Abstract:
A diffuser having fluidic actuation therein includes a diffuser inlet and an inner barrel extending from proximate the diffuser inlet in a direction relatively downstream of the diffuser inlet. The diffuser also includes an actuating opening in the inner barrel proximate the diffuser inlet. The diffuser further includes a suction opening in the inner barrel located downstream of the actuating opening. The diffuser yet further includes a flow manipulator disposed substantially within the inner barrel.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to turbines and, in particular, to diffusers for use with gas turbines and steam turbines. 
         [0002]    Typical gas turbines include a diffuser cone, or diffuser, coupled to a last stage bucket of a rotor. The diffuser serves, generally, to increase static pressure of exhaust gas by decreasing the kinetic energy of the exhaust gas. Generally, this may be achieved by increasing the cross-sectional area of the diffuser in the direction of exhaust gas flow. 
         [0003]    Often, gas turbines are not operated at full load, but are designed for efficiency under such a full load. Therefore, part load performance efficiency is sacrificed, based on the full load design. Such inefficiencies are due, at least in part, to flow separation on a diffuser inner barrel, leading to tip strong flow profiles. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    According to one aspect of the invention, a diffuser having fluidic actuation therein includes a diffuser inlet and an inner barrel extending from proximate the diffuser inlet in a direction relatively downstream of the diffuser inlet. The diffuser also includes an actuating opening in the inner barrel proximate the diffuser inlet. The diffuser further includes a suction opening in the inner barrel located downstream of the actuating opening. The diffuser yet further includes a flow manipulator disposed substantially within the inner barrel. 
         [0005]    According to another aspect of the invention, a diffuser for a gas turbine includes a diffuser inlet, a diffuser outlet, and an outer wall extending from proximate the diffuser inlet to proximate the diffuser outlet. The diffuser also includes an inner barrel having at least one actuating opening and at least one suction opening. The diffuser further includes a flow manipulator disposed substantially within the inner barrel. 
         [0006]    According to yet another aspect of the invention, a gas turbine includes a turbine casing that surrounds a portion of the gas turbine. The gas turbine also includes a diffuser coupled to the turbine casing. The diffuser includes a diffuser inlet, an inner barrel having an actuating opening and a suction opening, and a flow manipulator disposed substantially within the inner barrel. 
         [0007]    These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0008]    The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0009]      FIG. 1  is a side, cross-sectional view of a diffuser according to one aspect of the invention; 
           [0010]      FIG. 2  is a partial side, cross sectional view of the diffuser of  FIG. 1 ; 
           [0011]      FIG. 3  illustrates a diffuser flow profile associated with the diffuser illustrated in  FIG. 1 ; and 
           [0012]      FIG. 4  illustrates a diffuser flow profile exhibiting tip strong flow. 
           [0013]    The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]      FIGS. 1 and 2  illustrate one aspect of a diffuser  100  according to one embodiment of the present invention. In operation, exhaust gas from the gas turbine flows through the diffuser  100  in the direction shown by arrow A. In this description, an object is “downstream” of another object or location if it is displaced from it in the direction of arrow A and is “upstream” if it is displaced from it in a direction opposite of arrow A. 
         [0015]    The diffuser  100  includes an inner barrel  102  having an inner wall  104  that forms an inner chamber  108 . The diffuser  100  also has an inlet  111  located proximate a diffuser entry end  110  and an outlet  120  located proximate a diffuser exit end  122 . The inlet  111  is capable of being coupled to a turbine, while the outlet  120  is capable of being coupled to an adjacent object, such as a silencer. The diffuser  100  also includes an outer wall  106  radially spaced from the inner wall  104  of the inner barrel  102 . The area between the inner wall  104  and the outer wall  106  allows fluid or gas to flow downstream therethrough from the inlet  111  to the outlet  120  of the diffuser  100 . 
         [0016]    The diffuser  100  also includes one or more struts  116  formed between the inner wall  104  and the outer wall  106 . The strut  116  serves to hold the inner wall  104  and the outer wall  106  in a fixed relationship to one another. The number of struts  116  is variable and commonly ranges from about four to about ten. 
