Abstract:
A fuel injecting assembly for a combustor of a gas turbine engine has a gas supply structure, steam supply structure and oil fuel nozzle that are substantially separated to allow relative movement between a respective end section, end portion and end part due to thermal expansion and contraction.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a fuel injecting assembly for a gas turbine engine. More specifically, the present invention relates to a fuel injecting assembly suitable for use with liquid or gaseous fuels and having the capability for steam injection for nitrous oxide (NOx) control. 
       BACKGROUND OF THE INVENTION 
       [0002]    Gas turbine engines include one or more combustors adapted to produce a hot gas by burning a fuel in compressed air. A fuel injecting assembly or nozzle is employed to introduce the fuel into each combustor. To provide flexibility to the user, such fuel nozzles are often of the dual fuel type that are capable of burning either a liquid or a gaseous fuel, or both simultaneously. 
         [0003]    Combustion in gas turbine combustors results in the formation of oxides of nitrogen (NOx) in the combusted gas, which is considered undesirable. One method of minimizing the formation of NOx involves injecting steam, via the fuel injecting nozzle, into the combustor along with the fuel. 
         [0004]    U.S. Pat. No. 5,361,578 discloses a fuel nozzle assembly capable of burning either gaseous or liquid fuel, or both, along with steam injection. The fuel nozzle assembly includes an expansion bellows in an inner sleeve and an expansion bellows in a middle sleeve so as to reduce stresses in the inner and middle sleeves due to thermal expansion. While accommodating differential expansion between portions of the fuel nozzle assembly, bellows between the circumferential chambers have a limited life. 
       SUMMARY OF THE INVENTION 
       [0005]    In accordance with a first aspect of the present invention, a fuel injecting assembly for a gas turbine engine is provided comprising a gas supply structure, a steam supply structure and an oil fuel nozzle. The gas supply structure may have a base section including at least one gas inlet, an intermediate section and an end section having at least one gas outlet. The gas supply structure defines a passage extending from the at least one gas inlet to the at least one gas outlet. The steam supply structure may have a base portion including at least one steam inlet, an intermediate portion and an end portion having at least one steam outlet. The steam supply structure defines a passageway extending from the at least one steam inlet to the at least one steam outlet. The oil fuel nozzle may have a base part including at least one oil inlet, an intermediate part and an end part having at least one oil outlet. The oil fuel nozzle defines a path extending from the at least one oil inlet to the at least one oil outlet. The gas supply structure, the steam supply structure and the oil fuel nozzle are joined only at the base section of the gas supply structure, the base portion of the steam supply structure and the base part of the oil fuel nozzle. Thus, the end section of the gas supply structure, the end portion of the steam supply structure and the end part of the oil fuel nozzle are free to move independently of one another in an axial direction as the steam supply structure, the gas supply structure and the oil fuel nozzle thermally expand and contract. 
         [0006]    The gas supply structure may comprise a first inner surface defining a first inner bore for receiving the steam supply structure such that a first cooling gap is defined between the gas supply structure inner surface and the steam supply structure. The first cooling gap can receive cooling air. 
         [0007]    A first cooling air inlet may be defined in at least one of the gas supply structure base section and the steam supply structure base portion. The first cooling air inlet communicates with the first cooling gap. A first cooling air outlet may be defined between the end section of the gas supply structure and the end portion of the steam supply structure. The first cooling air outlet communicates with the first cooling gap. 
         [0008]    The end section of the gas supply structure may comprise a ring-shaped section having a plurality of circumferentially spaced apart gas outlets. The end portion of the steam supply structure may comprise a ring-shaped portion comprising a plurality of circumferentially spaced apart steam outlets. 
         [0009]    The ring-shaped section is capable of being separated from the intermediate section of the gas supply structure and the ring-shaped portion is capable of being separated from the intermediate portion of the steam supply structure. 
         [0010]    The steam supply structure may comprise a second inner surface defining a second inner bore. The oil fuel nozzle may have a generally cylindrical shape and may be positioned within the inner bore of the steam supply structure such that a second cooling gap is defined between the steam supply structure inner surface and the oil fuel nozzle. The second cooling gap is adapted to receive cooling air. 
