Abstract:
There is provided a combustor to burn fuel, comprising a bypass passage connected to one side of the combustor to supply air into the combustor; and an annular passage provided around the combustor and connected to the bypass passage, wherein air supplied through the bypass passage passes in the annular passage in the circumferential direction, and is uniformly supplied into the combustor in the circumferential direction thereof through an opening which connects the combustor and the annular passage. Accordingly, compressed air passing through the bypass passage can be supplied uniformly into a tail portion of the combustor, and unevenness of temperature distribution in a cross section of the combustor tail portion can be reduced.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a combustor, particularly to a gas turbine combustor in which additional air can be supplied by a bypass passage.  
           [0003]    2. Description of the Related Art  
           [0004]    In general, a gas turbine combustor is disposed between a compressor and a turbine. Fuel F is supplied to a gas turbine combustor through a fuel supplying passage of a nozzle portion in the gas turbine combustor. Compressed air A compressed by the compressor is supplied to a casing of the gas turbine combustor and, then enters the nozzle portion through an inlet portion of the nozzle portion and is supplied to the combustor through a swirler. Thus, the compressed air A and the fuel F are mixed and burned in the combustor. High temperature gas produced by combustion of the compressed air A and the fuel F is discharged from the combustor through a tail portion thereof to drive the turbine provided on the downstream side of the gas turbine combustor in the direction of air flow.  
           [0005]    A bypass passage having a bypass valve is provided on one side of the combustor tail portion. When the output of the turbine varies, the bypass valve is opened and closed so that the compressed air A in the casing is supplied to the combustor tail portion through the bypass passage from the inlet portion to an outlet portion thereof. Accordingly, additional compressed air A is supplied to the combustor tail portion so that the air-fuel ratio, i.e., the ratio of air to fuel in the gas turbine combustor can be maintained at an appropriate value.  
           [0006]    However, the bypass passage is attached to only one side of the combustor in a known gas turbine combustor. Therefore, when additional compressed air A is supplied to the combustor tail portion through the bypass passage, the concentration of fuel in the combustor tail portion is locally decreased in the vicinity of the outlet of the bypass passage.  
           [0007]    In general, when the ratio of combustion air to fuel is high, the flame becomes unstable due to lack of fuel. In addition, when the ratio of fuel to combustion air is high, NOx tends to easily occur. In other words, the flame tends to become unstable in the vicinity of the outlet of the bypass passage, and NOx tends to occur at the opposite side of the outlet, in a cross section of the combustor tail portion. Therefore, if the bypass valve is adjusted to maintain the air-fuel ratio at a substantially constant value, it is necessary for the additional compressed air passing through the bypass passage to be uniformly supplied to the combustor tail portion in the circumferential direction thereof.  
           [0008]    The additional compressed air A is supplied to the combustor, particularly to the combustor tail portion via the outlet of the bypass passage, so that the temperature in the vicinity of the outlet is locally decreased, and unevenness of the temperature distribution occurs in a cross section of the combustor tail portion.  
           [0009]    Accordingly, the object of the present invention is to provide a combustor in which the compressed air passing through the bypass passage is uniformly supplied into the combustor tail portion in the circumferential direction thereof, and unevenness of the temperature distribution in a cross section of the combustor tail portion is reduced.  
         SUMMARY OF THE INVENTION  
         [0010]    According to an embodiment of the present invention, the present invention provides a combustor to burn fuel, comprising a bypass passage connected to one side of the combustor to supply air into the combustor; and an annular passage provided around the combustor and connected to the bypass passage, wherein air supplied through the bypass passage passes through the annular passage in the circumferential direction, and is uniformly supplied into the combustor in the circumferential direction thereof through an opening which connects the combustor and the annular passage.  
           [0011]    Namely, according to the embodiment of the present invention, air passing through the bypass passage is uniformly supplied in the circumferential direction of the combustor and particularly to the combustor tail portion to thereby reduce unevenness of the temperature distribution in a cross section of the combustor tail portion.  
