Abstract:
A nozzle center body includes a unitary, one-piece, elongated tubular member having a forward end formed with a radially outwardly extending mounting flange; an aft end formed with a plurality of radially outwardly extending swirler vanes; and, an intermediate region, located axially between the forward and aft ends, formed with an inlet flow conditioner including an annular plate provided with plural, circumferentially-spaced flow openings therein. A related method of forming the nozzle center body by casting is also disclosed.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to gas turbine combustor technology and, more specifically, to the manufacture of an inlet flow conditioner integrated with a gas turbine combustor fuel nozzle. 
         [0002]    Inlet flow conditioners are used to remove both radial and circumferential variations in air flowing into a fuel nozzle. More specifically, the inlet flow conditioner reduces the large velocity and pressure gradients entering the fuel nozzle so that the air and gas fuel will mix in a uniform and predictable manner. If the air entering the fuel nozzle has substantial circumferential and radial flow variations, achieving the required precise fuel and air ratios becomes problematic. 
         [0003]    Not all combustor fuel nozzles utilize inlet flow conditioners. Many nozzles simply use an inlet Bell mouth configuration; however, when trying to achieve a very uniform inlet air stream in a combustor configuration where the fuel nozzles are densely-packed, a more complicated inlet flow conditioner arrangement becomes necessary. The typical inlet flow conditioner consists of a cylindrical tube containing many small round or oval holes, and several bell-mouth-shaped flow directors. These tightly-toleranced sheet metal components, which are very costly, create the potential for a large amount of variation in the air flow into the nozzle. A pressure drop is set up across the small holes in an effort to obtain a uniform flow of air into the downstream swirler. When a dimensional tolerance is specified on a small hole, however, the percentage of area variation is large when compared to the same tolerance applied to a large hole. 
         [0004]    Accordingly, it would be desirable to utilize a simpler, less-costly manufacturing technique for a fuel nozzle inlet flow conditioner that is also configured to yield less variation in the flow of air through the conditioner. 
       SUMMARY OF THE INVENTION 
       [0005]    In accordance with an exemplary but nonlimiting embodiment, the invention provides a nozzle center body comprising a unitary, one-piece elongated tubular member having a forward end formed with a radially outwardly extending mounting flange; an aft end formed with a plurality of radially outwardly extending swirler vanes; and, an intermediate region, located axially between the forward and aft ends, formed with an inlet flow conditioner including an annular plate provided with plural, circumferentially-spaced flow openings therein. 
         [0006]    In another exemplary but nonlimiting embodiment, there is provided an inlet flow conditioner for a gas turbine nozzle comprising an annular plate having a center opening adapted to receive a nozzle body; the annular plate comprising radially inner and radially outer rings connected by plural radially-extending struts, the radially inner and radially outer rings and the radially-extending struts defining plural air flow apertures, each having a peripheral edge shaped to provide predetermined air flow characteristics. 
         [0007]    In still another exemplary but nonlimiting embodiment, there is provided a method of forming a nozzle body comprising: casting a one-piece, unitary nozzle center body including an elongated tubular member having a forward end formed with a radially outwardly extending mounting flange; an aft end formed with a swirler comprised of a plurality of radially outwardly extending vanes; and, an intermediate region, located axially between the forward and aft ends, formed with an inlet flow conditioner including an annular plate provided with plural, circumferentially-spaced flow openings therein. 
         [0008]    The invention will now be described in greater detail in connection with the drawing figures identified below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a partial schematic cross section of a fuel nozzle fitted with an inlet flow conditioner; 
           [0010]      FIG. 2  is a perspective view of an inlet flow conditioner integrated with a fuel nozzle in accordance with an exemplary but nonlimiting embodiment of the invention; 
           [0011]      FIG. 3  is a cross section through the fuel nozzle shown in  FIG. 2  but with an outer support tube added; 
           [0012]      FIG. 4  is a partial end view illustrating an exemplary flow opening in an inlet flow conditioner in accordance with an exemplary aspect of the invention; 
           [0013]      FIG. 5  is a perspective view of an inlet flow conditioner in accordance with another exemplary but nonlimiting embodiment of the invention; 
           [0014]      FIG. 6  is a partial cross section taken along the line  6 - 6  of  FIG. 5 ; 
           [0015]      FIG. 7  is a partial cross section of an inlet flow conditioner in accordance with another exemplary embodiment of the invention; and 
           [0016]      FIG. 8  is a partial cross section of an inlet flow conditioner in accordance with still another exemplary embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]      FIG. 1  illustrates a gas turbine combustor nozzle  10  including a radially inner center body  12  and a radially outer support tube  14 . A mounting flange (not shown) is located at the forward end (i.e., to the left in  FIG. 1 ) of the nozzle and facilitates mounting the nozzle to the combustor. Fuel and air are supplied to the combustion chamber through plural passages indicated generally at  16  within the center body, exiting at the center body aft or outlet end  17  (i.e., to the right in  FIG. 1 ). An inlet flow conditioner  18  is secured to the outer nozzle support tube  14  at a location upstream of a swirler  20  where fuel is injected through apertures  22  in the hollow vanes  24  of the swirler into air that has passed through the conditioner  18 . The air and fuel mix within the annulus formed by the outer support tube  14  and the center body  12  and then burn once they enter the combustion chamber in a manner well understood by those skilled in the art. 
