GB2086031A - Gas Turbine Combustion System - Google Patents
Gas Turbine Combustion System Download PDFInfo
- Publication number
- GB2086031A GB2086031A GB8120977A GB8120977A GB2086031A GB 2086031 A GB2086031 A GB 2086031A GB 8120977 A GB8120977 A GB 8120977A GB 8120977 A GB8120977 A GB 8120977A GB 2086031 A GB2086031 A GB 2086031A
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- United Kingdom
- Prior art keywords
- fuel
- combustion
- zone
- rich
- air
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
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- 238000002485 combustion reaction Methods 0.000 title claims abstract description 177
- 239000000446 fuel Substances 0.000 claims abstract description 195
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 116
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 58
- 238000010791 quenching Methods 0.000 claims abstract description 42
- 238000002156 mixing Methods 0.000 claims abstract description 17
- 238000004519 manufacturing process Methods 0.000 claims abstract description 15
- 239000007788 liquid Substances 0.000 claims abstract description 7
- 230000008016 vaporization Effects 0.000 claims description 18
- 238000009834 vaporization Methods 0.000 claims description 14
- 238000006243 chemical reaction Methods 0.000 claims description 10
- 238000004891 communication Methods 0.000 claims description 3
- 230000001276 controlling effect Effects 0.000 claims description 2
- 230000001105 regulatory effect Effects 0.000 claims description 2
- 239000007789 gas Substances 0.000 abstract description 22
- 238000001816 cooling Methods 0.000 abstract description 10
- 239000000203 mixture Substances 0.000 abstract description 5
- 238000013461 design Methods 0.000 description 13
- 238000011144 upstream manufacturing Methods 0.000 description 9
- 239000010763 heavy fuel oil Substances 0.000 description 8
- 238000012546 transfer Methods 0.000 description 7
- 238000010790 dilution Methods 0.000 description 6
- 239000012895 dilution Substances 0.000 description 6
- 230000007704 transition Effects 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 4
- 238000000889 atomisation Methods 0.000 description 3
- 239000002648 laminated material Substances 0.000 description 3
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 2
- 230000003466 anti-cipated effect Effects 0.000 description 2
- 229910002091 carbon monoxide Inorganic materials 0.000 description 2
- 239000002826 coolant Substances 0.000 description 2
- 230000001419 dependent effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 238000009434 installation Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 230000035515 penetration Effects 0.000 description 2
- 230000000171 quenching effect Effects 0.000 description 2
- 238000007789 sealing Methods 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 239000000567 combustion gas Substances 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000004821 distillation Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000013011 mating Effects 0.000 description 1
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 125000006850 spacer group Chemical group 0.000 description 1
- 239000012720 thermal barrier coating Substances 0.000 description 1
- 230000005068 transpiration Effects 0.000 description 1
- 239000006200 vaporizer Substances 0.000 description 1
Classifications
-
- 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
- F23R3/26—Controlling the air flow
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
- F05B2250/00—Geometry
- F05B2250/40—Movement of component
- F05B2250/41—Movement of component with one degree of freedom
- F05B2250/411—Movement of component with one degree of freedom in rotation
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E20/00—Combustion technologies with mitigation potential
- Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
Abstract
A gas turbine combustion system for use in burning high viscosity liquid fuels with fuel bound nitrogen includes a fuel rich combustion zone 16 and air supply means for directing, all of the rich combustion zone inlet air flow to the combustion system through a cooling system 80, 82, 88, 90 which preheats all inlet air flow to the fuel rich zone combustion chamber 100; fuel mixing chamber means 12, which mixes fuel with the preheated inlet air flow for prevaporization of the fuel, and means 14 which directs a swirling air and fuel mixture into the fuel rich combustion zone. First variable geometry means 32 establishes a fuel/air ratio in the zone 16 with an equivalence ratio in the range of 1.2 to 2.5 to minimize emissions of oxides of nitrogen and quick quench mixer means 18 cools combustion products from zone 16 and reduces them to a temperature of less than 1371 DEG C to inhibit thermal production of oxides of nitrogen in a fuel lean zone combustor means 20 that receives combustion products from said quick quench mixer means 18 for further combustion in a lean combustion zone having an equivalence ratio in the range of 0.4- 0.6. <IMAGE>
Description
SPECIFICATION
Combustion System
This invention relates to gas turbine engine combustion systems and more particularly to gas turbine engine combustion systems for burning heavy fuels which contain bound nitrogen. Premix, prevaporization sections have been included in combustors for gas turbine engines to condition the fuel ahead of a combustion reaction zone therein so as to improve combustor air/fuel homogeneity and to avoid fuel droplet burning which is one source of oxides of nitrogen. It is desirable to operate the combustion zone at a lean fuel/air ratio to minimize formation of oxides of nitrogen.Combustor residence time to complete combustion of carbon monoxide and hydrocarbons is balanced by sufficient control of the equivalence ratio (the actual weight ratio of fuel to air within the combustion apparatus to the weight ratio of fuel to air to produce stoichiometric reaction of the air and fuel) to reduce emissions from the engine.