         [0011]    A second cooling air inlet may be defined in at least one of the steam supply structure base portion and the oil fuel nozzle base part. The second cooling air inlet communicates with the second cooling gap. A second cooling air outlet maybe defined between the steam supply structure end portion and the oil fuel nozzle end part. The second cooling air outlet communicates with the second cooling gap. Further, the end portion of the steam supply structure and the end part of the oil fuel nozzle may be configured such that the second cooling air outlet is shaped to cause cooling air exiting the second cooling air outlet to define an air shroud about oil exiting the end part of the oil fuel nozzle. 
         [0012]    The gas supply structure may comprise a first double-walled annular structure and the steam supply structure may comprise a second double-walled annular structure. 
         [0013]    In accordance with a second aspect of the present invention, a fuel injecting assembly is provided comprising a gas supply structure and a steam supply structure. The gas supply structure may have a base section including at least one gas inlet, an intermediate section and an end section having at least one gas outlet. The gas supply structure defines a passage extending from the at least one gas inlet to the at least one gas outlet. The steam supply structure may have a base portion including at least one steam inlet, an intermediate portion and an end portion having at least one steam outlet. The steam supply structure defines a passageway extending from the at least one steam inlet to the at least one steam outlet. The gas supply structure and the steam supply structure may be joined only at the gas supply structure base section and the steam supply structure base portion such that the gas supply structure end section and the steam supply structure end portion are free to move independently of one another in an axial direction as the steam supply structure and the gas supply structure thermally expand and contract. 
         [0014]    The gas supply structure may comprise a first inner surface defining a first inner bore for receiving the steam supply structure such that a first cooling gap is defined between the gas supply structure inner surface and the steam supply structure. The first cooling gap is adapted to receive cooling air. 
         [0015]    The first cooling air inlet may be defined in at least one of the gas supply structure base section and the steam supply structure base portion. The first cooling air inlet communicates with the first cooling gap. A first cooling air outlet may be defined between the gas supply structure end section and the steam supply structure end portion. The first cooling air outlet communicates with the first cooling gap. 
         [0016]    The gas supply structure end section may comprise a ring-shaped section having a plurality of circumferentially spaced apart gas outlets and the steam supply structure end portion may comprise a ring-shaped portion comprising a plurality of circumferentially spaced apart steam outlets. 
         [0017]    In accordance with a third aspect of the present invention, a process is provided for repairing a damaged one of an end section of a gas supply structure or an end portion of a steam supply structure in a fuel injecting assembly. The fuel injecting assembly may comprise the gas supply structure and the steam supply structure. The gas supply structure may have a base section including at least one gas inlet, an intermediate section and the end section having at least one gas outlet. The steam supply structure may have a base portion including at least one steam inlet, an intermediate portion and the end portion having at least one steam outlet. The gas supply structure and the steam supply structure may be joined only at the gas supply structure base section and the steam supply structure base portion. The process may comprise separating the damaged one end section or end portion from the corresponding intermediate section or intermediate portion, and coupling a new one end section or end portion to the corresponding intermediate section or intermediate portion. 
         [0018]    The separating may comprise cutting the damaged one end section or end portion from the corresponding intermediate section or intermediate portion. 
         [0019]    The coupling may comprise welding the new one end section or end portion to the corresponding intermediate section or intermediate portion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    While the specification concludes with claims particularly pointing out and distinctly claiming the present invention, it is believed that the present invention will be better understood from the following description in conjunction with the accompanying Drawing Figures, in which like reference numerals identify like elements, and wherein: 
           [0021]      FIG. 1  depicts a diagrammatic schematic of a gas turbine engine incorporating a fuel injecting assembly according to the present invention; 
           [0022]      FIG. 2  depicts a front view of an exemplary fuel injecting assembly according to a further embodiment of the present invention; 
           [0023]      FIG. 3  depicts a side cross sectional view along section line  3 - 3  in  FIG. 2 ; 
           [0024]      FIG. 4  depicts an enlarged view of an end section of a gas supply structure and an end portion of a steam supply structure; and 
           [0025]      FIG. 5  depicts a side cross section view along section line  3 - 3  in  FIG. 2  with a damaged end section of a gas supply structure and a damaged end portion of a steam supply structure both removed and new end section and new end portion shown in exploded view. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]    Referring to the drawings, there is shown in  FIG. 1  a schematic diagram of a gas turbine engine  100  according to one embodiment of the present invention. The gas turbine engine  100  is comprised of a compressor  102  that is driven by a gas turbine  104  via a shaft  106 . Ambient air  108  is drawn into the compressor  102  and compressed. Compressed air  110  produced by the compressor  102  is directed to one or more combustors  112  in which a fuel  114  and compressed air are mixed and burned. The fuel  114  may be a liquid, such as no. 2 distillate oil, or a gas, such as natural gas, and is introduced into each combustor  112  by a corresponding fuel injecting assembly  115 . Hot compressed gas  116  produced by each combustor  112  is directed to the gas turbine  104  where it is expanded, thereby producing shaft horsepower for driving the compressor  102 , as well as a load, such as an electric generator  117 . Expanded gas  118  produced by the turbine  104  is exhausted as exhaust gas  120 , either to the atmosphere directly or, in a combined cycle plant, to a heat recovery steam generator and then to atmosphere. 
