Abstract:
A system for reducing moisture in a gas turbine engine with one or more air ducts includes one or more one or more covers, each with an outer face and an inner face, with the inner face connectable to the air duct, wherein the cover is shaped to engage and close the air duct and a desiccant that is attachable to the cover.

Description:
BACKGROUND 
       [0001]    The present invention relates to gas turbine engines, and in particular, to miniature gas turbine engines being used in aeronautical vehicles. 
         [0002]    Miniature gas turbine engines are often utilized in single-usage applications such as reconnaissance drones, cruise missiles, decoy and other weapon applications, including air-launched and ground-launched weapon systems. The use of such an engine greatly extends the range of such vehicles in comparison to the more conventional solid fuel rocket engine. 
         [0003]    Miniature gas turbine engines are often stored for periods of time before use. During this time, there is a risk that environmental factors may contaminate the miniature gas turbine engine. A specific concern is that moisture may settle in the miniature gas turbine engine. Because of this threat, miniature gas turbine engines are sometimes stored in canisters. The canisters are meant to protect the engine from outside elements. Aeronautical vehicles have to be removed from their canisters prior to being launched. It is typical for aeronautical vehicles to be removed from their canisters at ground level and then be carried to many different elevations before they are launched. Aeronautical vehicles typically remain outside their canisters for long periods of time, increasing their exposure to moisture. 
       SUMMARY 
       [0004]    A system for reducing moisture build-up in gas turbine engines with an air inlet and an exhaust outlet includes a cover to be placed on an air inlet and/or an exhaust outlet, a desiccant that is attachable to the cover, and a means for removing the cover. The cover includes an inner face and an outer face, with the desiccant being located on the inner face, and is connectable to either the air inlet and/or the exhaust outlet. 
         [0005]    A method for preventing moisture build-up in gas turbine engines when not in use includes mounting a desiccant on an inner surface of a cover, sealing the cover over a duct opening of a gas turbine engine, and removing the cover from the gas turbine engine when the gas turbine engine is to be started. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a side view of an aeronautical vehicle. 
           [0007]      FIGS. 2A  is a cut-away side view of a propulsion system for the aeronautical vehicle shown in  FIG. 1 , showing covers located at the air inlet and the exhaust outlet. 
           [0008]      FIG. 2B  is a cut-away side view of the propulsion system of  FIG. 2A , showing the covers being blown off. 
           [0009]      FIG. 2C  is a cut-away side view of the propulsion system of  FIG. 2A , after the covers have been completely removed. 
           [0010]      FIG. 3  is an inner perspective view of an air inlet cover. 
           [0011]      FIG. 4A  is an inner perspective view of a first embodiment of an exhaust outlet cover. 
           [0012]      FIG. 4B  is an inner perspective view of a second embodiment of an exhaust outlet cover. 
           [0013]      FIG. 4C  is an inner perspective view of a third embodiment of an exhaust outlet cover. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    In general, the present invention prevents moisture build-up in gas turbine engines by sealing the inlet and exhaust openings of a gas turbine engine with a cover. The cover prevents humidity from entering into the gas turbine engine. A desiccant attached to the cover will absorb any built-up moisture in the gas turbine engine. 
         [0015]      FIG. 1  is a side view of aeronautical vehicle  10 . Aeronautical vehicle  10  includes airframe  12 , with one or more aerodynamic surfaces  14 . Vehicle  10  also includes propulsion system  20  with propulsion engine  22 , air inlet  24  and exhaust outlet  26 . Propulsion engine  22  is housed within airframe  12 . Air inlet  24  is connected to propulsion engine  22  at a first intake end, as shown by dashed lines  23 . Exhaust outlet  26  is connected to the opposite exhaust end of propulsion engine  22 . 
         [0016]    Propulsion system  20  propels aeronautical vehicle  10 . Ambient air is ingested by air inlet  24  and is passed to propulsion engine  22 . Propulsion engine  22  compresses the air in a compressor section, mixes the compressed air with fuel and ignites the fuel/air mixture in a combustor section to produce combustion gases, and routes the combustion gases through a turbine section to exhaust outlet  26 . The combustion gases cause rotation of rotor blades of the turbine section, which in turn causes rotation of rotor blades of the compressor section. Exhausted combustion gases and air provide thrust that propel aeronautical vehicle  10 . 