           [0012]    These and other objects, features and advantages of the present invention will be more apparent in light of the detailed description of exemplary embodiments thereof as illustrated by the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0013]    The present invention will be more clearly understood from the description as set below with reference to the accompanying drawings, wherein:  
         [0014]    [0014]FIG. 1 is a sectional view of a known gas turbine combustor;  
         [0015]    [0015]FIG. 2 is a side view of a combustor according to a first embodiment of the present invention;  
         [0016]    [0016]FIG. 3 is a sectional view taken along the line X-X in FIG. 2;  
         [0017]    [0017]FIG. 4 is a longitudinal partial sectional view of a combustor according to a first embodiment of the present invention;  
         [0018]    [0018]FIG. 5 is a longitudinal partial sectional view of a combustor according to a second embodiment of the present invention;  
         [0019]    [0019]FIG. 6 a  is an enlarged schematic view of an overlapped portion of a first cylinder portion and a second cylinder portion in FIG. 5;  
         [0020]    [0020]FIG. 6 b  is an enlarged schematic view of an overlapped portion of a first cylinder portion and a second cylinder portion in FIG. 5;  
         [0021]    [0021]FIG. 7 is a longitudinal partial sectional view of a combustor according to a third embodiment of the present invention;  
         [0022]    [0022]FIG. 8 is a longitudinal partial sectional view of a combustor according to another embodiment;  
         [0023]    [0023]FIG. 9 a  is an enlarged schematic view of a supporting member in FIG. 7;  
         [0024]    [0024]FIG. 9 b  is an enlarged schematic view of a supporting member in FIG. 7; and  
         [0025]    [0025]FIG. 10 is a longitudinal partial sectional view of a combustor according to a forth embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]    Before proceeding to a detailed description of the preferred embodiments, a prior art will be described with reference to the accompanying drawings relating thereto for a clearer understanding of the difference between the prior art and the present invention.  
         [0027]    [0027]FIG. 1 is a cross sectional view of a gas turbine combustor disclosed in a related art, for example, Japanese Unexamined Patent Publication (Kokai) No. 2000-130756. Such gas turbine combustor is disposed between a compressor and a turbine. Fuel F is supplied to a gas turbine combustor  100  through a fuel supplying passage  330  of a nozzle portion  300  in the gas turbine combustor  100 . Compressed air A compressed by a compressor  400  is supplied into a casing  800  of the gas turbine combustor  100 . The compressed air A enters the nozzle portion  300  through an inlet portion  350  of the nozzle portion  300  and is supplied into the combustor through a swirler  370 . Therefore, the compressed air A and the fuel F are mixed and burned in the combustor. High temperature gas produced by combustion of the compressed air A and the fuel F is discharged from the combustor through a tail portion thereof to drive a turbine (not shown) provided on the downstream side of the gas turbine combustor  100  in the direction of air flow.  
         [0028]    A bypass passage  900  having a bypass valve  970  is provided on one side of the combustor tail portion  500 . When the output of the turbine varies, the bypass valve  970  is opened and closed so that the compressed air A in the casing  800  is supplied to the combustor tail portion  500  through the bypass passage  900  from an inlet portion  950  to an outlet portion  990  thereof. Accordingly, the additional compressed air A is supplied to the combustor tail portion  500  so that the air-fuel ratio, i.e., the ratio of air to fuel in the gas turbine combustor  100  can be maintained at an appropriate value.  
         [0029]    An embodiment of the present invention will be described below with reference to accompanying drawings. In following drawings, the same members are designated by similar numerals.  
