Patent Publication Number: US-6907736-B2

Title: Gas turbine combustor having an acoustic energy absorbing wall

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a gas turbine combustor and, more particularly, to a structure of a gas turbine combustor. 
   2. Description of the Related Art 
     FIGS. 16A and 16B  show a conventional gas turbine combustor.  FIG. 16A  is a diagram showing the layout of the combustor within an intake chamber. A plurality of gas turbine combustors  10  are laid out in an approximately ring-shaped intake chamber  30  that is formed with a casing  20  consisting of an external casing  21  and an internal casing  22  (only one gas turbine combustor is shown in the drawing). 
   Air from a compressor enters the intake chamber  30 , and passes through the surrounding of the combustor  10  and enters the inside of the combustor  10  from an air inlet opening  11  at an upper portion of the combustor. The air is pre-mixed with a fuel separately introduced from a fuel nozzle  40 . The mixture is combusted within the combustor  10 , and the combustion gas is supplied to a turbine. 
     FIG. 16B  is a cross-sectional diagram of an enlarged portion of (B) in  FIG. 16A. A  wall  100  of the combustor  10  is constructed of a first wall  200  that extends straight at the fuel nozzle  40  side, and a second wall  200 ′ that is inclined at a turbine chamber side. The first wall  200  is a cooling wall provided with a clearance through which cooling air passes. The second wall  200 ′ is a double wall cooled with vapor. Both walls are connected to each other via a spring clip  105 . 
     FIGS. 17A and 17B  show a state where a combustor  10  is supplied with a cover  50  to form a convection cooling path  60 , based on the structure shown in  FIGS. 16A and 16B  respectively. The air from the compressor is guided to the convection cooling path  60  to cool the combustor  10 , and is then guided to the inside of the combustor  10 . A first wall  200  and a second wall  200 ′ of the combustor  10  have the same structures as those shown in  FIG. 16B  respectively. The first wall  200  and the second wall  200 ′ shown in FIG.  16 B and  FIG. 17B  respectively are acoustically very rigid boundaries, and they hardly transmit sound waves. Therefore, the resonance magnification of a sound field within the combustor  10  becomes high, and this can easily bring about what is called a combustion oscillation phenomenon. 
   The combustion oscillation is a phenomenon that a frequency component of a pressure variation of a combustion gas generated due to a generation of a combustion variation relative to a natural frequency of the sound field is amplified, and the pressure variation within the combustor  10  becomes larger. As a result, the quantities of the fuel and air introduced respectively into the combustor  10  vary, which makes the combustion variation much larger. 
   Particularly, a high-frequency combustion oscillation corresponding to an acoustic mode generated with a cross section of the combustor  10  is strongly influenced by the acoustic characteristics of the wall  100  of the combustor  10 . This combustion oscillation occurs very easily when the wall  100  of the combustor  10  is acoustically rigid. 
   In recent years, along a inforcement of exhaust gas emission controls and, particularly, the inforcement of the Nox restrictions, it has become necessary to increase the ratio of the quantity of air to the quantity of fuel. In other words, it has become necessary to implement lean combustion based on a large air-to-fuel ratio. When the lean combustion is implemented, a combustion variation can occur very easily. This easily brings about a variation in the pressure of the combustion gas. Therefore, it has been strongly demanded to provide a combustor that can prevent the amplification of the pressure variation of the combustion gas in the sound field, and can restrict the occurrence of the combustion oscillation. 
   SUMMARY OF THE INVENTION 
   In the light of the above problems, it is an object of the present invention to provide a gas turbine combustor capable of preventing the occurrence of combustion oscillation. 
   According to the present invention, there is provided a gas turbine combustor in which a part or whole of the wall of the combustor disposed within an intake chamber is formed with an acoustic energy absorbing member that can absorb the acoustic energy of a combustion variation generated within the combustor. 