         [0027]    The fuel injecting assembly  115  injects the fuel  114  into the combustor  112  as well as steam  122  at a higher temperature for mitigating undesirable exhaust emissions in the exhaust gas  120 . The fuel injecting assembly  115  incorporates features for increasing service life by mitigating thermal stresses between cooler structures that deliver the fuel  114  and the hotter structures that deliver the steam  122 . 
         [0028]    To that end, a gas supply structure  124  of the fuel injecting assembly  115  has a base section  126  including at least one gas inlet  128 , an intermediate section  130  and an end section  132  having at least one gas outlet  134 . The gas supply structure  124  has a passage  136  defined as extending from the at least one gas inlet  128  to the at least one gas outlet  134 . 
         [0029]    A steam supply structure  138  of the fuel injecting assembly  115  has a base portion  140  including at least one steam inlet  142 , an intermediate portion  144  and an end portion  146  having at least one steam outlet  148 . The steam supply structure  138  has a passageway  150  defined as extending from the at least one steam inlet  142  to the at least one steam outlet  148 . 
         [0030]    In the illustrated embodiment, the gas supply structure  124  and the steam supply structure  138  are joined only at the base section  126  of the gas supply structure  124  and the base portion  140  of the steam supply structure  138  such that the end section  132  of the gas supply structure  124  and the end portion  146  of the steam supply structure  138  are free to move independently of one another in an axial direction as the steam supply structure  138  and the gas supply structure  124  thermally expand and contract during operation of the gas turbine engine  100 . 
         [0031]    In one aspect, the gas supply structure  124  of the fuel injecting assembly  115  comprises a first inner surface defining a first inner bore for receiving the steam supply structure such that a first cooling gap  152  is defined between the inner surface of the gas supply structure  124  and the steam supply structure  138 . The first cooling gap can receive cooling air to further mitigate thermal stresses. 
         [0032]    In  FIGS. 2-5 , a fuel injecting assembly  200  constructed in accordance with a further embodiment of the present invention is illustrated. With particular reference to  FIG. 2  from a front view, a fuel nozzle face  202  is presented to an interior of a corresponding combustor (not shown in  FIG. 2 ) for injecting fuel and steam. For clarity, a swirl plate to aid in mixing the fuel and compressed air and cooling of the fuel nozzle face  202  and combustor  112  is omitted. In an exemplary aspect, the fuel can be dispensed from a ring-shaped section  206  having a plurality of circumferentially spaced apart gas outlets  208  of an end section  210  of a gas supply structure  212 . Alternatively, oil can be dispensed from an oil outlet  262  of an oil fuel nozzle  260 . An end portion  216  of a steam supply structure  218  comprises a ring-shaped portion  219  comprising a plurality of circumferentially spaced apart steam outlets  220 . 
         [0033]    With particular reference to  FIGS. 2 and 3 , a gas inlet conduit  224  is coupled to a base section  236  of the gas supply structure  212  so as to supply the base section  236  with a gas fuel. A first generally annular manifold  234  and an inlet  235  are formed in the base section  236  of the gas supply structure  212 . The inlet  235  communicates with the gas inlet conduit  224  and the manifold  234 . Gas fuel  249  supplied by the gas inlet conduit  224  passes through the inlet  235  of the gas supply structure  212  then into the manifold  234 . The gas supply structure  212  further comprises an intermediate section  213  defining a first annular pathway  214  and the end section  210  having the plurality of circumferentially spaced apart gas outlets  208 . A passage  250  extends from the inlet  235  to the outlets  208  and is defined by the manifold  234  and the annular pathway  214 . 