         [0030]    [0030]FIG. 2 and FIG. 4 show a side view and a longitudinal partial sectional view of a combustor according to a first embodiment of the present invention, respectively. As shown in FIG. 4, the fuel F is supplied to the gas turbine combustor  10  through a fuel supplying passage  33  provided in a nozzle  30 . The compressed air A compressed by a compressor (not shown) enters the nozzle  30  through the inlet portion  35  and is supplied into the gas turbine combustor  10  through a swirler  37 . The fuel F and the compressed air A are mixed and burned in the combustor.  
         [0031]    A bypass passage  90  is connected to one side of a combustor tail portion  50 . The bypass passage  90  contains a bypass valve  97  (not shown). As shown in FIG. 2, in the first embodiment, an annular passage containing member which contains an annular passage therein, i.e., an annular scroll  60 , is disposed between the combustor tail portion  50  and the bypass passage  90 . As shown in FIG. 3 which is a cross sectional view taken along the line X-X in FIG. 2, an annular passage  61  extending in the circumferential direction is formed in the annular scroll  60 . The annular scroll  60  is provided on the outer peripheral portion of the combustor tail portion  50  substantially coaxially to the center axis of the combustor. As shown in FIG. 3 and FIG. 4, a plurality of openings  51  are formed in a wall portion of the combustor tail portion  50 . In the first embodiment, the openings  51  formed in the wall portion of the combustor tail portion  50  are spaced at a substantially equal distance in the circumferential direction. Therefore, the bypass passage  90  and the annular scroll  60  are connected to each other via the outlet  99 , and the annular scroll  60  and the combustor tail portion  50  are connected to each other via the openings  51 .  
         [0032]    When the output of a turbine (not shown) varies and a partial load is applied to the gas turbine combustor  10 , the bypass valve  97  is opened. Accordingly, additional compressed air A can be supplied from a casing  80  into the bypass passage  90  through the inlet portion  95  of the bypass passage  90 . As shown in FIG. 3, the additional compressed air A enters the annular scroll  60  through the outlet portion  99  of the bypass passage  90 . The additional compressed air A enters the combustor tail portion  50  through the annular passage  61  of the annular scroll  60  and openings  51  formed in the wall portion of the combustor tail portion  50 . Therefore, the additional compressed air A is supplied substantially uniformly to the combustor, particularly to the combustor tail portion  50 , in the circumferential direction thereof. Accordingly, unevenness of the temperature distribution in the cross section of the combustor can be reduced when the partial load is applied. Slits can be formed on the wall portion of the combustor tail portion  50  in the circumferential direction thereof, in place of the openings  51 . In this case, the additional compressed air A can be more uniformly supplied into the combustor tail portion  50 .  
         [0033]    [0033]FIG. 5 is a longitudinal partial sectional view of a combustor according to a second embodiment of the present invention. In the second embodiment, the combustor contains a first cylinder portion  53  and a second cylinder portion  54 . As shown in FIG. 5, the first cylinder portion  53  and the second cylinder portion  54  are coaxially arranged and are partly overlapped with a predetermined space therebetween, so that an annular or cylindrical clearance  55  is formed between these cylinder portions. It is apparent from FIG. 5 that a superimposed portion  59 , in which these cylinder portions are overlapped, i.e., superimposed, is positioned in the annular scroll  60 . An upstream side end portion of the annular scroll  60  positioned on the upstream side in the flow direction of fuel F in the annular scroll  60  and a downstream side end portion of the annular scroll positioned on the downstream side are connected to the first cylinder portion  53  and the second cylinder portion  54 , respectively. Therefore, the additional compressed air A in the annular scroll  60  does not leak out.  
         [0034]    Additional compressed air A entering from the bypass passage  90  into the annular scroll  60  passes along the inner wall of the combustor tail portion  50  via the annular passage  61  and the annular space  55 . Accordingly, a thin layer of a low-temperature airflow (a so-called cooling film) is formed along the inner wall of the combustor tail portion  50 , and then the combustor tail portion  50  is cooled by the low-temperature airflow layer (such a cooling method is called “film cooling”). An annular cooling film is formed because the space  55  is annular, and thus the combustor tail portion  50  can be uniformly cooled in the circumferential direction thereof. In other words, according to the second embodiment, additional compressed air passing through the bypass passage can be uniformly supplied to the combustor, particularly to the combustor tail portion in the circumferential direction thereof, and unevenness of the temperature distribution in a cross section of the combustor tail portion can be reduced.  