         [0017]    The inner wall  104  of the inner barrel  102  extends from the diffuser inlet  111 , or diffuser entry end  110 , in a downstream direction toward the diffuser outlet  120 , or diffuser exit end  122 . The inner barrel  102 , and hence the inner wall  104 , includes a first end  124  located proximate the diffuser inlet  111  and a second end  126  located downstream toward the diffuser outlet  120  and takes on numerous longitudinal contours as the inner barrel  102  extends from the first end  124  to the second end  126 . The inner barrel  102  may slightly curve continuously from the first end  124  to the second end  126 , may curve slightly for only portions between the first end  124  and the second end  126 , may extend in a substantially straight direction, or may comprise segmented portions, where the overall longitudinal direction of the inner barrel  102  comprises any combination of the curvilinear paths described above. Irrespective of the shape of the inner barrel  102 , and more particularly the inner wall  104 , the inner barrel  102  and inner wall  104  extend toward the diffuser outlet  120 , or diffuser exit  122 , and it is conceivable that the inner barrel  102  and inner wall  104  extend completely to the diffuser outlet  120 . 
         [0018]    The inner wall  104  of the inner barrel  102  includes one or more actuator openings  130 . The inner wall  104  of the inner barrel  102  also includes one or more suction openings  132  that are located downstream of the one or more actuator openings  130 . Both the actuator opening  130  and the suction opening  132  may vary in size and shape and may be modified for the application. 
         [0019]    Disposed within the inner barrel  102  is a flow manipulating device  134  that may take the form of a pump capable of displacing fluid or gas flow that is captured through the suction opening  132 . Typically, weak flow through the diffuser  100  occurs proximate the inner barrel  102 , leading to what is characterized as “tip strong” flow, thereby creating system inefficiency. The suction opening  132  allows the common weak flow that passes directly over the inner wall  104  to enter the inner barrel  102  and enter an intake port  136  of the flow manipulating device  134  and is subsequently expelled out of a discharge port  138  of the flow manipulating device  134  with sufficient force to exit the actuating opening  130  in a manner that manipulates the flow profile of the diffuser  100 . The manipulation of flow reduces flow separation, thereby increasing diffusion area. The direction of airflow within the inner barrel  102  from a downstream location to an upstream location is illustrated by arrow  140 . Although it is envisioned that one flow manipulating device  134  will be sufficient to displace the flow, it is conceivable that a plurality of flow manipulating devices  134  may be employed within the inner barrel  102  to work in conjunction to provide the aforementioned desired function. 
         [0020]    As previously described, there may be a plurality of actuator openings  130  and/or suction openings  132 , but regardless of the number of each type of opening  130 ,  132 , the suction opening  132  is located downstream of the actuator opening  130 . The actuator opening  130  is typically located relatively adjacent the diffuser inlet  111  in order to reduce flow separation early on (i.e., substantially upstream) in the diffuser flow process. It is conceivable that the actuator opening  130  is located at an upstream location relative to one of the struts  116 , while the suction opening  132  is located downstream relative to one of the struts  116 . Additionally, in the case of multiple actuator openings  130  and suction openings  132 , the spacing of each respective group may vary, but in any event, the group of actuator openings  130  will typically be located upstream of the discharge port  138 , while the group of suction openings  132  will typically be located downstream of the intake port  136 . 
         [0021]      FIG. 3  shows a flow path profile in diffuser  100  shown in  FIG. 1 . As can be seen, the flow profile for the diffuser  100  of  FIG. 1  is strong throughout a large portion of the radial area of the diffuser  100 , even along the inner wall  104 . The diffuser  100  reduces flow separation, thereby improving diffuser performance over a diffuser flow profile exhibiting flow separation, as shown in  FIG. 4 .  FIGS. 3 and 4  represent what is characterized as “weak flow” by  150 , while what is characterized by healthy, efficient “strong flow” is represented by  160 . 
         [0022]    Advantageously, diffuser  100  reduces flow separation within the diffuser  100 , particularly during part load performance of the overall system, by energizing the weak flow boundary layer that is typically present along the inner barrel  102 . By providing the flow manipulating device  134 , such as a pump, weak flow may be taken from a downstream aft location and injected at an upstream location to improvingly modify the flow profile of the diffuser  100 . The result is significant improvement in diffuser performance. 
         [0023]    While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.