         [0034]    A steam inlet conduit  228  is coupled to a base portion  242  of the steam supply structure  218  so as to supply the base portion  242  with steam. A second generally annular manifold  244  and an inlet  245  are formed in the base portion  242  of the steam supply structure  218 . The inlet  245  communicates with the steam inlet conduit  228  and the manifold  244 . Steam supplied by the steam inlet conduit  228  passes through the inlet  245  of the steam supply structure  218  then into the manifold  244 . The steam supply structure  218  further comprises an intermediate portion  215  defining a second annular pathway  217  and the end portion  216  having the plurality of circumferentially spaced apart steam outlets  220 . A passageway  258  extends from the inlet  245  to the outlets  220  and is defined by the manifold  244  and the annular pathway  217 . 
         [0035]    The oil fuel nozzle  260  has a base part  264  including at least one oil inlet  266 , an intermediate part  268  and an end part  270  having the oil outlet  262 . A central bore  269  extends from the inlet  266  to the outlet  262 . The oil fuel nozzle bore  269  defines a path  272  extending from the oil inlet  266  to the oil outlet  262 . The path  272  may receive fuel oil  261 , naphtha or any other liquid fuel. The nozzle  260  further comprises an annular chamber  274  located radially outwardly from the central bore  269  for receiving water  263  to be dispensed via outlets  274 B near the oil outlet  262 , see  FIG. 4 . The water  263  may have a temperature of from about 10 degrees C. to about 40 degrees C. The water  263  is received at an inlet  274 A to the annular chamber  274 . The water  263  is dispensed from the annular chamber  274  through the outlets  274 B and functions to mitigate NOx emissions. 
         [0036]    The gas supply structure  212  comprise a first inner surface  280  defining a first inner bore  282  for receiving the steam supply structure  218  such that a first cooling gap  284  is defined between the gas supply structure inner surface  280  and the steam supply structure  218 . A first cooling air inlet  286  defined by one or more first cooling air supply bores  286 A and one or more second cooling air supply bores  286 B is provided in the gas supply structure base section  236 . The first cooling air inlet  286  communicates with the first cooling gap  284  for supplying cooling air to the first cooling gap  284 . Structure not shown provides the cooling air  285  from the compressor to the first cooling air inlet  286 . A first cooling air outlet  288  is substantially annular in shape and is defined between the end section  210  of the gas supply structure  212  and the end portion  216  of the steam supply structure  218 , see  FIGS. 3 and 4 . The first cooling air outlet  288  communicates with the first cooling gap  284 . 
         [0037]    The steam supply structure  218  may comprise a second inner surface  290  defining a second inner bore  292 , see  FIGS. 3 and 4 . The oil fuel nozzle intermediate part  268 , which has a generally cylindrical shape in the illustrated embodiment, is positioned within the inner bore  292  of the steam supply structure  218  such that a second cooling gap  294  is defined between the steam supply structure inner surface  290  and the oil fuel nozzle  260 . 
         [0038]    A second cooling air inlet  296  defined by one or more first cooling air supply bores  296 A and one or more second cooling air supply bores  296 B is provided in the steam supply structure base portion  242 . The second cooling air inlet  296  communicates with the second cooling gap  294  and the first cooling air inlet  286 . A second cooling air outlet  298  is defined between the steam supply structure end portion  216  and the oil fuel nozzle end part  270 . The second cooling air outlet  298  communicates with the second cooling gap  294 . As is apparent from  FIG. 4 , the steam supply structure end portion  216  has a radially extending part  216 A extending inward towards the oil fuel nozzle outlet  262  so as to cause cooling air  285  exiting the second cooling air outlet  298  to define an air shroud about oil  261  exiting the outlet  262 . The air shroud causes a resulting flame from oil burning to be pushed downstream from the oil fuel nozzle outlet  262  thereby keeping the outlet  262  cooler and reducing coking at the outlets  208 ,  220  and  262 . 
