Abstract:
A water supply system includes a water storage tank having a storage tank outlet, the water storage tank configured to store a volume of water at a first pressure. A pressure tank is in fluid communication with the water storage tank and is periodically fillable with water from the water storage tank. An air source is fluidly connected to the pressure tank to pressurize the volume of water in the pressure tank to a second pressure greater than the first pressure. A pressure tank output line is fluidly connected to the pressure tank to output water from the pressure tank.

Description:
BACKGROUND 
       [0001]    The subject matter disclosed herein relates to water systems. More specifically, the present disclosure relates to potable water systems utilizing conformal-shaped water storage tanks. 
         [0002]    Many applications, such passenger aircraft, passenger trains, or the like often include potable water systems to provide water for use by passengers during operation. In an aircraft, for example, some potable water systems include a large water storage tank which is pressurized with air. The air typically is bleed air from an auxiliary power unit or is provided by a standalone air compressor for the potable water system. Aircraft operators typically desire the tank to maximize water volume storage capability, while also minimizing interior aircraft space utilized by the water storage tank. For this reason, the water storage tank is often made to an irregular or conformal shape, meant to fit in an irregular-shaped space allotted for the water storage tank at the interior of the aircraft. When pressurized, however, it is difficult to maintain the conformal shape of the water storage tank as the pressure inside the tank attempts to force the tank into a spherical shape. As such, it is required to form the tank from high-strength pressure resistant materials, and it may also be necessary to include external and/or internal structural reinforcement or baffles to the tank to maintain the tank shape when the tank is pressurized. As a result, the water storage tank adversely affects the cost and weight of the potable water system. 
       SUMMARY 
       [0003]    In one embodiment, a water supply system includes a water storage tank having a storage tank outlet, the water storage tank configured to store a volume of water at a first pressure. A pressure tank is in fluid communication with the water storage tank and is periodically fillable with water from the water storage tank. An air source is fluidly connected to the pressure tank to pressurize the volume of water in the pressure tank to a second pressure greater than the first pressure. A pressure tank output line is fluidly connected to the pressure tank to output water from the pressure tank. 
         [0004]    Additionally or alternatively, in this or other embodiments the first pressure is substantially ambient pressure. 
         [0005]    Additionally or alternatively, in this or other embodiments a level sensor is located at the pressure tank to detect when a water level in the pressure tank is such that the pressure tank is in need of refill. 
         [0006]    Additionally or alternatively, in this or other embodiments the level sensor is operably connected to the water storage tank to initiate refill of the pressure tank from the water storage tank when the level sensor detects the pressure tank is in need of refill. 
         [0007]    Additionally or alternatively, in this or other embodiments the pressure tank is two pressure tanks arranged in parallel and flow through the pressure tank output line is switchable between a first pressure tank of the two pressure tanks and a second pressure tank of the two pressure tanks. 
         [0008]    Additionally or alternatively, in this or other embodiments an air valve is operably connected to the air source and the two pressure tanks to selectably admit pressurizing air to the first pressure tank and/or the second pressure tank. 
         [0009]    Additionally or alternatively, in this or other embodiments a storage output valve is operably connected to the water storage tank and the two pressure tanks to selectably admit water into the first pressure tank and/or the second storage tank from the water storage tank. 
         [0010]    Additionally or alternatively, in this or other embodiments a pump urges water from the water storage tank to the pressure tank. 
         [0011]    Additionally or alternatively, in this or other embodiments the water storage tank is formed from one of a plastic or composite material. 
         [0012]    Additionally or alternatively, in this or other embodiments the water storage tank is non-spherical and non-cylindrical. 
         [0013]    Additionally or alternatively, in this or other embodiments the second pressure is in the range of 20-45 pounds per square inch. 
         [0014]    In another embodiment, a method of operating a water supply system includes storing a volume of water at a first pressure at a water storage tank, urging a portion of the volume of water from the water storage tank into a first pressure tank, urging a volume of air from an air source into the first pressure tank to pressurize the first pressure tank to a second pressure greater than the first pressure, and releasing a flow of water from the first pressure tank via a pressure tank output line fluidly connected to the first pressure tank. 
         [0015]    Additionally or alternatively, in this or other embodiments a water level at the first pressure tank is detected, and the first pressure tank is refilled from the water storage tank based on the detected water level. 
