets body 90. Thejets swirlers 52. It will be appreciated that the jets may be positioned in between each swirler 52. Thejet 204 is shown larger in diameter thanjet 206 and they could be reversed to have the smaller jet on the outside of thering 200 with thelarger jet 204 positioned near the inside diameter of thering 200. -
FIG. 8 illustrates a schematic fluid diagram 250 of the fuel/air mixtures entering the combustion zones within thecombustor 18. The primary mixer orduct 46 represents the fluid mixing channel whereprimary fuel 252 andprimary air 254 are mixed to form the fuel/air mixture 64′. Themixed fuel 64′ is delivered to an injector ring of the styles shown atejectors mixture 64′ is atomized in the process and passes through theinjector ring 44 to theprimary combustion zone 56 which is at a leading portion of thecombustor 18. - The example shown has the
injector outlet passage 86 configured at an angle alpha which results in theplume 256 of atomized fuel or fuel-air mixture to enter theprimary combustion zone 56 along atrajectory 258. This results insmall pockets 260 of recirculation zones that are associated with eachswirler 52. Thus, for each swirler 52 that is spaced around the periphery of theinjector ring 44, asmall pocket 260 of recirculation zone is induced into theprimary combustion zone 56. Thesmall pockets 260 overlap with one another so as to enhance combustion and to maintain ignition within thecombustor 18. The performance of eachsmall pocket 260 is controlled by, in part, the angle alpha, the number and design of each blade for eachswirler 52, and other controllable features. As such theejector ring 44 is tunable to afford different performance characteristics which results in different fluid flow patterns within theprimary combustion zones 56 and thesecondary combustion zone 58. - The
secondary duct 48 is a mixing channel that receives thesecondary fuel 78 and thesecondary air 80 which in turn is heated and mixed to form amixture 64 within theflow path 60. Themixture 64 is delivered to the jet orswirler 50 and exits into thesecondary combustion zone 58 and forms arecirculation pattern 262. Therecirculation patterns combustor 18 so as to enhance ignition of the fuel particles and create heat for rotating the turbines. - The process of operating the
engine 10 using theinjector ring 44 will now be presented with reference to schematic ofFIG. 8 . Fuel and air mixtures are induced to theprimary duct 46 andsecondary duct 48. Thefuel mixtures respective combustion zones turbines 20 and 22. - The method of operation may be tuned by changing the
injector ring 44 to have a variety ofswirlers 52 andslots 152 and/orjets recirculation zone characteristics 202 within theprimary combustion zone 56 can be tuned to a desired performance. This results in part due to theindividual recirculation zones 260 that are generated by eachindividual swirler 52,slot 152 and orjets swirler 52,slot 152 and/orjet ejector ring 44, the user can influence the combustion, emission, and energy generated by theengine 10. - It will be appreciated that the aforementioned method and devices may be modified to have some components and steps removed, or may have additional components and steps added, all of which are deemed to be within the spirit of the present disclosure. Even though the present disclosure has been described in detail with reference to specific embodiments, it will be appreciated that the various modifications and changes can be made to these embodiments without departing from the scope of the present disclosure as set forth in the claims. The specification and the drawings are to be regarded as an illustrative thought instead of merely restrictive thought.
- All terms used in the claims are intended to be given their broadest reasonable constructions and their ordinary meanings as understood by those knowledgeable in the technologies described herein unless an explicit indication to the contrary is made herein. In particular, use of the singular articles such as “a,” “the,” “said,” etc. should be read to recite one or more of the indicated elements unless a claim recites an explicit limitation to the contrary.
Claims (20)
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US14/857,439 US20160201918A1 (en) | 2014-09-18 | 2015-09-17 | Small arrayed swirler system for reduced emissions and noise |
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US201462052149P | 2014-09-18 | 2014-09-18 | |
US14/857,439 US20160201918A1 (en) | 2014-09-18 | 2015-09-17 | Small arrayed swirler system for reduced emissions and noise |
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US20160201918A1 true US20160201918A1 (en) | 2016-07-14 |
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US14/857,439 Abandoned US20160201918A1 (en) | 2014-09-18 | 2015-09-17 | Small arrayed swirler system for reduced emissions and noise |
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US10823419B2 (en) | 2018-03-01 | 2020-11-03 | General Electric Company | Combustion system with deflector |
US11125437B2 (en) | 2017-05-16 | 2021-09-21 | Siemens Energy Global GmbH & Co. KG | Binary fuel staging scheme for improved turndown emissions in lean premixed gas turbine combustion |
US11598526B2 (en) | 2021-04-16 | 2023-03-07 | General Electric Company | Combustor swirl vane apparatus |
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