Abstract:
An industrial turbine engine comprises a combustion section, an air discharge section downstream of the combustion section, a transition region between the combustion and air discharge section, a combustion transition piece and a sleeve. The transition piece defines an interior space for combusted gas flow. The sleeve surrounds the combustor transition piece so as to form a flow annulus between the sleeve and the transition piece. The sleeve includes a first set of apertures for directing cooling air from compressor discharge air into the flow annulus. The transition piece includes an outer surface bounding the flow annulus and an inner surface bounding the interior surface, and includes a second set of apertures for directing cooling air in the flow annulus to the interior space. Each of the second set of apertures extends from an entry portion on the outer surface to an exit portion on the inner surface.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to means of cooling components of a gas turbine, and more particularly, to the cooling of a one-piece can combustor by a combination of convection cooling and effusion cooling. 
         [0003]    2. Description of the Related Art 
         [0004]    A gas turbine can operate with great efficiency if the turbine inlet temperature can be raised to a maximum. However, the combustion chamber, from which combusted gas originates before entering the turbine inlet, reaches operating temperatures well over 1500° F. and even most advanced alloys cannot withstand such temperatures for extended periods of use. Thus, the performance and longevity of a turbine is highly dependent on the degree of cooling that can be provided to the turbine components which are exposed to extreme heating conditions. 
         [0005]    The general concept of using compressor discharge air to cool turbine components is known in the art. However, developments and variations in turbine designs are not necessarily accompanied by specific structures that are implemented with cooling mechanisms for the turbine components. Thus, there is a need to embody cooling mechanisms into newly developed turbine designs. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0006]    Accordingly, it is an aspect of the present invention to enhance conventional gas turbines. 
         [0007]    To achieve the foregoing and other aspects and in accordance with the present invention, an industrial turbine engine is provided that comprises a combustion section, an air discharge section downstream of the combustion section, a transition region between the combustion and air discharge section, a combustor transition piece defining the combustion section and transition region, and a sleeve. Said transition piece is adapted to carry combusted gas flow to a first stage of the turbine corresponding to the air discharge section. The transition piece defines an interior space for combusted gas flow. The sleeve surrounds the combustor transition piece so as to form a flow annulus between the sleeve and the transition piece. Said sleeve includes a first set of apertures for directing cooling air from compressor discharge air into the flow annulus. The transition piece includes an outer surface bounding the flow annulus and an inner surface bounding the interior surface. The transition piece includes a second set of apertures for directing cooling air in the flow annulus to the interior space. Each of the second set of apertures extends from an entry portion on the outer surface to an exit portion on the inner surface. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The foregoing and other aspects of the present invention will become apparent to those skilled in the art to which the present invention relates upon reading the following description with reference to the accompanying drawings, in which: 
           [0009]      FIG. 1  shows an example embodiment of a one-piece can combustor in which the present invention can be implemented. 
           [0010]      FIG. 2  shows a close-up, perspective view of a sleeve with cooling air entry holes surrounding a transition piece with effusion holes. 
           [0011]      FIG. 3  shows a cross-sectional view across the cooling air entry holes of the sleeve and effusion holes of the transition piece. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    Example embodiments that incorporate one or more aspects of the present invention are described and illustrated in the drawings. These illustrated examples are not intended to be a limitation on the present invention. For example, one or more aspects of the present invention can be utilized in other embodiments and even other types of devices. 
         [0013]      FIG. 1  shows an embodiment of a single piece combustor  10  in which the present invention can be implemented. This example embodiment is a can-annular reverse-flow combustor  10  although the invention is applicable to other types of combustors. The combustor  10  generates gases needed to drive the rotary motion of a turbine by combusting air and fuel within a confined space and discharging the resulting combustion gases through a stationary row of vanes. In operation, discharge air from a compressor reverses direction as it passes over the outside of the combustors  10  and again enters the combustor  10  en route to the turbine. Compressed air and fuel are burned in the combustion chamber. The combustion gases flow at high velocity into a turbine section via a transition piece  120 . As discharge air flows over the outside surface of the transition piece  120 , it provides convective cooling to the combustor components. 
         [0014]    In  FIG. 1 , a transition piece  120  transitions directly from a circular combustor head-end  100  to a turbine annulus sector  102  (corresponding to the first stage of the turbine indicated at 16) with a single piece. The single piece transition piece  120  may be formed from two halves or several components welded or joined together for ease of assembly or manufacture. A sleeve  129  also transitions directly from the circular combustor head-end  100  to an aft frame  128  of the transition piece  120  with a single piece. The single piece sleeve  129  may be formed from two halves and welded or joined together for ease of assembly. The joint between the sleeve  129  and the aft frame  128  forms a substantially closed end to a cooling annulus  124 . It should be noted that “single” also means multiple pieces joined together wherein the joining is by any appropriate means to join elements, and/or unitary, and/or one-piece, and the like. 
