Abstract:
A turbomachine diffuser includes a body having an inner surface defining a diffuser flow path, a plurality of stationary struts extending from the inner surface, and a plurality of flow mixing lobes arranged in an annular array on the inner surface. The plurality of flow mixing lobes is configured and disposed to guide a substantially high momentum flow toward the inner surface of the body.

Description:
BACKGROUND 
       [0001]    The subject matter disclosed herein relates to the art of turbomachines and, more particularly, to a turbomachine diffuser including flow mixing lobes. 
         [0002]    Gas turbomachines typically include a compressor portion, a turbine portion, and a combustor assembly. The combustor assembly mixes fluid from the compressor portion with a fuel to form a combustible mixture. The combustible mixture is combusted forming hot gases that pass along a hot gas path of the turbine portion. The turbine portion includes a number of stages having airfoils mounted to rotors that convert thermal energy from the hot gases into mechanical, rotational energy. Additional fluid from the compressor is passed through the airfoils and other sections of the turbine portion for cooling purposes. Hot gases pass, as exhaust gases, from the turbine portion into an exhaust diffuser. The exhaust diffuser is geometrically configured to rapidly decrease the kinetic energy of flow and increase static pressure recovery within the exhaust diffuser. The exhaust diffuser typically includes one or more stationary struts for mechanical support. The exhaust gases may pass from the exhaust diffuser to a downstream component. 
       BRIEF DESCRIPTION 
       [0003]    According to one aspect of an exemplary embodiment, a turbomachine diffuser includes a body having an inner surface defining a diffuser flow path, a plurality of stationary struts extending from the inner surface, and a plurality of flow mixing lobes arranged in an annular array on the inner surface. The plurality of flow mixing lobes is configured and disposed to guide a substantially high momentum flow toward the inner surface of the body. 
         [0004]    According to another aspect of an exemplary embodiment, a turbomachine includes a compressor portion, and a turbine portion operatively connected to the compressor portion. The turbine portion includes an outlet. A combustor assembly including, at least one combustor, is fluidically connected to the compressor portion and the turbine portion. A diffuser is fluidically connected to the outlet of the turbine portion. The diffuser includes a body having an inner surface defining a diffuser flow path, a plurality of stationary struts extending from the inner surface, and a plurality of flow mixing lobes arranged in an annular array on the inner surface. The plurality of flow mixing lobes is configured and disposed to guide a substantially high momentum flow toward the inner surface of the body. 
         [0005]    According to yet another aspect of an exemplary embodiment, a method of passing exhaust gases from a turbomachine into a diffuser includes passing hot gases toward an outlet of a turbine portion of the turbomachine, delivering the hot gases into an inlet of the diffuser, directing a portion of the hot gases toward a plurality of flow mixing lobes arranged circumferentially about an inner surface of the diffuser, forming the portion of the hot gases into a substantially high momentum flow, guiding the substantially high momentum flow toward the inner surface of the diffuser, and mixing the substantially high momentum flow with a boundary layer flow passing along the inner surface. 
         [0006]    These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0007]    The subject matter, which is regarded as the present disclosure, 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 present disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0008]      FIG. 1  depicts a schematic view of a turbomachine system including an exhaust diffuser having flow mixing lobes, in accordance with an exemplary embodiment; 
           [0009]      FIG. 2  depicts a partial cross-sectional side view of the diffuser of  FIG. 1 ; 
           [0010]      FIG. 3  depicts a flow mixing lobe mounted to an inner surface of the diffuser of  FIG. 1 ; 
           [0011]      FIG. 4  depicts a perspective view of the flow mixing lobe of  FIG. 3 ; 
           [0012]      FIG. 5  depicts a flow mixing lobe, in accordance with another aspect of an exemplary embodiment; 
           [0013]      FIG. 6  depicts a flow mixing lobe, in accordance with yet another aspect of an exemplary embodiment; 
           [0014]      FIG. 7  depicts a flow mixing lobe, in accordance with still yet another aspect of an exemplary embodiment 
           [0015]      FIG. 8  depicts a flow mixing lobe, in accordance with yet still another aspect of an exemplary embodiment; 
           [0016]      FIG. 9  depicts a cross-sectional view of a flow mixing lobe including an airfoil portion, in accordance with an aspect of an exemplary embodiment; and 
           [0017]      FIG. 10  depicts a cross-sectional view of a flow mixing lobe including an airfoil portion, in accordance with another aspect of an exemplary embodiment. 
       
    
    
