Abstract:
A method of controlling the part-load performance of a turbine includes generating a bypass flow in the turbine by removing a portion of a compressed fluid from a compressor of the turbine, determining an operating load of the turbine, transmitting the bypass flow to a turbine section of the turbine; and selectively heating the bypass flow according to the determined operating load of the turbine.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to a turbine, such as a gas turbine. 
         [0002]    A gas turbine is designed to operate at a peak load or base load. The turbine has a compressor, to take in a fluid and compress the fluid, a combustion section to combust a fuel to heat the fluid, and a turbine section to generate power with the heated fluid. When the turbine operates at peak load, the turbine operates at a predetermined combustion level to drive a turbine section. However, when the turbine is operated off-peak, or at part-load, the efficiency of the turbine decreases. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0003]    According to one aspect of the invention, a turbine includes a compressor to intake a fluid and compress the fluid, a combustion section to combust a fuel to generate heated fluid by heating the fluid from the compressor, a turbine section to convert the heated fluid to work, an exhaust to output the heated fluid from the turbine section, and a bypass circuit to generate a bypass flow by taking in compressed fluid from the compressor, to heat the bypass flow with the heated fluid from the exhaust, and to output the heated bypass flow to the turbine section. 
         [0004]    According to another aspect of the invention, a power generation system comprises: a turbine having a compressor to take in and compress a fluid, a combustion section to heat the fluid from the compressor, a turbine section to drive a shaft with the heated fluid from the combustion section, an exhaust section to eject the heated fluid from the turbine section, and bypass circuit to generate a bypass flow by taking in a portion of the compressed fluid from the compressor and selectively directing the bypass flow to the turbine section and the exhaust section; and a turbine control unit to determine an operating mode of the turbine among a peak mode and a part-load mode, and to control the bypass circuit to transmit the bypass flow to one of the turbine section and the exhaust section according to the determined operating mode. 
         [0005]    According to yet another aspect of the invention, a method to control part-load performance of a turbine comprises generating a bypass flow in a turbine by removing a portion of a compressed fluid from a compressor of the turbine; determining an operating load of the turbine; transmitting the bypass flow to a turbine section of the turbine; and selectively heating the bypass flow according to the determined operating load of the turbine. 
         [0006]    These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0007]    The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0008]      FIG. 1  illustrates a turbine according to one aspect of the invention. 
           [0009]      FIG. 2  illustrates the turbine and a turbine control unit. 
           [0010]      FIG. 3  illustrates a turbine section according to an embodiment of the invention. 
           [0011]      FIG. 4  is a flow chart to illustrate a control operation of the turbine. 
           [0012]      FIG. 5  illustrates a turbine according to an embodiment of the invention. 
       
    
    
       [0013]    The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0014]      FIG. 1  illustrates a turbine  1  according to an embodiment of the invention. The turbine  1  includes an intake section, or compressor,  10 , a combustion section  20 , a turbine section  30 , and an exhaust section  40 . The compressor  10  intakes a fluid and compress the fluid before transmitting the fluid to the combustion section  20 . According to the present embodiment, the fluid is air, and the compressor  10  comprises a plurality of stages, each stage including an annular ring of blades rotating about a shaft and a subsequent annular ring of vanes. 
         [0015]    The combustion section  20  receives the compressed air and heats the compressed air by combusting fuel F in a combustion chamber  21 . The heated compressed air is transmitted to the turbine section  30 , where it drives a rotor including buckets rotating about a shaft, and the rotating shaft generates power. 
         [0016]    The exhaust section  40  receives the heated air from the turbine  30  and outputs the heated air. 
         [0017]    In the present embodiment of the invention, the turbine  1  also includes a bypass circuit  50 . The bypass circuit  50  includes a conduit  52  to transmit air from the compressor  10  to a valve  51 , a conduit  53  to transmit air to the turbine from the valve  51 , and a conduit  54  to transmit air to the exhaust section  40  from the valve  51 . In addition, a conduit  55  transmits air from the exhaust section  40  to the turbine section  30 . 
