Patent Publication Number: US-2022220978-A1

Title: Compressor system

Description:
TECHNICAL FIELD 
     The present invention relates to a compressor system. Priority is claimed on Japanese Patent Application No. 2019-059225, filed Mar. 26, 2019, the content of which is incorporated herein by reference. 
     BACKGROUND ART 
     For example, it is known that, if an operation point is changed to increase a pressure ratio while keeping the number of revolutions constant in turbo compressors including axial compressors and centrifugal compressors, a phenomenon called turning stall or surging may occur in some cases. Particularly, surging is likely to lead to backflow of a working fluid inside a compressor and vibration of a rotor shaft in some cases. For this reason, there is an increasing demand for techniques which can prevent or minimize surging. 
     As an example of such a technique, the technique described in Patent Literature 1 is known. Patent Literature 1 discloses various detection devices including a static pressure sensor, a dynamic pressure sensor, and a flow velocity sensor and a technique for perceiving changes that are indications of surging through frequency-processing a detection value using such detection devices. 
     CITATION LIST 
     Patent Literature 
     
         
         [Patent Literature 1] 
       
    
     Japanese Patent No. 4030490 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, in the device described in Patent Literature  1 , detection values using each of the detection devices may be included in noise (a fluctuation component) unless surging has progressed to some extent in some cases. Thus, it may not be possible to accurately detect an indication of surging in some cases. 
     The present invention was made to solve the above problems, and an object of the present invention is to provide a compressor system capable of detecting the occurrence of surging with higher accuracy and minimizing surging. 
     Solution to Problem 
     A compressor system according to an aspect of the present invention includes: a compressor having: an upstream region into which a working fluid flows, a downstream region that communicates with the upstream region and in which a pressure of the working fluid is greater than that in the upstream region, inlet guide vanes that are provided further upstream than the upstream region and are capable of altering a flow rate of the working fluid flowing into the upstream region, and an extraction part that is provided to a portion between the upstream region and the downstream region and is capable of extracting at least a portion of the working fluid; detection devices, at least one of which is provided in each of the upstream region and the downstream region, for detecting a physical quantity of the working fluid; and a control device for adjusting, on the basis of changes in the physical quantity detected by the detection devices, any one of an opening degree of the inlet guide vanes and an amount extracted by the extraction part. 
     According to the above constitution, at least one of the detection devices is provided in the upstream region and the downstream region of the compressor. The detection device detects a physical quantity of the working fluid. The control device detects an abnormality occurring in the flow of the working fluid on the basis of the changes in the physical quantity. The control device adjusts either the opening degree of the inlet guide vane or the extraction amount. Thus, it is possible to eliminate an abnormality occurring in the flow of the working fluid. 
     In the compressor system, each of the detection devices may include: a pair of temperature detection units that are arranged in a flow direction of the working fluid; and a heating unit that is disposed between the pair of temperature detection units and heats the working fluid, wherein the physical quantities may include a flow direction and a flow velocity of the working fluid based on a temperature difference of the working fluid detected by the pair of temperature detection units. 
     According to the above constitution, the detection device has the pair of temperature detection units arranged in the flow direction and the heating unit provided between them. When the working fluid passes through the pair of temperature detection units in the flow direction, the working fluid is heated by the heating unit. Thus, a difference occurs in a temperature which is detected between a temperature detection unit located on the downstream side in the flow direction and a temperature detection unit located on the upstream side. Therefore, it is possible to detect that the working fluid is flowing to a side on which the temperature detection unit having a higher detected temperature is located. That is to say, it is possible to detect the flow direction of the working fluid. In addition, when an absolute value of the temperature difference detected by the pair of temperature detection units is detected, it is also possible to detect changes in the flow velocity of the working fluid. Thus, for example, when backflow (that is, a change in the flow direction) occurs in the flow of the working fluid inside the compressor or a decrease in the flow velocity that is an indication of backflow occurs, it is possible to immediately detect the backflow and the decrease in the flow velocity. 
     In the above compressor system, the temperature detection unit and the heating unit may be directed exposed to the working fluid. 
     According to the above constitution, it is possible to immediately detect changes in the physical quantity of the working fluid. Thus, this makes it possible to improve the responsiveness of the entire device. 
     In the above compressor system, the control device may adjust the opening degree of the inlet guide vanes so that the opening degree increases when the temperature difference changes so that the temperature difference decreases in the downstream region. 
     According to the above constitution, when the temperature difference between the pair of temperature detection units detected by the detection devices in the downstream region decreases, it can be determined that the flow velocity of the working fluid has decreased in the downstream region. When the flow velocity continues to decrease, this is eventually likely to lead to a change in the flow direction. That is to say, it can be said that the decrease in flow velocity is an indication of backflow. In this case, it can be determined that the flow rate of the working fluid in the downstream region of the compressor becomes excessive and the flow of the working fluid begins to come to a standstill (surging is occurring). Thus, the control device adjusts the opening degree of the inlet guide vane so that the opening degree increases. Therefore, the flow rate of the working fluid supplied to the downstream region is reduced. As a result, surging can be prevented before the development thereof. 
     In the above compressor system, the control device may adjust the extraction amount so that the extraction amount increases when the temperature difference changes in the upstream region so that the temperature difference decreases. 
     According to the above constitution, when the temperature difference between the pair of temperature detection units detected by the detection devices in the upstream region decreases, it can be determined that the flow velocity of the working fluid has decreased in the upstream region. When the flow velocity continues to decrease, this is likely to eventually lead to a change in the flow direction. That is to say, it can be said that the decrease in the flow velocity is an indication of backflow. In this case, it can be determined that the flow rate of the working fluid in the upstream region of the compressor becomes excessive and the flow of the working fluid begins to come to a standstill (surging is occurring). Thus, the control device adjusts the extraction amount so that the extraction amount increases. Therefore, the working fluid that has come to a standstill in the upstream region is extracted and the standstill in the flow is eliminated. As a result, surging can be prevented before the development thereof. 