United States Patent No. 3,851 466, issued December 3, 1 972, to Verdouw, for Combustion
Apparatus has an elongated, imperforate prevaporization tube in association with a low emissions combustor. While satisfactory for its intended purpose, it does not take into account the use of heavy residual fuels of the type presently being considered for use in stationary gas turbine engine installations and especially those fuels with bound nitrogen.
More particularly, in such gas turbine engine combustors conditions favorable for minimal production of oxides of nitrogen are in opposition to combustion stability. Moreover, such conditions can increase emissions of carbon monoxide and unburned hydrocarbon through a range of combustor operation that will minimize production of oxides of nitrogen.
Additionally, the control of emissions of oxides of nitrogen in the combustion of fuels containing high levels of fuel bound nitrogen (FBN) can present further considerations for the design and operation of combustors. Current exploratory research of the type is reported in "Low NOx Combustor
Development for Stationary Gas Turbine Engines" Proceedings of the Third Stationary Source
Combustion Symposium, EPA-600/7-79-050C, Volume III, February, 1979 by R. M. Pierce, C. E. Smith and B. S. Hinton. This work indicates that emissions control from fuels with high levels of fuel bound nitrogen is improved by a staged combustion process utilizing a fuel rich initial combustion mode.
A combustion system according to the present invention, for use in burning liquid fuels with fuel bound nitrogen, comprises: a source of fuel having a high fuel bound nitrogen content, liner means forming a fuel rich combustion zone having an inlet and an outlet, air supply means for directing all of the rich combustion zone inlet air flow to the combustion system through a flow passage having an inlet in communication with a source of combustion air and heated by a first portion of said liner means for preheating all inlet air flow to the fuel rich zone combustion chamber, fuel vaporization means for mixing fuel from said source with said preheated inlet air flow for prevaporization of the high nitrogen content fuel mixed therewith, first variable geometry means for establishing a fuel/air ratio in the rich combustion zone with an equivalence ratio in the range of 1.2 to 2.5 to reduce production of oxides of nitrogen from the fuel bound nitrogen, quick quench means receiving the combustion products from said fuel rich combustion zone and reducing them to a temperature to inhibit high thermal reaction thereby to inhibit production of oxides of nitrogen, said quick quench mixer means including an inlet air supply for directing a predetermined amount of the quench air across a second portion of said liner means for reducing the temperature of combustion products at the outlet of said rich combustion zone, second variable geometry means for controlling the amount of quench air flow into said quick quench mixer means to maintain the equivalence ratio range in said fuel rich combustion chamber therein to reduce the production of oxides of nitrogen, and lean zone combustor means connected to receive quenched combustion products from said quick quench mixer means for further combustion in a fuel lean combustion zone with an equivalence ratio in the range of 0.4-0.6.
The invention and how it may be performed are hereinafter particularly described with reference to the accompanying drawings, wherein a preferred embodiment of the present invention is clearly shown, and in which:
Figure 1 is a longitudinal cross-sectional view of combustion apparatus constructed in accordance with the present invention;
Figure 2 is a cross-sectional view taken along the line 2-2 of Figure 1 looking in the direction of the arrows;
Figure 3 is a fragmentary, enlarged cross-sectional view taken along the line 3-3 of Figure 1 looking in the direction of the arrows;
Figure 4 is an enlarged cross-sectional view taken along the line 4-4 of Figure 1 looking in the direction of the arrows;
Figure 5 is an elevational view of a control ring of a quick quench air mixer of the present invention;;
Figure 6 is an enlarged cross-sectional view taken along the line 6-6 of Figure 1;
Figure 7 is a side elevational view of a dilution zone controller of the combustor taken along the lines 7-7 of Figure 6 looking in the direction of the arrows;
Figure 8 is an enlarged fragmentary elevational view along line 8-8 in Figure 1 looking in the direction of the arrows; and
Figure 9 is a sectional view taken along the line 9-9 of Figure 8 looking in the direction of the arrows.
Referring now to the drawings, a residual or heavy fuel combustion apparatus 10 is illustrated including a fuel supply section 12; a primary air mixer section 14; a vaporizing section 15; a fuel rich zone combustion chamber section 1 6; a quick quench section 18; a fuel lean combustion zone section 20 and a dilution zone section 22 all aligned in series flow relationship with one another.
