Abstract:
Premix nozzles and gas turbine engine systems involving such nozzles are provided. In this regard, a representative industrial gas turbine engine includes: a combustion section having a nozzle assembly operative to provide a fuel-air mixture for combustion, the nozzle assembly having an array of shuttered nozzles and non-shuttered nozzles; each of the shuttered nozzles being operative in an open position, in which air is directed through the shuttered nozzle for mixing with fuel, and a closed position, in which a reduced amount of air is directed through the shuttered nozzle; each of the shuttered nozzles being inoperative to independently alter an amount of air being directed therethrough.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The disclosure generally relates to industrial gas turbine engines. 
         [0003]    2. Description of the Related Art 
         [0004]    Industrial gas turbine engines are used in a variety of applications such as power generation, for example. Oftentimes, efforts to improve the efficiency of these engines become difficult as emission requirements tend, over time, to become more stringent. 
       SUMMARY 
       [0005]    Premix nozzles and gas turbine engine systems involving such nozzles are provided. In this regard, an exemplary embodiment of a premix nozzle for an industrial gas turbine engine comprises: a housing defining an interior and having an outlet communicating with the interior, the housing further having a housing opening communicating with the interior, the housing opening being operative such that air exterior to the housing is drawn into the interior of the housing through the housing opening, mixed with fuel, and directed out of the housing through the outlet; and a valve contacting the exterior of the housing and having a valve opening, the valve being movable between an open position, in which the valve opening is aligned with the housing opening such that air exterior to the housing is drawn into the interior of the housing through the valve opening and the housing opening, and a closed position, in which a reduced amount of air exterior to the housing is drawn into the interior. 
         [0006]    An exemplary embodiment of a nozzle assembly for a combustion section of an industrial gas turbine engine comprises: an array of shuttered nozzles, each of the shuttered nozzles comprising: a housing defining an interior and having an outlet communicating with the interior, a housing opening communicating with the interior, the housing opening being operative such that air exterior to the housing is drawn into the interior of the housing through the housing opening, mixed with fuel, and directed out of the housing through the outlet; and a valve located exterior to the housing and having a valve opening, the valve being movable between an open position, in which air exterior to the housing is drawn into the interior of the housing through the valve opening and the housing opening, and a closed position, in which a reduced amount of air exterior to the housing is drawn into the interior. 
         [0007]    An exemplary embodiment of an industrial gas turbine engine comprises: a combustion section having a nozzle assembly operative to provide a fuel-air mixture for combustion, the nozzle assembly having an array of shuttered nozzles and non-shuttered nozzles; each of the shuttered nozzles being operative in an open position, in which air is directed through the shuttered nozzle for mixing with fuel, and a closed position, in which a reduced amount of air is directed through the shuttered nozzle; each of the shuttered nozzles being operative to independently alter an amount of air being directed therethrough. 
         [0008]    Other systems, methods, features and/or advantages of this disclosure will be or may become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features and/or advantages be included within this description and be within the scope of the present disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0010]      FIG. 1  is a schematic diagram of an embodiment of an industrial gas turbine engine. 
           [0011]      FIG. 2  is a schematic diagram of the embodiment of  FIG. 1  showing orientation of premix nozzles of a nozzle assembly. 
           [0012]      FIG. 3  is a partially cut-away view of an embodiment of a premix nozzle. 
           [0013]      FIG. 4  is a partially cut-away view of the embodiment of  FIG. 3  as viewed along line 4-4. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Premix nozzles and gas turbine engine systems involving such nozzles are provide, several exemplary embodiments of which will be described in detail. In this regard, some embodiments involve the use of gas actuated shutter valves for metering the flow of air entering the nozzles. In some of these embodiments, such a shutter valve incorporates ports that selectively align with corresponding ports located on a housing of the nozzle. When the ports of the valve are aligned with the ports of the housing, air can enter the interior of the nozzle and mix with the fuel. 
         [0015]    Referring to the schematic diagram of  FIG. 1 , an exemplary embodiment of an industrial gas turbine engine is depicted. As shown in  FIG. 1 , engine  100  incorporates a compressor section  102 , a combustion section  104  and a turbine section  106 , each of which is oriented along a longitudinal axis  108 . Compressor section  102  includes a low pressure compressor  110  and a high pressure compressor  112 . The turbine section  106  includes a high pressure turbine  114 , a low pressure compressor  116  and a power turbine  118 . 
         [0016]    In operation, a fuel-air mixture provided to combustion section  104  is combusted and directed to the high pressure and low pressure turbines. A high shaft  120  interconnects the high pressure turbine and the high pressure compressor, and a low shaft  122  interconnects the low pressure turbine and the low pressure compressor. Exhaust from the low pressure turbine is directed to power turbine  118 , which is a free turbine, i.e., the power turbine is not rotated via a shaft that is interconnected with the high and/or low turbines. 
         [0017]      FIG. 2  schematically depicts a portion of combustion section  104 . In particular,  FIG. 2  depicts an annular assembly  130  of nozzles (e.g., nozzle  132 ) that provide fuel and air for combustion within combustion section  104 . In the embodiment of  FIG. 2 , two types of nozzles are depicted. Specifically, shuttered nozzles (e.g., nozzle  132 ) and non-shuttered nozzles (e.g., nozzle  133 ) are provided. In the embodiment of  FIG. 2 , each of the nozzle types forms an array of nozzles, with the eight nozzles of the array  134  of shuttered nozzles being interleaved with the eight nozzles of the array  135  of non-shuttered nozzles. This results in the nozzles of this embodiment alternating between shuttered and non-shuttered types about the circumference of assembly  130 . Notably, in other embodiments, various other numbers and/or orientations of nozzles can be used. 
