Abstract:
An airship ballast system includes an engine driven propeller and a cooling tube that is positioned coplanar with the propeller and outside its tip path. One end of the cooling tube is connected to receive exhaust gases from the engine while the other end is connected to a ballast tank. In operation, exhaust gases from the engine are cooled as they transit the cooling tube, and water condensed from the cooled exhaust gases is pumped to the ballast tank to maintain a ballast for the airship.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention pertains generally to systems and methods for maintaining ballast for a propeller-driven, lighter-than-air airship. More particularly, the present invention pertains to an airship ballast system wherein ballast is provided by condensed water that is scavenged from engine exhaust gases. The present invention is particularly, but not exclusively, useful as a system and method for maintaining ballast for an airship wherein the condensation of water from engine exhaust gases is enhanced by the action of propeller induced airflow.  
       BACKGROUND OF THE INVENTION  
       [0002]     An important factor for consideration in the flight of a lighter-than-air airship is its reliance on ballast to maintain flight at a selected flight level. Also, the ability of the airship to climb and descend is dependent on the control of the airship&#39;s ballast. It also happens that as the duration of flight is increased, the consequent increase in fuel burn exacerbates the ability to control the airship&#39;s ballast. In sum, the loss of fuel during an extended flight, without any ballast correction, can significantly increase the difficulty of descent, the landing of the airship, and the safe handling of the airship by a ground crew.  
         [0003]     As is well known, the combustion of fuel in an air-breathing, reciprocating engine is accompanied by a marked increase in the temperature of the air that is mixed with the fuel for combustion. It is also well known that as air is cooled, water vapors in the air are condensed, and are removed from the air as liquid water. On this point, data is available which indicates that the weight of water that can be condensed from the exhaust gases of an air-breathing, reciprocating engine can equal, or even exceed, the weight of fuel that is burned.  
         [0004]     Propeller theory clearly indicates that as a propeller is rotated, it draws air with increased velocity into the plane of the propeller rotation. The velocity of the air is then further increased as it passes through the propeller. At the same time, vortices are created at the tip of each propeller blade. The combined effect of all this is that air is moved with an increased velocity within a determinable distance beyond the tip of the propeller&#39;s rotating blades. From a thermodynamic perspective, it is also known that increased airflow velocities, such as are induced by a propeller rotation, can be used to enhance the cooling effect of an air mass.  
         [0005]     In light of the above it is an object of the present invention to provide a system and method for maintaining the ballast of an engine-driven, lighter-than-air airship that uses condensed water from engine exhaust gases for ballast. Another object of the present invention is to provide a system and method for maintaining the ballast of an airship that employs the increase in airflow around and through a rotating, engine-driven propeller to enhance water condensation from engine exhaust gases. Still another object of the present invention is to provide a system and method for maintaining the ballast of an airship that is simple to use, relatively easy to manufacture, and comparatively cost effective.  
       SUMMARY OF THE INVENTION  
       [0006]     In accordance with the present invention, a system and method for maintaining ballast for a lighter-than-air airship includes an air-breathing engine (motor) and an assembly for recovering condensed water from the engine&#39;s exhaust gases. The condensed water is then transferred to a ballast tank, where the water level in the tank is monitored to maintain ballast for the airship.  
         [0007]     As a component of the present invention, an air-breathing, combustion engine is mounted on the airship to rotate a propeller that provides thrust for moving the airship. More particularly, the propeller is rotated by the engine around an axis. As it rotates, the tips of the propeller blades define a tip path at a distance “r” from the axis of propeller rotation.  
         [0008]     A cooling tube is also mounted on the airship, and is positioned around the propeller to be substantially coplanar with the propeller tip path. As so positioned, the cooling tube is located at a distance “d” from the axis of propeller rotation that is greater than the distance “r” of the tip path from this axis. Operationally, the arrangement of the cooling tube around the propeller provides protection for ground personnel who may be working near the propeller. Structurally, the cooling tube has a first end that is connected in fluid communication with the engine (motor) to receive engine exhaust gases from the engine for transfer through the cooling tube. The second end of the cooling tube is then connected in fluid communication with an intercooler which, in turn, is connected in fluid communication with the ballast tank mentioned above.  
         [0009]     In operation, exhaust gases from the engine (motor) transit through the cooling tube where they are cooled by external airflow over the cooling tube. Cooling vanes mounted on the outside surface of the cooling tube may be added to enhance the cooling effect of the cooling tube. In any event, water is condensed from the exhaust gases as they are cooled in the cooling tube. This condensation process is continued in the intercooler. The condensed water is then scavenged from the cooling tube, and from the intercooler, for transfer to the ballast tank. As this water is transferred to the ballast tank, the now water-depleted exhaust gases are vented to the atmosphere.  
         [0010]     As indicated above, a ballast tank is mounted on the airship. Specifically, the ballast tank is connected in fluid communication with the cooling tube, and with the intercooler, for receiving the water that has been condensed from the engine&#39;s exhaust gases. Further, this ballast tank includes a dump valve that is selectively operable to dump water from the ballast tank, to thereby maintain a desirable ballast for the airship. In detail, this is done by monitoring a water level in the ballast tank, and simultaneously monitoring a fuel level in the engine&#39;s fuel tank. The water level in the ballast tank is then compared with the fuel level in the fuel tank to obtain an instantaneous ratio. The dump valve can then be selectively activated to dump water from the ballast tank when the instantaneous ratio exceeds a scheduled value. As contemplated by the present invention, the comparison of water and fuel levels, and the consequent selective activation of the dump valve can be accomplished either manually or by a computer. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which:  
         [0012]      FIG. 1  is an elevation side view of an airship in accordance with the present invention;  
         [0013]      FIG. 2  is a perspective view of the exhaust gas cooling components of the present invention; and  
         [0014]      FIG. 3  is a functional flow chart of the process components involved in the operation of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]     Referring initially to  FIG. 1 , an airship in accordance with the present invention is shown and is generally designated  10 . As shown, the airship  10  may be either rigid or non-rigid and includes an engine (motor)  12  that is used to rotate a propeller  14  (best seen in  FIG. 2 ).  FIG. 1  also shows that the propeller  14  may be surrounded by a shroud  16 . Preferably, the engine  12  for the airship  10  is an air-breathing, reciprocating engine of a type well-known in the pertinent art.  
