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1. WO1993022601 - BUSE DE COMBUSTION A PREMELANGE GAZ/LIQUIDE DESTINEE A ETRE UTILISEE DANS UN TURBOMOTEUR

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

[ EN ]

Description
PREMIX LIQUID AND GASEOUS COMBUSTION NOZZLE FOR USE WITH A GAS TURBINE ENGINE

Technical Field
The present invention relates to a low emission combustion nozzle. More particularly, the invention relates to a premix liquid and gaseous combustion nozzle for reducing emissions by
interaction of the gaseous fuel bubbles with the liquid fuel resulting in superior atomization.

Background Art
The use of fossil fuel as the combustible fuel in gas turbine engines results in the combustion products of carbon monoxide, carbon dioxide, water vapor, smoke and particulates, unburned hydrocarbons, nitrogen oxides and sulfur oxides. Of these above products, carbon dioxide and water vapor are
considered normal and unobjectionable. In most applications, governmental imposed regulation are further restricting the amount of pollutants being emitted in the exhaust gases.
In the past the majority of the products of combustion have been controlled by design
modifications. For example, at the present time smoke has normally been controlled by design modifications in the combustor, particulates are normally controlled by traps and filters, and sulfur oxides are normally controlled by the selection of fuels being low in total sulfur. This leaves carbon monoxide, unburned hydrocarbons and nitrogen oxides as the emissions of primary concern in the exhaust gases being emitted from the gas turbine engine.

Oxides of nitrogen are produced in two ways in conventional combustion systems. For example, oxides of nitrogen are formed at high temperatures within the combustion zone by the direct combination of atmospheric nitrogen and oxygen and by the presence of organic nitrogen in the fuel. The rates with which nitrogen oxides form depend upon the flame temperature and, consequently, a small reduction in flame
temperature can result in a large reduction in the nitrogen oxides.
Past and some present systems providing means for reducing the maximum temperature in the combustion zone of a gas turbine combustor have included schemes or introducing more air at the primary combustion zone, recirculating cooled exhaust products into the combustion zone and injecting water spray into the combustion zone. An example of such a system is disclosed in U.S. Patent No. 4,733,527 issued on March 29, 1988, to Harry A. Kidd. The method and apparatus disclosed therein automatically maintains the NOx emissions at a substantially
constant level during all ambient conditions and for no load to full load fuel flows. The water/fuel ratio is calculated for a substantially constant level of NOx emissions at the given operating conditions and, knowing the actual fuel flow to the gas turbine, a signal is generated representing the water metering valve position necessary to inject the proper water flow into the combustor to achieve the desired
water/fuel ratio.
An injector nozzle used with a water
injection system is disclosed in U.S. Patent No.
4,600,151 issued on July 15, 1986, to Jerome R.
Bradley. The injector nozzle disclosed includes an annular shroud means operatively associated with a plurality of sleeve means, one inside the other in spaced apart relation. The sleeve means form a liquid fuel-receiving chamber, a water or auxiliary
fuel-receiving chamber positioned inside the liquid fuel-receiving chamber. The fuel-receiving chamber discharges water or auxiliary fuel in addition or an alternatively to the liquid fuel. The sleeve means further forms an inner air-receiving chamber for receiving and directing compressor discharge air into the fuel spray cone and/or water or auxiliary fuel to mix therewith. Compressor discharge air is received and discharged into the fuel spray cone and/or water or auxiliary fuel for mixing purposes.
Another fuel injector is disclosed in U.S. Patent No. 4,327,547 issued May 4, 1982, to Eric
Hughes et al. The fuel injector includes means for water injection to reduce NOx emissions, an outer annular gas fuel duct with a venturi section with air purge holes to prevent liquid fuel entering the gas duct. Further included is an inner annular liquid fuel duct having inlets for water and liquid fuel. The inner annular duct terminates in a nozzle, and a central flow passage through which compressed air also flows, terminating in a main diffuser having an inner secondary diffuser. The surfaces of both diffusers are arranged so that their surfaces are washed by the compressed air to reduce or prevent the accretion of carbon to the injector, the diffusers in effect forming a hollow pintle.
The above system and nozzles used therewith are examples of attempts to reduce the emissions of oxides of nitrogen. The nozzles described above fail to efficiently mix the gaseous fluids with the liquid fluids to control the emissions of oxides of nitrogen emitted from the combustor.

