Abstract:
A venturi device for a turbine combustor includes a substantially annular outer liner; a substantially annular inner liner; a venturi channel located between the substantially annular outer and inner liners; the substantially annular outer and inner liners being substantially V-shaped in axial cross-section, thereby defining a throat region; the substantially annular outer liner formed with an array of impingement holes and the substantially annular inner liner formed with a plurality of vortex generators facing the substantially annular outer liner.

Description:
RELATED APPLICATION 
       [0001]    This application claims priority from Russian Application Serial No. 2010-107420, filed Mar. 2, 2010, which is hereby incorporated by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    This invention relates to gas turbine combustor technology and, more specifically, to a novel combustor venturi with improved cooling. 
         [0003]    It is known to achieve a significant reduction in NO x  emissions from a combustion turbine without aggravating ignition, unburnt hydrocarbon or carbon monoxide emission problems, by utilizing first and second combustion chambers or stages interconnected by a throat region. See for example, commonly-owned U.S. Pat. No. 4,292,801. 
         [0004]    In the more recent commonly-owned U.S. Pat. No. 5,127,221, there is disclosed a method and apparatus for creating a plenum about the throat region and cooling the throat wall sections utilizing compressor air flowing in an annular passage between the combustor liner and a surrounding casing or flow sleeve. 
         [0005]    In U.S. Pat. No. 6,427,446, there is disclosed a technique for cooling the throat wall by impingement cooling, again using cooling air flowing in a passage between the combustor liner and a surrounding flow sleeve. 
         [0006]    There remains a need for a venturi cooling system that achieves even greater cooling effectiveness. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0007]    In a first exemplary but nonlimiting embodiment, there is provided a venturi device for a turbine combustor comprising a substantially annular outer liner; a substantially annular inner liner; a venturi channel located between the substantially annular outer and inner liners; the substantially annular outer and inner liners being substantially V-shaped in axial cross-section, thereby defining a throat region; the substantially annular outer liner formed with an array of impingement cooling holes and said substantially annular inner liner formed with a plurality of vortex generators facing the substantially annular outer liner and the array of impingement cooling holes. 
         [0008]    In another exemplary but nonlimiting embodiment, there is provided venturi device for a turbine combustor comprising a substantially annular outer liner; a substantially annular inner liner; a venturi channel located between the substantially annular outer and inner liners; the substantially annular outer and inner liners being substantially V-shaped in axial cross-section, thereby defining a throat region; the substantially annular outer liner formed with an array of impingement cooling holes; and said substantially annular inner liner formed with a plurality of vortex generators facing the array of impingement cooling holes, and a plurality of upstanding fins in the throat region, extending radially outwardly into the venturi channel toward said substantially annular outer liner. 
         [0009]    In still another exemplary but nonlimiting embodiment, there is provided a turbine combustor comprised of a radially inner liner and a radially outer flow sleeve, the radially inner liner parallel with a venturi comprising a venturi device for a turbine combustor comprising a substantially annular outer liner; a substantially annular inner liner; a venturi channel located between said substantially annular outer and inner lines; said substantially annular outer and inner liners being substantially V-shaped in axial cross-section, thereby defining a throat region; said substantially annular outer liner formed with an array of impingement cooling holes; wherein said substantially annular inner and outer V-shaped liners form a plenum chamber closed by another annular member, said outer annular member having one or more apertures therein adapted to supply cooling air to said plenum chamber, and further wherein said venturi channel is open at opposite ends of said venturi channel such that cooling air entering the venturi channel through the one or more apertures flows in opposite directions at said throat region. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a side elevation view in cross section showing a prior art combustor incorporating a venturi cooled by impingement cooling; 
           [0011]      FIG. 2  is a partial cross-section of a combustor venturi in accordance with a exemplary but non-limiting embodiment of the invention; 
           [0012]      FIG. 3  is a perspective view of the venturi cross section shown in  FIG. 2 ; and 
           [0013]      FIG. 4  is another perspective view of the venturi cross section shown in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    Referring to  FIG. 1 , a prior venturi (or throat region) cooling system is illustrated. The venturi  10  is located axially between first and second combustion chamber regions  12 ,  14  defined by a combustor liner  16 . The venturi is comprised of a radially outer wall  18  and a radially inner wall  20 , with a cooling flow passage or channel  22  therebetween. The combustor liner  16  extends downstream and beyond the venturi  10  where typically it is joined to a transition piece or duct (not shown) that supplies the hot combustion gases to the turbine first stage. The combustor liner  16  extends upstream to a combustor end cover  24  that supports the nozzles  26 ,  28  projecting into the combustion chamber. An annular plenum  30  is formed by the liner  16  and the venturi  10 , such that the plenum surrounds the venturi and, via one or more apertures  32  spaced about the liner  16 , supplies cooling air to the venturi plenum  30 . More specifically, cooling air supplied to the plenum  30  flows into the passage or channel  22  through an array of impingement cooling holes  34  in both the converging portion  36  and diverging portion  38  of the outer venturi wall  18 . Channel  20  is closed at its upstream end and opens at its downstream end  40 . The cooling air exits the venturi channel via the downstream open end  40  where it joins the combustion gases flowing away from the combustion chamber toward the first stage of the turbine. 