     In the above compressor system, the compressor may include: a rotor shaft that is capable of rotating around an axis line; a plurality of rotor blade stages that are provided on the rotor shaft and arranged in a direction of the axis line; a casing that covers the rotor shaft and the rotor blade stages from an outer circumferential side; and a plurality of stator blade stages that are provided on an inner circumferential surface of the casing and arranged alternately with the plurality of rotor blade stages in the direction of the axis line, wherein the upstream region being a region further upstream than a rotor blade stage of the plurality of rotor blade stages that is a third stage from the furthest upstream side, and wherein the downstream region being a region further downstream than a rotor blade stage of the plurality of rotor blade stages that is a third stage from the furthest downstream side. 
     Here, in the compressor as described above, it is known that surging particularly easily occurs in the region further upstream than the third rotor blade stage from the furthest upstream side and the region further downstream than the third rotor blade stage from the furthest downstream side. According to the above constitution, since the regions are the upstream region and the downstream region, it is possible to promptly and accurately detect the occurrence of surging and an indication thereof. 
     In the above compressor system, each of the stator blade stages may extend in a radial direction with respect to the axis line and include a plurality of stator blades arranged in a circumferential direction and having a suction surface facing upstream and a pressure surface facing downstream, and the detection device may be provided on the suction surface. 
     Here, the separation and the backflow of the working fluid are particularly easily generated on the suction surface of the stator blade. According to the above constitution, since the detection device is provided on the suction surface, it is possible to promptly and accurately detect the separation and the backflow described above. 
     In the above compressor system, the compressor may include: a rotor shaft that is capable of rotating around an axis line; an impeller that is provided on the rotor shaft; 
     and a casing that covers the impeller from an outer circumferential side and forms a flow path through which the working fluid flows on an upstream side and a downstream side of the impeller, wherein the upstream region being a region in the flow path further upstream than the impeller, and wherein the downstream region being a region in the flow path further downstream than the impeller. 
     Here, it is known that, in the compressor as described above, surging particularly easily occurs in a region further upstream than the impeller and a region further downstream than the impeller. According to the above constitution, since the regions are the upstream region and the downstream region, it is possible to promptly and accurately detect the occurrence of surging and an indication thereof. 
     In the above compressor system, the flow path may have a diffuser flow path provided on a downstream side of the impeller and configured to guide the working fluid from an inner side to an outer side in the radial direction with respect to the axis line and a return flow path provided further downstream of the diffuser flow path and configured to guide the working fluid from the outer side to the inner side in the radial direction, and the detection device may be provided in at least one of the diffuser flow path and the return flow path. 
     According to the above constitution, since the detection device is provided in at least one of the diffuser flow path and the return flow path, it is possible to finely and accurately detect the occurrence of surging and an indication thereof in the downstream region. 
     A compressor system according to an aspect of the present invention includes: a compressor having: an upstream region into which a working fluid flows, a downstream region that communicates with the upstream region and in which a pressure of the working fluid is greater than that in the upstream region, inlet guide vanes that are provided further upstream than the upstream region and are capable of altering a flow rate of the working fluid flowing into the upstream region, and an extraction part that is provided to a portion between the upstream region and the downstream region and is capable of extracting at least a portion of the working fluid; detection devices, at least one of which is provided in each of the upstream region and the downstream region, for detecting a physical quantity of the working fluid; and a control device for adjusting, on the basis of changes in the physical quantity detected by the detection devices, an opening degree of the inlet guide vanes and an amount extracted by the extraction part, wherein the compressor includes: a rotor shaft that is capable of rotating around an axis line; a plurality of rotor blade stages that are provided on the rotor shaft and arranged in a direction of the axis line; a casing that covers the rotor shaft and the rotor blade stages from an outer circumferential side; and a plurality of stator blade stages that are provided on an inner circumferential surface of the casing and arranged alternately with the plurality of rotor blade stages in the direction of the axis line, wherein the upstream region is a region further upstream than a rotor blade stage of the plurality of rotor blade stages that is a third stage from the furthest upstream side, wherein the downstream region is a region further downstream than a rotor blade stage of the plurality of rotor blade stages that is a third stage from the furthest downstream side, wherein each of the stator blade stages extends in a radial direction with respect to the axis line and includes a plurality of stator blades arranged in a circumferential direction and having a suction surface facing upstream and a pressure surface facing downstream, and wherein each of the detection devices is provided on the suction surface. 
     At least one of the detection devices is provided in each of the upstream region and the downstream region of the compressor. The detection device detects a physical quantity of the working fluid. The control device detects an abnormality occurring in the flow of the working fluid on the basis of the changes in the physical quantity. The control device adjusts either the opening degree of the inlet guide vane or the extraction amount. Thus, it is possible to eliminate the abnormality occurring in the flow of the working fluid. In addition, it is known that, in the compressor as described above, surging particularly easily occurs in the region further upstream than the third rotor blade stage from the furthest upstream side and the region further downstream than the third rotor blade stage from the furthest downstream side. According to the above constitution, since the regions are the upstream region and the downstream region, it is possible to promptly and accurately detect the occurrence of surging and an indication thereof. Here, the separation and the backflow of the working fluid are particularly easily generated on the suction surface of the stator blade. According to the above constitution, since the detection device is provided on the suction surface, it is possible to promptly and accurately detect the separation and the backflow described above. 
     In the above compressor system, the detection device may include: a pair of temperature detection units that are arranged in a flow direction of the working fluid; and a heating unit that is disposed between the pair of temperature detection units and heats the working fluid, wherein the physical quantity may include a temperature difference of the working fluid detected by the pair of temperature detection units, and wherein the control device may determine a speed at which each of the inlet guide vanes is closed on the basis of a magnitude of the physical quantity when a command for reducing a load of the compressor is issued. 