         [0018]    The exhaust section  40  includes a heat exchanger  41  to heat the air from the conduit  54 . The heated air is then transmitted via the conduit  55  to the turbine section  30 . 
         [0019]    During peak operation or base-load operation, the valve  51  closes airflow to the conduit  54  and allows airflow from conduit  52  to conduit  53 . Thus, relatively cool air is provided to the turbine section  30  to cool components of the turbine section, such as a shaft, buckets, and nozzles. However, when cool air is provided to the turbine section  30  during part-load operation, efficiency of the turbine  1  decreases. 
         [0020]    Accordingly, during part-load operation, the valve  51  closes airflow to the conduit  53  and allows airflow through the conduit  54  to the exhaust section  40 . The air flows through the heat exchanger  41  of the exhaust section  40  and through the conduit  55  from the exhaust section  40  to the turbine section  30 . Consequently, the air that flows from the heat exchanger  41  through the conduit  55  to the turbine section  30  is heated, thereby increasing the efficiency of the turbine section by reducing heat loss of the air from the combustion section  20  to the turbine section  30 . 
         [0021]    In other words, according to the present embodiment of the invention, the components of the turbine section  30  are cooled by the bypass circuit  50  during peak-load operation to prevent overheating of the components while relatively high temperatures are output to the turbine section  30  from the combustion section  20 . However, during part-load operation, in which temperatures output from the combustion section  20  to the turbine section  30  are low relative to peak-load operation, the bypass circuit  50  provides heated air to the turbine section  30  to reduce heat-loss of the air provided from the combustion section  20 . Consequently, dual objectives of cooling components during peak-load operation and increasing efficiency during part-load operation are met. 
         [0022]      FIG. 2  illustrates a turbine control system. The turbine control system includes the turbine  1  and a turbine control unit  60 . The turbine control unit  60  includes, for example, a processing unit  61 , memory  62 , and an interface unit  63 . The turbine control unit  60  receives input data I via a terminal  68 , and outputs control signals A, B, C, and D via terminals  64 ,  65 ,  66 , and  67 . 
         [0023]    During operation, the turbine control unit  60  receives instructions or commands to operate the turbine  1  at part-load. The instructions are input to the interface unit  63 , which includes at least one of a wired port and a wireless port or antenna. The interface unit  63  transmits the instructions I to the processing unit  61 . The processing unit  61  determines whether the instructions I correspond to a part-load operation and controls the control signals A-D accordingly. According to one embodiment, the processing unit  61  compares a level of load in the instructions I with a predetermined level stored in memory  62  to determine whether the instructions I correspond to part-load operation. 
         [0024]    For example, the control signal A adjusts an air intake of the compressor  10  by adjusting characteristics of an intake control device  12 . In the present embodiment, the intake control device  12  is one of vanes having adjustable openings between adjacent vanes and a fan. Control signal B controls the inlet  22  of the combustion chamber  21  to reduce fuel input to the combustion chamber  21  in part-load operation. Control signal C adjusts fuel supplied from a fuel supply  23  to the combustion chamber  21  via the conduit  24 . Control signal D controls the valve  51  to close the outlet  57 , and to open the outlet  58 , in part-load operation. 
         [0025]    During peak-load operation, the bypass circuit  50  takes in air from the compressor  10  via the outlet  11 . The air enters the valve  51  via the inlet  56  and exits the valve  51  via the outlet  57 . The relatively cool air travels through the conduit  53  and enters the turbine section  30  via the inlet  31 . During off-peak or part-load operation, the relatively cool air exits the valve  51  via the outlet  58 , travels through the conduit  54 , and enters the heat exchanger  41  of the exhaust section  40  via the inlet  42 . The heated air exits the exhaust section  40  via the outlet  43 , travels through the conduit  55 , and enters the turbine section  30  via the inlet  32 . 
