Abstract:
An aircraft anti-icing system includes a source of high temperature gas, a housing, at least one conduit to carry the high temperature gas from the source to the housing, the at least one conduit coupled to the housing and the source, at least one nozzle coupled to the at least one conduit, at least one nozzle configured to impart a rotational motion to the high temperature gas before exhausting the high temperature gas into the housing, and a port for exhausting air from the housing.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to an improvement in anti-icing systems for aircraft jet engine propulsion systems. 
         [0002]    The formation of ice on aircraft wings, propellers, air inlets of engines, etc. has been a problem since the earliest days of heavier-than-air flight. Any accumulated ice adds considerable weight, and changes the airfoil or inlet configuration making the aircraft much more difficult to fly and in some cases has caused loss of aircraft. In the case of jet aircraft, large pieces of ice breaking loose from the leading edge of an engine inlet housing can damage rotating turbine blades or other internal engine components and cause engine failure. 
         [0003]    One of the most common anti-ice techniques has been the ducting of hot gases into a housing adjacent to the likely icing area. Current techniques to solve this problem generally fall into one of two types of systems: Impingement style ring systems or swirl nozzle systems. In each case, the hot gas conduits simply dump hot gases into a housing, such as the leading edge of a jet engine housing or a wing leading edge. While often useful, these systems are not fully effective due to the low quantity of hot gases introduced relative to the mass of air in the housing, the heating effect tending to be limited to the region near the hot gas introduction point, and the complexity of the hot gas duct system. 
         [0004]    In impingement style ring systems, hot air is impinged on the metal lipskin by strategically positioned holes in an annulus shaped tube that runs 360 degrees around the front of the inlet. The air impinges on the internal lipskin surface and causes the metal temperature to increase and break off any ice accretion. 
         [0005]    The existing swirl nozzles discharge the hot air through a few non-circular sub-nozzles that create a flow field. The air is discharged at a high velocity so that it creates a swirling effect in the forward most inlet compartment, commonly referred to as the D-duct. The air continues to move 360 degrees around the annular D-duct compartment. It circulates around the compartment several times until it exits into the ambient through an exhaust port. Since the inlet lipskin consists of most of the internal compartment surface area, the hot air heats the lipskin and causes any ice accretion to break loose. Although the figures and verbiage of the specification use nose cowl deicing for explanatory purposes, the invention disclosed herein may apply to any other housing subject to ice formation including, but not limited to, wing conduits and ducts. 
         [0006]    Both systems have limitations. The impingement ring style anti-ice systems have a cumbersome tube and support structure that runs 360 degrees around the front inlet compartment. While these systems generally have very high heat transfer ratios they are also very heavy. Swirl nozzle systems are generally significantly lighter than impingement ring style systems and use less air to de-ice but suffer from lower heat transfer. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0007]    In one embodiment, an aircraft anti-icing system is provided. The system includes a source of high temperature gas, a housing, at least one conduit to carry the hot gas from the source to the housing, the at least one conduit coupled to the housing and the source, at least one nozzle coupled to the at least one conduit, the at least one nozzle configured to impart a rotational motion to the hot gas before exhausting the gas into the housing, and a port for exhausting air from the housing. 
         [0008]    In a second embodiment, a method of anti-icing a jet airplane housing is provided. The method includes directing heated gasses from the engine to a housing, imparting both a rotational and translational movement to the heated gasses, channeling the heated gasses into the housing, and exhausting the gasses from the housing. 
         [0009]    In a third embodiment a jet aircraft anti-icing system is provided. The system includes a source of high temperature gas, a housing, at least one conduit to carry the hot gas from the source to the housing, the at least one conduit coupled to the housing and the source of high temperature gas, at least one nozzle coupled to the at least one conduit, the at least one nozzle configured to impart a rotational motion to the hot gas before exhausting the gas into the housing, and a port for exhausting air from the housing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIGS. 1-8  show exemplary embodiments of the method and apparatus described herein. 
           [0011]      FIG. 1  is a schematic representation of a typical jet turbine engine; 
           [0012]      FIG. 2  is a schematic view of a jet engine inlet; 
           [0013]      FIG. 3  is a partial view of a nose lip including the swirl nozzle; 
           [0014]      FIG. 4  is a schematic representation of the swirl nozzle assembly; 
           [0015]      FIGS. 5-7  show embodiments with different swirl nozzle locations and or orientations respective to the nose cowl; and 
           [0016]      FIG. 8  is a partial view of a wing housing including the swirl nozzle. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    Referring now to the drawings in detail and in particular to  FIG. 1 , there is seen a schematic representation of a jet turbine engine  10  of the type suitable for aircraft propulsion. The turbine engine  10  is housed within a central housing  12 . Air enters the engine  10  through an air inlet section  20 , between the spinner  16  of the engine and the nose lip or annular single skin housing  14  which constitutes the forward most section of the air inlet  20  of the engine nacelle, some of which components have been omitted from the figure for simplicity. Engine thrust is produced by burning incoming air and fuel within the central housing  12  and passing the hot, high pressure propulsion gases through exhaust outlet  22  and out the rear of the engine. 