     Here, when a command for reducing a load of the compressor is issued, if the inlet guide vane is closed at an excessively high speed to reduce the inflow of the working fluid, there is a risk of there being an insufficient amount of working fluid compressed in the downstream region and backflow of the working fluid to the upstream side (surging occurring). On the other hand, when the inlet guide vane is closed at an excessively low speed, the temperature of the combustion gas decreases due to an excessive supply of the working fluid to the combustor provided on the downstream side. 
     As a result, there is a risk of generating combustion vibration and increasing an amount of NOx which is emitted. According to the above constitution, the control determines the speed at which the inlet guide vane is closed on the basis of the temperature difference detected by the pair of temperature detection units, that is, the speed or the flow rate of the fluid. For this reason, it is possible to close the inlet guide vane at an appropriate speed while preventing the surge and the unstable combustion described above. As a result, it is possible to stably and quickly reduce a load on the compressor. 
     In the above compressor system, the control device may close the inlet guide vane at a relatively high speed when the physical quantity is greater than a predetermined threshold value and close the inlet guide vane at a relatively low speed when the physical quantity is smaller than the threshold value. 
     According to the above constitution, it is possible to determine an optimum speed at which the inlet guide vane is closed simply by evaluating the magnitude of the physical quantity on the basis of the predetermined threshold value. Thus, it is possible to quickly reduce the load on the compressor while minimizing the likelihood of surges and unstable combustion occurring. 
     In the above compressor system, the control device may determine to which numerical range of a plurality of predetermined numerical ranges the physical quantity belongs and close the inlet guide vane by selecting a predetermined speed to correspond to the numerical range to which the physical quantity belongs. 
     According to the above constitution, it is possible to close the inlet guide vane by selecting the speed determined to correspond to the numerical range to which the physical quantity belongs. That is to say, it is possible to finely determine the speed at which the inlet guide vane will be closed on the basis of the magnitude of the physical quantity. As a result, it is possible to more quickly reduce the load on the compressor while further minimizing the likelihood of surges and unstable combustion occurring. 
     In the above compressor system, the control device may determine a speed at which the inlet guide vane is closed with reference to a table in which a relationship between the physical quantity and an optimum speed at which the inlet guide vane is closed according to a value concerning the physical quantity is shown. 
     According to the above constitution, it is possible to close the inlet guide vane by selecting the speed in accordance with the table in which the relationship between the optimum speed at which the inlet guide vane is closed and the physical quantity is shown. That is to say, it is possible to more finely determine the speed at which the inlet guide vane is closed on the basis of the magnitude of the physical quantity. Thus, it is possible to more quickly reduce the load on the compressor while further minimizing the likelihood of surges and unstable combustion occurring. 
     A compressor system according to an aspect of the present invention includes: a compressor having: an upstream region into which a working fluid flows, a downstream region that communicates with the upstream region and in which a pressure of the working fluid is greater than that in the upstream region, and inlet guide vanes that are provided further upstream than the upstream region and are capable of altering a flow rate of the working fluid flowing into the upstream region; detection devices, at least one of which is provided in the downstream region, for detecting a physical quantity of the working fluid; and a control device for adjusting, on the basis of changes in the physical quantity detected by the detection devices, an opening degree of the inlet guide vanes, wherein each of the detection devices includes a pair of temperature detection units that are arranged in a flow direction of the working fluid; and wherein a heating unit that is disposed between the pair of temperature detection units and heats the working fluid, wherein the physical quantity includes a temperature difference of the working fluid detected by the pair of temperature detection units, and wherein when a command for reducing a load of the compressor is issued, the control device determines a speed at which each of the inlet guide vanes is closed on the basis of a magnitude of the physical quantity. 
     Here, when a command for reducing a load on the compressor is issued, if the inlet guide vane is closed at an excessively high speed to reduce the inflow of the working fluid, there is a risk of there being an insufficient amount of working fluid compressed in the downstream region and backflow of the working fluid to the upstream side (surging occurring). On the other hand, when the inlet guide vane is closed at an excessively low speed, the temperature of the combustion gas decreases due to an excessive supply of the working fluid to the combustor provided on the downstream side. As a result, there is a risk of generating combustion vibration and increasing an amount of NOx which is emitted. According to the above constitution, the control device determines the speed at which the inlet guide vane is closed on the basis of the temperature difference detected by the pair of temperature detection units, that is, the speed or the flow rate of the fluid. For this reason, it is possible to close the inlet guide vane at an appropriate speed while preventing the surge and the unstable combustion described above. As a result, it is possible to stably and quickly reduce a load on the compressor. 
     In the above compressor system, the control device may close the inlet guide vane at a relatively high speed when the physical quantity is greater than a predetermined threshold value and close the inlet guide vane at a relatively low speed when the physical quantity is smaller than the threshold value. 
     According to the above constitution, it is possible to determine the optimum speed at which the inlet guide vane is closed simply by evaluating the magnitude of the physical quantity on the basis of the predetermined threshold value. Thus, it is possible to quickly reduce the load on the compressor while reducing the likelihood of surges and unstable combustion occurring. 
     In the above compressor system, the control device may determine to which numerical range of a plurality of predetermined numerical ranges the physical quantity belongs and close the inlet guide vane by selecting a predetermined speed to correspond to the numerical range to which the physical quantity belongs. 
     According to the above constitution, it is possible to close the inlet guide vane by selecting the speed determined to correspond to the numerical range to which the physical quantity belongs. That is to say, it is possible to more finely determine the speed at which the inlet guide vane is closed on the basis of the magnitude of the physical quantity. As a result, it is possible to more quickly reduce the load on the compressor while further reducing the likelihood of surges and unstable combustion occurring. 
     In the compressor system, the control device may determine a speed at which the inlet guide vane is closed with reference to a table in which a relationship between the physical quantity and an optimum speed at which the inlet guide vane is closed according to a value concerning the physical quantity is shown. 
