Abstract:
An arrangement of devices as well as a method for improving the aerodynamics of an aircraft wing are disclosed. In embodiments, a plurality of vortex generators are attached in span-wise alignment on an deice boot along the wing&#39;s leading edge. The vortex generators are, in embodiments, constructed of a flexible material such that they are able to be expanded along with the boot during inflation and deflation thus mechanically involving the aerodynamic devices in the ice-shedding process.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to aerodynamics. More specifically, the invention relates to the field of aircraft wing design. 
     2. Description of the Related Art 
     The accumulation of ice and other contaminants on aircraft wings has been an ongoing problem. With respect to ice buildup, artisans have taken a number of approaches to dealing with the problem. Some solutions have involved the administration of heat to the leading edge or other locations on the wing. Other techniques involve the use of chemicals to induce shedding. Additional solutions have involved the use of mechanical arrangements. 
     One mechanical arrangement involves the use of what is referred to as a “deice boot.” Deice boots include flexible sheets of rubber which are adhered to the leading edge of the wing and have span-wise inflatable tubes which are stitched into the rubber matting. When the tubes are inflated, the boot causes the accumulated ice to be pushed away from the leading edge surface. This allows the free stream of impinging air to strip the ice off of the wing and then carry it away. The boot is then deflated, but will be periodically reinflated to help minimize the amount of ice which collects on the wing. Thus, the cycled expansions mitigate the ice problem, but do not eliminate it completely. 
     One problem created by residual ice occurs at or near a stall. A stall is an aerodynamic condition in which the angle of an aircraft wing&#39;s chord line and the incoming air (the angle of attack) increases to a point that the lift begins to decrease. The angle at which this transition occurs is called the critical angle of attack. The critical angle depends on many wing design parameters, but normally represents the boundary between the wing&#39;s linear and nonlinear airflow regimes. Once the critical angle is reached, flow separation occurs. This flow separation dramatically decreases lift (sometimes suddenly), increases drag, and immediately shifts the aircraft&#39;s pressure center forward. 
     Depending on the aircraft&#39;s design, a stall can expose extremely adverse properties of balance and control—even in ideal conditions. But these issues are exacerbated when the aerodynamically ideal wing surfaces become contaminated with some foreign substance, such as ice or frost. Ice, frost, or other contaminating surface roughness can increase the speed at which the stall occurs. Thus, conventionally, ice buildup has been shown to interfere with control, especially as the speed and attack angle are near or at stall conditions. 
     SUMMARY 
     The present invention is defined by the claims below. Embodiments of the present invention include an aircraft wing which has a deice boot. At least one protrusion exists on the deice boot. The deice boot, in some embodiments, includes a plurality of air tubes which extend in a span-wise direction. These air tubes can be inflated and then cyclically deflated to break off ice. 
     The protrusion is adapted such that it minimizes flow separation from the wing, especially when the aircraft approaches stall conditions. Structurally speaking, this flow separation minimization, in one embodiment, is achieved by configuring the protrusions such that each has a ramped upper face and two laterally converging sides. In some embodiments the protrusions are vortex generators. 
     In terms of orientation, the protrusions, in embodiments, are disposed such that each has a longitudinal axis which is vertically oriented; straddles a forward most point of the wing leading edge; and converges towards a vertical rear edge. In further embodiments the protrusions, when viewed in cross section, are located on the leading edge such that they partially overlap with, but are clocked slightly backward from the forward-most point of the leading edge. 
     In some embodiments the protrusions are comprised of a flexible material which is able to flex with said boot during operation. In some embodiments, the protrusion will be constructed of neoprene rubber. In other embodiments, the boot will also be constructed of the same neoprene material and thus, both the boot and protrusion are comprised of the same material. 
     In other embodiments, an aerodynamic device is provided. This aerodynamic device has a ramping upper face and two laterally converging sides and is able to be fixed onto and operational with a deice boot on a leading edge of an aircraft wing. 
     A method is also disclosed. Embodiments of the method include improving the aerodynamics of an aircraft wing by (i) providing a flexible inflatable member; (ii) installing the flexible inflatable member along the leading edge of an aircraft for the purpose of preventing ice buildup by inflating and deflating it; and attaching one or more aerodynamic devices to the inflatable member for the purpose of generating vortices. 
     In embodiments, the method includes constructing the aerodynamic devices of a flexible material such that said devices are able to flex along with said inflatable member which is also, in embodiments, constructed of a flexible material. For example, both could be constructed of a neoprene material in embodiments. In a further embodiment, the devices are adapted such that they minimize flow separation when the aircraft approaches a stall. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Illustrative embodiments of the present invention are described in detail below with reference to the attached drawing figures, which are incorporated by reference herein and wherein: 
         FIG. 1  is a perspective view showing an embodiment for an aircraft incorporating the disclosed devices and methods; 
         FIG. 2  is a breakout view of area— 2 —in FIG.  1 .; 
         FIG. 3  is a breakout view showing how the aerodynamic device of  FIG. 2  is adhered; 
         FIG. 4  is a cross-sectional view showing one embodiment for an orientation of an aerodynamic device on the leading edge of an aircraft; and 
         FIG. 5  is a perspective view of one embodiment for an aerodynamic device before installation. 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment for an aircraft  100  is shown in  FIGS. 1-5 . As can be seen from the figure, aircraft  100  includes first and second wings  102 . One will understand that the configuration of each is the flip-side equivalent of the other. Each wing has a leading edge  104  and a trailing edge  106 . With respect to each, the leading edge  104  includes a deice boot  108 . 