       [0018]    The detailed description explains embodiments of the present disclosure, together with advantages and features, by way of example with reference to the drawings. 
       DETAILED DESCRIPTION 
       [0019]    A turbomachine system, in accordance with an exemplary embodiment, is indicated generally at  2 , in  FIG. 1 . Turbomachine system  2  includes a turbomachine  4  having a compressor portion  6  operatively connected to a turbine portion  8  through a common compressor/turbine shaft  10 . A combustor assembly  12  is fluidically connected between compressor portion  6  and turbine portion  8 . Combustor assembly  12  includes at least one combustor  14  that directs products of combustion along a hot gas path (also not separately labeled) of turbine portion  8 . An intake system  20  is fluidically connected to an inlet (not separately labeled) of compressor portion  6 . A load  22  is mechanically linked to turbomachine  4 . 
         [0020]    In operation, air is passed through intake system  20  into compressor portion  6 . Intake system  20  may condition the air by, for example, lowering humidity, altering temperature, and the like. The air is compressed through multiple stages of compressor portion  6  and passed to turbine portion  8  and combustor assembly  12 . The air is mixed with fuel, diluents, and the like, in combustor  14  to form a combustible mixture. The combustible mixture is passed from combustor  14  into turbine portion  8  via a transition piece (not shown) as hot gases. The hot gases flow along the hot gas path of turbine portion  8  and pass as exhaust into an exhaust diffuser  30 . Exhaust diffuser  30  is geometrically configured to rapidly decrease kinetic energy of exhaust gases as well as increase static pressure recovery prior to delivery to a downstream device (not shown). The downstream device may direct the exhaust gases to ambient, or extract additional energy that may be used for other purposes. 
         [0021]    As shown in  FIG. 2 , exhaust diffuser  30  includes a body  40  having an outer surface  41  and an inner surface  42  that defines a diffuser flow path  44 . Exhaust diffuser  30  includes an inlet  46  fluidically coupled to an outlet (not separately labeled) of turbine portion  8  and an outlet  47 . Exhaust diffuser  30  is also shown to include a plurality of stationary struts, one of which is indicated at  50 , extending radially inwardly to diffuser flow path  44  from inner surface  42 . Stationary struts  50  condition exhaust gases flowing along diffuser flow path  44  toward outlet  47 . 
         [0022]    In accordance with an exemplary embodiment, exhaust diffuser  30  includes a plurality of flow mixing lobes, one of which is indicated at  54 , mounted to inner surface  42 . In accordance with an aspect of an exemplary embodiment, flow mixing lobes  54  may be arranged downstream of inlet  46  a distance between about 0.05 times a last stage blade height and about 10 times the last stage blade height. In an exemplary aspect shown, flow mixing lobes  54  may be arranged downstream of inlet  46  and upstream of struts  50 . In accordance with another aspect of an exemplary embodiment, flow mixing lobes  54  may be arranged about 2-inches (5.08-cm) downstream of inlet  46 . In accordance with yet another aspect of an exemplary embodiment, flow mixing lobes  54  may be arranged about 1.50-inches (3.81-cm) downstream of inlet  46 . Of course, it should be understood that the position of flow mixing lobes  54  may vary. Further, it should be understood that flow mixing lobes may be arranged downstream of struts  50 . 
         [0023]    As shown in  FIGS. 3 and 4 , flow mixing lobes  54  include a first lobe member  60  and a second lobe member  61 . Each lobe member  60  and  61  extends substantially perpendicularly outwardly from inner surface  42 . First lobe member  60  includes a first base section  64  and second lobe member  61  includes a second base section  65 . First base section  64  projects outwardly of first lobe member  60  in a first direction and second base section  65  projects outwardly of second lobe member  61  in a second direction that is opposite the first direction. First and second base sections  64  and  65  provide an attachment interface between respective ones of first and second lobe members  60  and  61  and inner surface  42 . 
         [0024]    In further accordance with an exemplary embodiment, flow mixing lobes  54  include an airfoil portion  70  extending between first and second lobe member  60  and  61 . Airfoil portion  70  is spaced from first and second base sections  64  and  65  such that, when attached to inner surface  42 , a channel  74  is formed. Channel  74  receives a portion of exhaust gases passing from turbine portion  8 . In accordance with an aspect of an exemplary embodiment, channel  74  guides a portion of a high momentum flow passing from turbine portion  6  radially outwardly toward inner surface  42 . More specifically, airfoil portion  70  directs the portion of the substantially high momentum flow radially outwardly toward inner surface  42  thereby generating flow vortices. The flow vortices reduce boundary layer growth at inner surface  42  resulting in a reduction in flow separation. The exemplary embodiments thus improve pressure recovery in exhaust diffuser  30  that leads to an enhancement in overall system efficiency. At this point, it should be understood that the term “substantially high momentum flow” describes a flow having a velocity of about 1000 ft/sec (about 305 m/s) or greater. 
         [0025]      FIG. 5  depicts a flow mixing lobe  90  in accordance with another aspect of an exemplary embodiment. Flow mixing lobe  90  includes first and second lobe portions  92  and  93  joined through an airfoil portion  94 . Each lobe portion  92  and  93  includes a corresponding terminal end portion  96  and  97  that directly interfaces with inner surface  42  of exhaust diffuser  30 .  FIG. 6  depicts a flow mixing lobe  100  including first and second lobe members  102  and  103  joined by an airfoil portion  105 . In the exemplary aspect shown, first and second lobe members  102  and  103  include corresponding terminal end portions  107  and  108  that are angled inwardly toward each other. 
         [0026]      FIG. 7  depicts a flow mixing lobe  110  including first and second lobe members  112  and  113  joined by an airfoil portion  115 . In the exemplary aspect shown, first and second lobe members  112  and  113  including corresponding terminal end portions  117  and  118  that are angled outwardly away from one another.  FIG. 8  depicts a flow mixing lobe  120  having first and second lobe members  122  and  123  joined by an airfoil portion  124 . In the exemplary aspect shown, airfoil portion  124  includes first and second airfoil members  128  and  129  that extend at an angle from corresponding ones of first and second lobe members  122  and  123  and are joined at an angled portion  130 .  FIG. 9  depicts a flow mixing lobe  140  including an airfoil portion  142  having a generally rectangular cross-section (not separately labeled).  FIG. 10  depicts a flow mixing lobe  150  including an airfoil portion  152  having a curvilinear cross-section (also not separately labeled). 
         [0027]    The Applicant respectfully submits that the term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. For example, “about” can include a range of ±8% or 5%, or 2% of a given value. 
         [0028]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the exemplary embodiment. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one more other features, integers, steps, operations, element components, and/or groups thereof. 
         [0029]    While the present disclosure has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the present disclosure is not limited to such disclosed embodiments. Rather, the present disclosure 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 present disclosure. Additionally, while various embodiments of the present disclosure have been described, it is to be understood that aspects of the present disclosure may include only some of the described embodiments. Accordingly, the present disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.