     According to the above constitution, it is possible to close the inlet guide vane by selecting the speed in accordance with the table in which the relationship between the optimum speed at which the inlet guide vane is closed and the physical quantity is shown. That is to say, it is possible to more finely determine the speed at which the inlet guide vane is closed on the basis of the magnitude of the physical quantity. Thus, it is possible to more quickly reduce the load on the compressor while further reducing the likelihood of surges and unstable combustion occurring. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to provide a compressor system capable of detecting the occurrence of surging with higher accuracy and minimizing surging. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram showing a constitution of a gas turbine according to a first embodiment of the present invention. 
         FIG. 2  is a cross-sectional view showing a constitution of a compressor system according to the first embodiment of the present invention. 
         FIG. 3  is a schematic diagram showing a constitution of a detection device according to the first embodiment of the present invention. 
         FIG. 4  is a diagram showing a constitution of hardware of a control device according to the first embodiment of the present invention. 
         FIG. 5  is a functional block diagram of the control device according to the first embodiment of the present invention. 
         FIG. 6  is a graph for describing an example of changes in temperature difference detected using the detection device according to the first embodiment of the present invention. 
         FIG. 7  is a perspective view showing a constitution of a stator blade according to a modified example of the first embodiment of the present invention. 
         FIG. 8  is a cross-sectional view showing a constitution of a compressor system according to a second embodiment of the present invention. 
         FIG. 9  is a diagram showing a constitution of a gas turbine according to a third embodiment of the present invention. 
         FIG. 10  is a functional block diagram of a control device according to the third embodiment of the present invention. 
         FIG. 11  is a flowchart for describing an operation of the control device according to the third embodiment of the present invention. 
         FIG. 12  is a flowchart for describing a modified example of an operation of the control device according to the third embodiment of the present invention. 
         FIG. 13  is a flowchart for describing another modified example of the operation of the control device according to the third embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
     A first embodiment of the present invention will be described with reference to  FIGS. 1 to 6 . As shown in  FIG. 1 , a gas turbine  100  according to the embodiment includes a compressor system  1 , a combustor  2 , and a turbine  3 . The compressor system  1  compresses external air (a working fluid) to generate high-pressure air. The combustor  2  mixes fuel with high-pressure air and burns the mixture to generate high-temperature and high-pressure combustion gas. The turbine  3  is rotationally driven using this combustion gas. The turbine  3  and the compressor system  1  are connected using a rotor shaft  4  extending along an axis line O. Therefore, the rotation of the turbine  3  is transmitted to the compressor system  1  via the rotor shaft  4 . 
     The compressor system  1  includes a compressor  11 , inlet guide vanes  11 C, detection devices  21 , a blow-off flow path L (an extraction part), a blow-off valve V, and a control device  90 . The compressor  11  compresses air guided from one side (an upstream side) in a direction of an axis line O and supplies the compressed air to the combustor  2  provided on the other side (a downstream side). That is to say, the compressor  11  is an axial compressor. Although being described in detail later, the compressor  11  includes an upstream region  11 A located on an upstream side in the direction of the axis line O and a downstream region  11 B located on a downstream side. The pressure of the working fluid (air) in the downstream region  11 B is greater than that in the upstream region  11 A. External air is introduced into the upstream region  11 A via the inlet guide vane  11 C. The inlet guide vane  11 C is provided to adjust an amount of air flowing through the upstream region  11 A. Opening degree of the inlet guide vane  11 C can be changed using an electrical signal transmitted from the control device  90  which will be described later. 
     In the upstream region  11 A, at least one (a first detection device  21 A) of the detection devices  21  which detect a physical quantity of air flowing through the upstream region  11 A is provided. Similarly, in the downstream region  11 B, at least one (a second detection device  21 B) of the detection devices  21  which detect a physical quantity of air flowing through the downstream region  11 B is provided. 
     Here, as shown in  FIG. 2 , the compressor  11  has the rotor shaft  4  which can rotate around the axis line O, a plurality of rotor blade stages  42  arranged on an outer circumferential surface of the rotor shaft  4  in the direction of the axis line O, a casing  30  which covers the rotor shaft  4  and the rotor blade stages  42  from an outer circumferential side, and a plurality of stator blade stages  41  provided on an inner circumferential surface of the casing  30 . The stator blade stages  41  are arranged alternately with the rotor blade stages  42  in the direction of the axis line O. The upstream region  11 A described above refers to a region further upstream than a rotor blade stage  42  of the plurality of rotor blade stages  42  that is a third stage from the furthest upstream side. That is to say, the first detection device  21 A is provided on the inner circumferential surface of the casing  30  corresponding to a rotor blade stage  42  that is on the furthest upstream side (a first rotor blade stage  42 A) and a rotor blade stage  42  that is a second stage from the upstream side (a second rotor blade stage  42 B). It is also possible to provide the first detection device  21 A for a first stator blade stage  41 A adjacent to the first rotor blade stage  42 A and a second stator blade stage  41 B adjacent to the second rotor blade stage  42 B. 
     Also, the downstream region  11 B described above refers to a region further downstream than a rotor blade stage  42  of the plurality of rotor blade stages  42  that is a third stage from the furthest downstream side. That is to say, the second detection device  21 B is provided on the inner circumferential surface of the casing  30  corresponding to a rotor blade stage  42  that is on the furthest downstream side (an outlet final rotor blade stage  42 D) and a rotor blade stage  42  that is a second stage from the downstream side (an outlet rotor blade stage  42 C). It is also possible to provide the second detection device  21 B for an outlet final stator blade stage  41 D adjacent to the outlet final rotor blade stage  42 D and an outlet stator blade stage  41 C adjacent to the outlet rotor blade stage  42 C. Furthermore, it is also possible to provide the second detection device  21 B on the inner circumferential surface of the casing  30  corresponding to a diffuser flow path stator blade stage  41 E provided on a downstream side of the outlet final rotor blade stage  42 D. 
