Abstract:
Occurrence of combustion vibration is prevented in a gas turbine plant by enhancing the degree of freedom in setting an airflow rate or a fuel flow rate in correspondence with a target load thereby enhancing combustion stability. A gas turbine controller comprises a first function generator ( 62 ) for setting the flow rate of fuel or air being supplied to a combustor ( 32 ) in correspondence with a target load, an suction air temperature sensor ( 22 ) for detecting intake temperature at the inlet of a compressor, a second function generator ( 69 ) for setting a correction amount of a set value of fuel flow rate or air flow rate based on the value detected by the suction air temperature sensor ( 22 ), a third function generator ( 66 ) for setting a modification amount of the correction amount while taking account of the target load, a first multiplier ( 68 ); for operating a modified correction amount from a correction amount set by the second function generator and a modification amount set by the third function generator, and a second multiplier ( 64 ) for calculating the flow rate of fuel or air being supplied to a combustor by adding the modified correction amount to the set value of fuel flow rate or air flow rate set by the first function generator.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a gas turbine control device that controls a gas turbine so that the gas turbine can maintain stable combustion without combustion vibrations even in a case where the ambient temperature, the fuel content, or the fuel calorific, value changes in the gas turbine plant in which the gas turbine is operated. 
       BACKGROUND OF THE INVENTION 
       [0002]    There are several types of combustion nozzles provided in a combustor of a gas turbine; for instance, there are a main nozzle that is used for premix combustion and a pilot nozzle that is used for diffusion combustion; further, a certain combustor is provided with a top-hat nozzle that is used for NOx reduction during high load operation as well as combustion stability during low load operation. An example of the configuration as to such a combustor is disclosed, for instance, in the patent reference 1 (JP2008-25910); the disclosed configuration as to the combustor in the patent reference 1 is hereby explained in consultation with  FIGS. 6 and 7 . 
         [0003]    Within the outer casing  102  of the combustor  100 , the inner tube  104  of the combustor is anchored to the outer casing so that the inner tube is supported by the outer casing and a predetermined space is kept between the outer casing and the inner tube; the tail pipe  106  of the combustor is connected to the tip end side of the inner tube  104  so that a casing of the combustor is formed. In the middle center area of the inner casing  104 , the pilot nozzle  108  is arranged; on the other hand, along the hoop direction of the inner surface of the inner tube  104 , a plurality of main nozzles  110  is arranged so as to surround the pilot nozzle  108 . The pilot cone  112  is fitted to the tip part of the pilot nozzle  108 . Further, a plurality of top-hat nozzles  114  is arranged along the hoop direction of the inner surface of the outer casing  102 . 
         [0004]    As shown in  FIG. 7 , an end part of the outer casing lid part  118  is fastened to the base end part of the outer casing body  116 , with a plurality of fastening bolts  120 ; at another end part of the outer casing lid part  118 , the base end part of the inner tube  104  is fitted so that the air passage  122  is formed between the outer casing lid part  118  and the inner tube  104 . Further, the tip end part of each main nozzle communicates with the main burner  124 . 
         [0005]    The top-hat forming part  126  is fitted into the outer casing lid part  118 , being fastened to the outer casing lid part  118  with a plurality of the fastening bolts  128 . As shown in  FIG. 7 , the top-hat nozzles  114  are configured in the top-hat forming part  126 ; namely, a plurality of fuel cavities  130  is formed along the hoop direction of the top-hat forming part  126 ; a plurality of first fuel passages  132  is formed from each cavity toward the outer casing lid part  118 . At the front end of each first fuel passage  132 , a second fuel passage  134  is formed toward the air passage  122 ; each second fuel passage  134  is connected to a peg  136  that is fitted to the inner surface of the top-hat forming part  126 . 
         [0006]    A pilot fuel line (not shown) is connected to the fuel port  138  for the pilot nozzle  108  and supplies pilot fuel f p  into the combustor; a main fuel line (not shown) is connected to the fuel port  140  for the main nozzles  110  and supplies main fuel f m  into the combustor; a top-hat fuel line (not shown) is connected to the fuel port  142  for the top-hat nozzles  114  and supplies main fuel f t  into the combustor. 
         [0007]    In the configuration described above, when the compressed air of a high temperature and a high pressure is supplied from the airflow channel  144  toward the air passage  122  along the direction of the arrow a, the compressed air is premixed with the fuel f t  that is injected through the top-hat nozzles  114 ; the premixed air-fuel mixture streams into the inner side of the inner tube  104 . 