         [0017]      FIGS. 2A-2C  are cut-away side views of the aft section of aeronautical vehicle  10  with a side view of propulsion system  20 .  FIG. 2A  shows covers attached to air inlet  24  and exhaust outlet  26 ;  FIG. 2B  shows the covers being blown off aeronautical vehicle  10 ; and  FIG. 2C  shows propulsion system  20  after the covers have been completely removed. Propulsion system  20  includes propulsion engine  22 , air inlet  24 , exhaust outlet  26 , inlet cover  28 , outlet cover  29 , pyrotechnics  27  and air duct  25 . Inlet cover  28  includes body  30 , outer face  32 , inner face  34  and desiccant  36 . Outlet cover  29  includes body  40 , outer face  42 , inner face  44  and desiccant  46 . Covers  28  and  29  can be made of a phenolic material, aluminum, plastic or any other suitable material. Desiccants  36  and  46  can include silica gel, activated charcoal, calcium sulfate, calcium chloride, montmorillonite clay or a molecular sieve, although any suitable hygroscopic substance can be used. 
         [0018]    Air duct  25  has one end connected to air inlet  24  its opposite end connected to propulsion engine  22 . Desiccant  36  is attached to inner face  34  of inlet cover  28 , and desiccant  46  is attached to inner face  44  of outlet cover  29 . Pyrotechnics  27  are attached to inlet cover  28 , located between inlet cover  28  and air inlet  24 , and to outlet cover  29 , located between outlet cover  29  and exhaust outlet  26 . Inlet cover  28  can be placed on air inlet  24 , with inner face  34  connecting to air inlet  24 . Outlet cover  29  can be placed on exhaust outlet  26 , with inner face  44  connecting to exhaust outlet  26 . 
         [0019]    Inner face  34  of inlet cover  28  can be sealingly attached to air inlet  24 , and inner face  44  of outlet cover  29  can be sealingly attached to exhaust outlet  26 , preventing any foreign matter from entering into propulsion system  20 . Desiccants  36  and  46  attached to inner faces  34  and  44 , respectively, can absorb moisture that gets induced from the environment into propulsion system  20 . 
         [0020]    Pyrotechnics  27  are remotely activated when aeronautical vehicle  10  is launched, thus blowing inlet cover  28  and outlet cover  29  off of air inlet  24  and exhaust outlet  26 , respectively. Inlet cover  28  and outlet cover  29  are blown off of aeronautical vehicle  10  in full, preventing a part of either inlet cover  28  or outlet cover  29  from being ingested by propulsion system  20 . After inlet cover  28  and outlet cover  29  are blown off of the engine, air inlet  24  can ingest ambient air. Ambient air flows into air inlet  24  through air duct  25  to propulsion engine  22 , as shown by the arrows in  FIG. 2C . Propulsion engine  22  can then create thrust that is expelled out of exhaust outlet  26 , propelling aeronautical vehicle  10 . 
         [0021]    As mentioned above, aeronautical vehicles can be stored in canisters for extended periods of time, and must be removed once they are slated for use. Moisture can enter into the propulsion system after the aeronautical vehicle has been taken out of its canister by entering through the air inlet or the exhaust outlet. The foreign matter that enters into the system can have damaging effects on the gas turbine engine. Moisture that gets into the engine, for example as humid air when the aeronautical vehicle is on the ground, can cause freezing on or within the engine at high altitudes and low temperatures, which could cause propulsion engine  22  to not start or to malfunction. 
         [0022]    Inlet cover  28  and outlet cover  29  prevent moisture, particulate matter or any foreign object from entering air inlet  24  or exhaust outlet  26 , thus creating a sealed and reduced moisture environment through the use of desiccants  36  and  46  in combination with covers  28  and  29 . This prevents moisture from settling in propulsion engine  22  when it is not in use prior to it being launched. Desiccants  36  and  46  keep propulsion system  20  dry by absorbing any moisture that gets into or remains in propulsion system  20  after inlet cover  28  and outlet cover  29  are placed on air inlet  24  and exhaust outlet  26 , respectively. Preventing moisture from getting into propulsion system  20  reduces the risk of engine freezing. This can improve engine reliability. 
         [0023]    A method for reducing moisture build-up in a gas turbine engine includes mounting a desiccant to an inner surface of a cover, sealing the cover over a duct opening of a gas turbine engine, and removing the cover from the gas turbine engine when the gas turbine engine is to be started. 
         [0024]    First, a desiccant is mounted to an inner surface of a cover. A first embodiment includes attaching the desiccant to the cover with an adhesive, when the adhesive is located between the desiccant and the inner surface of the cover. In an alternate embodiment, the desiccant can be attached to the inner surface of the cover with one or more fasteners, the fasteners being placed through the desiccant and entering into the body of the cover through the inner surface. The desiccant can be attached to the cover structure in any number of ways, with only two exemplary embodiments being shown here. The desiccant is integrated into the inner surface of the cover so it will be enclosed within a system when the cover is placed on a duct opening, allowing the desiccant to absorb any moisture in the system. 