   In the gas turbine combustor having the above structure, the acoustic energy of a combustion variation generated within the combustor is absorbed in the wall of the combustor. Therefore, it is possible to prevent an occurrence of a combustion oscillation phenomenon. 
   According to one aspect of the present invention, an acoustic energy-absorbing member is constructed of a corrugated thin plate in a circumferential direction. The acoustic energy of a combustion variation generated within the combustor is absorbed in the expanded thin corrugated plate in a radial direction. Further, corrugated plates divided in an axial direction may be connected together, with their end portions superimposed on each other. In this case, it becomes possible to absorb the acoustic energy of a combustion variation generated within the combustor, based on the friction between the superimposed corrugated plates as well as the expansion of the thin corrugated plates in a radial direction. Further, when the thickness and sizes of the divided corrugated plates are changed to match a plurality of frequency components of the combustion variation, it is possible to absorb the plurality of frequency components of the combustion variation. Further, when a clearance for allowing the passage of air is provided in a radial direction at each superimposed connection portion, it becomes possible to pass the cooling air through this clearance. As a result, it becomes possible to improve the cooling of the combustor. 
   According to another aspect of the present invention, the acoustic energy-absorbing member is a high-temperature-proof perforated material. Therefore, the acoustic energy of a combustion variation generated within the combustor can escape to the outside. As a result, it becomes possible to prevent the occurrence of a combustion oscillation phenomenon. 
   According to still another aspect of the present invention, the acoustic energy absorbing member is constructed of a perforated plate and a back plate disposed at the outside of the perforated plate, in a radial direction, at a distance from the perforated plate. A resonance-absorbing wall formed between the perforated plate and the back plate can absorb the acoustic energy of a combustion variation generated within the combustor. 
   When openings are formed on the back plate, it is possible to absorb the acoustic energy with these openings on the back plate. 
   Further, when a honeycomb plate is disposed between the perforated plate and the back plate to thereby partition the air in layers, it becomes possible to further improve the effect as a resonance-absorbing wall. 
   The diameter of holes in the perforated plate is preferably 5 mm or less. 
   Further, when a plurality of diameters are used for the openings on the perforated plate, it becomes possible to absorb the acoustic energy of different frequencies. 
   It is preferable that a distance L 1  between the openings in a longitudinal direction and a distance L 2  between the openings in a circumferential direction on the perforated plate respectively have a relationship of 0.25≦L 1 /L 2 ≦4. 
   When the distances between the perforated plates are not uniform, it is possible to absorb the acoustic energy of different frequencies. 
   Further, when the distance between the perforated plate and the back plate is not uniform, it is possible to absorb the acoustic energy of different frequencies. 
   Further, when the thickness of the perforated plate is not uniform, it is possible to absorb the acoustic energy of different frequencies. 
   It is also possible to cool the perforated plate with vapor. 
   When cooling air is introduced into a gap between the perforated plate and the back plate, it becomes possible to cool the perforated plate satisfactorily. 
   Further, according to still another aspect of the present invention, there is disposed a covering member at the outside of the acoustic energy absorbing member in a radial direction, for covering the acoustic energy absorbing member with a distance from the acoustic energy absorbing member. It is also possible to introduce cooling air into a gap between the acoustic energy absorbing member and the covering member. 
   Further, according to still another aspect of the present invention, the acoustic energy absorbing member and/or the covering member are reinforced with a frame that extends in a circumferential direction and/or a longitudinal direction. 
   The present invention will be more fully understood from the description of the preferred embodiments of the invention set forth below, together with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  is a cross-sectional diagram showing a structure of a first embodiment cut along a plane parallel with an axis. 
       FIG. 1B  is a cross-sectional diagram cut along the IB—IB line of FIG.  1 A. 
       FIG. 2A  is a cross-sectional diagram showing a structure of a first modification of the first embodiment cut along a plane parallel with an axis. 
       FIG. 2B  is a cross-sectional diagram cut along the IIB—IIB line of FIG.  2 A. 