The combustion apparatus 10, more particularly, is enclosed within an engine housing 24 that defines an inlet air plenum 26 that is connected to the output of a gasifier compressor 25 driven by a turbine 27 that receives motive fluid from the combustion apparatus 10.
The vaporizing section 15, in accordance with the present invention, has an imperforate fuel vaporizing tube 28 that has a length and a diameter to maintain a desired residence time for fuel components directed thereto that will produce vaporization of those fuel components without autoignition thereof during the different operating cycles of the gas turbine engine.
The tube 28 more particularly includes an inlet end 30 in which is located a combustor fuel nozzle 32. The combustorfuel nozzle 32 more particularly includes an axially movable shroud 34 and a cone head 36 adjusted relative to one another to variably control the quantity of air. Fuel flow is from a primary fuel line 38 that is adapted to be connected to a source of residual fuel of the type having low vaporization characteristics and including fuel bound nitrogen (FBN). The combustor fuel nozzle 32 in addition to having a variable air outlet additionally includes a radially inwardly directed air supply housing 40 having an outer annular swirler vane ring 42 and inner swirler vane ring 44 both in communication with an inlet air plenum 46. Plenum 46 also supplies air to swirler ports 48 in an outer wall 50 of the primary air mixer 14.The nozzle includes two constant fuel orifices 51, 53 and a fuel
prefilming orifice 55.
A rich zone convection cooling air preheater system 52 heats all of the inlet air to the fuel rich zone combustion chamber. System 52 is formed by an outer shell 54 surrounding the rich combustion zone section 1 6. The system 52 provides a source of heat energy directed into the fuel supply section 12 for improving vaporization of difficult to vaporize residual fuel that is directed from the air atomizing fuel nozzle 32. The apparatus is especially suited for the aforementioned residual fuel since heated inlet air after passing through a transition passage 56 into plenum 46 will be directed through swirl flow paths defined by swirler vane rings 42, 44 and ports 48 to produce an intense swirling effect on the nozzle atomized droplets of residual fuel to increase homogenization and vaporization of the fuel.The tube 28 has a length and diameter and a residence time to continually vaporize the fuel but maintain the mixture below a level where the residual fuels will autoignite prior to passage from the tube 28. As a result, the fuel supply section 12 constitutes a vaporizing section only without combustion and as a result will not produce any excessive emissions of oxides of nitrogen.
Furthermore, the system 52 constitutes a rich zone convection cooling system which is of a fin/tube type. More particularly, referring now to Figures 1 and 3, the convection cooling system 52 more particularly is seen to include an annular wall 58 directing cooling air along an outer surface 62 of a tubular wall portion 64 of the rich zone combustion chamber section 1 6. The outer surface 62 may be etched to have roughened surface features for improved heat transfer. The tubular wall portion 64 is connected by a transition dome 68 having a small diameter end 70 thereon connected to the outlet of the primary air mixer section 1 4 and an outlet end 72 thereon connected to the tubular wall portion 64.
The wall 58 merges with an inwardly convergent annular segment 74 of the outer shell 54 to define the transition passage 56 leading to the inlet air plenum 46.
The aft end of wall 58 has a radially outwardly flared edge 76 thereon defining an air inlet 78 to a plurality of convective air flow passages 80 formed between the wall 58 and the outer surface 62 by a plurality of longitudinally directed heat transfer fins 82 each with an inlet end 83 fitted in edge 76.
Each of the fins 82 has spaced tabs 84 thereon fitted within retention slots 86 in wall portion 64 as best seen in Figures 1 and 3. Each fin 82 has an outer edge 87 spaced from wall 58. The fins 82 transfer heat so as to cool the tubular wall portion 64 while heating the inlet air flow through the convective air flow passages 80. The extended surface area of the fins 82 extends the surface area of the outer surface 62 for improving its convective heat transfer. In the illustrated arrangement, the fins 82 are located and welded in place. Then they are brazed to ensure structural integrity. The heated air produces vaporization of fuel droplets directed from the air blast fuel nozzle 32 upstream of the fuel rich combustion zone 16.
In addition to the heat transfer fins 82 on the outer surface 62, the dome 68 includes a plurality of heat transfer fins 88 connected thereto that are staggered with respect to the fins 82. If desired, a third set of fins 90 dan be provided at the outlet of the transition passage 56. The fins 82, 88, 90 and the surfaces to which they are connected serve as an effective convection cooling system for the rich zone combustion process. In addition to the cooling effect of the fins, the inside surface 92 of the tubular wall portion 64 and the inside surface 94 of the dome 68 can be coated with a thermal barrier coating, to further thermally protect the wall of the fuel rich zone combustion chamber section 1 6.
The dome 68 includes an opening 96 therein accommodated by the position of the fins 88, 90 to
receive a torch igniter 98 for initiating a flame within the upstream end of a fuel rich combustion
chamber 100 within wall portion 64.