Disclosure of the Invention
In one aspect of the invention a fuel injector is comprised of a delivery tube having a passage therein and a tubular member coaxially
positioned about the delivery tube and having a passage surrounding the delivery tube. The delivery tube further has a plurality of passages therein being in fluid communication between the passage in the delivery tube and the passage in the tubular member. The fuel injector is further comprised of a first mixing chamber position in at least a portion of the passage within the delivery tube and a second mixing chamber in fluid communication with the mixture exiting the first mixing chamber.
In another aspect of the invention a fuel injector has been adapted for use in a gas turbine engine having a compressor section developing a flow of compressed air, a combustor section having a mixture of liquid fluid and gaseous fluid introduced therein and the gas turbine engine being operable on a predominantly gaseous fuel and having a quenching fluid communicating therewith. The fuel injector is comprised of a delivery tube having a passage therein and the quenching fluid therein, a tubular member coaxially positioned about the delivery tube, having a passage surrounding the delivery tube and a gaseous fluid within the passage surrounding the delivery tube. The delivery tube further has a plurality of passages therein being in fluid communication between the quenching fluid within the passage in the delivery tube and the gaseous fluid within the passage in the tubular member. The injector is further comprised of a first mixing chamber position in at least a portion of the passage within the delivery tube, a second mixing chamber in fluid communication with the partially mixed mixture exiting the first mixing chamber and a third mixing chamber in fluid
communication with the mixture exiting the second mixing chamber and having an additional gaseous fluid added thereto.
In another aspect of the invention a fuel injector has been adapted for use in a gas turbine engine having a compressor section developing a flow of compressed air, a combustor section having a mixture of liquid fluid and gaseous fluid introduced therein, the gas turbine engine being operable on a predominantly liquid fuel. The fuel injector is comprised of a delivery tube having a passage and having the liquid fluid therein, a tubular member coaxially positioned about the delivery tube and having a passage surrounding the delivery tube and having at least a portion of the compressed air therein. The delivery tube further has a plurality of passages therein in fluid communication between the liquid fluid within the passage in the delivery tube and the compressed air within the passage in the tubular member. The fuel injector is further
comprised of a first mixing chamber position in at least a portion of the passage within the delivery tube, a second mixing chamber in fluid communication with the mixture exiting the first mixing chamber and a third mixing chamber in fluid communication with the mixture exiting the second mixing chamber and having additional compressed air added thereto.
The operation of the injector reduces nitrogen oxide, carbon monoxide and unburned
hydrocarbon emissions and provides a reliable
injection nozzle. The injector when used with a water injection system reduces the flame temperature
resulting the rates with which nitrogen oxides form.

A small reduction in flame temperature will result in a large reduction in the nitrogen oxides. The
injector premixes the gaseous fuel with the water in a first mixing chamber, further mixes the mixture of water and gaseous fuel in a second mixing chamber and further mixes the premixed water and gaseous fuel with compressor air in a third mixing chamber prior to injection into the combustor. The combination of the mixing chambers results in an efficient homogeneous mixture which maintains gas turbine nitrogen oxide, carbon monoxide and unburned hydrocarbon emissions at a specific low level during operation of the gas turbine engine. When the injector is used to premix a liquid fuel with air, the combination of the mixing chambers results in an efficient homogeneous mixture which maintains gas turbine engine operations at an acceptable level during operation of the gas turbine engine.

Brief Description of the Drawings
FIG. 1 is a partially sectioned side view of a gas turbine engine having an embodiment of the present invention;
FIG. 2 is an enlarged sectional view of a gaseous fuel/water injector used in one embodiment of the present invention;
FIG. 3 is an enlarged sectional view of a portion of the water delivery tube having a portion of the plurality of passages therein;
FIG. 4 is an enlarged sectional view taken along line 4-4 of FIG. 2;
FIG. 5 is an enlarged sectional view of an alternate embodiment of a liquid fuel injector of the present invention; and FIG. 6 is an enlarged sectional view of a portion of the liquid fuel delivery tube having a portion of the plurality of passages therein.

