Abstract:
The present disclosure relates to an evaporative cooler for a turbine intake system. The evaporative cooler includes a reservoir for holding water, a media, a manifold for dispersing the water from the reservoir above the media, a manifold flow line extending from the reservoir to the manifold, a collector for collecting the water below the media, and a pump for pumping the water through the manifold flow line from the reservoir to the manifold. The evaporative cooler also includes a return line for returning the water from the collector to the reservoir, at least one water supply line for supplying the water to the reservoir, and a valve structure for controlling flow through the at least one water supply line. The evaporative cooler further includes a level sensor for indicating whether a top surface of the water within the reservoir is: (1) above or below a first water line; and (2) above or below a second water line positioned below the first water line. A controller interfaces with the valve structure and the level sensor. The controller causes the valve structure to: (1) start water flow to the reservoir at a first flow rate when the top surface of the water falls below the first water line; and (2) increase water flow to the reservoir from the first flow rate to a higher second flow rate when the top surface of the water falls below the second water line.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to evaporative coolers for use in gas turbine intake air systems. More particularly, the present invention relates to sumps used with turbine evaporative coolers. 
     BACKGROUND OF THE INVENTION 
     A gas turbine engine works more efficiently as the temperature of the intake air drawn into the gas turbine decreases. Turbine efficiency is dependent upon the temperature of the intake air because turbines are constant volume machines. The density of the intake air increases as the temperature of the intake air drops. Consequently, by decreasing the temperature of the intake air, the mass flow rate to the turbine is increased which increases the efficiency of the turbine. 
     Evaporative cooling is an economical way to reduce the temperature of the intake air drawn into the turbine. An evaporative cooler commonly includes a plurality of vertically stacked volumes of cooler media. A distribution manifold disperses water over the top of the cooler media. The water is drawn from a sump, distributed over the media by the distribution manifold, and then recycled back to the sump. Intake air for the gas turbine flows through the cooler media. As the water falls or flows through the cooler media, the air passing through the media evaporates some of the water. The evaporation process removes some energy from the air, thereby reducing the temperature of the air. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention relates to an evaporative cooler for a turbine air intake system. The evaporative cooler includes a reservoir or sump for holding water, a media, a manifold for dispersing the water from the reservoir above the media, a manifold flow line extending from the reservoir to the manifold, a collector for collecting the water below the media, and a pump for pumping the water through the manifold flow line from the reservoir to the manifold. The evaporative cooler also includes a return line for returning the water from the collector to the reservoir, at least one water supply line for supplying the water to the reservoir, and a valve structure for controlling flow through the at least one water supply line. The cooler further includes a level sensor for indicating whether a top surface of the water within the reservoir is: (1) above or below a first water line; and (2) above or below a second water line positioned below the first water line. A controller of the evaporative cooler interfaces with the valve structure and the level sensor. The controller causes the valve structure to: (1) start water flow to the reservoir at a first flow rate when the top surface of the water falls below the first water line; and (2) increase water flow to the reservoir from the first flow rate to a higher second flow rate when the top surface of the water falls below the second water line. 
     A variety of advantages of the invention will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned by practicing the invention. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several aspects of the invention and together with the description, serve to explain the principles of the invention. A brief description of the drawings is as follows: 
     FIG. 1A is a schematic end view of an embodiment of an evaporative cooler for a turbine air intake system; 
     FIG. 1B is a schematic left side view of the evaporative cooler of FIG. 1A; and 
     FIG. 2 is a schematic diagram of a flow control system for controlling flow through the evaporative cooler of FIG.  1 A. 
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to exemplary aspects of the present invention that are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     FIGS. 1A and 1B schematically illustrate an embodiment of an evaporative cooler  20  constructed in accordance with the principles of the present invention. The evaporative cooler  20  is adapted for cooling intake air that is drawn into a gas turbine  22 . As shown in FIG. 1A, warm air  24  flows into the left side of the cooler  20 , while cooled air  26  exits the right side of the cooler  20 . The cooled air  26  flows through a turbine air intake system to the turbine  22 . 