         [0008]    Inside of the inner tube  104 , the air-fuel mixture (being premixed as described above) is further premixed with the fuel f m  that is injected through the main nozzle  110 , turning into revolution flow and streaming into the inner side of the tail pipe  106  of the combustor. 
         [0009]    Further, the premixed air-fuel mixture is mixed with the fuel f p  that is injected through the pilot nozzle  108  so that the finally premixed air-fuel mixture is ignited by a pilot flame (not shown), is burnt, turns into combustion gas and blows out into the inner side of the tail pipe  106 ; thereby, a part of the combustion gas blows out into the inner side of the tail pipe  106 , accompanying the flame propagation so that the combustion gas diffuses; the combustion gas that diffuses in this way ignites the air-gas mixture that streams from the main nozzles toward the tail pipe  106 ; thus, the combustion continues. In other words, since the lean air-fuel mixture produced by the fuel from the main nozzles  110  can stably burns thanks to the diffusion frame propagation produced by the pilot fuel that is injected through the pilot nozzle  108 , the flame propagation can be prevented from reducing inflammation. Further, the compressed air is firstly mixed with the fuel injected through the top-hat nozzles  114 ; this approach can bring the reduction of NOx produced in the gas turbine. 
         [0010]    In the conventional gas turbine plants, the fuel flow rate and the airflow rate are predetermined on the basis of the generator output (demand power), the ambient temperature and so on; the fine adjustments of the operation conditions as to the gas turbine and the plant thereof are performed in the test operations or the commissioning operation; after commissioning, the gas turbine and the plant thereof are operated on the basis of the fine adjusted operation conditions. According to the conventional control device for the gas turbine plant, however, the operation state conditions cannot respond to, for example, the change of fuel contents during the operation. Accordingly, by the limitation of the ability of the conventional control device, the combustion stability is often hindered or the combustion vibrations are often caused. 
         [0011]    In a case where combustion vibrations occur, the vibrations seriously hinder the operation of the gas turbine; hence, it is strongly required to restrain the combustion vibrations of the gas turbine as far as possible, in view of the protection of the plant facility and the enhancement of the plant availability. 
         [0012]    The patent reference 2 (JP1993-187271) discloses a control device by which the airflow rate or the fuel flow rate as to the gas turbine combustor is controlled on the basis of the changes regarding the ambient temperature, the ambient humidity, the fuel calorific value and so on. According to the technology of the patent reference 2, in response to the technological requirement as described above, the bias control regarding the airflow rate or the fuel flow rate is made use of in order to improve the robustness for the combustion stability. 
         [0013]    In the control means disclosed in the patent reference 2, the airflow rate or the fuel flow rate is uniformly controlled when the bias control is applied; thus, the degree of freedom as to the control is limited; therefore, it is difficult to adjust the airflow rate or the fuel flow rate so that either of the flow rates converges to an optimally controlled value. 
       SUMMARY OF THE INVENTION 
       [0014]    In view of the difficulties in the conventional technologies as described above, the present invention aims at improving the stability of the combustion as well as preventing the combustion vibrations from happening, by enhancing the degree of freedom regarding the control settings in a case where the airflow rate or the fuel flow rate is optimally adjusted in response to the target power output corresponding to the load demanded on the generator in the gas turbine plant. 
         [0015]    In order to overcome the difficulties described above, the present invention discloses a gas turbine control device for controlling a fuel flow rate or an airflow rate in response to a target power output of the gas turbine, the fuel and the air being supplied to a plurality of combustors, the device comprising: 
         [0016]    a first function generator for establishing the fuel flow rate or the airflow rate, in response to the target power output, the fuel and the air being supplied to each combustor; 
         [0017]    a second function generator for establishing a correction value to correct the established fuel flow rate or the established airflow rate on the basis of the suction air temperature detected by a suction air temperature sensor that is provided so as to detect the suction air temperature at an air inlet of the compressor; 
         [0018]    a third function generator for establishing an amendment value to amend the established correction value as to the fuel flow rate or the airflow rate, in taking the target power output into consideration; 
         [0019]    a first computing element for computing a correction-amendment value by use of the correction value established by the second function generator and the amendment value established by the third function generator; 
         [0020]    a second computing element for computing an order fuel flow rate or an order airflow rate by adding the correction-amendment value to the fuel flow rate or the airflow rate either of which is established in the first function generator, the order fuel flow rate or the order airflow rate being used to determine the flow rate as to the fuel or the air to be supplied to the combustor. 
         [0021]    In the present invention, the fuel flow rate or the airflow rate is established in response to the target power output; a correction value to correct the established fuel flow rate or the established airflow rate is set by the second function generator, on the basis of the detected value as to the suction air temperature at the air inlet of the compressor. In other words, the present invention pays attention to the suction air temperature as a control variable (parameter) to be used for controlling the fuel flow rate or the airflow rate in order to maintain the stable combustion of the gas turbine. 
         [0022]    In the patent reference 2, the ambient air temperature is selected as a control variable; however, the ambient air temperature does not necessarily uniquely correspond to the suction air temperature. Both the ambient air temperature and the suction air temperature are correlated to some extent; the suction air temperature changes in response to the flow speed thereof; the greater the flow speed, the higher the temperature drop of the suction air temperature after being inhaled. 
         [0023]    By detecting the suction air temperature that is the temperature of the air inhaled into the gas turbine, rather than by detecting the ambient air temperature, the mass balance (the mass flow balance) and the heat balance as to the gas turbine can be known more correctly. Thus, in order to maintain the combustion stability without being influenced by the changes of weather condition, it is advantageous to use the suction air temperature rather than the ambient air temperature as a state variable (parameter) in relation to the gas turbine control. 
         [0024]    Further, in the third function generator, the amendment value to amend the correction value established in the second function generator as to the fuel flow rate or the airflow rate is set in taking the target power output into consideration; thus, the fuel flow rate or the airflow rate can be optimally adjusted in response to the target power output. Accordingly, in comparison with the approach of the patent reference 2, the present invention provides an approach of greater freedom of control thereby combustion vibrations are prevented and stable combustions are maintained. 
         [0025]    Further, another preferable embodiment of the present invention is the gas turbine control device, further comprising: 
         [0026]    a fourth function generator for establishing a second correction value to correct the fuel flow rate or the airflow rate established in the first function generator, in response to the contents or the calorific value of the fuel; 
         [0027]    a fifth function generator for establishing a second amendment value to amend the established second correction value, in taking the target power output into consideration; 
         [0028]    a third computing element for computing a second correction-amendment value by use of the second correction value established by the fourth function generator and the second amendment value established by the fifth function generator; 
         [0029]    a fourth computing element for computing an order fuel flow rate or an order airflow rate by adding the correction-amendment value and the second correction-amendment value to the fuel flow rate or the airflow rate, the order fuel flow rate or the order airflow rate being used to determine the flow rate as to the fuel or the air to be supplied to the combustor. 
         [0030]    As described above, the contents of the fuel or the calorific value of the fuel is also taken into consideration, as a parameter to be used for the control of the gas turbine; based on the parameter, a second correction value to correct the fuel flow rate or the airflow rate is established; further, a second correction-amendment value to amend the established second correction value is set, in taking the target power output into consideration; thus, the second correction-amendment value is computed; based on the second correction-amendment value, an order fuel flow rate or an order airflow rate is determined. Thus, the stable combustion of the gas turbine is maintained without producing combustion vibrations, even in a case where the contents of the fuel, the calorific value of the fuel, or the percentage content of the inert gas included in the fuel fluctuates. 
         [0031]    Further, another preferable embodiment of the present invention is the gas turbine control device, wherein a detecting means for detecting the contents or the calorific value of the fuel is provided on the fuel supply main-pipe at the upstream side of the combustor; and, the second correction value is established on the basis of the detected values detected by the detecting means. The contents of the fuel or the calorific value of the fuel can be specified in advance, or can be inputted every time the contents or the calorific value of the fuel changes. However, as described in this embodiment, the contents or the calorific value of the fuel is preferably detected by a detecting means provided on the fuel supply main-pipe. In addition, preferably, there may be an approach in which the calorific value is estimated through the arithmetic calculations by use of the values as to the generator output and the fuel flow rate. 
         [0032]    Hence, it becomes not necessary to specify the contents or the calorific value of the fuel in advance; further, the detecting means can detect the contents or the calorific value, even when the value thereof changes during the gas turbine operation; the contents or the calorific value can be detected without stopping the gas turbine operation; thus, the second correction value can be established in response to the changing value as to the contents or the calorific value of the fuel, while the gas turbine is placed under operation. 
         [0033]    Further, another preferable embodiment of the present invention is the gas turbine control device, wherein the target power output is a load index with respect to the load demanded on the generator connected to the gas turbine or the temperature of the combustion gas flowing into the combustor; and, to be controlled variable is one of: 
         [0034]    the opening of a plurality of fuel flow rate control valves provided on the fuel supply pipes connecting the fuel supply main-pipe with, each combustor; 
         [0035]    the attack angle of a plurality of inlet guide vanes provided in the compressor of the gas turbine; or, 
         [0036]    the opening of the bypass valves provided on each air bypass pipe passing the air compressed by the compressor so that the compressed air bypasses the combustion gas area in each combustor. 
         [0037]    As described above, by controlling the fuel flow rate control valves, the inlet guide vanes, or the bypass valves, it becomes easy to adjust the fuel flow rate or the airflow rate; the flow rate of the fuel or the air supplied to each combustor can be properly set in relation to the suction air temperature the contents of the fuel, or the calorific value of the fuel; accordingly, the combustion control can be realized thereby the gas turbine operation is hard to be influenced by the fluctuations regarding the suction air temperature, the contents of the fuel, or the calorific value of the fuel. 
         [0038]    Further, another, preferable embodiment of the present invention is the gas turbine control device, wherein the target power output is a load index with respect to the load demanded on the generator connected to the gas turbine or the temperature of the combustion gas flowing into the turbine; and, to be controlled variable is one of: 
         [0039]    the pilot fuel ratio that is the percentage ratio of the pilot fuel flow rate to the total fuel flow rate; or, 
         [0040]    the top-hat fuel ratio that is the percentage ratio of the top-hat fuel flow rate to the total fuel flow rate. 
         [0041]    As described above, by controlling the ratio of the pilot fuel flow rate or the top-hat fuel flow rate to the total fuel flow rate, the flow rate of the fuel supplied to each combustor can be properly set without fluctuating the total fuel flow rate, even in a case where the suction air temperature, the contents of the fuel, or the calorific value of the fuel fluctuates; accordingly, the combustion control can be realized thereby the gas turbine operation is hard to be influenced by the change in the load demanded on the generator or the combustion temperature, even in a case where the suction air temperature, the contents of the fuel, or the calorific value of the fuel fluctuates. 
         [0042]    As described above, the present invention provides a gas turbine control device for controlling the fuel flow rate or the airflow rate in response to the target power output of the gas turbine, the fuel and the air being supplied to a plurality of combustors, the device comprising: 
         [0043]    a first function generator for establishing the fuel flow rate or the airflow rate, in response to the target power output, the fuel and the air being supplied to each combustor; 
         [0044]    a second function generator for establishing a correction value to correct the established fuel flow rate or the established airflow rate on the basis of the suction air temperature detected by a suction air temperature sensor that is provided so as to detect the suction air temperature at the air inlet of the compressor; 
         [0045]    a third function generator for establishing an amendment value to amend the established correction value as to the fuel flow rate or the airflow rate, in taking the target power output into consideration; 
         [0046]    a first computing element for computing a correction-amendment value by use of the correction value established by the second function generator and the amendment value established by the third function generator; 
         [0047]    a second computing element for computing an order fuel flow rate or an order airflow rate by adding the correction-amendment value to the fuel flow rate or the airflow rate either of which is established in the first function generator, the order fuel flow rate or the order airflow rate being used to determine the flow rate as to the fuel or the air to be supplied to the combustor. 
         [0048]    In this way, the degree of freedom regarding the gas turbine control can be enhanced; further, in response to the target power output, the optimum control regarding the fuel flow rate or the airflow rate can be performed by use of the suction air temperature, as a parameter for the control; thus, even when the weather condition fluctuates, the combustion of the gas turbine can be stably maintained, and combustion vibrations can be prevented. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0049]    The present invention will now be described in greater detail with reference to the preferred embodiments of the invention and the accompanying drawings, wherein: 
           [0050]      FIG. 1  shows the configuration of the gas turbine plant according to a first embodiment of the present invention; 
           [0051]      FIG. 2  shows a block diagram regarding a gas turbine control unit according to a first embodiment; 
           [0052]      FIG. 3  shows a block diagram regarding a gas turbine control unit according to a second embodiment of the present invention; 
           [0053]      FIG. 4  shows a block diagram regarding a gas turbine control unit according to a third embodiment of the present invention; 
           [0054]      FIG. 5  shows a block diagram regarding the control mechanism of the fuel flow rate control valves according to the third embodiment; 
           [0055]      FIG. 6  shows a longitudinal cross-section of the combustor of the gas turbine; 
           [0056]      FIG. 7  shows an enlargement of a part of  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0057]    Hereafter, the present invention will be described in detail with reference to the embodiments shown in the figures. However, the dimensions, materials, shape, the relative placement and so on of a component described in these embodiments shall not be construed as limiting the scope of the invention thereto, unless especially specific mention is made. 
       First Embodiment 
       [0058]    The device as a first embodiment according to the present invention is now explained with reference to  FIGS. 1 and 2 .  FIG. 1  shows the configuration of the gas turbine plant according to a first embodiment of the present invention. In  FIG. 1 , a gas turbine  1  is provided with a gas-turbine body  10  and a combustor assembly  30 . The gas-turbine body (assembly)  10  is provided with a compressor  12  having a plurality of inlet guide vanes  14 , a rotating shaft  16 , and a turbine  18 ; a generator is connected to the turbine  18 . A suction air temperature sensor  22  for detecting the temperature of the suction air s passing through the space among the inlet guide vanes  14  is provided; the detected value (signal) detected by the suction air temperature sensor  22  is inputted into a gas turbine control unit  60  for controlling the gas turbine plant according to the present embodiment; incidentally, the explanation about the gas turbine control unit  60  will be given later. 
         [0059]    The turbine  18  is connected to a combustion gas guide pipe  26  and an exhaust gas pipe  28  that discharges combustion exhaust gas e outward; Further, the turbine  18  is connected to the compressor  12  and the generator  20  via the rotating shaft  16 . The produced combustion gas is supplied to the turbine  18  through the combustion gas guide pipe  26 ; the exhaust gas rotates the turbine  18 ; the rotation movement is transmitted to the generator  20  and the compressor  12 . The combustion gas that is used for the power generation is discharged outward as the exhaust gas e through the exhaust gas pipe  28 . At the combustion gas inlet of the turbine  18 , the temperature sensor  19  for detecting the temperature of the combustion gas guided through the combustion gas guide pipe  26  is fitted. The detected value (signal) detected by the temperature sensor  19  is inputted into the gas turbine control unit  60  as described later. 
         [0060]    The compressor  12  is connected to an ambient air guide pipe  13  and a compressed air guide duct  24 ; the compressor  12  is coupled with the turbine  18  and the generator  20  via the rotating shaft  16 ; the rotation movement of the turbine  18  is transmitted to the compressor  12  and the compressor  12  rotates; by the rotation movement of the compressor  12 , the ambient air is inhaled through the ambient air guide pipe  13 ; the suction air s thus inhaled is compressed and delivered to the combustors. 
         [0061]    The inlet guide vanes of the compressor are provided at the passage of the suction air s; the flow rate of the suction air s can be adjusted by adjusting the attack angles of the inlet guide vanes on the condition that the rotation speed of the compressor is constant. The gas turbine control unit  60  controls the attack angle, as described later. 
         [0062]    In the next place, the combustor assembly  30  is now explained. The combustor  32  is connected to the compressed air guide duct  24  and the combustion gas guide pipe  26 . The configuration of the combustor  32  is the same as that of a combustor assembly  100  shown in  FIGS. 6 and 7 . The suction air s is guided to the combustor  32  through the compressed air guide duct  24 . A bypass pipe  34  is connected to the compressed air guide duct  24  and the combustion gas guide pipe  26 ; on a part way of the bypass pipe  34 , a bypass valve is installed. The bypass valve  36  controls the flow rate of the suction air guided to the combustor  32 . The gas turbine control unit  60  controls the opening of the bypass valve, as described later. 
         [0063]    The fuel f is supplied to the combustor  32  from a fuel supply main-pipe  38  through three branch pipes  40 ,  42  and  44 ; on the fuel supply main-pipe  38 , a calorimeter  46  for detecting the calorific value of the fuel f is fitted; at the branch pipe  40 , namely, a main fuel supply pipe  40 , a main fuel flow rate control valve  48  is installed; between the control valve  48  and the combustor  32 , a main fuel supply valve  50  is installed; at the branch pipe  42 , namely, a top-hat fuel supply pipe  42 , a top-hat fuel flow rate control valve  52  is installed; between the control valve  52  and the combustor  32 , a top-hat fuel supply valve  54  is installed; at the branch pipe  44 , namely, a pilot fuel supply pipe  44 , a pilot fuel flow rate control valve  56  is installed; between the control valve  56  and the combustor  32 , a pilot fuel supply valve  58  is installed. 
         [0064]    In the configuration described thus far, as shown in  FIG. 7 , the fuel f m  delivered from the main fuel supply pipe  40  is supplied to a fuel port  140  communicating with a plurality of main (fuel) nozzles  110 ; the fuel f t  delivered from the top-hat fuel supply pipe  42  is supplied to a fuel port  142  communicating with a plurality of top-hat (fuel) nozzles  114 ; the fuel f p  delivered from pilot fuel supply pipe  44  is supplied to a fuel port  138  communicating with a pilot (fuel) nozzle  108 . Thus, the fuel f is burned in the combustor  32  according to the combustion method described above. 
         [0065]      FIG. 2  shows a gas turbine control unit  60  according to the first embodiment; in  FIG. 2 , the target power output of the gas turbine is specified. The target power output may be a target value corresponding to the load requirement (MW) on the generator or a target value that is specified on the basis of the temperature of the combustion gas guided into the turbine  18 . For instance, in a case where the target value corresponding to the load requirement (MW) is used, the target value as the target power output is specified as a non-dimensional value in an interval such as 50% to 100% ([0.5, 1.0]); thereby, the 100% corresponds to full load. 
         [0066]    On the basis of the specified target power output, the fuel flow rate as to the fuel flow delivered through the fuel supply main-pipe  38  is specified (established) in a first function, generator  62 ; the specified value (as to the fuel flow rate) is inputted into a first adder-subtractor  64 . 
         [0067]    In the next place, the suction air temperature detected by the suction air temperature sensor  22  is inputted into a second function generator  69  in which a correction value (a first correction value) is established in response to the suction air temperature; the correction value established in the second function generator  69  is inputted into a first multiplier  68 . In addition, since the combustion state fluctuates according to the target power output, the setting value as to the fuel flow rate needs to be amended under the condition that the combustion state fluctuations are taken into consideration; thus, another target power output (a second target power output) is inputted into a third function generator  66  in which an amendment value (a first amendment value) is established; the amendment value established in the third function generator  66  is inputted into the first multiplier  68 . 
         [0068]    In the first multiplier  68 , a correction-amendment value (an overall correction value for the fuel flow rate setting value) is computed on the basis of the a first correction value established in the second function generator  69  in response to the suction air temperature and the first amendment value established in the third function generator  66  in response to the second target power output; and, the correction-amendment value (the overall correction value for the fuel flow rate setting value) is inputted into the first adder-subtractor  64 ; in the first adder-subtractor  64 , the correction-amendment value is added to (or subtracted from) the fuel flow rate setting value specified in a first function generator  62 . Thus, the fuel flow rate in response to the first target power output and the second target power output is determined. 
         [0069]    On the basis of the determined fuel flow rate, the opening of each of the fuel valves  48 ,  52 , and  56  is determined according to a function expressed with the parameters as to the valve opening characteristics of each valve as well as the parameters such as fuel temperature and fuel pressure; the order signals for controlling the opening of each of the fuel valves  48 ,  52 , and  56  are issued from the gas turbine control unit  60  toward each of the fuel valves  48 ,  52  and  56 . 
         [0070]    As described above, the fuel flow rates through each of the fuel valves  48 ,  52 , and  56  are determined; the opening of each of the fuel valves  48 ,  52 , and  56  can respond to the detected suction air temperature at the air inlet of the compressor  12 ; further, since the opening of each of the fuel valves is controlled so that the valve opening reflects the combustion characteristics regarding the target power output, the each fuel flow rate can be optimal in response to the target power output. Hence, the operation of the gas turbine can be continued in a stable combustion condition, without combustion vibrations. Moreover, the degree of freedom regarding the control settings can be enhanced, in comparison with the bias control (regarding the airflow rate or the fuel flow rate) disclosed in the patent reference 2. 
         [0071]    In addition, in this first embodiment, the fuel flow rate as to the fuel flow delivered through the fuel supply main-pipe  38  is specified by the first function generator  62 ; the summation of the first correction value and the first amendment value is calculated by the first adder-subtractor  64 , and, the fuel flow rate in response to the target power output is determined. However, preferably, there may be an approach in which each of the fuel flow rates through the main fuel supply pipe  40 , the top-hat fuel supply pipe, and the pilot fuel supply pipe  42  is specified by the first function generator  62 ; and, the correction-amendment value (for the summation of the fuel flow rates) is calculated by the first adder-subtractor  64  so that the main fuel flow rate, the top-hat fuel flow rate, and the pilot fuel flow rate are determined in response to the target power output. 
         [0072]    Further, in this first embodiment, an approach in which the fuel flow rate is controlled is adopted; instead, preferably, there may be an approach in which the flow rate of the compressed air guided from the compressed air guide duct  24  into the combustor  32  is controlled. In this case, the attack angle of each inlet guide vane  14  is adjusted so as to control the compressed airflow rate; or, the opening of the bypass valve  36  is adjusted so as to control the compressed airflow rate. Further, preferably, there may be an approach in which both the fuel flow rate and the compressed airflow rate are controlled at the same time. 
         [0073]    Further, in this first embodiment, at the inlet of the turbine  18 , the temperature sensor  19  for detecting the temperature of the combustion gas is provided. However, preferably, there may be an approach in which the temperature of the combustion gas is estimated through arithmetic calculations as to the detected-values detected by other temperature sensors and flow rate meters, with respect to heat balance and mass balance. 
       Second Embodiment 
       [0074]    In the next place, a second embodiment according to the present invention is now explained with reference to  FIG. 3 . In  FIG. 3 , the components (such as the function generators, the adder-subtractors or the multipliers) that are marked with the same numeral or symbol, as the components in  FIG. 2  in relation to the first embodiment are common components over  FIGS. 2 and 3 ; naturally, the common components have the same function. In this second embodiment, in addition to the control approach shown in  FIG. 2 , a calorimeter  46  is provided on the fuel supply main-pipe so as to detect the specific heat value of the fuel f; and, in response to the detected-value detected by the calorimeter  46 , a second correction value is established in a fourth function generator  78 , the second correction value being a correction value for the setting of the fuel flow rate. Further, in a fifth function generator  74 , a second amendment value for amending the second correction value in consideration of the target power output (the first target power output) is established. 
         [0075]    In the next place, the second correction value established in the fourth function generator  78  and the second amendment value established in the fifth function generator  74  are inputted into a second multiplier  76 , in which a second correction-amendment value is calculated. The second correction-amendment value is inputted into a second adder-subtractor  72 . Further, as is the case with the first embodiment, in the first adder-subtractor  64 , the first correction-amendment value is added to (or subtracted from) the fuel flow rate setting value specified in the first function generator  62  in response to the target power output; subsequently, in a second adder-subtractor  72 , the second correction-amendment value is added to (or subtracted from) the first correction-amendment value. Thus, the flow rate of the fuel supplied to the combustor  32  is determined; based on the determined fuel flow rate, the opening of each of the fuel valves  48 ,  52 , and  56  is to be determined according to a function expressed with the parameters as to the valve opening characteristics of each valve as well as the parameters such as fuel temperature and fuel pressure. 
         [0076]    According to this second embodiment, the detected calorific value of the fuel f is taken into consideration as a parameter of an additional kind. On the basis of the detected suction-air temperature at the inlet of the compressor and this detected calorific value of the fuel, the fuel flow rate setting value is corrected; further, the corrected value is amended in response to the target power output; thus, in addition to the effect brought by the first embodiment, the second embodiment can realize the effectiveness of maintaining the stable combustion without producing combustion vibrations, even in a case where the contents of the fuel, the calorific value of the fuel, or the percentage content of the inert gas included in the fuel fluctuates. 
         [0077]    Further, in this first embodiment, an approach in which the fuel flow rate is controlled is adopted; instead, preferably, there may be an approach in which the flow rate of the compressed air guided from the compressed air guide duct  24  into the combustor  32  is controlled. In this case, the attack angle of each inlet guide vane  14  is adjusted so as to control the compressed airflow rate; or, the opening of the bypass valve  36  is adjusted so as to control the compressed airflow rate. Further, preferably, there may be an approach in which both the fuel flow rate and the compressed airflow rate are controlled at the same time. Moreover, in this first embodiment, the calorimeter  46  is provided on the part way of the fuel supply main-pipe. However, preferably, there may be an approach in which the calorific value is estimated through the arithmetic calculations by use of the values as to the generator output and the fuel flow rate. 