         [0015]    In  FIG. 1 , there is an annular flow of the discharge air that is convectively processed over the outside surface of the transition piece  120 . In the example embodiment, the discharge air flows through the sleeve  129  which forms an annular gap so that the flow velocities can be sufficiently high to produce high heat transfer coefficients. The sleeve  129  surrounds the transition piece  120  forming a flow annulus  124  therebetween. As indicated by arrows, cross flow cooling air traveling in the annulus  124  continues to flow upstream in a direction perpendicular to cooling air flowing through holes, slots, openings or other apertures  400  formed about the circumference of the sleeve  129 . The sleeve  129  has a series of holes, slots, openings or other apertures  400  that allow the discharge air to move into the sleeve  129  at velocities that properly balance the competing requirements of high heat transfer and low pressure drop. A circled area of the transition piece  120  will be discussed in more detail in  FIGS. 2-3 . 
         [0016]    In conventional combustors, a combustor liner and a flow sleeve are generally found upstream of the transition piece and the sleeve respectively. However, in the one-piece can combustor of  FIG. 1 , the combustor liner and the flow sleeve have been eliminated in order to provide a combustor of shorter length. The major components in a one-piece can combustor include a circular cap  134 , an end cover  136  supporting a plurality of fuel nozzles  138 , the transition piece  120  and sleeve  129 . 
         [0017]      FIG. 2  shows a close-up, perspective view of the transition piece  120  and the sleeve  129 . The sleeve  129  is radially outward with respect to the transition piece  120  and surrounds the transition piece  120  forming the flow annulus  124  in between. The sleeve  129  is formed with a plurality of first apertures or holes  400  to allow compressor discharge air to enter the flow annulus  124  from the exterior space  302 . The single-piece transition piece  120  is formed with a plurality of second apertures or effusion holes  200 . It must be noted that  FIG. 2  shows one example arrangement of the first and second apertures  200 ,  400  which is not to be construed as a limitation on the invention. The formation of the apertures  200 ,  400  may be at or extend to other selected areas or over the entire surface of the transition piece  120  and the sleeve  129  respectively. The apertures  200 ,  400  may be formed in a circumferentially dispersed manner or may extend from an upstream portion to a downstream portion of the transition piece  120  and the sleeve  129  respectively. Moreover,  FIG. 2  shows only one of multiple possible arrangements in which the plurality of apertures  200 ,  400  can be patterned. For example,  FIG. 2  shows the second apertures  200  in orthogonal arrangement about one another. In another example, each second aperture  200  in a row may be slightly offset relative to second apertures in an adjacent row. The first apertures  400  are also arranged in rows and columns but the spacing between the first apertures  400  may differ in a row direction relative a column direction. The spacing between the first apertures  400  may also differ from the second apertures  200  as shown in  FIG. 3  in part due to the difference in their sizes. Such variety in arrangement is within the scope of the present invention. 
         [0018]      FIG. 3  shows a cross-section through the sleeve  129  and the transition piece  120 . Again, a limited number of apertures  200 ,  400  are shown on the transition piece  120  and the sleeve  129  for simplicity of illustration. In particular,  FIG. 3  shows a wall  500  that is part of the sleeve  129  and a wall  300  that is part of the transition piece  120 . The wall  500  separates an exterior space  302  from the flow annulus  124 . The distance between the wall  300  and the wall  500  may range from 0.5 inch to 3.0 inches. 
         [0019]    The first apertures  400  are configured to be normal to the wall  500  such that air flow I is adapted to not strike or directly impinge an outer surface  300   a  of the transition piece  120  perpendicularly. The first apertures  400  may be formed directly above the second apertures  200  ( FIG. 3 ), may be formed to be offset from the second apertures  200  ( FIG. 2 ) so that no second apertures are found below the first apertures  400 , or may be formed to be above an area of the wall  300  that in part includes the second apertures  200  and in part does not include the second apertures  200 . In a configuration where the first apertures  400  are not directly above the second apertures  200 , a greater portion of the air flow I is allowed to flow over an outer surface  300   a  of the transition piece  120  rather than enter the apertures  200  upon arrival at the outer surface  300   a.    