An upstream end of the fuel rich zone combustion section 1 6 includes an annular connection
flange 102 on the aft end of the tubular wall portion 64. It is connected to a connection flange 104 by
a ring of circumferentially spaced bolts 106 and nuts 107. Flanges 102, 104 have mating surfaces
sealed by an O-ring 109 in flange 102.
The connection flange 104 is connected to a tubular wall portion 108 on the aft end of the fuel
rich zone combustion chamber section. Wall portion 108 has a diameter like that of the tubular wall
portion 64. An outlet 110 is provided from wall portion 108. The aft end of the outer shell 54 includes
a tubular segment 112 with an outwardly flared inlet end 114 thereon defining an inlet 116 for flow of
air to the quick quench section 1 8 of the combustion apparatus. The tubular segment 11 2 is spaced
radially outwardly of a plurality of longitudinally directed fins 11 8 like the fins 82 on the forward
section of the rich combustion zone.The fins 11 8 include tabs like those on the fins 82 connected
through an outer surface 120 of the tubular wall portion 108. Outer surface 120 is roughened for
improved heat transfer. Accordingly, a plurality of circumferentially spaced convective cooling
passages 122 are formed between the fins 11 8. These passages 1 22 are arranged to direct inlet air flow to the quick quench section 1 8 through a downstream ring of fins 124 offset from the fins 11 8 at
equally spaced circumferentially spaced points around the outside of outlet 110 to supply air through a
convoluted spacer ring 126 for seating outlet 110 in a bore 127 through an end wall 128 of the quick
quench section 1 8 which co-operates with an opposite end wall 130 and an outer circular wall 1 31 to
define a chamber 133. Flow of air through the aforedescribed network will cool the aft end of the fuel
rich combustion chamber 100 to protect the wall thereof during combustion therein.
In accordance with the present invention the design rationale is to control the formation of oxides
of nitrogen from fuel bound nitrogen in the residual fuel a like heavy viscosity fuel directed into the fuel
rich combustion chamber 100 by carefully regulating the amount of inlet air flow thereto so as to
maintain an equivalence ratio in the fuel rich combustion zone in the range 1.2 to 2.5 because of the
use of the variable air flow geometry in the combustor fuel nozzle 32. In the illustrated arrangement the
diameter of the rich combustion zone section is interrelated to combustor throughout the velocity and
the diameter is dependent upon the number of combustors which can be incorporated in an annular
combustion system of the type set forth in United States Patent No. 2,711 072 (Wetzler).In the case
of heavy fuels having fuel bound nitrogen, the vaporization time requirements are a direct function of
the length of the rich combustion zone section.
Combustion stability limits and pressure drop are the factors considered in establishing a design reference velocity. Fuel rich combustion zone stability is adequate where the combustors are operated at pressure levels of the type typically found in combustion zone operating ranges in industrial gas turbine engine installations. The pressure drop limitations of such combustors will produce adequate mixing of the air fuel mixture upstream of the rich combustion chamber 1 00. The overall design length of the fuel rich combustion section 1 6 is set by the lower power operating conditions of a gas turbine engine. The selected design lengths are such that there will be complete fuel vaporization over the anticipated range of droplet sizes of the fuel supplied for rich zone equivalence ratios under all operating conditions of the gas turbine engine except idle.The idle condition of operation is an intermittent condition which is not considered significant in calculated emissions pollutants in industrial gas turbine applications. The provisions of inlet swirl at primary air mixer section 14 is to provide stable flow recirculation and vigorous mixing patterns within the fuel rich combustion chamber 1 00. The variable geometry air flow area provisions within the combustor fuel nozzle 32 will establish a range of rich equivalence ratios from 1.2 to 2.5 in chamber 100 as previously mentioned.Additionally, the quick quench section 1 8 includes a variable geometry inlet air controller 1 35 that will concurrently produce a lean zone equivalence ratio of 0.4 to 0.6 and the respective inlet air control to the fuel rich combustion chamber 100 and the fuel lean combustion zone section 20 will provide uniform transitions between these zones throughout the operating range. For a fixed lean zone equivalence ratio increased quantities of air must be injected into the quick quench section 1 8 as the rich zone equivalence ratio increases. This can cause mixer area increases at a fixed pressure.However, as the rich zone equivalence ratio increases the momentum ratio of the mixer (jet momentum through the inlet ports