       FIG. 3A  is a cross-sectional diagram showing a structure of a second modification of the first embodiment cut along a plane parallel with an axis. 
       FIG. 3B  is a cross-sectional diagram cut along the IIIB—IIIB line of FIG.  3 A. 
       FIG. 4  is a cross-sectional diagram showing a structure of a third modification of the first embodiment. 
       FIG. 5A  is a cross-sectional diagram showing a structure of a second embodiment cut along a plane parallel with an axis. 
       FIG. 5B  is a cross-sectional diagram cut along the VB—VB line of FIG.  5 A. 
       FIG. 6A  is a cross-sectional diagram showing a structure of a modification of the second embodiment cut along a plane parallel with an axis. 
       FIG. 6B  is a cross-sectional diagram cut along the VIB—VIB line of FIG.  6 A. 
       FIG. 7A  is a cross-sectional diagram showing a structure of a third embodiment cut along a plane parallel with an axis. 
       FIG. 7B  is a cross-sectional diagram cut along the VIIB—VIIB line of FIG.  7 A. 
       FIG. 8A  is a cross-sectional diagram showing a structure of a first modification of the third embodiment cut along a plane parallel with an axis. 
       FIG. 8B  is a cross-sectional diagram cut along the VIIIB—VIIIB line of FIG.  8 A. 
       FIG. 9A  is a cross-sectional diagram showing a structure of a second modification of the third embodiment cut along a plane parallel with an axis. 
       FIG. 9B  is a cross-sectional diagram cut along the IXB—IXB line of FIG.  9 A. 
       FIG. 10  is a cross-sectional diagram cut along the X—X line of FIG.  9 B. 
       FIG. 11  is a cross-sectional diagram cut along the XI—XI line of FIG.  9 B. 
       FIG. 12  is a cross-sectional diagram showing a structure of a third modification of the third embodiment cut along a plane parallel with an axis. 
       FIG. 13A  is a diagram showing a layout of openings formed on a perforated plate in the third modification of the third embodiment. The positions of openings adjacently arrayed in a row of a circumferential direction are differentiated so that the positions of the openings in every other row are aligned in a longitudinal direction. 
       FIG. 13B  is a diagram showing a layout of openings formed on a perforated plate in the third modification of the third embodiment. The positions of openings adjacently arrayed in a row of a circumferential direction are the same for each row. 
       FIG. 14  is a cross-sectional diagram showing a structure of a fourth modification of the third embodiment. 
       FIG. 15  is a cross-sectional diagram showing a structure of a fifth modification of the third embodiment. 
       FIG. 16A  is a cross-sectional diagram showing a structure of a combustor cut along a plane parallel with an axis, according to a conventional technique. 
       FIG. 16B  is an enlarged diagram of a portion (B) of FIG.  16 A. 
       FIG. 17A  is a cross-sectional diagram showing a structure of a combustor having a convection cooling layer cut along a plane parallel with an axis, according to another conventional technique. 
       FIG. 17B  is an enlarged diagram of a portion (B) of FIG.  17 A. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Embodiments of the present invention will be explained below with reference to the attached drawings. 
   A first embodiment will be explained first. FIG.  1 A and  FIG. 1B  are diagrams showing a structure of a wall  100  of a combustor  10  according to a first embodiment. A first wall  110  and a second wall  110 ′ that constitute the wall  100  of the combustor  10  in the first embodiment are constructed of thin corrugated plates having a corrugation in a circumferential direction. The first wall  110  and the second wall  110 ′ are connected to each other with a spring clip  105  in mutually simple cylindrical shapes instead of corrugated shapes. 
   Both the first wall  110  and the second wall  110 ′ have small thickness, and therefore, they are reinforced with frames  111  and  111 ′ in a circumferential direction, respectively. Depending on need, these walls are also reinforced with frames  112  and  112 ′ in an axial direction, respectively. 