         [0025]    Second, the cover is sealed over a duct opening of a gas turbine engine. The cover can be secured to the duct opening in many ways. One embodiment would include casting the cover to fit sealingly around the duct opening. An alternate embodiment would be to attach the cover to the duct opening with one or more fasteners. 
         [0026]    Sealing covers to the duct openings of the gas turbine engine will close the gas turbine engine system. This will prevent any moisture, particulate matter or foreign objects from entering the gas turbine engine and it will allow the desiccant that is attached to the inner surface of the cover to absorb any moisture that remains in the system. Maintaining a dry and uncontaminated system is important for having a reliable and effective gas turbine engine. 
         [0027]    Third, the covers can be removed from the gas turbine engine when the engine is to be started. The covers can be removed in a number of ways. One embodiment includes employing pyrotechnics that can be remotely activated to blow the covers off of the duct openings of the gas turbine engine prior to starting to the gas turbine engine. In other embodiments, covers could also be removed through the use of any suitable mechanical or electromechanical actuators. 
         [0028]      FIG. 3  is an inner perspective view of inlet cover  28 . Inlet cover  28  includes body  30 , outer face  32 , inner face  34 , desiccant  36  and pyrotechnics  27 . Desiccant  36  is attached to inner face  34  of inlet cover  28  with fasteners  59 . Pyrotechnics  27  are located on inner face  34  of inlet cover  28 . 
         [0029]    Inner face  34  of inlet cover  28  can be sealingly connected to air inlet  24 . This allows desiccant  36  to absorb any moisture that is retained in propulsions system  20 . Inlet cover  28  can be any size or shape in order to accommodate different air intakes. 
         [0030]      FIGS. 4A-4C  are inner perspective views of outlet cover  29 .  FIG. 4A  shows desiccant  46  attached to outlet cover  29 A with one or more fasteners  59 .  FIG. 4B  shows desiccant  46  attached to outlet cover  29 B with adhesive  57 .  FIG. 4C  shows outlet cover  29 C with pocket  53  for holding desiccant  46 . Cover  29  has body  40 , outer face  42 , inner face  44 , desiccant pack  46  and pyrotechnics  27 .  FIG. 3B  shows outlet cover  29 B with recess  58 . Recess  58  is located on inner face  44  of outlet cover  29 B.  FIG. 3C  shows outlet cover  29 C with pocket  53 . Pocket  53  is located on inner face  44  of outlet cover  29 C. 
         [0031]      FIG. 4A  shows desiccant pack  46  attached to outlet cover  29 A through the use of one or more fasteners  59 . Fastener  59  can be a nut, bolt, screw or any other suitable fastener.  FIG. 4B  shows desiccant pack  46  placed in recess  58  of outlet cover  29 B. Desiccant pack  46  is attached to outlet cover  29 B through the use of adhesive  57 . Adhesive  57  or fastener  59  can secure desiccant  46  to inner face  44  or recess  58  of outlet cover  29 . 
         [0032]      FIG. 4C  shows outlet cover  29 C with pocket  53 . Desiccant  46  can be placed in pocket  53 . Pocket  53  can be attached to inner face  44  by any suitable means. Pocket  53  can be made of any material that will allow moisture to pass through. 
         [0033]    As shown in  FIGS. 2A-2C , inlet cover  28  and outlet cover  29  can be placed on an inlet or outlet to prevent moisture from entering into propulsion system  20 . Inner faces  34  and  44  will come into contact with the inlet or outlet, thus allowing desiccants  36  and  46  to absorb any moisture from the system. Preventing moisture build-up in propulsion system  20  during periods of storage or non-use is important so that propulsion engine  22  can operate properly when needed to propel aeronautical vehicle  10 . 
         [0034]    Reducing the moisture that is in the environment of a gas turbine engine during storage/non-use will help to prevent the engine from freezing. The cover is placed on the duct openings of the gas turbine engine to prevent moisture, particulate matter and foreign objects from entering into and contaminating the gas turbine engine. Further, the desiccant that is located on the cover structure will absorb any moisture that remains in the gas turbine engine to prevent any moisture build-up. This will prevent the gas turbine engine from freezing, which will increase the effectiveness and reliability of the gas turbine engine. 
         [0035]    While a cover for a miniature gas turbine engine with desiccant has been shown, other moisture reducing materials could be used. Additionally, the shape, connection and/or size of covers and desiccant shown are for example purposes only and can vary according to system requirements. 
         [0036]    While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.