Patent Publication Number: US-2011052377-A1

Title: Gas-turbine inlet-air cooling system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No, 2009-200696, filed Aug. 31, 2009; and No, 2010-056953, filed Mar. 15, 2010; the entire contents of all of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a gas-turbine inlet-air cooling system which cools the inlet air of a gas turbine to increase power output. 
     2. Description of the Related Art 
     For a thermal power plant including a simple cycle gas turbine facility or a combined-cycle plant which is made up of a combination of a gas turbine facility, a steam turbine facility, and an exhaust heat recovery boiler, for example, it is an important object or challenge to increase power efficiency. 
     Conventionally, there is known an inlet-air cooling system as means for increasing the power efficiency. The inlet-air cooling system is a system for cooling the inlet air of a compressor to thereby increase an inlet air mass flow rate of the compressor. The inlet-air cooling system operates to spray water into inlet air to thereby evaporate the water in an inlet system or the compressor and then to cool the inlet air. 
     JP2002-322916A (Patent Document 1) discloses an inlet-air cooling system which surely cools inlet air by reducing a size of droplets sprayed into the inlet air to thereby increase power output and prevent compressor blades from being damaged. Specifically, the inlet-air cooling system disclosed in the Patent Document 1 is equipped with a spray device composed of a plurality of water distribution pipes and spray nozzles and a plurality of cooling-water feed pipes connected to the spray device. In this way, the inlet-air cooling system is designed to surely cool inlet air with a larger amount of spray water and increase power output. 
     In general, it is required for the inlet-air cooling system to minimize the size of droplets sprayed into the air inlet system. This is because with large droplet size, the water droplets directly attack rotor and stator blades of the compressor, which may cause erosion and damage the rotor and stator blades. In order to achieve the object, there is provided a method of spraying small-size droplets by using a positive displacement pump capable of delivering cooling water at high pressure for an inlet-air cooling system. 
     Then, it will be conceivable to apply the positive displacement pump to a plurality of cooling-water feed pipes of the inlet-air cooling system disclosed in the Patent Document 1. However, there is such a fear that the positive displacement pump might cause pressure pulsations in piping on the suction and discharge sides. In particular, in an inlet-air cooling system in which a positive displacement pump is installed for each of the cooling-water feed pipes to properly control the droplets, the pressure pulsations in the pipes may be increased by interfering with each other, which may result in increasing mechanical vibrations of surrounding equipment including the pumps and pipes and hence damaging them. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in consideration of the circumstances mentioned above and an object thereof is to provide a gas-turbine inlet-air cooling system capable of improving the reliability of an entire system. 
     To achieve the above object, a gas-turbine inlet-air cooling system of the present invention includes: a spray device configured to spray cooling water into inlet air of a compressor of a gas turbine facility to thereby cool the inlet air; and a cooling-water feed system configured to feed the cooling water to the spray device. The cooling-water feed system including: at least one tank configured to reserve the cooling water; a plurality of pipes connected to the tank independently of each other and configured to feed the cooling water to the spray device; and pumps installed for the pipes, respectively. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a schematic system diagram showing a first embodiment of a gas-turbine inlet-air cooling system according to the present invention; 
         FIG. 2  is a schematic system diagram showing a modification of the first embodiment of the gas-turbine inlet-air cooling system according to the present invention; 
         FIG. 3  is a schematic system diagram showing another modification of the first embodiment of the gas-turbine inlet-air cooling system according to the present invention; 
         FIG. 4  is a schematic system diagram showing a second embodiment of the gas-turbine inlet-air cooling system according to the present invention; and 
         FIG. 5  is a schematic system diagram showing a third embodiment of the gas-turbine inlet-air cooling system according to the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Each embodiment of a gas-turbine inlet-air cooling system according to the present invention will be described hereunder with reference to the accompanying drawings. 
     First Embodiment 
       FIG. 1  is a schematic system diagram representing a first embodiment of a gas-turbine inlet-air cooling system according to the present invention. 
     A gas turbine facility  1 , to which the gas-turbine inlet-air cooling system according to the first embodiment is applied, mainly includes an air inlet system  3 , a compressor  5 , a gas turbine  6 , and a power generator  7 , which are arranged along a fluid flow direction in the described order. 