     As shown in FIGS. 1A and 1B, the evaporative cooler  20  includes a plurality of vertically stacked volumes of cooling media  28 . The volumes of cooling media  28  are supported on trays  30 ,  31 . The trays  30  are collection trays and function to collect water that drains downward through the volumes of cooling media  28 . The trays  31  are flow-through trays that support volumes of cooling media  28 , but have openings for allowing water to pass through the trays  31 . The trays  30 ,  31  are preferably connected to a rigid frame work (not shown) that holds the trays  30 ,  31  and volumes of cooling media  28  in vertically stacked alignment. 
     The volumes of cooling media  28  can be made of any type of material conventionally used in evaporative coolers. For example, the cooling media can comprise a honeycomb of cellulose based product with resins to enhance rigidity. Suitable cooling media are sold by Munters Corporation of Fort Myers, Fla. 
     The evaporative cooler  20  also includes a sump or reservoir  32  for holding a volume of water  34 . The reservoir  32  preferably has a volume that is at least ten percent the total volume occupied by the volumes of cooling media  28 . In use of the evaporative cooler  20 , the water  34  from the reservoir  32  is circulated through the volumes of cooling media  28 . As the warm air  24  flows through the volumes of cooling media  28 , the air evaporates some of the water that is being circulated through the cooling media  28 . The evaporation process removes energy from the air, thereby reducing its temperature. 
     To circulate the water  34  through the volumes of cooling media  28 , the water  34  is pumped upward from the reservoir  32  through a manifold flow line  36 . The manifold flow line  36  conveys the water  34  to a plurality of manifolds  38 . The manifolds  38  include a plurality of upwardly facing spray or orifices for spraying the water  34  in an upward direction. As best shown in FIG. 1A, the water  34  is sprayed from the manifolds  38  in an upward direction against curved dispersion plates  40 . After being dispersed by the dispersion plates  40 , the water  34  flows downward through the volumes of cooling media  28  via gravity and is collected in the collection trays  30 . From the collection trays  30 , the water  34  flows downward via gravity through a return line  42  that conveys the water  34  back to the reservoir  32 . While a single return line  42  is schematically shown, it will be appreciated that multiple return lines can also be used. For example, a separate return line can be used for each column or bay of the evaporative cooler  20 . 
     FIG. 2 illustrates a schematic valving and control diagram for the evaporative cooler  20 . As shown in FIG. 2, the manifold flow line  36  is connected to a plurality of branch lines  44  that extend from the manifold flow line  36  to the manifolds  38 . Each branch line  44  includes a globe valve  46  and a flow meter  48 . By adjusting the globe valves  46  while viewing the flow meters  48 , an operator can adjust the water flow rate through each branch line  44 . 
     The manifold flow line  36  also includes a pump such as a centrifugal pump  50  for providing sufficient pressure head to drive the water  34  from the reservoir  32  up through the manifold flow line  36  to each of the manifolds  38 . A pressure gauge  52  is positioned upstream from the pump  50 . A flow switch  54  is positioned between the pump  50  and the pressure gauge  52 . The flow switch  50  measures or monitors the rate of water flow through the manifold flow line  36 . If the flow rate through the manifold flow line  36  falls below a preset limit, such as about 10 gallons per minute, the flow switch  54  signals a controller  56  which deactivates the pump  50 . In this manner, the flow switch  54  prevents the pump  50  from continuing to pump when insufficient water is being drawn from the reservoir  32 . Hence, the flow switch  54  assists in improving the life of the pump  50 . 
     It will be appreciated that the controller  56  can include any type of control unit such as a microcontroller, a mechanical controller, an electrical controller, a hardware driven controller, a firmware driven controller or a software driven controller. 