of the quick quench mixer to the momentum of main hot gas flow passing from the rich combustion chamber 100) will increase. This is due to the decrease in mass flow and temperature of the combustion products from the fuel rich combustion chamber 100. The combination of the fuel rich combustion process and the fuel lean combustion process, are therefore in the direction of increasing mixing jet penetration as the fuel rich combustion zone equivalence ratio increases. Prior quick quench devices caused non-optimum mixing over such wide range of equivalence ratios as required in the present case to prevent excessive oxides of nitrogen from the combustion apparatus. Accordingly, one feature of the invention is the manner of design of the quick quench section 18. The quick quench zone section 18, in the illustrated arrangement, has optimum mixing over the entire operating range of the industrial gas turbine engine to produce the desired relationship of the inlet air jet momentum to the overall gas flow momentum axially through the compressor. To accomplish this, the controller 135 in quick quench section 1 8 receives preheated air from pressurized chamber 133. A variable geometry band 1 32 is used to meter the flow through two rows of slots 134, 1 36, each row including twelve slots in a ring 137. Each of the slots 1 34, 1 36 have a 4-1 aspect ratio defining the quench air entry ports for the quick quench section 1 8.The variable geometry band 1 32 is accurately, slidably adjustable on ring 1 37. Band 1 32 has larger openings 1 38 therein of a somewhat trapezoidly configured form to overlie the upstream row of slots 134 to produce an almost linear variation in effective flow area therethrough. For a fuel rich zone equivalence ratio in the order of approximately 1.2 the upstream slots 1 34 are partially opened while the downstream slots 136 are closed. As the equivalence ratio increases the band is rotated to cause opening of the upstream slots 1 34.When those slots are almost fully opened additional area for airflow is added by opening the downstream row of slots 1 36 through openings 140 in band 1 32. The increased flow through the open area will increase equivalence ratio in the fuel rich zone for combustion. Since jet to free stream momentum ratio also increases as the rich zone equivalence ratio increases, the aforesaid design of the quick quench section 1 8 also provides for uniform mixing over the operating range and parameter variations of operation of the combustion device to produce a controlled equivalence range within the fuel rich zone combustion chamber 100 to avoid production of oxides of nitrogen therein.
The careful control of the equivalence ratio in the fuel rich combustion chamber 1 00 is established to control formation of oxides of nitrogen from fuel bound nitrogen in the fuel rich burning process. Additionally, the quick quench section 1 8 will quickly reduce the temperature of the hot combustion gases exiting from the combustion zone 100 through the outlet 110 so that a minimum of oxides of nitrogen will be thermally produced in the fuel lean reaction zone section 20.
The illustrated variable geometry controller 135 has a capability of rapidly mixing the hot gas exiting from the rich combustion chamber 100 with air to minimize thermal NOx and will prevent stoichiometric combustion in the lean zone. The lean combustion section has an outer wall 142 of porous laminated material which is transpiration cooled. The material is of the type set forth in United
States Patent No. 3,584,972 issued June 15, 1971 to Bratkovich et al for Porous Laminated Material.
The wall 142 is configured to utilize a minimum amount of air to cool the outer wall 142 during the fuel lean combustion zone combustion process. The variable geometry controller 1 35 will maintain an equivalence ratio within a lean combustion chamber 144 defined by the outer wall 142 so as to further control the production of oxides of nitrogen during the combustion process.
The dilution zone 22 includes a variable geometry dilution zone band 146 that rides on elevated pedestals in the form of thimbles 148 inserted through circumferentially spaced holes 1 50 in the porous outer wall 1 42 adjacent an outlet end 1 52 thereon. The thimbles 148 will space the band 146 from the outer surface of the wall 142 so that cooling air will be free to flow through the full planar extent thereof to prevent hot spots at the dilution zone section 22. More particularly, each of the thimbles 148 includes a pair of guide flanges 1 54, 1 56 on either side thereof that locate the band 146 for sliding sealing relationship with the outer sealing surface 1 58 of an outer flange 1 60 as best seen in
Figures 6 through 9.The band 146 includes a plurality of air holes 1 62 therein that are positioned into greater or lesser overlapping relationship with the passage 1 64 through the thimbles 1 48 as set by an operator connected to a control arm 1 66 directed radially outwardly of the band 146.