   Both the first wall  110  and the second wall  110 ′ of the wall  100  of the combustor  10  in the first embodiment are constructed of thin corrugated plates, and they can be expanded in a radial direction according to a change in pressure. Therefore, when a sound field has been induced in a cross-sectional direction, the first wall  110  and the second wall  110 ′ are expanded in a radial direction according to the mode. This exhibits a sound absorption effect, and the amount of sound within the combustor  10  becomes smaller. Consequently, the resonance magnification becomes smaller, and combustion oscillation does not occur easily. Further, as the first wall  110  and the second wall  110 ′ have a small thickness, they can be sufficiently cooled with air that flows from the outside. 
     FIGS. 2A and 2B  are diagrams showing a structure of a first modification of the first embodiment. The first modification shows an example of walls of a gas turbine combustor applied with a convection-cooling path  60  in a similar manner to that explained with reference to  FIGS. 17A and 17B  for the conventional technique. 
     FIGS. 3A and 3B  are diagrams showing a second modification of the first embodiment. This modification is different from the first embodiment in that a first wall  110  and a second wall  110 ′ are divided into a plurality of walls  110   a ,  110   b ,  110   c , etc. and  110 ′ a ,  110 ′ b , etc. in an axial direction respectively, and these divided walls are connected together with end portions of the divided walls superimposed on each other.  FIG. 3B  is an enlarged diagram for facilitating understanding. 
   Based on the above structure, oscillation occurs easily at the superimposed portions, and there is an effect that it is possible to attenuate the oscillation with the friction generated at the mutually superimposed portions. 
     FIG. 4  is a diagram showing a characteristic portion of a third modification of the first embodiment. This third modification is effective as a measure against a shortage in the cooling of the combustor  10 . As compared with the second modification, a fine corrugated shape is formed on one side of the superimposed portion, that is, on an inside wall  110   b  in this example, as shown in the drawing. Cooling air is introduced into the combustor  10  via a clearance  115  formed as a result of this corrugation. 
   A method of forming the clearance  115  is not limited to this, and it is also possible to form the clearance by other method, such as, by providing a groove with a cut on one side, or by sandwiching a discontinuous spacer in a circumferential direction, for example. 
   Further, when the wall has a convection cooling path as explained in the second modification, it is also possible to connect the walls by superimposition, and further forming an air passage at the connection portions, as in the third and fourth modifications. 
   Further, when the sizes and thickness of the divided corrugated plates are changed to match a plurality of frequency components of combustion variation, it is also possible to absorb a plurality of frequency components of the combustion variation. 
   A second embodiment will be explained next.  FIGS. 5A and 5  are diagrams showing a second embodiment. In the second embodiment, a first wall  120  and a second wall  120 ′ constitute a wall  100  of the combustor  10 . The first and second walls are formed by sandwiching perforated materials  121  and  121 ′ such as ceramic having heat-resistance and a very large flow resistance, between perforated plates  122  and  123 , and  122 ′ and  123 ′ from the outside in a radial direction and the inside in a radial direction respectively. The external perforated plates  122  and  122 ′ are further supported with frames  124  and  124 ′ in a circumferential direction and frames  125  and  125 ′ in an axial direction respectively, for the purpose of reinforcement. 
   Based on the above structure of the second embodiment, acoustic energy can easily escape to the outside, and the amount of sound within the combustor  10  becomes smaller. As the resonance magnification becomes smaller, combustion oscillation does not occur easily. 
     FIGS. 6A and 6B  are diagrams showing a modification of the second embodiment. This modification is different from the second embodiment in that a convection-cooling path  60  is provided at the outside. With this arrangement, a reinforcement wall exists at the outside of perforated plates  121  and  121 ′ via a back air layer, when viewed from the inside of the combustor  10 . This forms a sound-absorbing wall tuned by the thickness of the back air layer. Therefore, the amount of sound inside the combustor  10  becomes smaller, and combustion oscillation does not occur easily. 