         [0018]    In operation, the non-shuttered nozzles of array  135  are used to provide fuel and air to combustion section  104  regardless of the demand for power. However, as an increase in power is requested, fuel and air is provided from the shuttered nozzles of array  134  in increasing increments that correspond to the amount of power requested. In this embodiment, each incremental increase in the metered flow of fuel and air corresponds to actuating another of the shuttered nozzles. Specifically, at 50% power, nozzle assembly  130  is controlled so that only the non-shuttered nozzles provide fuel and air for combustion. As an increase in power is requested, such as when power is requested at 56.66% power, for instance, a first shuttered nozzle is controlled so that fuel and air is now also provided from that shuttered nozzle. For each additional increment of requested power (in this case, each 6.66% increment), another shuttered nozzle is controlled to direct fuel and air. Notably, each increment in this embodiment corresponds to a 6.66% increase in power because there are eight shuttered nozzles providing additional fuel and air over a power range of 50%. In other embodiments, various other numbers and/or increments can be used. 
         [0019]    The opening sequence of the shuttled nozzles of array  134  involves opening nozzles on opposite sides of the array sequentially in order to promote balanced combustion. By way of example, after nozzle  132  is opened, nozzle  142  is opened. Thereafter, nozzles  138 ,  146 ,  136 ,  144 ,  148  and  140  are opened in sequence. Clearly, various other opening sequences can be used in other embodiments. A representative closing sequence involves closing the nozzles sequentially, but in the reverse order. 
         [0020]    It should be noted that in the embodiment of  FIG. 2 , each shuttered nozzle selectively exhibits a closed position, in which air and fuel are not provided by the nozzle for combustion, an open position, in which air and fuel are provided, or an intermediate position, in which the nozzle is transitioning between the open and closed positions. In other embodiments, shuttered nozzles can be controlled to selectively maintain one or more of a range of intermediate positions that provide varying flows of fuel and air between the flow available at the closed position (i.e., no flow) and the open position (i.e., maximum flow). In such an embodiment, one or more of the shuttered nozzles can be modulated as desired (such as responsive to a feedback signal) for distributing the fuel and air among the nozzles. 
         [0021]    An embodiment of a shuttered nozzle is depicted in  FIG. 3 . As shown in  FIG. 3 , nozzle  150  incorporates a housing  152  that extends between an end  154  and an end  156 . End  154  is used for mounting the nozzle to the combustion section of an engine and, in this embodiment, receives fuel provided by fuel lines  157 ,  158 . Fuel and air mixed within the nozzle are expelled via an outlet  159  located at end  156 . Notably, housing  152  incorporates housing openings (e.g., opening  160 ) that permit air to flow from the exterior of the housing to the interior  162  of the housing for mixing with the fuel. 
         [0022]    As shown in  FIG. 4 , airflow to the interior of the housing is controlled by valve  170 , which also incorporates valve openings (e.g., opening  172 ). In the open position of the nozzle, valve  170  is controlled so that openings of the valve align with openings of the housing. In contrast, in the closed position of the nozzle, valve  170  is controlled so that openings of the valve do not align with openings of the housing, thereby restricting the flow of air into the nozzle. 
         [0023]    In particular, when engine power reduction is required fuel is reduced. At a predetermined setting fuel is shut off to a nozzle and valve  170  is closed. Fuel is redistributed among the open nozzles (and/or partially open nozzles). Simultaneously, air also is redistributed among the nozzles that are at least partially opened. Notably,  FIG. 4  depicts an intermediate position (i.e., partially opened), in which the openings of the valve are partially aligned with openings of the housing. This tends to promote lower exhaust emissions at reduced power settings. 
         [0024]    Positioning of valve  170  is controlled by providing pressurized fluid to one side or the other of a piston head  180  that is housed within an annular cavity  182 . By way of example, providing pressurized fluid to side  184  of piston head  180  via line  185  causes the piston head (and the attached piston body  186 , which defines the valve openings) to move toward end  156  to achieve the open position. In contrast, providing pressurized fluid to side  188  via line  189  causes the piston head and piston body to move to the closed position. 
         [0025]    It should be noted that the pressurized fluid can be one of a variety of fluids and, in some embodiments, may even be the same fluid used as the fuel, e.g., natural gas. In some embodiments, providing of pressurized fluid for controlling the piston position can be accomplished by use of one or more solenoids, for example. 
         [0026]    Note also that, in the embodiment of  FIGS. 3 and 4 , the piston body  185  is cylindrical in shape to correspond to the exterior shape of the corresponding portion  190  of the housing. In other embodiments, various other shapes of piston bodies and housings can be used. 
         [0027]    In some applications, shuttered nozzles, such as the exemplary embodiments described above, can be used as retrofit components on gas turbine engines. By way of example, some engines may incorporate nozzles (e.g., non-shuttered nozzles) that are not configured for selectively reducing both the amount of fuel and air provided for combustion. That is, when fuel is cut off to a nozzle, air may still be provided for combustion via that nozzle. In such an engine, at least a subset of the nozzles may be replaced using shuttered nozzles. As such, an improvement in emission quality may be exhibited as a decrease in requested power of the retrofit engine may result in fuel and air being cut off to one or more of the shuttered nozzles and redistributed to the non-shuttered nozzles. 
         [0028]    It should be emphasized that the above-described embodiments are merely possible examples of implementations set forth for a clear understanding of the principles of this disclosure. Many variations and modifications may be made to the above-described embodiments without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the accompanying claims.