Operation of the aforedescribed combustion apparatus 10 includes directing a high viscosity residual fuel or similar combustible fuel having a high content of fuel bound nitrogen to the combustor fuel nozzle 32. Fuel flows through the constant area orifices 51, 53 and the fuel prefilming orifice 55 and is subjected to the variable air flow through the inner swirler vane ring 44 and the outer swirler vane ring 42 and this preheated mixture is passed through the tube section 28 to vaporize the fuel. The primary air swirler 14 further agitates and vaporizes the fuel flow prior to its entrance into the combustion chamber 100. An air to fuel ratio greater than 6 to 1 from the nozzle 32 is maintained for good atomization of the fuel issuing from the nozzle.The variable area air metering feature of the nozzle allows a controlled parametric investigation for a wide range of fuel rich zone equivalence ratios in the device. The illustrated swirl arrangement will establish an inflow condition of the primary air entry into the fuel rich combustion chamber to provide stable flow recirculation and vigorous mixing patterns within the fuel rich combustion chamber 100. In the illustrated arrangement all the fuel rich zone air enters through the nozzle and the swirl generator and there are no primary holes in the rich combustion chamber wall portion 108 to reinforce circulation.More specifically, the fuel rich zone inlet air enters through the fuel nozzle 32 thus making it necessary to design the fuel nozzle 32 in part as a swirl generator to provide adequate fuel atomization as well as the desired circulating flow pattern within the rich combustion chamber 1 00. In one working embodiment a 700 annular swirler at the primary air mixer section 14 having a swirl number of 1.83 will cause approximately 3% of the air to be recirculated within the rich combustion chamber 100. This is due to the tip oriented tangential velocity profile from the radial swirler at the primary air mixer section 14.
The variable area of air flow through the combustor fuel nozzle 32 and the primary air mixer section 14 will be correlated with the air flow through the variable geometry controller 135 at the quick quench section to establish a fuel rich equivalence ratio of from 1.2 to 2.5 and a lean zone equivalence ratio in the range of 0.4 through 0.6 and the ratios will be established to provide uniform transition between the zones throughout this operating range.For a given rich zone equivalence ratio, the momentum of inlet air flow through the variable geometry controller 135 and the slots 134,136 therein will maintain a momentum ratio of the jet momentum of air passing through the slots 134,136 to the momentum of axial gas flow through the quick quench section 18 so as to control the mixing jet penetration as the rich zone equivalence ratio increases thereby to maintain optimum mixing over the equivalence ranges. The requirement for upstream fuel preparation is important when operating with heavy fuels requiring substantial preheating and mixing to adequately vaporize the fuel components as they enter the rich combustion chamber. The design of the vaporizer will maintain vaporization without
autoignition of the heavy fuel.This will be dependent upon the amount of resident time of the heavy fuel as it passes through the combustion apparatus up-stream of the rich combustion chamber 100.
The capability to vaporize such fuel is a direct function of the properties of the fuel, performance of the fuel injection in the combustion fuel nozzle 32 and the restrictions against autoignition of the fuel as it is vaporized up-stream of the rich combustion chamber 100.
The maintenance of the equivalence range from 1.2 to 2.5 in the rich combustion chamber is effective to control oxide of nitrogen emissions from the fuel having the fuel bound nitrogen therein.
The rich reaction zone combustion will raise the temperature of the combustion products to a level that requires rapid quenching by air flow through the slots 1 34 or 1 36 as the lean reaction zone equivalence ratio is established. The cooling at quench section 1 8 prevents the production of oxides of nitrogen. This is accomplished by maintaining reaction temperatures in the order of 2,5000F (1371 0C) or less as gas flows into the lean combustion chamber 144. The illustrated arrangement is capable of handling residual petroleum fuels with a distillation range with end points up to 1 1 000 F (5930C). A ring of coolant orifices 1 68 in the wall 130 flows air across an inlet 1 71 to combustion zone 144.
Based on vaporization reaction criteria as well as flame stability, pressure drop and engine size considerations, one embodiment included combustor liners having a diameter of 5.53 inches, (14.05 cm).
The resulting combustor cold flow reference velocity is 55.6 feet per second (16.95 m per second) at maximum continuous levels of gas turbine engine operation. The selected combustion zone design lengths, compared to the calculated requirements for two fuel rich zone fuel/air ratios are as follows:
Rich Zone Lean Zone
Design Length 11.00" (27.94 cm) 5.50" (13.97 cm)
Requirement Rich Zone Vaporization Lean Zone Reaction (0) 0=1.8 46=1.3 0=0.6 Max. Rated 8.23" (20.91 cm) 10.28" (26.11 cm) 2.77" (7.04cm)
Max.Con- 8.20" (20.83) 10.24" (26.01) 3.62" (9.19) tinuous 70% Power 8.32" (21.13) 10.40" (26.42) 4.33" (11.00) 50% Power 8.55" (21.72) 10.70" (27.18) 5.42" (13.77) Idle 8.95" (22.74) 11.24" (28.55) 8.37" (21.26)
From the above data, design length specification is set by the low power operating conditions.
This is because the velocity in the rich zone is lower and fuel atomization is reduced at this point of operation. The aforedescribed design lengths provide complete fuel vaporization over the anticipated range of droplet size from the air atomizing fuel nozzle and the reaction for rich zone equivalence ratios at all operating conditions except idle. This point is not considered to be a significant point for emissions of oxides of nitrogens.