         [0039]    The first and second cooling gaps  284  and  294 , whether provided with or without cooling air, can increase the lifetime of the fuel injecting assembly  200  since the gaps  284  and  294  serve as insulating layers that lower the overall rate at which energy in the form of heat transfers from the relatively hot steam supply structure  218  to the relatively cold gas supply structure  212  and the oil fuel nozzle  260 . 
         [0040]    In the illustrated embodiment, the gas supply structure  212 , the steam supply structure  218  and the oil fuel nozzle  260  are joined only at the base section  236  of the gas supply structure  212 , the base portion  242  of the steam supply structure  218  and the base part  264  of the oil fuel nozzle  260 . More specifically, each of a plurality of circumferentially spaced apart bolts  300  passes through a corresponding bore  236 A in the base section  236  of the gas supply structure  212  and a corresponding bore  242 A of the base portion  242  of the steam supply structure  218  so as to couple the base section  236  to the base portion  242 . Further, each of one more bolts  302  extends through a corresponding bore  270 A in the base part  264  of the oil fuel nozzle  260  and a corresponding bore  242 B of the base portion  242  of the steam supply structure  218  so as to couple the oil fuel nozzle  260  to the steam supply structure  218 . Hence, the intermediate section  213 , the intermediate portion  215  and the intermediate part  268  as well as the end section  210 , the end portion  216  and the end part  270  are not directly coupled to one another. Thus, the end section  210  of the gas supply structure  212 , the end portion  216  of the steam supply structure  218  and the end part  270  of the oil fuel nozzle  260  are free to move or expand independently of one another in an axial direction as the steam supply structure  218 , the gas supply structure  212  and the oil fuel nozzle  260  thermally expand and contract. 
         [0041]    As noted above, gas fuel  249  supplied by the gas inlet conduit  224  passes through the inlet  235  of the gas supply structure  212  then into the manifold  234 . From the manifold  234 , the gas fuel travels through the first annular pathway  214  and exits the passage  250  through the circumferentially spaced apart gas outlets  208  into a corresponding combustor. Thereafter, the gas fuel  249  is mixed with compressed air and burned in the combustor to produce hot working gases. 
         [0042]    Superheated steam  256  is injected into the combustor while at a temperature of from about 200 degrees C. to about 350 degrees C. via the fuel injecting assembly  200  in order to minimize the formation of NOx. As noted above, steam  256  supplied by the steam inlet conduit  228  passes through the inlet  245  of the steam supply structure  218  then into the manifold  244 . From the manifold  244 , the steam moves through the second annular pathway  217  and exits the passageway  258  via the steam outlets  220 . Thereafter, the steam mixes with the gas fuel and the compressed air so as to reduce NOx formation during combustion of the fuel gas/compressed air mixture. 
         [0043]    As noted above, the oil fuel nozzle  260  supplies fuel oil or the like via its outlet  262 . Thus, the fuel injecting assembly  200  is capable of injecting gas fuel via the gas supply structure  212  or liquid fuel oil via the oil fuel nozzle  260  for burning, or both simultaneously, as well as injecting steam into the combustor via the steam supply structure  218  so as to reduce NOx emissions. As also noted above, the oil fuel nozzle  260  is capable of injecting water near its oil outlet  262  so as to further mitigate NOx emissions. 
         [0044]    In  FIG. 5 , in an exemplary aspect the fuel injecting assembly  200  can be repaired by removing a damaged end section  210  and/or a damaged end portion  216  and attaching a new end section  210 ′ and/or a new end portion  216 ′. Thus, if the end section  210  or the end portion  216  shows cracks, the damaged part can easily be replaced separately from the other parts. 
         [0045]    To that end, the present disclosure provides a process for repairing a damaged one of the end section  210  of the gas supply structure  212  or the end portion  216  of the steam supply structure  218 . The process comprises separating, such as by cutting, the damaged one end section  210  or end portion  216  from the corresponding intermediate section or intermediate portion. The process further comprises coupling, such as by welding, a new one end section  210  or end portion  216  to the corresponding gas supply structure intermediate section  213  or steam supply structure intermediate portion  215 . 
         [0046]    While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.