         [0015]    Turning now to  FIGS. 2-4 , a venturi  42  is illustrated in accordance with an exemplary but nonlimiting embodiment of the invention. The venturi  42  is formed in part by the combustor liner  44 , and includes an inner liner wall  46  and an outer liner wall  48 , with a venturi flow passage or channel  50  therebetween. The inner liner wall  46  is formed with a converging portion  52  and a diverging portion  54  (relative to a left-to-right combustion gas flow direction) and, similarly, the outer liner wall  48  is formed with corresponding converging and diverging portions  56 ,  58  respectively, thus defining a narrowed venturi throat region  60 . Note that the flow passage or channel  50  is open at both the upstream end  62  and the downstream end  64 . 
         [0016]    An annular combustor wall portion  66  surrounds the venturi  42 , forming an annular plenum chamber  68 . In the exemplary embodiment, cooling air is supplied to the plenum chamber  68  via a plurality of cooling bushings or thimbles  70 . Unlike the above-described prior arrangement, however, the cooling air is supplied directly from the CDC extraction air rather than from the flow in the annular passage  72  between the combustor liner  44  and surrounding flow sleeve  74 . The CDC extraction air is not only cooler than the flow in the annular passage  72  between the combustor liner and the flow sleeve, but it is also at a higher pressure resulting in more effective impingement cooling of the inner venturi wall  80 ,  82 . 
         [0017]    More specifically, the cooling air in the plenum chamber  68  is supplied to the passage or channel  50  via an annular array of circumferentially spaced impingement cooling holes  76  provided in both the converging and diverging portions  56 ,  58  of the outer liner wall  48 . 
         [0018]    The inner liner wall  46  is formed with an annular array of axially-spaced annular vortex generator ribs (or turbulators)  78  on both the converging and diverging (or fore and aft) surfaces  80 ,  82  of the inner liner wall. The ribs  78  are staggered axially relative to the annular rows of impingement holes  76 . In other words, the ribs  78  are located between adjacent rows of impingement holes  76  and the respective pitches of the holes and ribs are maintained about the venturi. This arrangement produces a complex interaction between air jets, secondary flows, the annular turbulators and spent cooling air, providing benefits such as intense mixing of cooling air in the annular passage or channel  50 ; significantly reduced impact of cross-flows on air jets; and effective destruction of the boundary layer along the surfaces  80 ,  82 . Different rib cross-sectional shapes may be employed so long as heat transfer is increased and so long as the pitch alignment with the rows of impingement cooling holes  76  is maintained. 
         [0019]    At the venturi throat or throat region  60 , the inner liner wall  46  is formed (or provided) with axially extending fins  84 , spaced annularly about the throat  60 , and extending along both the converging and diverging portions  52 ,  54  of the inner liner wall  46 . These fins, in side elevation, may have a V or chevron shape and greatly enhance cooling at the throat. 
         [0020]    In addition, an array of film cooling holes  86  (best seen in  FIGS. 3 and 4 ) may be provided in the radially inner liner, upstream of the fins  84 , and, for example, between adjacent turbulators or ribs  78 , and adjacent the throat region  60 . The film cooling holes provide local film cooling flow along the inner surface of the converging portion  52  of the inner liner wall  46  proximate and upstream of the throat  60 . 
         [0021]    In use, the air supplied to the flow passage  50  flows in opposite directions, exiting the passage  50  at both the upstream and downstream ends  62 ,  64 , respectively. Note in this regard that the wall profile at downstream end  64  is turned at the “bull nose” configuration (or bull nose curve)  88  to re-direct the exiting cooling air in an upstream direction, i.e., the same direction as air exiting the upstream end  62 . Note that some of the impingement cooling holes  76  are directed generally at the bull nose curve to ensure adequate cooling at the turn. 
         [0022]    In addition, the dual-direction flow at the throat substantially eliminates cross-flow at the throat edge internal surface which is essential for local cooling efficiency. 
         [0023]    This venturi configuration arrangement permits fine tuning of the cooling effectiveness of the venturi to enable the possibility of having variable cooling effectiveness in different areas of the system; optimal cooling of the venturi throat; and reduced impact of cross-flow on the air jets in the venturi throat region. 
         [0024]    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.