Patent Publication Number: US-7707835-B2

Title: Axial flow sleeve for a turbine combustor and methods of introducing flow sleeve air

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a gas turbine combustor having a flow sleeve and a liner for supplying compressor discharge air to combustor burners and particularly relates to a casing for turning compressor discharge air flowing radially through holes in the flow sleeve in an axial direction for flow in a generally parallel direction relative to the free stream air in the flow sleeve. The invention also relates to methods for turning the flow. 
   In current combustors, a plurality of openings are provided about the flow sleeve for injecting air in a generally radial direction into the flow sleeve for impingement cooling the liner. The radially injected air is generally normal to the free stream air flowing within the flow sleeve. It will be appreciated that compressor discharge air flows through openings in the impingement sleeve of a transition piece and forms part of a free stream air flow in an aft direction and between the combustion flow sleeve and liner. This air flow mixes with fuel at the aft end of the combustor and the fuel/air mixture is combusted within the liner. The air injected in the radial direction through the flow sleeve openings and into the free stream has a momentum exchange with the axially flowing air and must be accelerated by the axially flowing free stream air until the cross flowing air reaches the free stream velocity. This process causes a net loss in energy. 
   In certain combustors, it is desirable to impingement cool the liner of the combustor, necessitating the net loss in energy to cool the liner. In other combustors, however, the magnitude of cooling required to cool the liner is such as to not require impingement cooling flows. Consequently, there is a need to provide a mechanism and a method for reducing energy losses due to cross flow while affording cooling of the liner. 
   BRIEF DESCRIPTION OF THE INVENTION 
   In accordance with a preferred aspect of the present invention, the flow sleeve is provided with an inlet which enables the air flowing into the inlet to change direction and enter the free flow stream of compressor discharge air between the liner and flow sleeve in a generally co-flow or coaxial direction, thus eliminating energy losses due to cross flow and accompanying momentum exchange. The inlet includes an annular plenum between the forward end of the flow sleeve and an annular casing about the inside of the flow sleeve. The flow sleeve is provided with a plurality of circumferentially spaced openings for injecting compressor discharge air into the plenum. The casing is provided with a plurality of circumferentially spaced apertures at its aft end for injecting the air from the plenum in a generally axial or co-flow direction with and into the free flow air stream. The inlet thus affords a precise control and metering of the air while simultaneously cooling the liner. 
   In a preferred embodiment according to the present invention, there is provided a combustor for a gas turbine comprising a combustor housing including a flow liner extending in a generally axial direction and a flow sleeve surrounding and spaced from the flow liner defining a flow path for flowing air in a generally axial direction between the liner and the flow sleeve; and an inlet to the flow sleeve for introducing air into the flow path in substantially the same axial direction as the direction of air flow along the flow path. 
   In a further preferred embodiment according to the present invention, there is provided a combustor for a gas turbine comprising a combustor housing including a flow liner and a flow sleeve surrounding and spaced from the flow liner defining a flow path therebetween for flowing air generally in a first direction between the liner and the flow sleeve toward one end of the combustor; and an inlet to the flow sleeve for introducing air into the flow path for flow in substantially the first direction and substantially without cross flow between the introduced air and the air flowing along the flow path. 
   In a further preferred embodiment according to the present invention, there is provided a combustor for a gas turbine having a flow liner, a fuel injector adjacent to one end of the liner and a flow sleeve surrounding and spaced from the liner defining a flow path for flowing air in a direction generally toward the one end, a method of introducing air into the air flowing along the flow path comprising step of injecting air directly into the air flow stream in the general direction toward the one end. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a fragmentary cross sectional view of a prior art combustor illustrating the radial inward flow of compressor discharge air into the flow sleeve; 
       FIG. 2  is an enlarged fragmentary cross sectional view of a portion of the combustor illustrating axial introduction of compressor discharge air into the free flow stream in accordance with a preferred aspect of the present invention; 
       FIG. 3  is a fragmentary enlarged cross sectional view thereof taken generally about line  3 - 3  in  FIG. 2 ; and 
       FIG. 4  is an enlarged fragmentary plan view of the openings through the flow sleeve taken generally about on line  4 - 4  in  FIG. 2 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to the drawing figures, and particularly to  FIG. 1 , there is illustrated a combustor generally designated  10  according to the prior art. The combustor includes burners  12  at the aft end of the combustor, a flow sleeve  14  and liner  16  and a transition including a transition section piece body  18  and impingement sleeve  20 . It will be appreciated that the area surrounding the flow sleeve  14  and the impingement sleeve  20  is supplied with compressor discharge air which in turn flows through openings (not shown) in the impingement sleeve and openings  22  in the flow sleeve for supplying compressor discharge air in a generally axial flow direction aft toward the burner end of the combustor. The supplied air mixes with the fuel in the burners  12 , the fuel/air mixture combusts and flows forward within the liner  16 . The energetic gases of combustion flow through the transition piece  18  toward the turbine section, not shown, of the gas turbine. 
