Abstract:
An apparatus for affecting airflow in a gap between a lead vehicle and a connected trailing vehicle, includes a guide vane having a leading edge, a trailing edge, a gap side surface, and an outward facing surface, and a support apparatus mountable on a vehicle for supporting the guide vane in a vertical orientation relative to the vehicle with a space between the vehicle and the guide vane gap side surface and with at least a portion of the vane extending beyond an end of the vehicle. The flow guide divides an air flow at the trailing edge of a vehicle to avoid the creation of turbulence in the air flow as it encounters the gap between the vehicle and the trailing vehicle,

Description:
[0001]    This application claims the benefit of U.S. Provisional Patent Application No. 61/373,409, filed Aug. 13, 2010. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to devices for improving the aerodynamics of a vehicle combination, and more particularly, to a device for reducing the drag effect of the gap between a truck tractor and towed trailer. 
       BACKGROUND AND SUMMARY OF THE INVENTION 
       [0003]    The gap between a truck tractor and a trailer connected to the tractor is needed to allow the articulated movements for steering and to accommodate road risings and dips while avoiding contact between the tractor and trailer. The gap, however, is a well-known source of aerodynamic drag on the vehicle combination. Many devices have been proposed to solve this problem, including U.S. Pat. No. 3,71,146 showing telescoping panels to close the gap; U.S. Pat. No. 6,991,281 showing a roof fairing and U.S. Pat. No. 6,846,035 and U.S. Pat. No. 5,078,448 showing side fairings to direct air flow around or past the gap; U.S. Pat. No. 3,945,677 disclosing a flexible bag-like device filling the gap; U.S. Pat. No. 3,697,120 showing flow guides to create a swirl in the gap; U.S. Pat. No. 4,257,640 disclosing a baffle to block air flow across the gap; and, U.S. Pat. No. 7,216,923 disclosing a device to inject air into the gap to increase the pressure in the gap. 
         [0004]    One problem in fairings is that the relatively high pressure air coming off the fairing trailing edge of the fairing is drawn into the relatively lower pressure air in the gap, creating turbulence and increased drag. 
         [0005]    The inventor has posited that if a boundary layer of the flow along the side of truck tractor can be bled off of the fairing into the gap, that is, divided from the main flow and directed into the gap, a higher pressure region can be created in the gap along with an accompanying lower pressure along the fairing. This would equalize the pressure at the trailing edge of the fairing and prevent the formation of turbulence. 
         [0006]    The invention proposes a device to control the air flow boundary layer at the gap to prevent turbulent flow at the gap. The invention concerns a flow guiding device placed where a cab side fairing is conventionally positioned on the truck tractor, the flow guiding device shaped to divide an air flow over the truck tractor at a boundary layer, directing a portion of the air flow into the gap between the tractor and the trailer, and directing the remainder to flow past the trailer. The divided portion rejoins the main portion of the air flow in such a way that turbulence in the air gap is prevented or reduced. 
         [0007]    According to the invention, a flow guiding device is disposed at the rear of a truck tractor cab to extend vertically at the front portion of the gap between the truck tractor and a trailer. The device is spaced laterally from the truck tractor to provide a space at the forward end of the device between the device and the side of the truck tractor. The device extends longitudinally (parallel to the long axis of the truck) from a point adjacent the truck tractor to a point rearward of the truck tractor along the gap. The device divides the air flow, directing a relatively higher pressure stream into the gap side of the device, which causes the pressure at the trailing end of the device to equalize when the flows rejoin, reducing turbulence in the gap, and promoting a lower drag flow directed to the trailer. The longitudinal dimension of the device is sufficient to produce the flow effect from the trailing edge of reduced turbulence in the gap and a directed flow to the trailer. 
         [0008]    An air guiding device according to the invention has two opposing surfaces shaped so that flow on one surface is slower than flow on the other surface. The device may be shaped as an airfoil, having a concave surface and an opposite convex surface. Alternatively, the device may have a convex surface and an opposite flat surface. 
         [0009]    The device is mounted by brackets to the truck cab, the number of brackets being selected to prevent excessive flexing or bending of the device. 