         [0016]    Additionally or alternatively, in this or other embodiments a portion of the volume of water is urged from the water storage tank into a second pressure tank arranged in parallel with the first pressure tank. A volume of air is urged from the air source into the second pressure tank to pressurize the second pressure tank to a second pressure greater than the first pressure. A flow of water is selectably released from the first pressure tank and/or the second pressure tank via a pressure tank output line fluidly connected to the first pressure tank and the second pressure tank. 
         [0017]    Additionally or alternatively, in this or other embodiments the first pressure tank and/or the second pressure tank are selectably filled from the water storage tank through operation of a storage output valve operably connected to the first pressure tank and the second pressure tank. 
         [0018]    Additionally or alternatively, in this or other embodiments the first pressure tank and/or the second pressure tank are selectably pressurized through operation of an air valve operably connected to the air source, first pressure tank and second pressure tank. 
         [0019]    Additionally or alternatively, in this or other embodiments water is urged from the water storage tank via a pump. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The subject matter is particularly pointed out and distinctly claimed at the conclusion of the specification. The foregoing and other features, and advantages of the present disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0021]      FIG. 1  is a schematic view of an embodiment of a potable water system; and 
           [0022]      FIG. 2  is a schematic view of another embodiment of a potable water system. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Referring now to  FIG. 1 , shown is an exemplary embodiment of potable water system (PWS)  10  for use in, for example, a passenger aircraft cabin. The PWS  10  includes a water storage tank  12 , configured to contain a volume of water  14  or other fluid at ambient pressure, or at about 1 atmosphere. The water storage tank  12  is not constructed as a pressure vessel. In some embodiments, the water storage tank  12  may have an interior volume of between 10 and 30 gallons. The water storage tank  12  may be of a substantially uniform shape, such as a cylinder, or as shown in  FIG. 1  may be irregularly-shaped to fit or conform to an aircraft space  16  in which the water storage tank  12  is located. Since it is not configured as a pressure vessel, the water storage tank  12  may be formed from relatively low strength materials, such as lightweight metals, plastic, composite or rubber materials. Further, because the water storage tank  12  is not constructed as a pressure vessel, it may be formed without internal baffles or internal or external ribs for strength, thereby simplifying construction of the water storage tank  12  and reducing its cost compared to an equivalently-sized pressure vessel. 
         [0024]    The water storage tank  12  includes a storage tank fill port  18 , in some embodiments located at an uppermost tank surface  20 . The water storage tank  12  further includes a storage tank outlet  22 , in some embodiments located at a lowermost tank surface  24 . Further, the water storage tank  12  may include one or more storage tank level sensors  26 , to detect a level of the water volume  14  inside the water storage tank  12 . 
         [0025]    The water storage tank  12  is connected to a pressure tank  28  via a storage tank output line  30 . In some embodiments, the pressure tank  28  is a pressure vessel configured to hold a volume of between one quart and one gallon of water at any one time. The flow of water through the storage tank output line  30  from the water storage tank  12  to the pressure tank  28  may be controlled by a storage output valve  32  located along the storage tank output line  30 . While in the embodiment of  FIG. 1 , it is located along the storage tank output line, it is to be appreciated that in other embodiments the storage output valve  32  may be positioned elsewhere, for example, at the water storage tank  12  or at the pressure tank  28 . Flow of water from the water storage tank  12  and the pressure tank  28  may be achieved through gravity if, for example, the storage tank outlet  22  is at a higher elevation that the pressure tank  28 , or may be achieved via a motorized pump  34  which may be located, for example, a submersible pump located inside of the water storage tank  12  or may be located along storage tank output line  30 . The pressure tank  28  further includes one or more level sensors, for example a full level sensor  36  that indicates when pressure tank  28  is full of water, and a refill level sensor  38  that indicates when the water level in the pressure tank  28  is at a level such that it should be refilled from the water storage tank  12 . 
         [0026]    The pressure tank  28  is pressurized to a pressure above ambient, or above 1 atmosphere through the introduction of air pressure from an air source  40 . The air source may be, for example, bleed air from an aircraft engine or auxiliary power unit compressor (not shown). The air flow is urged from the air source  40  along an air line  42  and into the pressure tank  28 , under the control of an air valve  44  located along the air line  42 . Further components, such as an air pressure regulator  46  to control the air pressure entering the air line  42 , a check valve  48  to protect the air line  42  from reversing flow, and an air filter  50  to remove contaminants from the air, may also be located along the air line  42 . A vent  52  is connected to the air valve  44  to allow for venting air from the pressure tank  28  to reduce the pressure in the pressure tank  28 . The pressure tank  28  is connected to a pressure tank output line  54  through a water valve  56  to provide a pressurized water supply upon request. 