     The air inlet system  3  is connected to the compressor  5  and to take inlet air entered into the compressor  5  from an air inlet  4 . Although a description here is made on a case where gas entered into the compressor  5  is air, the gas entered into the compressor  5  can be another gas. 
     The compressor  5  compresses the air entered from the inlet system  3  and discharges the compressed air to a combustor  8 . The discharged compressed air is then supplied together with fuel  9  to the combustor  8 , thus generating combustion gas. The gas turbine  6  is driven by the combustion gas generated by the combustor  8 , and an exhaust gas  10  from the gas turbine  6  is discharged to the atmosphere. The power generator  7  is coupled to a turbine shaft of the gas turbine  6 , and when the gas turbine is driven, the power generator  7  generates electricity. 
     The gas turbine facility  1  includes a thermometer, a hygrometer and an inlet air flow meter, which are not shown, installed at specified locations. For example, the thermometer measures atmospheric temperature, the hygrometer measures humidity in the inlet system  3 , and the inlet air flow meter measures a mass flow rate of the air entered into the compressor  5 . 
     The inlet system  3  includes a spray device  11  which sprays cooling water into the inlet air at the inlet system  3  (and then to the compressor  5 ). The spray device  11  sprays cooling water to cool the inlet air. The spray device  11  is designed to spray fine droplets through spray nozzles  13   a ,  13   b , . . . ,  13   n  (hereinafter referred to collectively as the spray nozzles  13  when there is no need to distinguish individual spray nozzles) mounted to a plurality of water distribution pipes  12   a ,  12   b , . . . ,  12   n  (collectively, water distribution pipes  12 ). Although a description here is made on a case where water droplets are sprayed into the air entered into the compressor  5 , can be another fluid. 
     The spray device  11  is connected to a cooling-water feed system  20  which feeds the cooling water to the spray device  11 . The cooling-water feed system  20  includes one tank  22  and a plurality of feed pipes  23   a ,  23   b , . . . ,  23   n  (collectively, feed pipes  23 ). The tank  22  is open to the atmosphere and configured to reserve the cooling water. The feed pipes  23  are connected to the tank  22  independently of each other and feed the cooling water to the spray device. Furthermore, the feed pipes  23  are connected with pumps  28   a ,  28   b , . . . ,  28   n  (collectively, pumps  28 ), pressure-regulator valves  29   a ,  29   b , . . . ,  29   n  (collectively, pressure-regulator valves  29 ), and accumulators  31   a ,  31   b , . . . ,  31   n  (collectively, accumulators  31 ), respectively. 
     The tank  22  reserves cooling water  21  supplied from a demineralized water system or service-water system (neither is shown). The tank  22  should preferably have a capacity corresponding to a discharge quantity of the pumps  28  at a maximum discharge flow rate for 2 minutes or more (e.g., 2 to 10 minutes). This is preferred for supplying cooling water smoothly without mixing air cavities into pumps  28  in operation. 
     The feed pipes  23  are, for example, steel pipes and are arranged in two or more lines. Each of the feed pipes  23  includes a suction-side feed pipe  24  (a suction side portion) and a discharge-side feed pipes  25  (a discharge side portion) on a suction side and a discharge side, respectively, of each pump  28 . The resultant suction-side feed pipes  24  including individual suction-side feed pipes  24   a ,  24   b , . . . ,  24   n  of the feed pipes  23  are connected to the tank  22  independently of each other, and the resultant discharge-side feed pipes  25  including individual discharge-side feed pipes  25   a ,  25   b , . . . ,  25   n —of the feed pipes  23  are respectively connected to water distribution pipes  12  based on the number of lines of the feed pipes  23 . 
     Positive displacement pumps capable of delivering cooling water at a high pressure may be used as the pumps  28  to reduce size of droplets sprayed from the spray device  11 . The positive displacement pump is designed to extrude a liquid from the suction side to the discharge side through movement or variation of an enclosed space between a casing and a movable parts assembled within and in contact with the casing. 
     The pressure-regulator valve  29  may be a spring-loaded valve which is designed to open when discharge pressure of the pump  28  reaches or exceeds a rated value. The pressure-regulator valves  29  are used to keep constant the discharge pressure of the pumps  28 , i.e., upstream pressure of the spray nozzles  13 . The pressure-regulator valves  29  are connected to the discharge-side feed pipes  25 . Outlet pipes  30   a ,  30   b , . . . ,  30   n  (collectively, outlet pipes  30 ) at downstream of the pressure-regulator valves  29  are respectively connected to the tank  22  to thereby open to the atmosphere. 
