Abstract:
Gas turbine combustor with a specific fuel and oxidizer flow arrangement which provides high combustion efficiency for stoichiometric diffusion combustion in gas turbine applications operating with oxygen deficient working fluids.

Description:
[0001]    The present invention relates to a gas turbine combustor geometry with a specific fuel and oxidizer flow arrangement that provides high combustion efficiency for stoichiometric diffusion combustion in gas turbine applications operating with oxygen-deficient working fluids. 
       BACKGROUND OF THE INVENTION 
       [0002]    Gas turbine applications utilizing low oxygen working fluids are known. Examples of such applications are carbon capture, oxyfuel, and high exhaust gas recirculation, all of which require high combustion efficiency to be economically viable. However, achieving such high combustion efficiency has not been attainable to date. 
         [0003]    A need exists for high efficiency combustion in gas turbine applications where a low oxygen working fluid is used. The present invention seeks to satisfy that need. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    In one aspect, the invention provides a combustor comprising a housing having an inner surface, an interior volume, and a nozzle and a liner assembly positioned within the housing. The liner is provided with at least one liner mixing hole and at least one liner dilution hole. The liner assembly is spaced apart from the inner surface of the housing to define a path extending longitudinally along the combustor between the liner assembly and the inner surface of the housing for transporting working fluid to the interior volume through the liner mixing and dilution holes. The liner mixing and dilution holes are axially positioned in the liner assembly at specific positions as a function of the diameter of the liner. 
         [0005]    The combustor of the invention provides a stable flame and high combustion efficiency while ensuring adequate hardware durability. Since the applications of carbon capture, oxyfuel, and high exhaust gas recirculation require near stoichiometric combustion, the combustor of the present invention provides high efficiency combustion to ensure combustion is completed before fuel and oxidizers are diluted with the gas turbine working fluid. 
         [0006]    The combustor of the invention thus provides a cost effective solution in gas turbine applications where a low oxygen working fluid is used to achieve improved combustion efficiency as compared to that obtained using conventional combustors. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a perspective partial interior view of a combustor of the invention; 
           [0008]      FIG. 2  is a side view of the liner assembly of the combustor of the invention showing the mixing and dilution holes; 
           [0009]      FIG. 3  is a perspective view of the nozzle structure employed in the combustor of the invention; 
           [0010]      FIG. 4  is a schematic cross-sectional view of the combustor; 
           [0011]      FIG. 5  is a schematic illustration of the counter-swirl nozzle architecture; 
           [0012]      FIG. 6  is a schematic illustration of the co-swirl nozzle architecture; 
           [0013]      FIG. 7  is a partial side view of the nozzle showing an integrated igniter. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    Referring to the drawings,  FIG. 1  shows a perspective interior view of the combustor  2  of the invention having a housing  4  with an inner surface  6  and an interior volume  8 . A liner assembly  10  is provided within the housing  4  and is spaced apart from the inner surface  6  of the housing to define a path  12  extending longitudinally along the length of the combustor  2  between the liner assembly  10  and the inner surface  6 , along which gas turbine (GT) diluent rich working fluid flows. 
         [0015]      FIGS. 1 and 3  also show a nozzle  14  provided at one end of the combustor  2 . The nozzle  14  is in flow communication with the interior volume  8  of the combustor  2 . The nozzle  14  is provided with a series of concentric apertures defining fuel holes  16 . 
         [0016]    The nozzle structure employed in the present invention is described in detail in commonly assigned US 2009/0223227, filed Mar. 5, 2008 (herein incorporated by reference). 
         [0017]      FIG. 2  shows the liner assembly  10  provided with liner mixing holes  18 , 20 , liner dilution holes  40 , 42  and liner cooling holes  44 , 46 , 48  at different axial locations along the liner  10 . According to the invention, the liner mixing holes  18 , 20  are sized and positioned in the liner assembly  10  at axial locations to provide good mixing of fuel components and complete combustion. In one embodiment, for example, the liner mixing holes  18 , 20  are sized to provide about 10% of the GT flow, i.e., the flow available for the combustor from the compressor. Jets injected from the fuel nozzle through the liner mixing holes restrict the expansion of the oxidizer stream which promotes shear mixing between fuel and oxidizer. The location of the liner mixing holes may be optimized to avoid flame quenching. The is discussed below in relation to  FIG. 4 . 