   A third embodiment will be explained next.  FIGS. 7A and 7B  are diagrams showing a third embodiment. A first wall  130  and a second wall  130 ′ constitute a wall  100  of the combustor  10 . The first wall  130  and the second wall  130 ′ are constructed of perforated plates  131  and  131 ′ that are inside, in a radial direction, and back plates  133  and  133 ′ disposed at the outside, in a radial direction, with a clearance from the perforated plates  131  and  131 ′ via spacers  132  and  132 ′ respectively. The perforated plates  131  and  131 ′ and the back plates  133  and  133 ′ are formed with openings  134  and  134 ′ and openings  135  and  135 ′ respectively. 
   Based on the above structure of the third embodiment, what is called a resonance-absorbing wall is formed between the perforated plate  131  and the back plate  133 . The perforated plate becomes a resistor against sound pressure, and this reduces sound pressure energy. This resonance absorbing wall is different from a general resonance absorbing wall in that air is introduced into the resonance absorbing wall from the openings  135  and  135 ′ of the back plates  133  and  133 ′, and this air is guided to the inside of the combustor after cooling the resonance absorbing wall. 
   In order to attenuate a plurality of acoustic eigen values of the combustor  10 , a clearance distance between the perforated plate  131  and the back plate  133  for the first wall  130  is set to be not uniform corresponding to these acoustic eigen values. Further, the thickness of the perforated plate  131  is set to be not uniform, and the diameter of the perforated plate  131  is set to be not uniform also. The diameters of the openings on the back plate  133  are set to be uniform. 
   In this example, the thickness of the perforated plate  131  and the distance of the clearance are changed in an axial direction, and the diameters of the openings  134  are changed in a circumferential direction. However, these parameters can be changed in any direction. 
     FIGS. 8A and 8B  are diagrams showing a structure of a first modification of the third embodiment. This first modification is different from the third embodiment in that a convection-cooling path  60  is provided at the outside. With this arrangement, as in the first modification of the first embodiment, a reinforcement wall exists at the outside of a sound absorbing wall that is formed with perforated plates  131  and  131 ′ and back plates  133  and  133 ′, when viewed from the inside of the combustor  10 . This forms a sound-absorbing wall tuned by the thickness of the back air layer. Therefore, the amount of sound inside the combustor  10  becomes smaller, and combustion oscillation does not occur easily. 
     FIGS. 9A and 9B  are diagrams showing a structure of a second modification of the third embodiment.  FIG. 10  is a cross-sectional diagram cut along the X—X line of  FIG. 9B , and  FIG. 11  is a cross-sectional diagram cut along the XI—XI line of FIG.  9 B. The second modification of the third embodiment is different from the third embodiment in that honeycomb materials  136  and  136 ′ are disposed in place of the spacers  132  and  132 ′ respectively. 
   Based on the above structure of the second modification of the third embodiment, it is possible to exhibit an effect similar to that of the third embodiment. 
   It is also possible to provide a convection-cooling layer  60  in the second modification, as in the first modification. 
   A third modification of the third embodiment will be explained next.  FIG. 12  is a cross-sectional diagram showing a structure of a third modification of the third embodiment. A first wall  140  and a second wall  140 ′ constitute a wall  100  of the combustor  10 . The first wall  140  and the second wall  140 ′ are constructed of perforated plates  141  and  141 ′ that are inside, in a radial direction, and a common back plate  142  disposed at the outside, in a radial direction, with a clearance from the perforated plates  141  and  141 ′. The perforated plates  141  and  141 ′ are formed with openings  143  and  143 ′, and the back plate  144  is formed with openings  144 , as in the third embodiment and the first and second modifications. 
   However, the back plate  142  is disposed at a position similar to that of the cover  50  that forms the convection cooling path  60  in the modification of the first embodiment, the first modification of the second embodiment, and the first modification of the third embodiment, respectively. This back plate  142  is different from the covers  50  in the third embodiment and the first and second modifications in that the distances of the clearance between the back plate  142  and the perforated plates  141  and  141 ′ respectively are large. 