         [0016]      FIG. 2  shows that the propeller  14  includes blades  18 , of which the blades  18   a  and  18   b  are only exemplary. Further, each blade  18   a,b  has a respective tip  20   a,b  which travels along a tip path  22  as the propeller  14  is rotated about an axis  24  by the engine (motor)  12 . As indicated, each blade  18   a,b  is a distance “r” in length and, correspondingly, the tip path  22  is at a distance “r” from the rotation axis  24 .  
         [0017]     Still referring to  FIG. 2 , it will be seen that the present invention includes a plurality of substantially circular cooling tubes  26 , of which the cooling tubes  26   a  and  26   b  are exemplary. As contemplated by the present invention, however, it is possible to use only one cooling tube  26  or, alternatively, more than two cooling tubes  26 . Nevertheless, for purposes of this disclosure, the airship  10  is considered to have two cooling tubes  26   a  and  26   b . As shown, the circular cooling tubes  26   a,b  are centered on the axis  24  and are positioned substantially coplanar with the rotational plane of the propeller  14 . More specifically, it is recognized that for a plurality of cooling tubes  26 , some of the cooling tubes  26  may define a plane that is substantially parallel to the plane of the tip path  22 . Recognizing this minor variation, each cooling tube  26  can still be considered as being substantially coplanar with the tip path  22 . In any event, each cooling tube  26  is located at a distance “d” from the axis  24 . Importantly, the distance “d” is greater than the distance “r” of the tip path  22  from the rotation axis  24 . Thus, the cooling tubes  26  are positioned to protect personnel from the propeller  14  as it rotates.  
         [0018]     As indicated in  FIG. 2 , each cooling tube  26  can include a plurality of vanes  28 . For the present invention, the purpose of the vanes  28  are two-fold. For one, they can be used to enhance the cooling capability of the cooling tube  26 . For another, the vanes  28  can be employed to provide additional structural support for the cooling tubes  26 . In another aspect, each of the cooling tubes  26   a,b  is connected with a respective intercooler  30   a,b.    
         [0019]     The operation of the present invention will, perhaps, be best appreciated by cross referencing  FIG. 3  with  FIG. 2 . As intended for the operation of the airship  10 , the engine (motor)  12  is run to rotate the propeller  14 . A consequence of this is that the engine  12  generates exhaust gases  32 . These exhaust gases  32  are then sent to a water recovery unit  34  that is mounted on the airship  10 . Specifically, the water recovery unit,  34  for the present invention is a combination of the elements disclosed above, which are shown and collectively designated  34  in  FIG. 2 .  
         [0020]     In detail, the exhaust gases  32  are directed from the engine  12  to intakes  36   a  and  36   b , which are respectively connected in fluid communication with the cooling tubes  26   a  and  26   b . The exhaust gases  32  then traverse through the cooling tubes  26   a  and  26   b . As they do so, airflow (indicated in  FIG. 2  by the arrows  38 ) over the cooling tubes  26   a  and  26   b  and the vanes  28  (if used) will cool the exhaust gases  32 . During this cooling, water vapors in the exhaust gases  32  condense as liquid water. This process of cooling and condensation then continues in the intercoolers  30   a,b  after the exhaust gases  32  have passed through the cooling tubes  26   a,b . As will be appreciated by the skilled artisan, the airflow  38  that cools the exhaust gases  32  in the cooling tubes  26   a,b , and in the intercoolers  30   a,b , is created by the operation of the propeller  14 , as well as by in-flight movements of the airship  10 .  
         [0021]     After passing through the cooling tubes  26   a,b  and the intercoolers  30   a,b , the cooler exhaust gases  32 ′, with water removed, are then vented to the atmosphere. On the other hand, as shown in  FIG. 3 , the water that has been scavenged and removed from the exhaust gases  32  is transferred to a main ballast tank  40 .  
         [0022]     With the above in mind, it will be appreciated that ballast for the airship  10  becomes a trade-off between the amount of fuel from fuel cell  42  that is burned by the engine  12 , and the amount of water that is recovered by the recovery unit  34 . Accordingly, the fuel cell  42  is provided with a sender  44  that indicates the amount of fuel (fuel level) remaining in the cell  42 . Similarly, the ballast tank  40  is provided with a sender  46  that indicates the amount of water (water level) in the ballast tank  40 . The information from both sender  44  and sender  46  is then transmitted to a monitor  48 . The instantaneous ratio (fuel level)/(water level) can then be continuously evaluated by the monitor  48  to indicate whether ballast is being maintained for the airship  10 . If not, corrective action may be taken. Specifically, if the ratio (fuel level)/(water level) ever exceeds a scheduled value, a dump valve  50  in the ballast tank  40  can be activated. This action dumps water from the ballast tank  40 , to thereby maintain ballast for the airship  10 .  
         [0023]     While the particular Airship Ballast System as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.