         [0035]    [0035]FIG. 6 a  and FIG. 6 b  are schematic views of the superimposed portion  59  of the first cylinder portion  53  and the second cylinder portion  54 . In the second embodiment, as shown in FIG. 6 a , the first cylinder portion  53  and the second cylinder portion  54  are separate members, and define the annular space  55 . However, as shown in FIG. 6 b , the first cylinder portion  53  and the second cylinder portion  54  may be integrally formed as a single member, and a plurality of through holes  56  extending in the axial direction of the combustor tail portion  50  may be formed in the superimposed portion  59 . The through holes  56  are spaced at an equal distance in the circumferential direction. In this case, since the cooling film extends to a portion further downstream to that of the embodiment shown in FIG. 6 a , the combustor tail portion  50  can be cooled over a wider area.  
         [0036]    [0036]FIG. 7 is a longitudinal partial sectional view of a third embodiment of a combustor according to the present invention. The combustor contains the first cylinder portion  53  and the second cylinder portion  54 . In the third embodiment, the superimposed portion  59  in which the first cylinder portion  53  and the second cylinder portion  54  are partially superimposed extends beyond the annular scroll  60  on the downstream side, in the flow direction of fluid, in the combustor. Additional compressed air A entering from the bypass passage  90  into the annular passage  61  of the annular scroll  60  enters the annular space  55  of the superimposed portion  59 . The additional compressed air A passes through the annular space  55  to thereby effectively cool the combustor, particularly the combustor tail portion  50 , by convection cooling. The combustor tail portion  50  can be cooled substantially uniformly in the circumferential direction over a wide area by convection cooling. In other words, according to the third embodiment, air passing through the bypass passage can be uniformly supplied in the circumferential direction of the combustor tail portion, and unevenness of the temperature distribution in the cross section of the combustor tail portion can be reduced over a wide area.  
         [0037]    As a matter of course, as shown in FIG. 6 b , the first and second cylinder portions  53 ,  54  are formed as a single member, and a plurality of through holes  56  may be formed in the superimposed portion  59  in place of the annular space  55 . In the above-described second embodiment, it is apparent that convection cooling is partially carried out in the superimposed portion  59 .  
         [0038]    [0038]FIG. 8 is a longitudinal partial sectional view of another embodiment of a combustor according to the present invention. The combustor contains the first cylinder portion  53  and the second cylinder portion  54 . Similar to the above-described third embodiment, the annular space  55  is formed in the superimposed portion  59  in which the first cylinder portion  53  and the second cylinder portion  54  are partially superimposed. In this embodiment, a plurality of supporting members  57  are disposed between the first cylinder portion  53  and the second cylinder portion  54  and in the superimposed portion  59 . FIG. 9 a  and FIG. 9 b  are partially enlarged views of the first cylinder portion  53  having the supporting member  57 . In FIG. 9 a , a plurality of columnar supporting members  57  are spaced at an equal distance with each other on the outer wall of the first cylinder portion  53 . The inner wall of the second cylinder portion  54  is disposed on the top face of the supporting member  57 . However, for ease of understanding, the second cylinder portion  54  is omitted in FIG. 9 a  and FIG. 9 b . The first cylinder portion  53  and the second cylinder portion  54  can be supported by the supporting members  57 , against combustion vibration caused during the operation of the combustor. Therefore, the annular space  55  can be maintained without being crushed by combustion vibration. Furthermore, the supporting member  57  can improve heat transferring between the first cylinder portion  53  and the second cylinder portion  54 . Thus, according to the embodiment, air passing through the bypass passage is uniformly supplied to the combustor, particularly to the combustor tail portion in the circumferential direction thereof, so that the unevenness of the temperature distribution in the cross section of the combustor tail portion can be reduced. As a matter of course, in the above-described second embodiment, the arrangement of the supporting member in the annular space  55  is included within the scope of protection of the present invention.  