         [0027]    At initial start-up of the PWS  10 , the water storage tank  12  is filled with the water volume  14 , controller  58  reads the level sensors  36 ,  38  at the pressure tank  28  and determines that pressure tank  28  needs to be refilled. Storage output valve  32  is opened and the pressure tank  28  is filled until level sensor  36  indicates a full condition. Once pressure tank  28  is filled, storage output valve  32  is closed and air valve  44  is opened, providing air pressure to pressure tank  28  which is pressurized to the selected pressure. In some embodiments, the selected pressure of the pressure tank  28  is in the range of about 20 to 45 pounds per square inch (psi). In operation, water valve  56  is opened allowing the flow of water from pressure tank  28  as needed. When the water level in pressure tank  28  reaches refill level sensor  38 , indicating need for a refill of pressure tank  28 , water valve  56  is closed, and air valve  44  is switched to a vent position, allowing the air from pressure tank  28  to proceed through vent  52 . Storage output valve  32  is opened to refill pressure tank  28  with water from water storage tank  12  and then closed to stop the flow of water from the water storage tank  12  when the water in the pressure tank  28  reaches a selected level. The pressure tank  28  is then re-pressurized via air valve  44  and air line  42 . Once refilled and re-pressurized, water valve  56  is opened, allowing for the use of water from pressure tank  28 . 
         [0028]    During the time pressure tank  28  is vented, refilled and re-pressurized, the water supply will be unavailable for use. Alternatively, additional level sensors may be utilized in pressure tank  28  to refill the pressure tank  28  before it is fully emptied. Additionally, as shown in  FIG. 2 , seamless continuous operation of the PWS  10  may be achieved by adding one or more additional pressure tanks  28 . 
         [0029]    Referring to  FIG. 2 , the embodiment shown includes two pressure tanks,  28   a  and  28   b . It is to be appreciated, however, that other embodiments may include three or more pressure tanks  28 . Storage output valve  32  has four positions: fully closed, open to both pressure tank  28   a  and pressure tank  28   b , open to pressure tank  28   a  and closed to pressure tank  28   b , and open to pressure tank  28   b  and closed to pressure tank  28   a . Alternatively, individual storage output valves  32  may be utilized. The air valve  44  and water valve  56  similarly have multiple operating positions. 
         [0030]    Initial startup operation is similar to the embodiment of  FIG. 1 , except that both pressure tanks  28   a  and  28   b  are filled by actuation of storage output valve  32  and pressurized via the air valve  44  and air line  42 . The pressure tanks  28   a  and  28   b  may be filled and pressurized either simultaneously with each other, or one after another. In operation, water is initially drawn off of one pressure tank, for example pressure tank  28   a , for use by actuation of water valve  56 . When the level sensor  38  of pressure tank  28   b  indicates a need to refill pressure tank  28   a , controller  58  switches water valve  56  to draw off pressure tank  28   b , instead of pressure tank  28   a . Air valve  44  is switched to vent pressure tank  28   a  and storage output valve  32  is switched to allow water to fill pressure tank  28   a . Once pressure tank  28   a  is refilled, storage output valve  32  is closed and air valve  44  is operated to pressurize pressure tank  28   a . When pressure tank  28   b  reaches an empty level, a similar process is used to refill pressure tank  28   b  while water is drawn from pressure tank  28   a  for use. This process may be repeated as needed until water volume  14  in water storage tank  12  is depleted. 
         [0031]    The potable water system  10  disclosed herein allows for lower cost and lower weight conformal water storage tank because there is no need for pressurization of the water storage tank, since the pressurization is performed at smaller pressure tanks downstream of the water storage tank. Further, in some embodiments, uninterrupted operation of the potable water system is provided by switching between two or more pressure tanks. 
         [0032]    While the present disclosure has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the present disclosure is not limited to such disclosed embodiments. Rather, the present disclosure can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate in spirit and/or scope. Additionally, while various embodiments have been described, it is to be understood that aspects of the present disclosure may include only some of the described embodiments. Accordingly, the present disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.