     The accumulators  31  (gas damper) are installed to damp pressure pulsations resulting from operation of the pumps  28 . The accumulators  31  are mounted to the discharge-side feed pipes  25  or discharge casings (not shown) of the pumps  28 . Preferably, the accumulators  31  are mounted as close as possible to the respective pumps  28 . 
     Now, an operation of the cooling-water feed system  20  and spray device  11  included in the gas-turbine inlet-air cooling system according to the first embodiment will be described. 
     The droplets from the spray nozzles  13  of the spray device  11  are sprayed into the air taken into the inlet system  3  from the air inlet  4 . The cooling-water feed system  20  feeds cooling water from the tank  22  to the spray device  11  by the pumps  28 . In so doing, the cooling-water feed system  20  feeds the cooling water to the spray device  11  after optimizing, for example, the flow rate of the cooling water depending on the atmospheric temperature, the humidity in the inlet system  3 , and the inlet air mass flow rate of the compressor  5 , so as to feed the optimized of the cooling water flow. The atmospheric temperature, humidity, and inlet air mass flow rate are measured by the thermometer, the hygrometer, and the inlet air flow meter described above. 
     The positive displacement pumps used as the pumps  28  are liable to cause pressure pulsations in the suction and discharge piping. 
     However, with the cooling-water feed system  20  according to the first embodiment, the suction-side feed pipes  24  of the plurality of feed pipes  23  connected with the pumps  28  are connected to the tank  22  independently of each other and the suction side of the pumps  28  is opened to the atmosphere via the tank  22 . This is effective to reduce mutual interference by pressure pulsations occurring in respective suction-side feed pipes  24  at simultaneously operations of the plural pumps  28 . 
     On the other hand, the accumulators  31  are mounted to the discharge casings of the pumps  28  or the discharge-side feed pipes  25 . This is effective to reduce pressure pulsations in the discharge-side feed pipes  25  positioned on the discharge side of the pumps  28 . 
     The discharge-side feed pipes  25  of the pumps  28  are also connected with the pressure-regulator valves  29 . Each pressure-regulator valve  29  reduces changes in the discharge pressure of the pump  28  by an operation thereof when a pressure of the discharge-side feed pipe  25  reaches or exceeds a rated value. This reduces pressure pulsations in the discharge-side feed pipes  25 . The outlet pipes  30  of the pressure-regulator valves  29  are open to the atmosphere via the tank  22 . The pressure-regulator valves  29  can stabilize outlet pressure (back pressure) and thereby stabilize operation. This enables proper pressure control of the discharge-side feed pipes  25  as well. Incidentally, since the outlet pipes  30  of the pressure-regulator valves  29  are connected to the tank  22 , an excess flow from the pressure-regulator valves  29  is returned to the tank  22  and reused as cooling water. 
     As the pressure-regulator valves  29  regulate the discharge pressure of the pumps  28 , the upstream pressure of the spray nozzles  13  is also stabilized. Consequently, the droplets sprayed from the spray device  11  can be securely finely, protecting rotor and stator blades of the compressor  5  from erosion by the droplets attack. 
     With the gas-turbine inlet-air cooling system according to the first embodiment, even when plural pumps  28  are operated simultaneously, pressure pulsations in the feed pipes  23  on the suction and discharge sides of the pumps  28  can be reduced properly. As the pressure pulsations are reduced, mechanical vibrations of surrounding equipment including the pumps and pipes can be reduced as well. This improves reliability of the entire gas-turbine inlet-air cooling system which uses the plurality of positive displacement pumps in the cooling-water feed system  20 . 
     Incidentally, in the gas-turbine inlet-air cooling system according to the first embodiment described above, the plural feed pipes  23  connected with respective pumps  28  are connected to the single tank  22  independently of each other. However, the plural tanks  22  may be connected instead of the single tank. 
       FIG. 2  is a schematic system diagram showing a modification of the first embodiment of the gas-turbine inlet-air cooling system according to the present invention. 
     In the example shown in  FIG. 2 , plural tanks  32   a ,  32   b , . . . ,  32   n  (collectively, tanks  32 ) are connected corresponding to the number of feed pipes  23  of a cooling-water feed system  35  so that each tank  32  is connected with one feed pipe  23 . In this way, by connecting one tank  32  with each feed pipe  23 , it is possible to prevent mutual interference by pressure pulsations in the feed pipes  23  more properly. 