     The detection device  21  detects, as physical quantities, changes in flow direction Df and flow velocity of air in the compressor  11 . As shown in  FIG. 3 , the detection device  21  has a pair of temperature detection units  61  arranged at intervals in the flow direction Df and a heating unit  62  provided between the temperature detection units  61 . 
     Both of the temperature detection units  61  and the heating unit  62  are directly exposed to the working fluid. That is to say, the temperature detection units  61  and the heating unit  62  are exposed in a surface (an inner circumferential surface) of the casing  30 . Each of the temperature detection units  61  detects a temperature of air in contact with the temperature detection unit  61  itself. The heating unit  62  heats air flowing in the vicinity of the heating unit  62  itself. Since the air is heated by means of the heating unit  62 , a temperature Td of air detected by the temperature detection unit  61  located on the downstream side in the flow direction Df is higher than a temperature Tu of the air detected by the temperature detection unit  61  located on the upstream side. Furthermore, a value of a temperature difference (Td−Tu) of these values increases as a flow velocity of the air increases. In addition, when the flow direction Df of the air changes (that is, the flow direction is reversed), the temperature difference (Td−Tu) has a negative value.  FIG. 6  is a graph for describing an example of a change over time in this temperature difference. In the example in  FIG. 6 , a temperature difference is temporarily reduced at time t 1 . In this case, it can be determined that a flow velocity of air in a corresponding region has temporarily decreased. Furthermore, at time t 2 , the temperature difference is zero. In this case, it can be determined that a flow velocity of air in a corresponding region is zero (that is, a fluid comes to a standstill). 
     As shown in  FIG. 1 or 2  again, the compressor  11  according to the embodiment includes the blow-off flow path L capable of extracting a portion of air flowing through a region (an intermediate stage) between the upstream region  11 A and the downstream region  11 B and the blow-off valve V provided on the blow-off flow path L. The blow-off flow path L is connected to an exhaust flow path Le communicating with an exhaust port of the turbine  3 . When an opening degree of the blow-off valve V is adjusted, it is possible to change an amount of air extracted through the blow-off flow path L (an extraction amount). 
     The control device  90  adjusts an opening degree of the inlet guide vane  11 C and an opening degree of the blow-off valve V on the basis of the physical quantity detected by the detection device  21  described above. As shown in  FIG. 4 , the control device  90  is a computer which includes a central processing unit (CPU)  91 , a read only memory (ROM)  92 , a random access memory (RAM)  93 , a hard disk drive (HDD)  94 , and a signal receiving module  95  (input/output: I/O). The signal receiving module  95  receives the physical quantity detected by the detection device  21  as an electric signal. The signal receiving module  95  may receive a signal amplified via, for example, a charge amplifier or the like. 
     As shown in  FIG. 5 , the CPU  91  of the control device  90  has a control unit  81 , a flow velocity calculation unit  82 , a flow direction calculation unit  83 , a storage unit  84 , and a determination unit  85  by executing a program stored in advance in the control device  90  itself. The control unit  81  controls other functional units provided in the control device  90 . Values of the temperature differences described above detected by the detection devices  21  are input to the flow velocity calculation unit  82  and the flow direction calculation unit  83  as numerical value information. 
     The flow velocity calculation unit  82  calculates a flow velocity of air on the basis of an absolute value of the temperature difference. The flow direction calculation unit  83  calculates a flow direction of air on the basis of the positive and negative of the temperature difference. The determination unit  85  compares the flow velocity calculated by the flow velocity calculation unit  82  and the flow direction calculated by the flow direction calculation unit  83  with threshold values stored in the storage unit  84 . For example, when a decrease in flow velocity or a reversal of a flow direction is detected only by the second detection device  21 B disposed in the downstream region  11 B (that is, a temperature difference changes so that the temperature difference decreases), an electric signal used for adjusting the opening degree of the inlet guide vane  11 C so that the opening degree increases is transmitted to the inlet guide vane  11 C. On the other hand, when a decrease in flow velocity or a reversal of a flow direction is detected only by the first detection device  21 A disposed in the upstream region  11 A (that is, a temperature difference changes so that the temperature difference decreases), the determination unit  85  transmits an electric signal used for adjusting the opening degree of the blow-off valve V so that the opening degree increases to the blow-off valve V. 
     An operation of the gas turbine  100  according to the embodiment will be described below. When the gas turbine  100  is operated, first, the compressor  11  is driven using an electric motor or the like (not shown). When the compressor  11  is driven, external air is taken into the compressor  11  via the inlet guide vane  11 C and high-pressure air is generated. The combustor  2  mixes fuel with this high-pressure air and burns the mixture to generate high-temperature and high-pressure combustion gas. The turbine  3  is rotationally driven using the combustion gas. A rotational force of the turbine  3  is taken out from a shaft end and used for driving an electric generator (not shown) or the like. 
     Here, it is known that, when an operation point is changed so that a pressure ratio is increased while the number of revolutions is kept constant in the compressor  11  as described above, a phenomenon called turning stall or surging occurs. Particularly, surging is likely to lead to backflow of a working fluid inside the compressor or vibration of the rotor shaft in some cases. Thus, in the embodiment, the detection device  21  described above detects a flow velocity and a flow direction as physical quantities of air and the control device  90  adjusts either the opening degree of the inlet guide vane  11 C and the opening degree of the blow-off valve V on the basis of the flow velocity and the flow direction. 
     To be specific, it can be determined that, when the temperature difference between the pair of temperature detection units  61  detected by the second detection device  21 B for the downstream region  11 B decreases, the flow velocity of the working fluid has decreased in the downstream region  11 B. When the flow velocity continues to decrease, this is likely to eventually lead to a change in the flow direction in some cases. That is to say, it can be said that a decrease in flow velocity is an indication of backflow. In this case, it can be determined that a flow rate of the working fluid in the downstream region  11 B of the compressor  11  becomes excessive and a flow of the working fluid begins to come to a standstill (surging is occurring). Thus, the control device  90  adjusts the opening degree of the inlet guide vane  11 C so that the opening degree increases. 