The effective quenching produced by the aforedescribed quick quench section 1 8 will reduce the temperature of the hot gas exiting from the fuel rich combustion chamber 100 and will thereby minimize thermal production of oxides of nitrogen and prevent stoichiometric combustion within the fuel lean combustion chamber 144. This is accomplished by the aforedescribed variable geometry controller 135 in association with especially configured slots 134, 1 36.
The non-stoichiometric lean combustion zone process within the combustion chamber 144 is further moderated at the outlet thereof by air flow through the dilution zone section 22 and positioning of the control band 146 thereof so that the temperature of the combustion products due to burning within the lean combustion chamber 1 44 will maintain the combustion process in a temperature range to prevent production of thermally produced oxides of nitrogen at the outlet of the combustion apparatus 10.
The present invention provides low emission combustion apparatus for use in gas turbine engines of the type for burning fuels containing bound nitrogen including series arranged stages with an upstream fuel rich combustion section, an intermediate quench section and a downstream fuel lean combustion section and further including a variable geometry fuel and air controller admitting fuel bound nitrogen and air into the rich combustion section and operative to maintain a rich fuel combustion zone equivalence ratio in the range of 1.2 to 2.5 and wherein the quench section includes mixer means operative to quickly reduce the temperature of combustion products from the rich fuel combustion zone prior to passage thereof into a lean fuel combustion zone having an equivalence ratio in the range of 0.4 to 0.6 so as to control the formation of oxides of nitrogen during series combustion in the fuel rich combustion section and in the lean fuel combustion section.
A preferred embodiment of the present invention provides an improved low emission combustion apparatus for use in gas turbine engines for burning fuels containing fuel bound nitrogen by the provision of a variable geometry fuel and air supply means including air blast or air assist nozzle means to admit high viscosity fuel with fuel bound nitrogen and air into the combustor and including a variable geometry air inlet means to regulate the equivalence ratio in a range of from 1.2 to 2.5 in a fuel rich combustion zone in order to control emissions of oxides of nitrogen from the fuel bound nitrogen and wherein means are provided to regeneratively cool the fuel rich combustion zone in accordance with the quantity of combustion air directed into the fuel rich combustion zone so as to prevent excessive temperature increases in the fuel rich combustion zone during increased quantities of air flow thereto and wherein quench means are provided to rapidly mix the products of combustion from the fuel rich combustion zone to rapidly reduce the temperature thereof so as to minimize or prevent thermal production of oxides of nitrogen in a downstream fuel lean combustion zone having a variably controlled air input therein so as to maintain a lean combustion zone equivalence ratio in the range of 0.4 to 0.6.
In such an improved combustor the fuel rich zone combustion section is defined by an imperforate combustor wall having an inlet end of a reduced diameter and a larger diameter outlet end and there are means for directing a blast of vaporized air and fuel into the small diameter end in mixed relationship with a variably controlled inlet air flow to establish said fuel rich combustion zone equivalence ratio in the range of 1.2 to 2.5 and high velocity air mixer means directing quench air into combustion products from the large diameter end of the rich zone combustor wall quickly reduces the temperature of the rich zone combustion products to reduce autoignition or thermoproduction of oxides of nitrogen during combustion within a fuel lean zone combustion tube downstream of the mixer means; the tube having a wall of porous laminated material to reduce the amount of air required to cool the combustion apparatus during its operation and the rich zone air for combustion therein being directed by heat exchange means into convective coolant flow relationship with the combustor wall of the fuel rich combustion zone.
Claims (5)
1. A combustion system for use in burning liquid fuels with fuel bound nitrogen comprising: a source of fuel having a high fuel bound nitrogen content, liner means forming a fuel rich combustion zone having an inlet and an outlet, air supply means for directing all of the rich combustion zone inlet air flow to the combustion system through a flow passage having an inlet in communication with a source of combustion air and heated by a first portion of said liner means for preheating all inlet air flow to the fuel rich zone combustion chamber, fuel vaporization means for mixing fuel from said source with said preheated inlet air flow for prevaporization of the high nitrogen content fuel mixed therewith, first variable geometry means for establishing a fuel/air ratio in the rich combustion zone with an equivalence ratio in the range of 1.2 to 2.5 to reduce production of oxides of nitrogen from the fuel bound nitrogen, quick quench means receiving the combustion products from said fuel rich combustion zone and reducing them to a temperature to inhibit high thermal reaction thereby to inhibit production of oxides of nitrogen, said quick quench mixer means including an inlet air supply for directing a predetermined amount of the quench air across a second portion of said liner means for reducing the temperature of combustion products at the outlet of said rich combustion zone, second variable geometry means for controlling the amount of quench air flow into said quick quench mixer means to maintain the equivalence ratio range in said fuel rich combustion chamber therein to reduce the production of oxides of nitrogen, and lean zone combustor means connected to receive quenched combustion products from said quick quench mixer means for further combustion in a fuel lean combustion zone with an equivalence ratio in the range of 0.4-0.6.