         [0018]    In flight, ice tends to form on the nose lip  14  (in addition to other aircraft components omitted for simplicity). The ice changes the geometry of the inlet area  18  between the nose lip  14  and the spinner  16 , adversely affecting the required quantity, flow path and quality of incoming air. Also, pieces of ice may periodically break free from these components and enter the engine, damaging rotor blades and other internal engine components. 
         [0019]    Within the compressor section  24  of the jet engine  10  there is a region containing hot gases. A suitable conduit means  26  or tube is connected at a first end  28  to that hot region. In one embodiment the hot region is the environmental bleed air manifold although in other embodiments the hot region may be any other hot air source such as the compressor discharge bleed air manifold. The other end  30  penetrates a bulkhead  32  that substantially closes the nose lip  14  to form the D-duct to enclose a quantity of air with the annular space created by such bulkhead  32  and the nose lip  14 . 
         [0020]    The conduit  30  carrying the hot, high pressure gas from the compressor section of a jet engine  10  extends through the bulkhead  32  that closes off the annular nose lip  14  of the inlet  18  to create an annular chamber filled with air. The conduit  30  has an outlet nozzle  34  connected to its outlet end. The outlet nozzle  34  is preferably bent substantially 90 degrees so that the very end of the outlet nozzle  34  is approximately tangent to the centerline of the annular nose lip  14 . In other embodiments the angle may be substantially greater or less. In even more embodiments, as shown in  FIGS. 5-7 , the outlet nozzle  34  may be rotated with respect to any other axis and translated either up or down and fore or aft in the nose lip  14 . 
         [0021]    The nozzle  34  is configured to impart a rotational flow as the hot gas moves inside the nozzle  34 . In one embodiment the nozzle  34  contains a plurality of fluid flow passages  38  twisted in a helical pattern. In the preferred embodiment four to six fluid flow passages  38  are used, however in other embodiments the number of passages could be substantially more or less. Additionally other means may be used to cause the rotation including but not limited to internal vanes or nozzles. As the hot gas moves inside the nozzle  34  the fluid flow passages  38  impart a rotational movement to the gas and then eject it out the nozzle outlet  40  into the nose lip  14 . It will be recognized that the injection of the hot gas stream into the housing air will cause the entrained mass of air to rotate within the nose lip  14  in a swirling rotational direction. Also, as seen in  FIG. 2 , as the mass of entrained air rotates within the nose lip  14  a suitable exhaust means, shown as suitably sized holes  36  formed in an outboard position of the nose lip  14 , permit a portion of such entrained air to escape the nose lip  14  equal to the mass flow rate of hot gas being injected into the nose lip  14  to maintain an equilibrium of flow. In other embodiments holes  36  may be located in other areas including but not limited to the rear of housing  14 . 
         [0022]    It will be recognized that as the hot gas is emitted from the nozzle  34  the hot gases rapidly mix with the ambient air in the nose lip  14 , to rapidly reach a temperature intermediate between the entering hot gas temperature and that of the stagnant air. The temperature of the air within the nose lip  14  will continue to rise until an equilibrium condition is reached. As the temperature in the nose lip  14  rises higher amounts of energy will be lost through the skin in the form of conduction and will be lost in the air leaving the nose lip  14 . When the amount of energy leaving the nose lips  14  equals the amount entering then the temperature will hold steady at a maximum temperature. With the nozzle  34  and the enhanced mixing of the hot, high pressure gas and the air contained within the housing  14 , any tendency of the rotating heated air mass to generate a localized area of elevated temperature in the skin of the nose lip  14  will be materially reduced. 
         [0023]    In another embodiment the conduit  30  carries hot, high pressure gas from the jet engine  10  to a wing  42 . The conduit  30  runs away from the aircraft substantially parallel to the leading edge  44  of the wing  42 . Near the end of wing  42  the conduit  30  bends approximately 90 degrees and passes though a bulkhead  46  into a wing duct  48 . Outlet nozzle  34  is coupled to the conduit  30  and oriented to eject the swirling, hot, high pressure gas into wing duct  48  substantially parallel to leading edge  44  in the direction of the main body of the airplane. Exhaust vents (not shown) are provided to exhaust heated air from the wing duct  48 . 
         [0024]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.