         [0018]    The inlet flow conditioner  18  is comprised of an outer sheet-metal tube or sleeve  26  provided with a plurality of apertures  28  about the circumference thereof, and a forward wall  30  also provided with an array of apertures  32 . Within the tube or sleeve  26 , there are two, concentrically-arranged, bell-mouth-shaped bodies  34 ,  36  which establish three separate paths for air entering the nozzle, indicated at P 1 , P 2  and P 3 . While the size and pattern of the various holes or apertures may be designed to establish a uniform flow of air past the swirler  20 , the manufacturing issues related to the formation and assembly of the flow conditioner  18  makes flow uniformity problematic. The resulting fabricated flow conditioner is very expensive due to its labor-intensive process which involves punching hundreds of holes, several forming and turning operations, complicated-splitting operations, welding operations and the inspections associated with these steps. 
         [0019]      FIGS. 2 and 3  illustrate a fuel nozzle with an integrated inlet flow conditioner in accordance with an exemplary but nonlimiting embodiment of the invention. Specifically, the nozzle  38  includes, generally, a fuel nozzle body  40  provided at a forward end with a fuel supply/mounting flange  42 . Downstream of the flange  42 , there is an inlet flow conditioner  44  and, downstream of the flow conditioner is a swirler  46 , adjacent or proximate the aft or outlet end portion  47  welded to the nozzle body (seen only in  FIG. 3 ). An outer support tube or sleeve  48  (see  FIG. 3 ) surrounds the nozzle body  40  and is engaged by the radially outer tip surfaces of the swirler  46  and the radially outer annular ring  50  of the inlet flow conditioner  44 . It will be appreciated that because the invention here relates to the flow conditioner configuration and to the manner in which the flow conditioner is formed, no further discussion is needed with respect to the remaining details of the nozzle body/nozzle construction. 
         [0020]    The inlet flow conditioner  44  is shown in  FIGS. 2 and 3  as a substantially planar annular plate comprised of the outer annular ring  50  already mentioned, and an inner annular ring  52  ( FIG. 2 ) connected by a series of radially-extending, circumferentially-spaced spokes or struts  54  which create an array of openings  56  about the circumference of the flow conditioner. 
         [0021]    A new method of manufacturing the inlet flow conditioner  44  in accordance with this invention takes advantage of the fact that the swirler  46 , located downstream of the inlet flow conditioner  44 , is made using an investment casting process. In accordance with the exemplary but nonlimiting embodiment disclosed herein, the inlet flow conditioner  44  may be manufactured with the other nozzle features, e.g., the swirler  46 , by forming each feature in the wax state and then joining them together (by e.g., wax welding or gluing) to form a single wax core. In this way, the entire component, including the center body  40 , mounting flange  42 , inlet flow conditioner  44  and swirler  46  may be cast as a single, unitary (one-piece) component. To produce the inlet flow conditioner feature concurrently with the other nozzle features in the wax state is a very inexpensive process, yet highly repeatable, which leads to highly-consistent and repeatable air flow results. Investment casting, while preferred, is not required and the individual components  42 ,  44  and  46  may be formed, for example, by machining, and then joined to the nozzle body  40  using a welding or brazing operation. If machined, the inner annular ring  52  would define a center opening for receiving the nozzle body  40 . 
         [0022]    It is also possible with investment casting (or machining) to vary the sizes and shapes of the openings  56  around the perimeter of the inlet flow conditioner  44 . With reference to  FIG. 4 , for example, the openings  56  as defined by inner and outer rings  50 ,  52  and radial struts  54 , may have an edge contoured to provide the desired airflow characteristics.  FIG. 4  merely illustrates that fairly complex profiles, as defined by an aperture peripheral edge  58 , can be easily cast in place at little comparative expense, providing, for example, differential flow characteristics in both radial and circumferential direction. 
         [0023]      FIGS. 5 and 6  illustrate a non-planar inlet flow conditioner  60  in accordance with another exemplary but nonlimiting embodiment. Here, the inner and outer rings  62 ,  64  are axially offset so that the radial struts  66  extend at an acute angle to the axis A of the nozzle body. A series of concentrically-arranged, axially offset rings  68 ,  70  and  72  supported by the struts  66 , create an array of flow openings  74  that, in addition to being non co-planar, increase in size from their radially inner ends to their radially outer ends, thus creating a unique air flow pattern upstream of the swirler. 
         [0024]      FIG. 7  illustrates a generally similar inlet flow conditioner  76  but in this variant, the series of concentric rings  78 ,  80  and  82  are curved to match the inflow of air and extend in an upstream direction beyond the radially inner and outer rings  84 ,  86  and beyond the radial struts  88 . 
         [0025]      FIG. 8  illustrates yet another exemplary embodiment of a flow conditioner  90  where the radial struts  92  are more upright, but still slightly sloped, and where the concentric rings  94 ,  96  and  98  have a shorter length in the upstream direction, and differential degrees of curvature. 
         [0026]    It will thus be appreciated that the inlet flow conditioner as described herein may take on any of several suitable configurations that are amenable to a simplified manufacturing process, and that provide the ability to tune the openings in the conditioner to achieve air flow characteristics that, in turn, produce the desired uniformity in the fuel/air mixture in the nozzle. 
         [0027]    While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.