     On the other hand, it can be determined that, when the temperature difference between the pair of temperature detection units  61  detected by the first detection device  21 A for the upstream region  11 A decreases, a flow velocity of the working fluid has decreased in the upstream region  11 A. In this case, it can be determined that a flow rate of the working fluid in the upstream region  11 A of the compressor  11  becomes excessive and a flow of the working fluid begins to come to a standstill (surging is occurring in some cases). Thus, the control device  90  adjusts the opening degree of the blow-off valve V so that the opening degree increases and adjusts an amount of air extracted through the blow-off flow path L so that the extraction amount increases. Thus, for example, when backflow (that is, a change in the flow direction) occurs in the flow of the working fluid inside the compressor or a decrease in the flow velocity that is an indication of backflow occurs, it is possible to immediately detect the backflow and the decrease in the flow velocity. 
     As described above, according to the constitution associated with the embodiment, at least one of the detection devices  21  is provided for the upstream region  11 A and the downstream region  11 B of the compressor  11 . The detection device  21  detects a physical quantity of the working fluid. The control device  90  detects an abnormality occurring in a flow of the working fluid on the basis of the changes in the physical quantity. The control device  90  adjusts either the opening degree of the inlet guide vane  11 C or the extraction amount. Thus, it is possible to eliminate the abnormality occurring in the flow of the working fluid. 
     Also, according to the above constitution, the detection device  21  has the pair of temperature detection units  61  arranged in the flow direction Df and the heating unit  62  provided between them. When the working fluid passes through the pair of temperature detection units  61  in the flow direction Df, the working fluid is heated by the heating unit  62 . Therefore, a difference occurs in a temperature which is detected between the temperature detection unit  61  located on the downstream side in the flow direction Df and the temperature detection unit  61  located the upstream side in the flow direction Df. Therefore, it is possible to detect that the working fluid is flowing toward a side on which the temperature detection unit  61  having a higher detected temperature is located. That is to say, it is possible to detect the flow direction Df of the working fluid. Furthermore, when an absolute value of the temperature difference detected using the pair of temperature detection units  61  is detected, it is also possible to detect changes in the flow velocity of the working fluid. Thus, for example, when backflow (that is, a change in the flow direction) occurs in the flow of the working fluid inside the compressor  11  or a decrease in the flow velocity that is an indication of backflow occurs, these can be detected immediately. 
     In addition, according to the above constitution, it can be determined that, when the temperature difference between the pair of temperature detection units  61  detected by the detection device  21  of the downstream region  11 B decreases, the flow velocity of the working fluid has decreased in the downstream region  11 B. When the flow velocity continues to decrease, this is likely to eventually lead to a change in the flow direction. That is to say, it can be said that the decrease in flow velocity is an indication of backflow. In this case, it can be determined that the flow rate of the working fluid in the downstream region  11 B of the compressor  11  becomes excessive and the flow of the working fluid begins to come to a standstill (surging is occurring). Thus, the control device  90  adjusts the opening degree of the inlet guide vane  11 C so that the opening degree increases. Therefore, the flow rate of the working fluid supplied to the downstream region  11 B increases. As a result, surging can be prevented before the development thereof. 
     Furthermore, according to the above constitution, it can be determined that, when the temperature difference between the pair of temperature detection units  61  detected by the detection device  21  of the upstream region  11 A decreases and the flow velocity of the working fluid has decreased in the upstream region  11 A. When the flow velocity continues to decrease, this is likely to eventually lead to a change in the flow direction. That is to say, it can be said that the decrease in flow velocity is an indication of backflow. In this case, it can be determined that the flow rate of the working fluid in the upstream region  11 A of the compressor  11  becomes excessive and the flow of the working fluid begins to come to a standstill (surging is occurring). Thus, the control device  90  performs adjustment so that an amount of extraction through the blow-off flow path L increases. Therefore, the working fluid coming to a standstill in the upstream region  11 A is extracted and the standstill in the flow is eliminated. As a result, surging can be prevented before the development thereof. 
     Here, it is known that, in the compressor  11  as described above, surging particularly easily occurs in a region further upstream than a rotor blade stage  42  that is a third stage from the furthest upstream side and a region further downstream than a rotor blade stage  42  that is a third stage from the furthest downstream side. According to the above constitution, since these regions are the upstream region  11 A and the downstream region  11 B, it is possible to detect the occurrence of surging and the indication promptly and accurately. 
     The first embodiment of the present invention has been described above. Various changes and modifications can be provided to the above constitution without departing from the gist of the present invention. For example, in the above embodiment, the constitution in which the detection device  21  is provided on the inner circumferential surface of the casing  30  in the upstream region  11 A and the downstream region  11 B has been described. 
     However, as another example, as shown in  FIG. 7 , it is also possible to provide a detection device  21  on a stator blade  41   p  in a stator blade stage  41 . To be more specific, the stator blade stage  41  has a plurality of stator blades  41   p  arranged in a circumferential direction along an inner circumferential surface of a casing  30 . It is possible to provide the detection device  21  on at least one of the stator blades  41   p . Each of the stator blades  41   p  has an airfoil-shaped cross section in which the stator blade extends from an upstream side toward a downstream side in a flow direction Df. A surface facing downstream in the flow direction Df is concave toward the downstream side to serve as a pressure surface S 1 . A surface facing downstream is convex toward the upstream side to serve as a suction surface S 2 . Furthermore, an upstream edge is a leading edge Ef and a downstream edge is a trailing edge Ed. It is preferable that the detection device  21  be provided at a position biased outward or inward in a radial direction on the suction surface S 2  and closer to the trailing edge Ed than the leading edge Ef. 