     The connection of one tank  32  for each feed pipe  23  increases flexibility of tank layout and thereby allows the tanks  32  to be connected at such locations that can reduce distances between the pumps  28  and the tanks  32  in the feed pipes  23  as well as reduce pump suction heads. Thus, the suction-side feed pipes  24  of the feed pipes  23  can be reduced in length, while the suction-side feed pipes  24 , when over increased in length, can cause pressure pulsations. 
     Incidentally, in an example of the first embodiment described above, the feed pipes  23  are equipped with respective pressure-regulator valves  29  and accumulators  31 . However, the gas-turbine inlet-air cooling system requires only that the feed pipes  23  are connected to the tank  22  independently of each other, and the pressure-regulator valves  29  and accumulators  31  may be installed on the feed pipes  23  only as required. 
     Also, in the gas-turbine inlet-air cooling system described above, the spray device  11  is installed in the inlet system  3 . However, the spray device  11  can also be installed outside the inlet system  3 , so as to cool the inlet air in front of the air inlet  4 . 
       FIG. 3  is a schematic system diagram showing another modification of the first embodiment of the gas-turbine inlet-air cooling system according to the present invention. 
     Water feed pipes  112   a ,  112   b , . . . ,  112   n  (collectively, water feed pipes  112 ) of the gas-turbine inlet-air cooling system shown in  FIG. 3  are placed in front of the air inlet  4  and along a plane almost perpendicular to a inlet flow direction into the inlet system  3 . The feed pipes  112  are also placed along a side of the air inlet  4  to cool the inlet air through the side of the air inlet  4  as well. The water feed pipes  112  are equipped with respective spray nozzles  113   a ,  113   b , . . . ,  113   n.    
     The installation of the spray device  111  outside the inlet system  3  to cool the inlet air eliminates the construction work such as drilling which would be required in the case of installing the spray device  111  in the inlet system  3 . Furthermore, a construction schedule for the installation of the gas-turbine inlet-air cooling system can be shortened. 
     Also, since the spray device  111  is placed outside an inlet filter installed in the air inlet  4 , erosion in the compressor  5  due to water droplets can be reduced. 
     Second Embodiment 
       FIG. 4  is a schematic system diagram showing a second embodiment of the gas-turbine inlet-air cooling system according to the present invention. 
     The gas-turbine inlet-air cooling system according to the second embodiment differs from the first embodiment mainly in that unloader valves  41   a ,  41   b , . . . ,  41   n  (collectively, unloader valves  41 ) are connected to the respective feed pipes  23   a ,  23   b , . . . ,  23   n  (feed pipes  23 ) of a cooling-water feed system  40 . In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals as the corresponding components in the first embodiment, and respective description thereof will be omitted. The cooling-water feed system  40  shown in  FIG. 4  as an example is not equipped with the pressure-regulator valves  29  and accumulators  31  illustrated in  FIG. 1 , but these components may be equipped as required. 
     The unloader valves  41  come into operation when the respective pumps  28   a ,  28   b , . . . ,  28   n  (pumps  28 ) are started or stopped. The unloader valves  41  are pressure control valves which operate the pump  28  under no-load conditions when the discharge pressure of the pump  28  reaches a rated value. The unloader valves  41  are connected to the discharge-side feed pipes  25   a ,  25   b , . . . ,  25   n  (discharge-side feed pipes  25 ) of the feed pipes  23 . Also, outlet pipes  42   a ,  42   b , . . . ,  42   n  (collectively, outlet pipes  42 ) of the unloader valves  41  are respectively connected to the tank  22 . 
     Now, an operation of the gas-turbine inlet-air cooling system according to the second embodiment will be described, particularly about around the cooling-water feed system  40 . 
     When the pumps  28  are started in service of the gas-turbine inlet-air cooling system  40 , the unloader valves  41  are open. Normally, when the pumps  28  are started rapidly, the pumps  28  are over loaded. However, in the gas-turbine inlet-air cooling system according to the second embodiment, the unloader valves  41  are connected with the discharge side of the pumps  28 . This reduces the loads on the pumps  28 . Also, since the pumps  28  can be operated under no load on start running-in and system air-bleeding can be carried out. Consequently, the cooling-water feed system  40  can properly prevent unexpected fluid vibrations due to air contaminant. 