     One skilled in the art will recognize that devices like boot  108  typically are constructed of a flexible material which is capable of being elastically expanded out, and then contracted back while maintaining structural integrity. In one embodiment, this boot is constructed of neoprene rubber, which is a well-known synthetic material which is abrasion-resistant, chemical-resistant, waterproof, and elastic. It is, of course, possible that boot  108  could be constructed of other materials. 
     Functionally speaking, boot  108  is expanded using a plurality of spanwise extending inflatable tubes which are stitched into the neoprene matting in a known manner. When the tubes inflate, this causes accumulated ice to be shed away from the leading edge surface and then carried off by the high velocity impinging air. The boot is then deflated and then cyclically reinflated in a known manner. 
     In the  FIG. 1  embodiment, at least one protrusion  110  is attached to boot  108 . A plurality of these protrusions are shown in  FIG. 1 . Each of the protrusions, in one embodiment, are adhered to the boot using an adhesive or some other known bonding technique. The protrusions could be adhered before or after installation of the boot. In some instances it is desirable to adhere the protrusions after the boot has already been installed on the aircraft to avoid improper positioning, which might affect aerodynamics. Alternatively, the protrusions could be manufactured integrally with the boot by known processes, or connected using some fastening mechanism or system.  FIG. 3  shows the flexible nature of these protrusions  110  and how they might be positioned and then adhered to the leading edge.  FIG. 5  shows the  FIGS. 1-4  embodiment as it appears before installation. 
     In one embodiment, each of these protrusions  110  are constructed of a flexible material such that they are able to be expanded along with the boot. In an embodiment, neoprene rubber is used as the material—the same material the boot is constructed of. This material selection makes the protrusion elastically expandable along with the boot during deicing. Thus, the protruding vortex generator devices  110  are actively involved in the mechanical removal of the ice. Because of this, ice may also be shed from the protrusion itself, as well as the rest of the boot more effectively during the inflate/deflate cycling. 
     These protrusions  110 , because of their shapes, are aerodynamically active, and in the  FIG. 1-5  embodiments, the protrusions are vortex generators. As is known in the art, vortex generators are aerodynamic devices which create vortices and are often used in aircraft design. They are useful here in that their location and orientations at the leading edge tends to maintain attached airflow over the control surfaces at the rear of the wing. Here they are sloped and substantially triangular, but one skilled in the art will recognize that numerous other shapes (e.g., angled raised walls, curved sides, give shaped) might be used as well and would still fall within the scope of these disclosures. Here, the vortex generators  110  run in a span-wise line across the front of each wing. It should be noted that, although some shedding from the vortex generators may be experienced, that the devices will still have the desired aerodynamic functionality even if coated with ice. 
     The protrusion configuration details may best be seen as they appear after installation in  FIG. 2 , and are shown in  FIG. 4  as they appear before installation. As can be seen, each aerodynamic protrusion  110  includes an outer margin  116 . Each protrusion also includes a protrusion body  111 . Protrusion body  111  (which includes all of protrusion  110  except for margin  116 ) begins at a forward edge  124  and then has an upper face  112  which ramps upward until it reaches a terminal point of convergence  130 . Protrusion  110  is further configured with two lateral walls/sides  126  and  128  which converge into a rear terminus  114  which is substantially normal (when installed) to the leading edge surface. 
     The orientation of the protrusion on the wing leading edge can best be seen in  FIG. 4 . Referring to the figure, the protrusions  110 , are disposed such that each has a longitudinal axis which is then conformed (upon installation) tangentially around the leading edge surface; slightly overlaps a forward most point  122  of the wing leading edge  104 ; and diverges from the forward edge  124  to the rear normal terminus  114 . Further, it can be seen in  FIG. 4  that the overlap by the leading edge  124  of protrusion  110  with the foremost point  124  of the leading edge  104  is slight, and that substantially most of the rest of the device  110  is positioned such that it is clocked backward from point  124  (when viewed in cross section). 
     In terms of aerodynamic function, these vortex generators  110 , in embodiments, create two tip vortices which draw energetic, rapidly-moving air from outside the slow-moving boundary layer into contact with the aircraft skin. The boundary layer normally thickens as it moves along the aircraft surface. Thus, the vortex generators disclosed in the figures can be used to reenergize the boundary layer. Vortex generators  110  will provide this benefit regardless of weather conditions, especially at near-stall conditions where the vortex generators will noticeably improve handling characteristics. 
     The vortex generators, however, have also been shown to perform especially well in preventing premature stall conditions caused by ice buildup and/or other contamination of the wing in adverse weather conditions. Again, the deice boot structures  108  do not remove all of the ice buildup. But the vortex generators  110  minimize the separated flow created by the residual ice (the ice not removed by boot activation) to the extent that aircraft handling characteristics are not compromised. 
     Many different arrangements of the various components depicted, as well as components not shown, are possible without departing from the spirit and scope of the present invention. Embodiments of the present invention have been described with the intent to be illustrative rather than restrictive. Alternative embodiments will become apparent to those skilled in the art that do not depart from its scope. A skilled artisan may develop alternative means of implementing the aforementioned improvements without departing from the scope of the present invention. 
     It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations and are contemplated within the scope of the claims. Not all steps listed in the various figures need be carried out in the specific order described.