     Here, separation or backflow of the working fluid particularly easily occurs on the suction surface S 2  of the stator blade  41   p . According to the above constitution, since the detection device  21  is provided on the suction surface S 2 , it is possible to promptly and accurately detect the separation and the backflow described above. 
     Second Embodiment 
     A second embodiment of the present invention will be described below with reference to  FIG. 8 . Constituent elements in the second embodiment that are the same as those of the first embodiment described above will be denoted by the same reference numerals and detailed description thereof will be omitted. As shown in  FIG. 8 , in the embodiment, the detection devices  21  described above are provided in a compressor  211  as a centrifugal compressor. 
     The compressor  211  has a rotor shaft  50  which can rotate around an axis line O, an impeller  5  that is integrally fixed to the rotor shaft  50 , and a casing  55  which covers the impeller  5  from an outer circumferential side. The impeller  5  has a disk  51  extending in the radial direction of the axis line O, a plurality of blades  52  provided on a surface of the disk  51  facing upstream, and a cover  53  which covers the blades  52  from the upstream side. An impeller flow path P 2  through which air as a working fluid flows is formed between the cover  53 , the disk  51 , and the blades  52  adjacent to each other. 
     A guide flow path P 1 , a diffuser flow path P 3 , a return bend section P 4 , and a return flow path P 5  communicating with the impeller flow path P 2  are provided inside the casing  55 . The diffuser flow path P 3  communicates with a radially outer end portion of the impeller flow path P 2  and extends outward in the radial direction. The return bend section P 4  communicates with the radially outer end portion of the diffuser flow path P 3  and extends in a direction in which the return bend section P 4  is reversed to be directed inward in the radial direction. The blow-off flow path L′ described in the first embodiment described above is connected to the most radially outer side of the return bend section P 4 . The return flow path P 5  communicates with a downstream side of the return bend section P 4  and communicates with the guide flow path P 1  of a subsequent stage located on the downstream side. A return vane  54  is provided in the return flow path P 5 . 
     In such a compressor  211 , a region further upstream than the impeller  5  is an upstream region  211 A and a region further downstream than the impeller  5  is a downstream region  211 B. One (the first detection device  21 A) of the detection devices  21  described in the first embodiment described above is provided in the upstream region  211 A. To be specific, the first detection device  21 A is provided on an inner circumferential surface of the casing  55  in the guide flow path P 1 . Second detection devices  21 B are provided in the downstream region  211 B. To be specific, each of the second detection devices  21 B are provided on each upstream side wall surface and each downstream side wall surface of the diffuser flow path P 3 . In addition, each of the second detection devices  21 B is provided on an upstream end portion and a downstream end portion of the return vane  54 . It is also possible to adopt a constitution in which the second detection device  21 B is provided in only one of the diffuser flow path P 3  and the return vane  54 . 
     Here, it is known that, in the compressor  211  as described above, surging particularly easily occurs in a region further upstream than the impeller  5  and a region further downstream than the impeller  5 . According to the above constitution, since the regions are the upstream region  211 A and the downstream region  211 B and the detection device  21  is provided each of the regions, it is possible to promptly and accurately detect the occurrence of surging and an indication thereof. 
     Also, according to the above constitution, since the detection device  21  is provided in at least one of the diffuser flow path P 3  and the return flow path P 5 , it is possible to finely and accurately detect the occurrence of surging and an indication thereof in the downstream region  211 B. 
     The second embodiment of the present invention has been described above. Various changes and modifications can be provided to the above constitution without departing from the gist of the present invention. 
     Third Embodiment 
     A compressor system  200  according to a third embodiment of the present invention will be described below with reference to  FIGS. 9 to 11 . Constituent elements in the third embodiment that are the same as those of each of the above embodiments will be denoted by the same reference numerals and detailed description thereof will be omitted. In the embodiment, the control of an inlet guide vane  11 C when a command for reducing a load of a gas turbine  100  is issued will be described. 
     As shown in  FIG. 9 , in the compressor system  200  according to the embodiment, a detection device  21  has only the second detection device  21 B described above. Furthermore, the compressor system  200  does not have the blow-off flow path L (the extraction part) and the blow-off valve V described above. In addition, a constitution of a control device  90  is different from that of each of the embodiments described above. 
     As shown in  FIG. 10 , the control device  90  includes a control unit  81 , a flow velocity calculation unit  82 , a closing speed determination unit  83   b  , a storage unit  84 , and a determination unit  85 . The control unit  81  controls other functional units provided in the control device  90 . The above value concerning the temperature difference detected by the detection device  21  is input to the flow velocity calculation unit  82  as numerical value information. 
     The flow velocity calculation unit  82  calculates a flow velocity (or a flow rate) of air on the basis of an absolute value of the temperature difference. The determination unit  85  compares a flow velocity calculated by the flow velocity calculation unit  82  with a threshold value stored in the storage unit  84 . The closing speed determination unit  83   b  determines a closing speed of the inlet guide vane  11 C on the basis of the determination result of the determination unit  85 . To be more specific, as shown in  FIG. 11 , after a load reduction command (Step S 1 ) is issued, magnitudes between a value concerning the above temperature difference (that is, the flow velocity) and a predetermined threshold value are compared (Step S 2 ). When it is determined that the temperature difference is greater than the threshold value, the inlet guide vane  11 C is closed at a relative high speed (Step S 31 ). On the other hand, when it is determined that the temperature difference is smaller than the threshold value, the inlet guide vane  11 C is closed at a relatively low speed. After that, a determination concerning whether an output of the gas turbine  100  has decreased to a target output is performed (Step S 4 ). When it is determined that the output of the gas turbine  100  has not decreased to the target output, Step S 2  to Step S 4  described above are repeatedly performed again. When it is determined that the output of the gas turbine  100  has dropped to the target output, the process is completed. 