         [0020]      FIG. 3  also shows an outer surface  300   a  and an inner surface  300   b  of the wall  300 . The area above the wall  300  is the flow annulus  124  while the area below the wall is the interior space  304  of the transition piece  120 . A right side of  FIG. 3  corresponds to an upstream area within the turbine while a left side of  FIG. 3  corresponds to a downstream area within the turbine. Flow C, made up of compression discharge air which is cooler than combusted hot gas, originates from the compressor but approaches the transition piece  120  in the flow annulus  124  from a downstream area of the turbine and moves upstream as is typical in a can-annular, reverse flow combustor. Flow I, also made up of compressor discharge air, moves upstream in the exterior space  302  from a downstream area of the turbine and enters the flow annulus  124  through the first apertures  400 . Flow H, made up of hot gas, originates from the combustion chamber and is directed downstream in the interior space  304  of the transition piece  120 . 
         [0021]    As shown in  FIG. 3 , the second apertures  200  extend from the outer surface  300   a  to the inner surface  300   b  of the wall  300 . The present invention encompasses second apertures  200  formed to be normal to the wall  300  and formed at an angle θ to the wall  300 . In  FIG. 3 , the apertures  200  are shown at the angle θ such that exit portions  200   b  of the apertures  200  are downstream or rearward relative to entry portions  200   a  of the apertures  200 . In one embodiment, the angle θ formed by the longitudinal axes  200   c  of the apertures  200  and a direction  202  that is tangential to the wall  300  and is pointed downstream may be acute at 30 degrees and may range from 20 to 35 degrees. However, other smaller and larger angles are also contemplated. In  FIG. 3 , the downstream tangent points to the left. Although the second apertures  200  are substantially cylindrical, the entry portions  200   a  and the exit portions  200   b  will have elliptical shapes if the apertures  200  are not normal to the wall  300 . However, the apertures  200 ,  400  may have a cross section that is not circular and, for example, is polygonal. 
         [0022]    Another variation of the apertures  200  is that the angular position of the entry portion  200   a  may be different from the angular position of the exit portion  200   b  on the circumference of the transition piece  120 . Moreover, the exit portion  200   b  of the apertures  200  may be upstream or forward relative to the entry portion  200   a  of the apertures  200  thereby creating an obtuse angle between the longitudinal axes of the apertures  200  and the direction  202 . 
         [0023]    In  FIG. 3 , the second apertures  200  have a substantially cylindrical geometry with a constant diameter from the entry portion to the exit portion. In one embodiment, the diameter may be 0.03 inch and alternatively may range from 0.02 inch to 0.04 inch. However, other dimensions for the apertures  200  are also contemplated. 
         [0024]    The first apertures  400  also have a substantially cylindrical geometry with a constant diameter. In one embodiment, the diameter may range from 0.1 inch to 1.0 inch. However, other dimensions for the apertures  400  are also contemplated. 
         [0025]    Also, the apertures  200 ,  400  may gradually increase or decrease in diameter through the walls  300 ,  500  respectively. 
         [0026]    The second apertures  200  may be formed on the wall  300  of the transition piece  120  by laser drilling or other machining methods selected based on factors such as cost and precision. The larger dimensions of the first apertures  400  allow for more tolerance and thus similar or more cost-effective machining methods may be used to form the apertures  400 . 
         [0027]    In  FIG. 3 , flow I caused by the first apertures or holes  400  cools the transition piece  120  by forming jets of air that do not strike or directly impinge on the outer surface  300   a . Flow C in the flow annulus provides convective cooling of the transition piece  120  by removing heat while traveling along the outer surface  300   a . Flow E created by the second apertures or effusion holes  200  provides jets of air at all or selected areas of the transition piece  120  that cool the transition piece  120  as the cooling air passes through the apertures  200  contacting internal surfaces therein. Effusion cooling is a form of transpiration cooling. An aperture that is angled to the wall will have a larger internal surface area compared to an aperture normal to the wall due to increased length so that heat transfer is prolonged and greater cooling of the transition piece  120  can be achieved. Moreover, after the cool air exits the exit portion  200   b  of the apertures  200 , a layer or film of cooling air is formed adjacent the inner surface  300   b  of the wall  300  of the transition piece  120 . Formation of such a layer of cooling air on the inner surface  300   b  further cools the transition piece  120 . The formation of such a layer is facilitated by an angled aperture compared to a normal aperture since the degree of change required in direction by the cool air is reduced. However, the present invention encompasses the two variations of normal and angled apertures. Cooling by the film formed on the inner surface can improve as the hole sizes and angles are decreased. However, smaller holes are more prone to blockage from impurities. In comparison, larger holes can cause excessive penetration of the hot gas stream by the cool air jets and reduce the efficiency of the turbine. Therefore, such benefits and drawbacks must therefore be collectively considered when determining the geometry of the effusion holes. 
         [0028]    The invention has been described with reference to the example embodiments described above. Modifications and alterations will occur to others upon a reading and understanding of this specification. Example embodiments incorporating one or more aspects of the invention are intended to include all such modifications and alterations insofar as they come within the scope of the appended claims.