   Therefore, it is not necessary to provide the cover  50  in the third modification of the third embodiment. 
   It is preferable to introduce cooling air into the gap between the back plate  142  and the perforated plates  141  and  141 ′ in order to improve the cooling of the perforated plates  141  and  141 ′. 
   As the distances of the clearance between the back plate  142  and the perforated plates  141  and  141 ′ respectively are large as explained above, it is easy to carry out the tuning. As a result of experiment, it has been confirmed that it is possible to obtain an optimum effect when the diameter of each opening  143  is 5 mm or less, and also when a distance L 1  between the openings  143  in a longitudinal direction and a distance L 2  between the openings  143  in a circumferential direction are set to have a relationship of 0.25≦L 1 /L 2 ≦4. 
     FIG. 13A  shows a layout of openings  143  that are formed on the perforated plate  141 . The positions of openings adjacently arrayed in a row of a circumferential direction are differentiated so that the positions of the openings in every other row are aligned in a longitudinal direction. 
   On the other hand,  FIG. 13B  is a diagram showing a layout of openings  143 ′ that are formed on the perforated plate  141 ′. As the perforated plate  141 ′ has pipes  141   s ′ for vapor cooling inside the perforated plate, the positions of the openings adjacently arrayed in a row of a circumferential direction are the same for each row. 
   It is also possible to arrange the layout of the openings  141 ′ as shown in FIG.  13 A and to arrange the layout of the openings  141  as shown in FIG.  13 B. Further, it is also possible to standardize the layout of the openings of both perforated plates based on one of these layouts. 
     FIG. 14  shows a fourth modification of the third embodiment. This fourth modification is different from the third modification in that openings are not formed on a back plate  142 . In this case, the back plate  142  has the same function as that of the cover  50  that forms the convection cooling path  60  in the modification of the first embodiment, the first modification of the second embodiment, and the first modification of the third embodiment respectively. In other words, there is formed a sound absorbing wall tuned by the thickness of the air layer that is formed between the perforated plate  141  and  141 ′ and the back plate  142 . Therefore, this work effect is added to the resistance effect of the openings  143  and  143 ′ on the perforated plates  141  and  141 ′ respectively. 
     FIG. 15  is a diagram showing a fifth modification of the third embodiment. This fifth modification is different from the third modification in that the range of a sound absorbing structure is smaller than that of the third modification. In other words, in the third modification, a sound absorbing structure is formed over the whole length of the combustor  10 . On the other hand, in the fifth modification, only a range of an elliptical portion indicated with a sign (B) in FIG.  16 A and  FIG. 17A  is a sound absorbing structure. It is possible to lower the cost by limiting the portion of the sound absorbing structure. A portion having a sound absorbing structure is determined based on a portion of the occurrence of combustion oscillation. Therefore, this portion having a sound absorbing structure is not limited to the portion shown in FIG.  15 . It is possible to have a sound absorbing structure in the portion near the fuel nozzle  40  or the portion near the turbine, depending on the characteristics of each combustor. 
   It is also possible to limit the range of this sound absorbing structure in the first and second embodiments including their modifications, and in the first, second and fourth modifications of the third embodiment respectively. 
   As explained above, according to the present invention, there is provided a gas turbine combustor in which a part or whole of the wall of the combustor disposed within an intake chamber is formed with an acoustic energy absorbing member that can absorb the acoustic energy of a combustion variation generated within the combustor. Further, the acoustic energy of a combustion variation generated within the combustor is absorbed in the wall of the combustor. Therefore, it is possible to prevent an occurrence of a combustion oscillation phenomenon. 
   While the invention has been described by reference to specific embodiments chosen for purpose of illustrations, it should be apparent that numerous modifications could be made thereto by those skilled in the art without departing from the basic concept and scope of the invention.