         [0039]    [0039]FIG. 10 is a longitudinal partial sectional view of a forth embodiment of a combustor according to the present invention. In the forth embodiment, a sleeve  70  is arranged substantially coaxially to the center axis of the combustor tail portion  50 , between the outer wall of the combustor tail portion  50  and the inner wall of the annular scroll  60 . Therefore, the sleeve  70  and the outer wall of combustor tail portion  50  are substantially parallel. The length in the axial direction of the sleeve  70  is substantially identical to that of the annular scroll  60 . As shown in FIG. 10, a plurality of holes  71  are formed in the sleeve  70 . A plurality of openings  51  are formed in the combustor tail portion  50  within the annular scroll  60 . In the forth embodiment, the plural openings  51  and the plural holes  71  are disposed in a staggered configuration.  
         [0040]    The additional compressed air A entering the annular scroll  60  through the bypass passage  90  passes through the annular passage  61  and the hole  71  of the sleeve  70  and impinges on the outer wall of the combustor tail portion  50 . The sleeve  70  and the combustor tail portion  50  are coaxial to each other, so that the additional compressed air A passing through the hole  71  of the sleeve  70  impinges substantially vertically on the outer wall of the combustor tail portion  50 . A cooling method in which fluid is vertically supplied onto the surface of the object to be cooled is called “impinge cooling” or “impingement cooling”. Then, the additional compressed air A enters the combustor tail portion  50  through the opening  51  of the combustor tail portion  50 .  
         [0041]    In the forth embodiment, the additional compressed air passing through the bypass passage  90  is uniformly supplied to the combustor, particularly to the combustor tail portion in the circumferential direction thereof, so that unevenness of the temperature distribution in the cross section of the combustor tail portion can be reduced by impinge cooling. It is preferable that the opening  51  not be formed at a position of the combustor tail portion  50  corresponding to the hole  71 , since this improves the effect of impinge cooling. The sleeve  70  functions as an acoustic liner so that combustion vibration produced when the combustor is operated can be decreased.  
         [0042]    As a matter of course, any combination of the embodiments described above to produce the combustor is included within the scope of the present invention. For example, to form an annular passage on the wall portion of the combustor without the annular scroll is within the scope of the present invention.  
         [0043]    According to an embodiment of the present invention, the common effect can be obtained that the additional air passing through the bypass passage is supplied to the combustor, particularly to the combustor tail portion uniformly in the circumferential direction thereof, so that unevenness of the temperature distribution in a cross section of the combustor tail portion can be reduced.  
         [0044]    According to another embodiment of the present invention, the effect can be obtained that the additional air can be further uniformly supplied from the bypass passage to the combustor, particularly to the combustor tail portion.  
         [0045]    According to yet another embodiment of the present invention, the effect can be obtained that the combustor, particularly, the combustor tail portion, can be effectively cooled by a cooling film.  
         [0046]    According to yet another embodiment of the present invention, the effect can be obtained that the combustor, particularly, the combustor tail portion, can be effectively cooled by convection cooling.  
         [0047]    According to yet another embodiment of the present invention, the effect can be obtained that the supporting member is provided between the first cylinder portion and the second cylinder portion to support the same, and what can improve the heat transferring.  
         [0048]    According to yet another embodiment of the present invention, the effect can be obtained that the combustor, particularly, the combustor tail portion, can be effectively cooled by impinge cooling, and the sleeve functions as an acoustic liner to reduce combustion vibration.  
         [0049]    Although the invention has been shown and described with exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made therein and thereto without departing from the spirit and scope of the invention.