     Referring again to FIG. 2, the evaporative cooler  20  also includes first and second water supply lines  58  and  60 . The first and second water supply lines  58  and  60  convey water from a source of water  62  to the reservoir  32 . A manual gate valve  64  opens and closes flow between the source of water  62  and the first and second water supply lines  58  and  60 . Flow through the first water supply line  58  is controlled by a valve structure such as a first solenoid valve  66 . Similarly, flow through the second water supply line  60  is controlled by a valve structure such as a second solenoid valve  68 . Conventional strainers  70  are positioned upstream from the solenoid valves  66  and  68 . The strainers  70  remove contaminants from the water and assist in extending the working lives of the solenoid valves  66  and  68 . 
     The reservoir  32  also includes an overflow weir  72  for draining water from the reservoir  32  when the top surface  74  of the water  34  reaches a predetermined level  76 . For example, a spillway  78  is positioned at the predetermined level  76 . When the top surface  74  of the water  34  reaches the predetermined level  76 , the water spills over the spillway  78  and into a drain line  80 . The drain line  80  conveys the overflow water to a water disposal location  82  such as a sewer system. 
     The reservoir  32  also includes a quick drain  84  for draining the water  34  from the reservoir  32 . The quick drain  84  includes a quick drain line  86  having one end in fluid communication with the bottom of the reservoir  32 , and another end in fluid communication with the drain line  80 . A gate valve  88  is used to open and close the quick drain line  86 . 
     During start up of the evaporative cooler  20 , the pump  50  draws water from the reservoir  32  and forces the water through the manifold flow line  36  to the manifold  38 . As the pump  50  draws water from the reservoir  32 , the water level within the reservoir  32  has a tendency to drop. If the water level falls below a certain level, pump cavitation is possible and the cooling efficiency or effectiveness of the evaporative cooler  20  is compromised. To inhibit the water level within the reservoir  32  from dropping too low at start up conditions, the evaporative cooler  20  uses a multi-level sensor  90  that interfaces with the controller  56 . By using input provided by the multi-level sensor  90 , the controller  56  can selectively open and close the first and second solenoid valves  66  and  68  to adjust the flow of water into the reservoir  32  from the source of water  62 . For example, if the top surface  74  of the water  34  falls below a first level, the controller  56  can open the first solenoid valve  66  such that water is conveyed through the first water supply line  58  into the reservoir  32  at a first flow rate. Additionally, if the top surface  74  of the water  34  falls below a second level located below the first level, the controller  56  can cause the second solenoid valve  68  to open such that water is supplied to the reservoir  32  through both the first and second water supply lines  58  and  60 . When both supply lines  58  and  60  are open, water flows into the reservoir at a second flow rate that is faster than the first flow rate. 
     It will be appreciated that a variety of known level sensors or switches can be used to monitor the depth of the water within the reservoir  32 . For example, suitable liquid multi-level switches are sold by Gems Company, Inc., of Farmington, Conn. Such liquid level switches can include multiple floats that trigger switches corresponding to certain liquid levels. 
     Referring again to FIG. 2, the level sensor  90  monitors multiple water levels that include water level  92 , water level  94 , water level  96 , water level  98 , and water level  100 . Water level  92  is the lowest water level, while water level  100  is the highest water level. When the top surface  74  of the water  34  falls below water level  92 , the level sensor  90  signals the controller  56  which in turn triggers an alarm  102 . Similarly, if the top surface  74  of the water  34  rises above water level  100 , the level sensor  90  signals the controller  56  which activates the alarm  102 . Water level  100  is located above the level  76  of the spillway  78 . Consequently, the water level within the reservoir  32  would typically only reach water level  100  in situations in which the drain line  80  has become clogged. In such situations, the alarm  102  gives an operator sufficient time to shut off the water supply gate valve  64  before the water  34  overflows the reservoir  32 . 