   As illustrated in  FIG. 1 , compressor discharge air indicated by the arrows  24  is supplied through the openings  22  in a generally radially inward direction. Openings  22  are, of course, provided at axially and circumferentially spaced intervals about the flow sleeve  14 . Because a portion of the compressor discharge air from between the impingement sleeve  20  and transition piece  18  body flows generally axially aft toward the burner, the air injected radially through openings  22  for impingement cooling purposes, crosses perpendicular to this axially flowing air within the flow sleeve. While the radial impingement of this injected air onto the liner  16  affords impingement cooling, this cross flow results in an appreciable net loss of energy. That is, the axially flowing compressor discharge air in the annular space between the flow sleeve and liner effects a momentum change in the impinging cross flow air which must be accelerated until the cross flow air changes direction and reaches the free stream velocity. 
   Referring now to  FIG. 2 , there is illustrated a portion of an axial flow sleeve in accordance with a preferred aspect of the present invention wherein compressor discharge air is introduced into the axially aft flowing stream within the flow sleeve  30  in a general axial or co-flow direction with the flow stream from the impingement sleeve  36  thereby substantially eliminating or minimizing any net energy loss due to the mixing of these flow streams while simultaneously affording beneficial cooling of the liner. In  FIG. 2 , there is illustrated a flow sleeve  30  and a liner  32  defining a generally annular axial flow passage  34  for directing compressor discharge air in an aft direction toward the burners. A portion of the compressor discharge air, as in the prior art, is supplied in the passage  35  between the impingement sleeve  36  and transition piece body  38  for flow into the passage  34 . 
   To introduce compressor discharge air through the flow sleeve  30  in a generally co-flow direction, there is provided an inlet generally designated  40  including an annular interior casing  42  defining with a portion of the flow sleeve at the forward end a plenum  46 . It will be appreciated the casing  42  and plenum  46  extend annularly about the interior surface of the flow sleeve  30 . Compressor discharge air is introduced into the plenum  46  through a plurality of circumferentially spaced openings  48  in the forward end of the flow sleeve  30  thereby isolating plenum cavity flow  46  from the flow that is migrating aft from region  35  into region  34 . It will be appreciated that additional axial spaced openings  48  may also be provided to supply compressor discharge air to the plenum  46 . The air injected through openings  48  is uniquely turned within the plenum by the casing  42  for flow through apertures  50  at the aft end of casing  42 . As illustrated in  FIG. 4 , openings  48  extend axially and are spaced circumferentially from one another. Thus, the flow in the plenum  46  is turned from a radial flow direction through the openings  48  into the plenum to an axial flow direction within the plenum  46  for exit through the apertures  50  into and in a flow direction generally corresponding to the axially flowing free air stream from passage  35  into passage  34 . The energy loss previously due to the radial cross flow with the free air stream is minimized or eliminated. Also, there is a positive momentum exchange since the axially injected air flowing through apertures  50  is moving faster than the free stream air flowing from passage  35  into passage  34 . This results in an energy addition to the free stream air and a net reduction in combustor pressure drop as compared to prior art. Also, the casing  42  is secured, e.g., by welding or any other variety of metallic joining techniques, along the inside surface of the flow sleeve  30  and radially outward of the exit throat  52 . Thus, casing  42  does not interfere physically or pneumatically with the air flow from passage  35  into passage  34 . 
   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 any number of various modifications and equivalent arrangements included within the spirit and scope of the appended claims.