         [0026]      FIG. 2  illustrates conduits  53  and  55  connected to opposite sides of the turbine section  30  for clarity and for purposes of illustration. However, according to some embodiments the conduits  53  and  55  each introduce air into the turbine section  30  at a plurality of locations around the turbine section. 
         [0027]    While  FIG. 2  illustrates separate conduits  53  and  55  connected to separate inlets  31  and  32 , according to some embodiments, the conduits  53  and  55  are connected to each other.  FIG. 3  illustrates an example of the conduits  53  and  55  connected to each other to introduce air into the same inlets. As illustrated in  FIG. 3 , each of the conduits  53  and  55  is connected to a connection conduit  71 , which feeds to the inlets  72  in the casing  76  of the turbine section  30 . The inlets  72  correspond to the inlets  31  and  32  of  FIG. 2 . The turbine section  30  comprises a shaft  73  having buckets  74  that rotate around the shaft  73 , and nozzles comprising vanes  75  with openings between the vanes  75  to direct air from a direction of the combustion section  20  onto the buckets  74  to drive the shaft  73 . In the present embodiment, the inlets  72  are located at positions corresponding to the vanes  75 . The air from the bypass circuit  50 , represented by arrows into the turbine section  30 , flows into the inlets  72 , down the length of the vanes  75  in tubes located within the vanes  75 , out of the vanes  75  in the vicinity of the shaft  73 , and into the space between the vanes  75  and the buckets  74 . 
         [0028]    While  FIG. 3  illustrates the conduits  53  and  55  connected to the connection conduit  71 , according to alternative embodiments, the conduits  53  and  55  are connected to separate inlets corresponding to each vane  75 . In other embodiments, the conduits  53  and  55  are connected to alternating vanes  75 . 
         [0029]      FIG. 4  is a flow diagram illustrating a control operation of the turbine  1 . In operation  301 , an operation mode is detected. The turbine control unit  60  receives an input instruction or command Ito operate the turbine  1  at a predetermined load. If it is determined in operation  302  that the turbine  1  is operating at peak-load, then air from the compressor  10  in the bypass circuit  50 , or a bypass flow, is channeled directly to the turbine section  30 , bypassing the exhaust section  40 . In such a case, the turbine control unit  60  outputs control signals B-D to provide peak-load levels of fuel to the combustion chamber  21 , to close the outlet  58  from the bypass valve  51  to the exhaust section  40 , and to open the outlet  57  from the bypass valve  51  to the turbine section  30 . In addition, according to some embodiments, the turbine control unit  60  controls the level of intake air to a peak-load level by controlling the intake control device  12  with control signal A. 
         [0030]    If it is determined in operation  302  that the turbine  1  is operating at part-load, the bypass flow from the compressor  10  is diverted through the heat exchanger  41  of the exhaust section  40  to heat the bypass flow. The turbine control section  60  detects that the instruction I is to operate the turbine  1  at part-load, and adjusts control signals B-D to reduce the fuel provided to the combustion chamber  21 , to close the outlet  57  from the bypass valve  51 , and to open the outlet  58  from the bypass valve  51 . The bypass flow from the bypass valve  51  flows through the conduit  54  to the heat exchanger  41 , and the heated bypass flow is returned to the turbine section  30  via the conduit  55 . 
         [0031]    Accordingly, during peak-load operation, a cooling bypass flow is applied to a turbine section  30  to maintain within a predetermined range a temperature of the components of the turbine section  30 , and during part-load operation, the cooling bypass flow is heated and supplied to the turbine section  30  to improve operating efficiency of the turbine  1 . 
         [0032]    While the embodiments above have described the bypass flow as being heated by the exhaust section  40 , according to alternative embodiments, any heating source may be used to heat the exhaust.  FIG. 5  illustrates a turbine  1  in which the bypass circuit  50  selectively transmits the bypass flow through a heating unit  80 . The heating unit  80  includes any one of the exhaust  40 , a steam source, a heat exchanger, and a fuel combustion unit, for example. 
         [0033]    While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.