     Water level  94  is positioned above water level  92 , while water level  96  is positioned above water level  94 . When the top surface  74  of the water  34  falls below water level  96 , the level sensor  90  signals the controller  56  which causes the first solenoid valve  56  to open such that water flows through the first water supply line  58  into the reservoir  32 . If the water level within the reservoir  32  continues to drop and the top surface  74  of the water  34  falls below water level  94 , the controller causes the second solenoid valve  68  to open such that water flows into the reservoir  32  through both the first and second water supply lines  58  and  60 . The second solenoid valve  68  stays open until the level sensor  90  detects that the water level in the reservoir  32  has risen back to water level  96 . When the water level in the reservoir  34  reaches water level  96 , the controller  56  causes the second solenoid valve  68  to close the second water supply line  60  such that only the first water supply line  58  continues to supply water to the reservoir  32 . The first solenoid valve  66  remains open until the water level in the reservoir  32  reaches water level  98 . When the level sensor  90  detects that the water level in the reservoir  32  has reached water level  98 , the controller causes the first solenoid valve  66  to close the first water supply line  58 . 
     During start up of the evaporative cooler  20 , the pump  50  begins to draw water from the reservoir  32  causing the water level in the reservoir  32  to drop from the spillway level  76  past level  98  to level  96 . When the water level reaches water level  96 , the controller opens the first solenoid valve  66  such that fresh water is provided to the reservoir  32  through the first water supply line  58 . Under certain conditions, the water level within the reservoir  32  may continue to drop and may fall below water level  94 . When the water level falls below water level  94 , the controller  56  opens the second solenoid valve  68  such that additional water is supplied to the reservoir  32  through the second water supply line  60 . The combined flow provided by the first and second water supply lines  58  and  60  causes the water level in the reservoir  32  to begin to rise. Additionally, recirculated water from the return line  42  will also cause the water level in the reservoir  32  to rise. When the water level rises above level  96 , the second flow line  60  is closed such that only the first flow line  58  continues to supply water to the reservoir  32 . When the water within the reservoir  32  rises above water level  98 , the controller  56  causes the first solenoid valve  66  to close the first water supply line  58 . At this point in time, the evaporative cooler  20  will operate generally at steady state conditions with the water being circulated from the reservoir  32  up through the manifold flow line  36  to the volumes of cooling media  28 , and then back to the reservoir through the return line  42 . As the water flows through the volumes of cooling media  28 , small amounts of water are evaporated by the warm air  24  passing through the volumes of cooling media  28 . Consequently, the water level within the reservoir  32  will gradually drop. When the water level falls below water level  96 , the controller again opens the first water supply line  58  such that new water is again supplied to the reservoir  32 . The first water supply line  58  remains open until the water level within the reservoir again reaches water level  98 . 
     When the evaporative cooler  20  is shut down, the pump  50  is deactivated and a relatively large volume of water from the volumes of cooling media  28  flows into the reservoir  32  through the return line  42 . The water from the volumes of cooling media  28  causes the water level in the reservoir  32  to rise up to the spillway level  78  and overflow into the drain line  80 . Consequently, when the evaporative cooler  20  is again started up, the water level within the reservoir  32  will be approximately at the spillway level  76 . 
     In one particular embodiment of the present invention, the sump has a volume of 1900 gallons (gal), new water is supplied to the reservoir at a flow rate of 125 gal/minute (min) when the first flow line is open, new water is supplied to the reservoir at a flow rate of 250 gal/min when both the first and second flow lines are open, and water is withdrawn from the reservoir at a rate of 400 gal/min. In such a non-limiting example, the reservoir has a depth of 22 inches, water level  100  is located 20 inches from the bottom of the reservoir, water level  98  is 4 inches below water level  100 , water level  96  is 2 inches below water level  98 , water level  94  is 2 inches below water level  96 , and water level  92  is 2 inches below water level  94 . 
     With regard to the foregoing description, it is to be understood that changes may be made in detail, especially in matters of the construction materials employed, and the size, shape and arrangement of the parts without departing from the scope of the present invention. For example, the number of media volumes, manifolds and pumps can be varied from those specifically illustrated. It is intended that the specification and the depicted aspects be considered exemplary only, with the true scope and spirit of the invention being indicated by the broad meaning of the following claims.