Best Mode for Carrying Out the Invention
In reference to FIGS. 1 and 2, a gas turbine engine 10 having a premix gaseous/liquid fuel
injection nozzle 12 for reducing nitrogen oxide, carbon monoxide and unburned hydrocarbon emissions therefrom is shown. The gas turbine engine 10 has an outer housing 14 having therein a plurality of
openings 16 having preestablished positions and relationship to each other and threaded holes 18 positioned relative to the plurality of openings 16. In this application, the housing 14 further includes a central axis 20 and is positioned about a compressor section 22 centered about the axis 20, a turbine section 24 centered about the axis 20 and a combustor section 26 interposed the compressor section 22 and the turbine section 24. The engine 10 has an inner case 28 coaxially aligned about the axis 20 and is disposed radially inwardly of the combustor section 26. The turbine section 24 includes a power turbine 30 having an output shaft, not shown, connected thereto for driving an accessory component such as a generator. Another portion of the turbine section 24 includes a gas producer turbine 32 connected in driving relationship to the compressor section 22. The compressor section 22, in this application, includes an axial staged compressor 36 having a plurality of rows of rotor assemblies 38, of which only one is shown. When the engine 10 is operating, a flow of compressed air exits the compressor section designated by the arrows 40. As an alternative, the compressor section 22 could include a radial compressor or any suitable source for producing compressed air.
The combustor section 26 includes an annular combustor 42 being radially spaced a preestablished distance from the housing 14 and being supported from the housing 14 in a conventional manner. The
combustor 42 has an annular outer shell 44 being coaxially positioned about the central axis 20, an annular inner shell 46 being positioned radially inwardly of the outer shell 44 and being coaxially positioned about the central axis 20, an inlet end portion 48 having a plurality of generally evenly spaced openings 50 therein and an outlet end portion 52. Each of the openings 50 has the injector 12 having a central axis 60 being generally positioned therein in communication with the inlet end 48 of the combustor 42. As an alternative to the annular combustor 42, a plurality of can type combustors or a side canular combustor could be incorporated without changing the gist of the invention.
As best shown in FIG. 2, in this application each of the injectors 12 are of the gaseous fuel/water injection type 62 and is supported from the housing 14 in a conventional manner. For example, each of the injectors 12 includes a multipiece outer tubular member 70 comprised of a pair of straight portions 72 having an end of one of the straight portions 72 sealed and a generally curved or angled portion 74 each having a passage 76 therein. A threaded fitting 77 is fixedly attached to the straight portion 72 of the multipiece outer tubular member 70 and is in fluid communication with the passage 76. The tubular member 70 extends radially through one of the plurality of openings 16 in the housing 14 and has a mounting flange 78 extending therefrom. The flange 78 has a plurality of holes 88 therein to receive a plurality of bolts 82 for threadedly attaching within the threaded holes 16 in the housing 14. Thus, the injector 62 is removably attached to the housing 14. The multipiece tubular member 70 further includes a combustor end portion 84 and an exterior end portion 86. The combustor end portion 84 of the tubular member 70 is attached to a cylindrical connector member 90 having an axis corresponding to the central axis 60 of the injector 12, a stepped outer surface