2. A combustion system for use in burning liquid fuels with fuel bound nitrogen according to claim 1 , in which the system includes third variable geometry means for regulating the fuel/air ratio in the fuel lean combustion zone to control the temperature of the combustion products to maintain a combustion process therein for minimizing the emissions of oxides of nitrogen from the combustion system following release of the bound nitrogen from the high nitrqgen content fuel supply in the combustion process within said fuel rich combustion zone.
3. A combustion system for use in burning liquid fuels with fuel bound nitrogen according to claim 1 or 2, in which said fuel vaporization means comprises fuel mixing chamber means for mixing fuel from said source with said preheated inlet air flow for prevaporization of the fuel mixed therewith, and swirler means for directing a swirling air and fuel pattern from said fuel mixing chamber means through the inlet into said fuel rich combustion zone.
4. A combustion system for use in burning liquid fuels with fuel bound nitrogen according to any one of the preceding claims, in which said flow passage contains a first plurality of fins connected to said first portion of said liner and extending into said flow passage for preheating inlet air flow to the fuel rich zone combustion chamber, and said predetermined amount of quench air directed across said second portion of said combustor liner passes over a second plurality of fins connected to said second portion for reducing the temperature of combustion products at the outlet of said rich combustion zone while preheating the quench air.
5. A combustion system for use in burning liquid fuels with fuel bound nitrogen substantially as hereinbefore particularly described and as shown in Figures 1 to 9 of the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US19958680A | 1980-10-22 | 1980-10-22 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2086031A true GB2086031A (en) | 1982-05-06 |
| GB2086031B GB2086031B (en) | 1984-04-18 |
Family
ID=22738169
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8120977A Expired GB2086031B (en) | 1980-10-22 | 1981-07-07 | Gas turbine combustion system |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2086031B (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4343332A1 (en) * | 1993-12-20 | 1995-06-22 | Abb Management Ag | Convective cooling device for sealed combustion chamber |
| EP0660046A1 (en) * | 1993-12-22 | 1995-06-28 | Westinghouse Electric Corporation | Combustor bybass system for a gas turbine |
| EP0890795A3 (en) * | 1997-07-07 | 2000-03-22 | General Electric Company | Rapid-quench axially staged combustor |
| US6311473B1 (en) * | 1999-03-25 | 2001-11-06 | Parker-Hannifin Corporation | Stable pre-mixer for lean burn composition |
| DE10312971B4 (en) * | 2003-03-24 | 2017-04-06 | General Electric Technology Gmbh | Method for operating a gas turbine group |
| US10451278B2 (en) | 2015-02-06 | 2019-10-22 | Rolls-Royce Plc | Combustion chamber having axially extending and annular coolant manifolds |
| US10823413B2 (en) | 2016-08-01 | 2020-11-03 | Rolls-Royce Plc | Combustion chamber assembly and a combustion chamber segment |
| US20230072621A1 (en) * | 2021-09-06 | 2023-03-09 | Rolls-Royce Plc | Controlling soot |
-
1981
- 1981-07-07 GB GB8120977A patent/GB2086031B/en not_active Expired
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4343332A1 (en) * | 1993-12-20 | 1995-06-22 | Abb Management Ag | Convective cooling device for sealed combustion chamber |
| EP0660046A1 (en) * | 1993-12-22 | 1995-06-28 | Westinghouse Electric Corporation | Combustor bybass system for a gas turbine |
| US5557920A (en) * | 1993-12-22 | 1996-09-24 | Westinghouse Electric Corporation | Combustor bypass system for a gas turbine |
| EP0890795A3 (en) * | 1997-07-07 | 2000-03-22 | General Electric Company | Rapid-quench axially staged combustor |
| US6311473B1 (en) * | 1999-03-25 | 2001-11-06 | Parker-Hannifin Corporation | Stable pre-mixer for lean burn composition |
| DE10312971B4 (en) * | 2003-03-24 | 2017-04-06 | General Electric Technology Gmbh | Method for operating a gas turbine group |
| US10451278B2 (en) | 2015-02-06 | 2019-10-22 | Rolls-Royce Plc | Combustion chamber having axially extending and annular coolant manifolds |
| US10823413B2 (en) | 2016-08-01 | 2020-11-03 | Rolls-Royce Plc | Combustion chamber assembly and a combustion chamber segment |
| US20230072621A1 (en) * | 2021-09-06 | 2023-03-09 | Rolls-Royce Plc | Controlling soot |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2086031B (en) | 1984-04-18 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |