Abstract:
The present invention provides a gas turbine combustor that has a fuel injection nozzle using a fluid other than liquid fuel to atomize the liquid fuel and that can suppress a reduction in power generation efficiency resulting from a heat loss while promoting the atomization of the liquid fuel. The gas turbine combustor is adapted to mix liquid fuel with combustion air led from a compressor, burn the mixture, and supply combustion gas generated to a gas turbine. The gas turbine combustor includes a fuel injection nozzle that atomizes the liquid fuel into fine liquid droplets. The fuel injection nozzle includes a first system adapted to supply the liquid fuel and a second system adapted to supply a fluid for atomizing the liquid fuel. Low-boiling liquid fuel is supplied to the second system as the fluid. The second system is adapted to heat and supply the low-boiling liquid fuel.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a gas turbine combustor. 
         [0003]    2. Description of the Related Art 
         [0004]    Liquid-fueled combustors generally use a fuel nozzle to atomize liquid fuel, promote mixing of a group of reduced-diameter fuel droplets atomized with combustion air, and then burn the mixture. 
         [0005]    Examples of fuel nozzles adapted to atomize liquid fuel include a two-fluid fuel nozzle and a single-fluid fuel nozzle. The two-fluid fuel nozzle is adapted to atomize liquid fuel using the shear force of a fluid other than liquid fuel, e.g., high-pressure air. The single-fluid fuel nozzle is adapted to atomize liquid fuel by increasing the supply pressure of liquid fuel and thereby accelerating the jet velocity of the liquid fuel. 
         [0006]    The former two-fluid fuel nozzle is superior in atomization performance to the single-fluid fuel nozzle and has an effect of suppressing the discharge amount of soot, which is one of the problems in the liquid-fueled combustor. However, since the two-fluid fuel nozzle needs air for atomization, when, for example, the two-fluid fuel nozzle may use the air extracted from the compressor of a gas turbine, it is necessary to increase the pressure of the air thus extracted. Therefore, the power for increasing the pressure of the air is needed, and the extracted air is cooled and then supplied to the combustor. Thus, there is concern about the efficiency degradation of the gas turbine. 
         [0007]    On the other hand, the single-fluid fuel nozzle does not need an atomized air supply system; therefore, it is advantageous to the above-mentioned efficiency degradation and the simplification of an installation. However, the single-fluid fuel nozzle is inferior in atomization performance to the two-fluid fuel nozzle. Such a tendency is prominent particularly under the condition of low supply pressure. 
         [0008]    Liquid fuel nozzles have much diversity in spray type and structure and have heretofore been proposed in large numbers, for example, by JP-2007-155170-A, JP-T-2002-519617 and Japanese Utility Model Laid-Open No. Hei 2-28923. 
       SUMMARY OF THE INVENTION 
       [0009]    One of the important subjects for development of liquid fossil fueled combustors is to improve the suppression of the discharge amount of white smoke and soot generated during start-up. To suppress the discharge amount of white smoke and soot, it is effective means to atomize fuel into fine liquid droplets, thereby promoting mixing of the fuel with air. Therefore, it can be said that the atomization technique of liquid fuel is very important. 
         [0010]    As described above, it is effective to use a fluid other than liquid fuel in order to promote the atomization of fuel. In general, high-pressure air is frequently used as the fluid. To obtain the high-pressure air, air is extracted from the compressor of a gas turbine, the air thus extracted is cooled and increased in pressure, and such air is supplied to the combustor. Thus, a thermal loss and power for the compressor will lower the efficiency of the overall gas turbine. 
         [0011]    It is an object of the present invention, therefore, to provide a gas turbine combustor that can reduce the lowering of gas turbine efficiency as much as possible and promote the atomization of liquid fossil fuel. 
         [0012]    According to an aspect of the present invention, there is provided a gas turbine combustor adapted to mix liquid fuel with combustion air led from a compressor, burn the mixture and supply combustion gas generated to a gas turbine. The gas turbine combustor includes: a fuel injection nozzle that atomizes the liquid fuel into fine liquid droplets. The fuel injection nozzle includes a first system adapted to supply the liquid fuel and a second system adapted to supply a fluid for atomizing the liquid fuel. The fluid to be used is low-boiling liquid fuel. The gas turbine combustor further includes means for heating the low-boiling liquid fuel. 
         [0013]    The present invention can provide the gas turbine combustor that can promote atomization of liquid fossil fuel while reducing the lowering of gas turbine efficiency as much as possible. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is an overall configuration diagram of a gas turbine according to a first embodiment. 
           [0015]      FIG. 2  is a longitudinal cross-sectional view of a fuel injection nozzle according to the first embodiment. 
           [0016]      FIG. 3  is an overall configuration diagram of a gas turbine according to a second embodiment. 
           [0017]      FIG. 4  is a longitudinal cross-sectional view of a fuel injection nozzle according to the second embodiment. 
           [0018]      FIG. 5  is a longitudinal cross-sectional view of a fuel injection nozzle according to a third embodiment. 
           [0019]      FIG. 6  is a longitudinal cross-sectional view of a fuel injection nozzle according to a fourth embodiment. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    Preferred embodiments of gas turbine combustors employing the present invention will hereinafter be described with reference to the drawings. 
         [0021]    Incidentally, gas turbine combustors burning liquid fossil fuel according to the embodiments of the present invention described below have respective fuel injection nozzles as means for atomizing liquid fossil fuel. The fuel injection nozzles are configured to heat and gasify low-boiling liquid fuel and use the shear force of the low-boiling liquid fossil fuel thus heated and gasified to atomize the liquid fossil fuel. Thus, the gas turbine combustors can promote the atomization of the liquid fossil fuel while suppressing the lowering of gas turbine efficiency. 
         [0022]    The embodiments of the present invention described below exemplify alcohol fuel as the low-boiling liquid fuel. Specifically, the low-boiling liquid fuel is supposed which has a boiling point falling within the range from ordinary temperature to about 150° C. and which is liquid in an ordinary temperature state. 
       First Embodiment 
       [0023]    A first embodiment of the present invention will hereinafter be described with reference to  FIGS. 1 and 2 .  FIG. 1  includes a longitudinal cross-sectional view illustrating the configuration of a gas turbine combustor according to the first embodiment of the present invention and a schematic configuration diagram illustrating the overall configuration of a gas turbine plant equipped with the gas turbine combustor. 
         [0024]    The gas turbine plant illustrated in  FIG. 1  mainly includes a compressor  1 , a combustor  3  and a turbine  2 . The compressor  1  compresses air to generate high-pressure combustion air. The combustor  3  mixes liquid fossil fuel  18  with combustion air  16  led from the compressor  1  to generate combustion gas  17 . The turbine  2  receives the combustion gas  17  generated in the combustor  3 . Incidentally, the respective shafts of the compressor  1 , the turbine  2  and the generator  4  are connected to one another. 
         [0025]    The combustor  3  includes an inner cylinder  9 , a transition piece  13 , an outer cylinder  10  and an end cover  14 . The inner cylinder  9  forms a combustion chamber  23  for burning the combustion air  16  and fuel to generate the combustion gas  17 . The transition piece  13  is adapted to lead the combustion gas  17  generated in the combustion chamber  23  to the turbine  2 . The outer cylinder  10  houses the inner cylinder  9  and the transition piece  13 . 
         [0026]    An air swirler  11  is disposed at an axial-central position of the inner cylinder  9  on the upstream side in the flow direction of the combustion gas. The air swirler  11  is adapted to swirl the combustion air  16  to promote the mixing of the swirling combustion air  16  with liquid fossil fuel  18  for stable formation of flames. A fuel injection nozzle  12  for atomizing the liquid fossil fuel  18  is disposed upstream of the air swirler  11 . 
         [0027]      FIG. 2  is a configuration view of the fuel injection nozzle  12 . The fuel injection nozzle  12  has a liquid fossil fuel system  100  for the liquid fossil fuel  18  as a first system formed at the axial center thereof. In addition, the fuel injection nozzle  12  includes a swirler  101  installed in the middle of the liquid fossil fuel system  100 . The liquid fossil fuel  18  is swirled by the swirler  101  and jetted. An alcohol fuel system  102  as a second system adapted to supply a fluid for atomization of the liquid fossil fuel  18  is formed on the outer circumference of the liquid fossil fuel system  100 . Similarly to the liquid fossil fuel, the fluid is swirled by a swirler  103  installed in the middle of the alcohol fuel system  102  and is jetted. 
         [0028]    The gas turbine combustor according to the first embodiment of the present invention configured as described above uses low-boiling liquid fuel (alcohol fuel in the present embodiment) as the fluid for atomization of the liquid fossil fuel  18 . In addition, the gas turbine combustor has a supply system including an alcohol fuel tank  6  for storing alcohol fuel therein, a pump  7  and a supply pipe  19 , a heat exchanger  8  for heating and gasifying the alcohol fuel  21 , and a system  20  for supplying gasified fuel alcohol. 
         [0029]    According to the gas turbine combustor according to the first embodiment of the present invention configured as above, the liquid fossil fuel  18  and the gasified or partially gasified alcohol fuel  21  are jetted from the fuel injection nozzle  12 . Thus, the gas turbine combustor has an effect of promoting the atomization of the liquid fossil fuel  18  through the shear force of the alcohol fuel  21 . 
         [0030]    Even if gas and liquid is jetted as a two-phase flow because the alcohol fuel  21  is not gasified completely, the alcohol fuel as liquid jetted from the fuel injection nozzle  12  is evaporated inside the high-temperature combustion chamber. Thus, also more effective atomization of the liquid fossil fuel  18  through volume expansion energy resulting from the evaporation can be expected. 
         [0031]    Further, the supply of the liquid fossil fuel  18  can be reduced according to the supply of the alcohol fuel  21  compared with the single combustion of the liquid fossil fuel  18  as long as under the same combustion temperature condition. In general, as the flow rate of the liquid fossil fuel  18  is lower, the two-fluid fuel injection nozzle can promote atomization. Therefore, also the promoted atomization resulting from the reduced flow rate can be expected. Further, if the flow rate of the liquid fossil fuel  18  is reduced, also the amount of soot generated by combustion can be reduced. 
         [0032]    In this way, the gas turbine can be reduced in efficiency degradation compared with the system using high-pressure air. In addition, the atomization-promoting effect of the liquid fossil fuel  18  and the effect resulting from the reduced flow rate of the liquid fossil fuel  18  can reduce the discharged amount of soot. 
         [0033]    When the liquid fossil fuel  18  is used to start the gas turbine, if an ignition failure occurs, colored smoke (white smoke) is likely to be discharged. However, the gas turbine combustor configured according to the present invention can be ignited, for example, only by the alcohol fuel  21  without supplying the liquid fossil fuel  18  when the gas turbine is started. If the gas turbine combustor is operated so as to be ignited only by the alcohol fuel  21 , the occurrence of colored smoke can be prevented also in the event that the ignition failure occurs. 
         [0034]    As described above, the fuel injection nozzle  12  uses the alcohol fuel  21 , which is low-boiling liquid fuel. Therefore, if not only the alcohol fuel  21  is completely gasified but also it becomes the two-phase flow of gas and liquid and is jetted, satisfactory atomization performance can be maintained. Therefore, a heat source with unstable temperature can be used as a heat source for heating and gasifying the alcohol fuel  21 . Specifically, an approach to use an electric heater or exhaust heat of a gas turbine can be considered as an approach to heat and gasify the alcohol fuel  21 . However, if natural energy such as solar heat or ground heat is used, the efficiency of the overall plant can further be improved. 
         [0035]    If plant-based bioethanol is used as the low-boiling liquid fuel, also CO2 reduction can be achieved because of carbon neutrality. Since bioethanol has greater density than LNG, which is common gas fuel, when the bioethanol is jetted at any velocity, kinetic energy thereof increases. Thus, also the atomization promotion of liquid fuel can be expected. 
       Second Embodiment 
       [0036]    A second embodiment of the present invention will hereinafter be described with reference to  FIGS. 3 and 4 .  FIG. 3  includes a longitudinal cross-sectional view illustrating the configuration of a gas turbine combustor according to the second embodiment of the present invention and a schematic configuration diagram illustrating the overall configuration of a gas turbine plant equipped with the gas turbine combustor.  FIG. 4  is a partial detailed cross-sectional view of a fuel injection nozzle  12  of  FIG. 3 . The basic configuration of the second embodiment is the same as that of the first embodiment. The second embodiment is different from the first embodiment in that the heat of high-pressure atomization air is used as means for heating low-boiling liquid fuel (alcohol fuel in the present embodiment). As illustrated in  FIG. 4 , the fuel injection nozzle  12  of the present embodiment has a triple-tube structure including a high-pressure atomization air system  104 , as a third system, for supplying high-pressure atomization air, in addition to a liquid fossil fuel system  100  as a first system and an alcohol fuel system  102  as a second system. 
         [0037]    Atomization air  22  is usually generated as below: Air discharged from a compressor  1  is partially extracted. The extracted air is reduced in temperature by a water-cooled heat exchanger. The temperature-reduced air is pressurized to a predetermined pressure by an atomization air compressor  5 . The pressurized air is then supplied to the high-pressure atomization air system  104  of the fuel injection nozzle  12 . The heat removed by the water-cooled heat exchanger is not recovered by a gas turbine; therefore, the efficiency of the gas turbine is lowered. 
         [0038]    On the other hand, the second embodiment of the present invention includes a heat exchanger  8  which exchanges heat between the atomization air extracted from the compressor  1  and alcohol fuel, in place of the conventional water-cooled heat exchanger. Alcohol fuel is used in place of water to cool the atomization air. In contrast, the heat of the atomization air is used to heat and gasify the alcohol fuel and the gasified alcohol fuel is supplied to the fuel injection nozzle  12 . This contributes to the atomization of the liquid fossil fuel  18  while recovering the heat of the extracted air. 
         [0039]    As illustrated in  FIG. 4 , the fuel injection nozzle  12  is formed at its axial-center position with a jet hole adapted to jet alcohol fuel  21 ; at the outer circumference of the jet hole for the alcohol fuel  21 , with a jet hole adapted to jet liquid fossil fuel  18 ; and at the further outer circumference of the jet hole for the liquid fossil fuel  18 , with a jet hole adapted to jet atomization air  22 . Among swirlers  101 ,  103 ,  105  installed on respective systems, only the swirler  101  for the liquid fossil fuel  18  is made to have a swirl direction reverse to those of the swirlers  103 ,  105 . In this way, the alcohol fuel  21  is jetted along the inner circumference of the jetted liquid fossil fuel  18  and the atomization air  22  is jetted along the outer circumference of the jetted liquid fossil fuel  18 . The atomization of the liquid fossil fuel  18  can be promoted by the shear forces of the alcohol fuel  21  and the atomization air  22 . Thus, more effective reduction of soot than the first embodiment can be expected. 
         [0040]    Also the present system may not need to gasify the alcohol fuel completely, which produces the same effect as that of the first embodiment. 
       Third Embodiment 
       [0041]    A third embodiment of the present invention will hereinafter be described with reference to  FIG. 5 . The basic configuration of the present embodiment is the same as that of the second embodiment. The present embodiment is different from the second embodiment in the configuration of a fuel injection nozzle  12 . The fuel injection nozzle  12  of the present embodiment is formed, at its center, with a jet hole adapted to jet liquid fossil fuel  18 ; at the outer circumference of the jet hole for the liquid fossil fuel  18 , with a jet hole adapted to jet alcohol fuel  21 ; and at the further outer circumference of the jet hole for the alcohol fuel  21 , with a jet hole adapted to jet atomization air  22 . 
         [0042]    In general, temperature at which a coking phenomenon starts differs depending on the kind of fuel. The coking phenomenon is such that liquid fossil fuel is subjected to surrounding heat to become solidified. It is said that if the fuel is e.g. light oil, such temperature is about 180° C. Therefore, it has heretofore been necessary to control the temperature of the high-pressure atomization air to be supplied to the fuel injection nozzle at a level not higher than such temperature in view of the prevention of coking. 
         [0043]    However, in the present embodiment, an alcohol fuel system  102  is disposed between a high-pressure atomization air system  104  and a liquid fossil fuel system  100 ; therefore, the heat of the atomization air  22  does not directly transfer to the liquid fossil fuel  18 . In addition, since the alcohol fuel is oxygen-contained fuel, it is hard to be coked. Therefore, it is possible to more improve reliability for coking in the liquid fossil system  100 . 
         [0044]    The present embodiment does not need to excessively cool the atomization air  22 ; therefore, it has also an effect capable of reducing the lowering of gas turbine efficiency. 
       Fourth Embodiment 
       [0045]    A fourth embodiment of the present invention will hereinafter be described with reference to  FIG. 6 .  FIG. 6  is a longitudinal cross-sectional view of a fuel injection nozzle  12  according to the fourth embodiment of the present invention. The basic configuration of the present embodiment is the same as that of the second embodiment. In the present embodiment, a high-pressure atomization air system  104  is configured to merge with an alcohol fuel system  102  in the fuel injection nozzle  12 , whereby atomization air  22  and alcohol fuel  21  are mixed with each other and then jetted. 
         [0046]    With the embodiment of the present invention configured as above, the alcohol fuel  21  is supplied to the fuel injection nozzle  12  as it is liquid. The alcohol fuel  21  is then heated and gasified by the heat of the atomization air  22  in the fuel injection nozzle  12  and jetted. This eliminates a heat exchanger for cooling the atomization air  22  and heating the alcohol fuel  21 , which allows for a cost reduction. Since the flow rate of the atomization air  22  can be reduced according to the supply of the alcohol fuel, an improvement in efficiency due to a reduction in the amount of bleed air can be expected. 
         [0047]    The combination of the liquid fossil fuel  18  with e.g. the alcohol fuel  21  has been described thus far. However, it goes without saying that even if alcohol fuel may be used in place of the liquid fossil fuel  18 , the effect of the present invention can be expected.