92, a first end 94 and a second end 96. The connector member 90 has a stepped passage 98 generally centered therein and extending between the first end 94 and the second end 96. The end of the stepped passage 98 exiting the first end 94 has a generally cylindrical configuration and a first end 100 of a water delivery tube 102 having a passage 104 therein is fixedly attached within the passage 98 of the connector member 90. The end of the passage 98 exiting the second end 96 has a generally conical configuration. The water delivery tube 102 extends from the first end 100 and is coaxially positioned within the passage 76 along the axis of the multipiece tubular member 70. The passage 76 within the tubular member 70 surrounds the water delivery tube 102. The water delivery tuber 102 includes a straight portion 106 and a curved portion 108. The passage 104 within the curved portion 108 of the water delivery tube 102 forms a first mixing chamber 110 therein. A second end portion 112 of the water delivery tube 102 sealingly extending through the wall of the tubular member 70 and has a threaded fitting 114 fixedly attached thereto for attaching a tube or hose, not shown, for communicating with a source of water or quenching liquid. The water delivery tube 102 further includes a plurality of passages 120, best shown. in Fig. 3, communicating between the passage 104 within the water delivery tube 102 and the passage 76 within the multipiece tubular member 70. The plurality of passages 120 are
positioned intermediate the first end 100 and the second end 112 along a portion of the water delivery tube 102 which in this application corresponds to the curved portion 108 of the water delivery tube 102. Each of the plurality of passages 120 have a
preestablished area through which, in this application gaseous fuel under a predetermined pressure is
introduced through the plurality of passages 120 into the passage 104 in the water delivery tube 102. The water within the passage 120 of the water delivery tube 102 is at a pressure less than the predetermined pressure of the gaseous fuel entering through the plurality of passages 120 and partially mixes
therewith. The relationship of the total area of the plurality of passages 120 is controlled to insure that the pressure drop within the injectors 62 will
function properly. For example, in this application, each of the plurality of passages 120 has a diameter of about 1.5 mm and are positioned in fourteen (14) annular rows having six (6) equally spaced openings per row along the curved portion 108 and a portion of the straight portion 72 of the fuel tube 102. As an alternative, it is anticipated that each of the plurality of passages 120 could have a diameter of about 1.5 mm and could be positioned in six (6) annular rows having six (6) equally spaced openings per row along the curved portion 108 and a portion of the straight portion 72 of the fuel tube 102. The total preestablished cross-sectional area is formed by the plurality of rows of the plurality of passages 120 spaced along the portion of the water delivery tube 102. A cup shaped main body 122 has a first end 124 attached to the stepped outer surface 92 of the connector member 90, a second end 126, an outer surface 128 extending between the ends 124,126 and an inner surface 130. The inner surface 130 includes a cylindrical portion 132 and an end or cone portion 134 which when combined with the generally conical
configuration of the second end 96 of the connector member 90 defines a second mixing chamber 136. The second mixing chamber 136 is serially aligned with the first mixing chamber 110. The main body 122 further includes a plurality of passages 138, best shown in Fig. 4, positioned therein that extend between the outer surface 128 and the cylindrical portion 132 of the inner surface 130. Each of the plurality of passages 138 have an axis 140 which is obliquely angled to the outer surface 128 and parallel to the first end 124 of the main body 122. For example, in this application the angle is about 45 degrees. A cap member 150 includes a cylindrical portion 152 positioned about the outer surface 128 and is fixedly attached to the main body 122 near the first end 124 by a plurality of swirlers 154. A combustor end 156 of the cap member 150 is axially spaced a
preestablished distance from the second end 126 of the main body 122 and has an end portion 158 blendingly necked down toward the central axis 60. In this application, the combustor end 156 of the cap member 150 extends a preestablished distance of approximately 10 mm from the second end 126 of the main body 122. A third mixing chamber 160 is formed in the annular area between the cap member 150 and the main body 122. The third mixing chamber 160 is serially aligned with the second mixing chamber 136. The cap member 122 is sealingly positioned within each of the openings 50 within the combustor section 26.
As an alternative and best shown in FIG. 5, the injectors 12 could be of the liquid fuel/air injector type 166. It is noted that the same
reference numerals of the first embodiment, the gaseous fuel/water injection nozzle 62, are used to designate similarly constructed counterpart elements of this embodiment. For example, the primary
difference being, each of the injectors 166 include a liquid fuel delivery tube 170 corresponding to the water delivery tube 102 and an air passage 172
corresponding to the passage 76 within the multipiece tubular member 70 and a threaded fitting 173
communicates with the air passage 172 corresponding to the threaded fitting 77. The liquid fuel delivery tube 170 has a passage 174 therein and a first end 175 is fixedly attached within the stepped passage 98 of the connector member 90. The liquid fuel delivery tube 170 is positioned within the air passage 172 within the multipiece tubular member 70 and the air passage 172 surrounds the liquid fuel delivery tube 170. The liquid fuel delivery tube 170 coaxially extends along the axis of the multipiece tubular member 70. The liquid fuel delivery tube 170 has a pair of straight portions 176 and a generally curved or angled portion 178. The passage 174 within the curved portion 178 of the liquid fuel tube 170 forms a mixing chamber 180 corresponding to the first mixing chamber 110. A second end portion 182 of the liquid fuel tube 170 sealingly extends through the tubular member 70 and has a threaded fitting 184 fixedly attached thereto for attaching a tube or hose, not shown, for communicating with a source of liquid combustible fuel such as #2 diesel fuel. The liquid fuel tube 170 further includes a plurality of passages 186 communicating between the passage 174 within the liquid fuel delivery tube 170 and the air passage 172 within the multipiece tubular member 70. The
plurality of passages 186 are positioned along a portion of the liquid fuel tube 170 which in this application corresponds to the curved portion 178 thereof. Each of the plurality of passages 186 have a preestablished area through which, in this
application, compressed air within the air passage 172 under a predetermined pressure is introduced into the liquid fuel within the passage 174. The compressed air introduced through the passages 186 is at a pressure greater than a predetermined pressure of the liquid fuel within the passage 174 and partially mixes therewith. The relationship of the total area of the plurality of passages 186 is controlled to insure that the pressure drop within the injectors 166 will function properly. For example, in this application, each of the plurality of passages 174 have a diameter of about 1.0 mm and are positioned in fourteen (14) rows having six (6) equally spaced openings per row along the curved portion 178 and a portion of the straight portion 176 of the liquid fuel tube 170. As an anticipated alternative, each of the plurality of passages 174 could have a diameter of about 1.0 mm and could be positioned in six (6) annular rows having six (6) equally spaced openings per row along the curved portion 178 and a portion of the straight portion 176 of the liquid fuel tube 170. The total preestablished cross-sectional area is formed by the plurality of rows of the plurality of passages 184 spaced along the portion of the liquid fuel delivery tube 170.