         [0018]      FIG. 4  shows the liner mixing holes  18 ,  20  situated at an axial distance L from the nozzle  14  which is typically 0.65-1.05D, where D is the internal diameter of the liner  10 . The liner mixing holes generate a jet penetration into the interior volume  8  of the liner of 1.05-1.4 D 1 , where D 1  is the diameter of the mixing hole. 
         [0019]    The cooling holes  44 , 46 , 48  are positioned at different axial locations and are designed to accommodate, for example, about 30-32% of the GT working fluid at compressor discharge (i.e., the exit station of the compressor and starting station of the combustor). The size and number of cooling holes at any particular location is based on the desired effective heat transfer at that location. 
         [0020]    Crown hole  28  accommodates about 6-9% of the GT working fluid at compressor discharge. The crown hole  28  creates a recirculation bubble  50  of length L 2  of 0.65-1.05D where D is the internal diameter of the liner  10 . This provides for higher combustion efficiency. 
         [0021]    The dilution holes  40 , 42  are situated at an axial distance L 3  of 1.3-1.7 D, where D is the internal diameter of the liner. The dilution holes create a jet penetration of L 4  which is 1.4-1.6 times D 2 , where D 2  is the diameter of the dilution hole. Strong shear mixing occurs between the oxidizer and fuel resulting in rapid reaction with a short residence time promoting a larger reaction zone. In addition, the mixing with the GT working fluid helps in controlling the peak flame temperature while keeping the flame away from the nozzle. The dilution holes accommodate 8-11% of the total combustor flow. 
         [0022]    The center passage  24  of the nozzle is generally used for oxidizer flow, such as air, oxygen, diluted oxygen or fuel. The outer passages  22 , 26  are intended for gas turbine (GT) working fluid (typically a diluent rich fluid). The passages  22 ,  24 ,  26  are typically inclined such that they produce counter-rotating flow between the oxidizer and GT working fluid. This is illustrated in  FIG. 5  which illustrates schematically the gases exiting the nozzle into the interior volume  8  in a counter-swirling manner.  FIG. 6  illustrates an example of co-swirling where the gases exit the nozzle into the interior volume  8  in a co-swirling manner. 
         [0023]    The center passage  24  of the nozzle  14  typically contains angled fuel injection holes with an angle range from 40-60 degrees to produce high swirling flow. The center annular passage  24  of the nozzle is intended for gaseous fuel flow and is typically inclined with a cone angle of 20-26 degrees and a swirl angle of 5-16 degrees to the nozzle axis to induce counter-clockwise swirling (see  FIG. 5 ). The outer annular passage  26  is generally intended for diluent flow and is inclined with a cone angle of 30-36 degrees and swirl angle of 5-16 degrees to the nozzle axis to induce clockwise rotation. In such a flow arrangement, the strong shear mixing between the oxidizer and fuel results in the rapid reaction with a short residence time promoting larger reaction zone than in prior arrangements. 
         [0024]    The center passage  24  of the nozzle is designed to flow a blended fluid containing 20-80% of the oxidizer and 80-20% of the GT working fluid at compressor discharge. The blending is optimized to control the reaction rates, and flame temperature to lower the dissociation loss from the reaction zone. The outer passage  26  is designed to flow 25-30% of the total combustor flow. This flow arrangement acts to delay the combustion reaction downstream of the nozzle and thereby avoid potential risk of hardware damage. 
         [0025]      FIG. 7  shows an integrated igniter  30  on the nozzle  14  for igniting the combustible charge. The igniter is typically located at an angle of 25-30 degrees to the nozzle longitudinal axis. A pilot nozzle  52  may alternatively be provided for startup application. The pilot nozzle, if present, is usually located in the middle of the fuel nozzle that passes liquid fuel. 
         [0026]    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.