     When the pumps  28  operate under a rated condition, the unloader valves  41  are closed and the discharge pressure of the pumps  28  rises. 
     On the other hand, when the pumps  28  in a rated operation are changed to a stop, the unloader valves  41  are opened. When stopped rapidly, the pumps  28  are over loaded as in the case of a rapid start. However, by operating the unloader valves  41 , the pumps  28  can be stopped under no-load conditions. Consequently, the pumps  28  are not stopped rapidly, and the loads on the pumps  28  can be reduced. Since the outlet pipes  42  of the unloader valves  41  are connected to the tank  22 , the cooling water through the unloader valves  41  is returned to the tank  22  again. This is advantageous in that the cooling water through the unloader valves  41  can be reused, allowing operating costs to be reduced. 
     In addition to the advantages of the first embodiment, the gas-turbine inlet-air cooling system according to the second embodiment provides the advantage of being able to reduce the loads on the pumps  28  during start and stop. This improves reliability of the entire gas-turbine inlet-air cooling system including start-up and shut-down. 
     Third Embodiment 
       FIG. 5  is a schematic system diagram showing a third embodiment of the gas-turbine inlet-air cooling system according to the present invention. 
     The gas-turbine inlet-air cooling system according to the third embodiment differs from the first embodiment mainly in that a part of feed pipes  53   a ,  53   b , . . . ,  53   n  (collectively, feed pipes  53 ) in a cooling-water feed system  50  is made of a non-metallic material. The rest of the configuration is almost the same as the first embodiment, and thus the same components as those in the first embodiment are denoted by the same reference numerals as the corresponding components in the first embodiment and respective description thereof will be omitted. The cooling-water feed system  50  shown in  FIG. 5  as an example is not equipped with the pressure-regulator valves  29  and accumulators  31  illustrated in  FIG. 1  and the unloader valves  41  illustrated in  FIG. 4 , but these components may be installed as required. 
     The suction-side feed pipes  54   a ,  54   b , . . . ,  54   n  (collectively, suction-side feed pipes  54 ) of the feed pipes  53  partially include suction-side hoses  64   a ,  64   b , . . . ,  64   n  (collectively, suction-side hoses  64 ) made of a non-metallic material. Discharge-side feed pipes  55   a ,  55   b , . . . ,  55   n  (collectively, discharge-side feed pipes  55 ) of the feed pipes  53  partially include discharge-side hoses  65   a ,  65   b , . . . ,  65   n  (collectively, discharge-side hoses  65 ) made of a non-metallic material. 
     The suction-side hoses  64  and discharge-side hoses  65  are made of a non-metallic material, such as rubber or plastics, lower in rigidity than the feed pipes  53 . Also, the discharge-side hoses  65  are hydraulic hoses which can resist the discharge pressure of the pumps  28 . 
     Now, an operation of the gas-turbine inlet-air cooling system according to the third embodiment will be described, particularly about the cooling-water feed system  50 . 
     The suction-side feed pipes  54  connected to the suction side of the pumps  28  partially include the suction-side hoses  64 . The suction-side hoses  64  are lower in rigidity than the suction-side feed pipes  54  and function as dampers against pressure pulsations in the suction-side feed pipes  54  on the suction side of the pumps  28 . This is effective to reduce the pressure pulsations on the suction side of the pumps  28  and prevent mechanical vibrations from being transmitted to surrounding equipment. 
     Similarly, the discharge-side feed pipes  55  partially include the discharge-side hoses  65 . This is effective to reduce pressure pulsations on the discharge side of the pumps  28  and prevent mechanical vibrations from being transmitted to surrounding equipment. 
     In addition to the advantages of the first embodiment, the gas-turbine inlet-air cooling system according to the third embodiment provides the advantage of being able to more properly reduce pressure pulsations in the feed pipes  53 . This is effective to prevent mechanical vibrations of surrounding equipment and thereby improves reliability of the entire gas-turbine inlet-air cooling system. 
     The features described above are focused on characteristic features of the first to third embodiments, separately, and the features of the first to third embodiments can be used in combination as required. In particular, the example of arrangement in which the spray device  111  is installed outside the inlet system  3  as illustrated in  FIG. 3  can be applied also to the gas-turbine inlet-air cooling systems according to the second and third embodiments.