Industrial Applicability
In use the gas turbine engine 10 is started and allowed to warm up and is used to produce
either electrical power, pump gas, turn a mechanical drive unit or another application. As the demand for load or power produced by the generator is increased, the load on the engine 10 is increased. When using the gaseous fuel/water injector 62, as shown in Fig. 2, as the power demand increases the flow of
combustible fuel and water increases and the mixing takes place as follows. Water from the external source is introduced through the fitting 114 at a predetermined pressure and flow rate through the passage 104 within the water delivery tube 102.
Gaseous fuel, from an external source is supplied to the threaded fitting 77 and is introduced into the passage 76 in the multipiece tubular member 70 at a predetermined pressure greater than that of the water within the passage 104. As the gaseous fuel enters through each of the passages 120 gas bubbles are formed and are interspersed in the flow of water within the first mixing chamber 110. As the mixture of gaseous fuel and water exits the cone shaped second end 96 of the connector member 90 the mixture expands, contacting the cylindrical portion 132 and the cone portion 136 of the inner surface 130 and the water and the gas bubbles further mix within the second mixing chamber 136. From the second mixing chamber 136, the mixture of gaseous fuel and water exits the plurality of passages 138 within the cup shaped main body 122 and enters into the third mixing chamber 160 causing a swirling motion due to the oblique angle of each of the passages 138 relative to the outer surface 128 and the central axis 60. Thus, compressed air from the compressor section 22 enters through the swirlers 154 and mixes with the premixed water and gaseous fuel prior to entering into the combustor 42. The second end 126 of the main body 122 with the blendingly necked down configuration directs the mixture of combustion air and premixed water and gaseous fuel toward an extension of the central axis 60. The mixture exits the injector 62 in an inwardly conical shape and impinges at the apex of the cone further mixing and dispersing into the combustor to burn in an efficient and low emission mode.
When using the liquid fuel/air injector type 166, as shown in Fig. 5, liquid fuel from the external source is introduced through the fitting 184 at a predetermined pressure and flow rate through the passage 174 within the liquid fuel delivery tube 170. Compressed air, from the engine 10 compressor section 22 or, as an alternative, an external source is supplied to the threaded fitting 173 and is introduced into the passage 172 in the multipiece tubular member 70 at a predetermined pressure greater than that of the liquid fuel within the passage 174. As the compressed air enters through each of the plurality of passages 186 air bubbles are formed and are
interspersed in the flow of liquid fuel within the first mixing chamber 180. As the mixture of liquid fuel and air exits the cone shaped second end 96 of the connector member 90 the mixture expands,
contacting the cylindrical portion 132 and the cone portion 136 of the inner surface 130 and the liquid fuel and the air bubbles further mix within the second mixing chamber 136. From the second mixing chamber 136, the mixture of liquid fuel and air exits the plurality of passages 138 within the cup shaped main body 122 and enters into the third mixing chamber 160 causing a swirling motion due to the oblique angle of each of the passages 138 relative to the outer surface 128 and the central axis 60. Thus, additional
compressed air from the compressor section 22 enters through the swirlers 154 and mixes with the premixed liquid fuel and air prior to entering into the
combustor 42. The second end 126 of the main body 122 with the blendingly necked down configuration directs the mixture of combustion air and premixed liquid fuel and air toward an extension of the central axis 60. The mixture exits the injector 62 in an inwardly conical shape and impinges at the apex of the cone further mixing and dispersing into the combustor to burn in an efficient and low emission mode.
As a further alternative, the injector 12 could be used to supplement a low calorific fuel, of either a gaseous or liquid state. For example, the low calorific liquid fuel could be introduced through the delivery tube 102,170 and a further rich calorific gaseous fuel could be introduced through the passage 76,172 in the multipiece tubular member 70.
Similarly, the low calorific gaseous fuel could be introduced through the passage 76,172 in the
multipiece tubular member 70 and the rich calorific liquid fuel could be introduced through the delivery tube 102,170. Functionally, the mixing would be similar to that as described above. The size, location and quantity of the plurality of passages 120,186 may need to be altered to provide the most efficient combination of mixtures and or pressure ratios for use in the gas turbine engine 10.
Other aspects, objectives and advantages of this invention can be obtained from a study of the drawings, the disclosure and the appended claims.