       Third Embodiment 
       [0078]    In the next place, a third embodiment according to the present invention is now explained with reference to  FIGS. 4 and 5 . In  FIG. 4  according to the present embodiment, the temperature of the combustion gas at the gas inlet of the turbine  18  is adopted as a variable (parameter) to be established corresponding to the target power output. The temperature sensor  19  detects the temperature of the combustion gas. The gas inlet temperature as an index of the target power output is, for instance, directed to a value between 1480 to 1500° C. In  FIG. 4 , the configuration components (such as the function generators, the adder-subtractors or the multipliers) of a gas turbine control unit  80  are the same as those in  FIG. 3 ; the common components over FIGS.  3  and  4  are marked with the same numerals or symbols. 
         [0079]    In the gas turbine control unit  80 , the combustion temperature is used as a variable (parameter) that corresponds to the target power output; as is the case with the second embodiment, the control parameters comprise the suction air temperature detected by the suction air temperature sensor  22  and the calorific value of the fuel f detected by the calorimeter  46 ; In the present embodiment, the first function generator  62  establishes the fuel ratios that are, for instance, the percentage ratios of the main fuel flow rate, the top-hat fuel flow rate and the pilot fuel flow rate in the total fuel flow rate. In the first adder-subtractor  64 , the first correction-amendment value is added to (or subtracted from) each fuel ratio; subsequently, in the second adder-subtractor  72 , the second correction-amendment value is added to (or subtracted from) the each result by the first correction-amendment. Incidentally, the ratio of the top-hat fuel flow rate to the total fuel flow rate, the ratio of the pilot fuel flow rate to the total fuel flow rate, and the ratio of the main fuel flow rate to the total fuel flow rate are called the top-hat fuel flow ratio, the pilot fuel flow ratio, and the main fuel flow ratio, respectively. 
         [0080]    In this way, on the basis of the determined fuel flow rate ratios, the order signal as to the opening of each of the fuel valves  48 ,  52 , and  56  is issued. 
         [0081]    The steps of determining the opening of each of the fuel valves  48 ,  52 , and  56  are on the basis of the determined fuel flow rate ratios are now explained with reference to  FIG. 5 ; thereby, the pilot fuel flow rate is calculated by use of the pilot fuel flow ratio and the total flow rate; the top-hat fuel flow rate is calculated by use of the top-hat fuel flow ratio and the total flow rate; further, at the comparator  84 , the main fuel flow rate is calculated by subtracting the pilot fuel flow rate and the top-hat fuel flow rate from the total fuel flow rate. 
         [0082]    Subsequently, according to a relation expressed with the parameters as to the valve opening characteristic of each of the fuel flow rate control valves  48 ,  52  and  56 , as well as, the parameters such as fuel temperature and fuel pressure, the order signal for controlling the opening of each of the fuel flow rate control valves  48 ,  52 , and  56  is issued toward the corresponding fuel flow rate control valve; thereby, before being issued, each signal for each corresponding fuel flow rate control valve is corrected, at correctors  86 ,  88  and  90  (in  FIG. 5 ), so as to reflect the effect of the parameters such as fuel temperature and fuel pressure. 
         [0083]    Further, in this third embodiment, at the inlet of the turbine  18 , the temperature sensor  19  for detecting the temperature of the combustion gas is provided. However, preferably, there may be an approach in which the temperature of the combustion gas is estimated through arithmetic calculations as to the detected-values detected by other temperature sensors and flow rate meters, with respect to heat balance and mass balance. 
         [0084]    According to the this third embodiment, as is the case with the second embodiment, the control parameters comprise the suction air temperature detected by the suction air temperature sensor  22  and the calorific value of the fuel f detected by the calorimeter  46 ; further, the temperature of the combustion gas at the gas inlet of the turbine  18  is adopted as a variable (parameter) to be established corresponding to the target power output; thus, in addition to the effect brought by the second embodiment, the third embodiment can realize the effectiveness of restraining the influence of the seasonal change in the suction air temperature on the combustion stability inside the combustor, to a minimal level. 
       INDUSTRIAL APPLICABILITY 
       [0085]    According to the present invention, a stable combustion operation of a gas turbine plant can be realized with a simple control mechanism, without producing combustion vibrations, in a case where the suction air temperature changes or the calorific value of the supplied fuel fluctuates, for instance, because of the increase of the inert gas components in the fuel.