     Here, when a command for reducing a load of the compressor  11  (the gas turbine  100 ) is issued, if the inlet guide vane  11 C is closed at an excessively high speed to reduce an amount of air to flow in, there is a risk of there being an amount of air compressed in the downstream region  11 B being insufficient and air flowing back to the upstream side (a surge may occur). On the other hand, when the inlet guide vane  11 C is closed at an excessively low speed, a temperature of combustion gas decreases due to an excessive amount of air supplied to a combustor  2  provided on the downstream side. As a result, there is a risk of generating combustion vibration and increasing an amount of NOx to be discharged. According to the above constitution, the control device  90  determines a speed at which the inlet guide vane  11 C is closed on the basis of the temperature difference detected by means of a pair of temperature detection units  61 , that is, a velocity or a flow rate of a fluid. For this reason, it is possible to close the inlet guide vane  11 C at an appropriate speed while preventing the surge and the unstable combustion described above. As a result, it is possible to stably and quickly reduce a load of the gas turbine  100 . 
     Also, according to the above constitution, it is possible to determine an optimum speed at which the inlet guide vane  11 C is closed simply by evaluating the flow velocity or the flow rate  9  on the basis of the predetermined threshold value. Thus, it is possible to quickly reduce a load of the gas turbine  100  while reducing the likelihood of surges and unstable combustion occurring. 
     The third embodiment of the present invention has been described above. Various changes and modifications can be provided to the above constitution without departing from the gist of the present invention. For example, the control device  90  described in the third embodiment (that is, the control device  90  further including the closing speed determination unit  83   b ) can also be combined with and applied to the constitution described in the first embodiment (that is, the constitution in which the first detection device  21 A, the blow-off flow path L, and the blow-off valve V are included). 
     Also, an operation of the closing speed determination unit  83   b  in the third embodiment is an example. In addition, as another example, it is also possible to constitute a closing speed determination unit  83   b  so that the process shown in  FIGS. 12 and 13  is performed. 
     In the example of  FIG. 12 , the control device  90  determines a detailed numerical range of a temperature difference (that is, a flow velocity or a flow rate) detected by means of a temperature detection device  21  included in a plurality of predetermined continuous numerical ranges (Step  2 B). In addition, the inlet guide vane  11 C is closed by selecting a predetermined closing speed to correspond to the numerical range to which the temperature difference belongs (Steps S 3 A to S 3 C). Although three speeds (a high speed, a medium speed, and a low speed) are set as speeds for closing the inlet guide vane  11 C in the example of  FIG. 12 , the number of speed ranges is not limited to three and four or more speed ranges can be set. 
     According to the above constitution, it is possible to close the inlet guide vane  11 C by selecting a speed determined to correspond to the numerical range to which the detection result of the temperature detection device  21  belongs. That is to say, it is possible to finely determine a speed for closing the inlet guide vane  11 C on the basis of the magnitude of the temperature difference (that is, the flow velocity or the flow rate). As a result, it is possible to more quickly reduce a load of the gas turbine  100  while further reducing the likelihood of surges and unstable combustion occurring. 
     In the example of  FIG. 13 , the control device  90  determines a speed at which the inlet guide vane  11 C is closed with reference to a table in which a relationship between the detection result of the temperature detection unit  21  and the optimum speed at which the inlet guide vane  11 C is closed according to the value concerning the temperature difference is shown (Step S 2 C). After that, the inlet guide vane  11 C is closed at the determined speed (Step S 3 C). 
     According to the above constitution, it is possible to close the inlet guide vane  11 C by selecting the speed in accordance with the table in which the relationship between the optimum speed at which the inlet guide vane  11 C is closed and the temperature difference (that is, the flow velocity or the flow rate) is shown. That is to say, it is possible to more finely determine the speed at which the inlet guide vane  11 C is closed on the basis of the magnitude of the temperature difference. Thus, it is possible to more quickly reduce a load of the gas turbine  100  while further reducing the likelihood of surges and unstable combustion occurring. 
     INDUSTRIAL APPLICABILITY 
     According to the present invention, it is possible to provide a compressor system capable of detecting the occurrence of surging with higher accuracy and minimizing surging. 
     REFERENCE SIGNS LIST 
       100 ,  200  Gas turbine 
       1  Compressor system 
       2  Combustor 
       3  Turbine 
       4 ,  50  Rotor shaft 
       5  Impeller 
       11 ,  211  Compressor 
       11 A,  211 A Upstream region 
       11 B,  211 B Downstream region 
       11 C Inlet guide vane 
       21  Detection device 
       21 A First detection device 
       21 B Second detection device 
       30 ,  55  Casing 
       41  Stator blade stage 
       41 A First stator blade stage 
       41 B Second stator blade stage 
       41 C Outlet stator blade stage 
       41 D Outlet final stator blade stage 
       41 E Diffuser flow path stator blade stage 
       42 A First rotor blade stage 
       42 B Second rotor blade stage 
       42 C Outlet rotor blade stage 
       42 D Outlet final rotor blade stage 
       51  Disk 
       52  Blade 
       53  Cover 
       54  Return vane 
       61  Temperature detection unit 
       62  Heating unit 
       81  Control unit 
       82  Flow velocity calculation unit 
       83  Flow direction calculation unit 
       83   b  Closing speed determination unit 
       84  Storage unit 
       85  Determination unit 
       90  Control device 
       91  CPU 
       92  ROM 
       93  RAM 
       94  HDD 
       95  I/O 
     Df Flow direction 
     Ed Trailing edge 
     Ef Leading edge 
     L, L′ Blow-off flow path 
     Le Exhaust flow path 
     O Axis line 
     P 1  Guide flow path 
     P 2  Impeller flow path 
     P 3  Diffuser flow path 
     P 4  Return bend section 
     P 5  Return flow path 
     S 1  Pressure surface 
     S 2  Suction surface 
     Td, Tu Temperature 
     V Blow-off valve