         [0010]    The device may be mounted with a convex surface facing the gap, and oriented to bleed off a layer of air flow into the gap, so that the outer and inner flows (relative to the device) rejoin without producing turbulence. Alternatively, the device may be mounted with the concave or flat surface facing the gap. It is expected that the orientation of the device relative to the gap, that is, the angle the device forms with the longitudinal direction, will influence the flow dividing and pressure equalizing effect. 
         [0011]    The device may be mounted to be freely pivotable along its vertical axis to allow for self-adjustment. Alternatively, the orientation can be controlled by actuators responsive to electronic pressure sensing devices monitoring pressure on the outer and inner sides of the device. A controlled system can continuously adjust the device for optimum air flow. 
         [0012]    A preferred embodiment of the invention includes an airfoil shaped device positioned to divide the flow and which device can be tuned to equalize the pressure in the outer and inner flows, as well as direct a slip stream to the trailer. Further, a preferred embodiment of the invention is a device that dynamically adjusts to air flow conditions to optimize air flow across the gap, and creates a substantially laminar flow directed to the leading edge of the trailer. 
         [0013]    An airfoil device according to the invention may take any of a number of shapes capable of producing a flow effect to equalize pressure in an air flow downstream of the airfoil device, including, but not limited to, cambered, symmetrical, non-symmetrical, and circular arc, among others. 
         [0014]    The device may include vortex generators formed or disposed at the trailing edge of the device to generate vortices in the flow directed to the trailer. Vortices in the air flow on a surface such as the trailer outer surface reduce surface friction. 
         [0015]    According to another embodiment, the device of the invention is a vented fairing, a conventional fairing shaped or mounted on the truck tractor to bleed a layer of air into the tractor-trailer gap from the air flow and allow the divided flows to rejoin at a trailing edge. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The invention will be better understood by reference to the following detailed description read in conjunction with the appended figures, in which: 
           [0017]      FIG. 1  is a view of a first embodiment of a flow guiding device according to the invention having a non-symmetric cambered body; 
           [0018]      FIG. 2  is a view of an additional embodiment of a flow guiding device according to the invention having a non-symmetric body with a curved side and a flat side; 
           [0019]      FIG. 3  is a view of yet another embodiment of a flow guide device according to the invention having a symmetric cambered body; 
           [0020]      FIG. 4  is a view of an additional alternative embodiment of a flow guide according to the invention showing a circular arc body shape; 
           [0021]      FIG. 5  is a view of an alternative embodiment of a flow guide according to the invention showing a form having concave curvatures on both sides; 
           [0022]      FIG. 6  is a section view of another embodiment of a flow guiding device including vortex generators; 
           [0023]      FIG. 7  is a schematic view of a first arrangement of a flow guiding device on a truck tractor; and, 
           [0024]      FIG. 8  is a schematic view of an alternative arrangement of a flow guiding device on a truck tractor. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    The invention is directed to an air flow guide apparatus that may be mounted on a lead vehicle connected to a trailing vehicle to influence the air flow characteristics in a gap between the vehicles. More specifically, the air flow guide apparatus of the invention divides an air flow at a trailing edge of the lead vehicle to create a higher pressure flow on a gap side of the apparatus and a lower pressure flow on an outward facing side of the apparatus to avoid the creation of turbulence in the gap. It is believed that while some of the air flow, in particular, air flow in the boundary layer on the vehicle surface, will flow into the gap and create turbulence, the overall effect of the flow guide is less turbulence and an improvement in drag. The pressures on the gap side and outward side of the flow guide will come to equilibrium where they rejoin at a trailing end of the flow guide to create a laminar flow directed to the trailing vehicle and prevent or diminish the amount of air entering the gap downstream of the flow guide for an overall reduction in aerodynamic drag. 
         [0026]    A first embodiment of a flow guide  10  in accordance with the invention is shown a top view in  FIG. 1 . The flow guide  10  of  FIG. 1  is a rigid element having a cambered teardrop shape, as that of a vane or airfoil, having a leading edge  12  and a trailing edge  14 . The leading edge  12  is bulbous and the flow guide  10  tapers to the trailing edge  14 , providing a convex curved side  16  and a concave curved side  18 . The flow guide  10  has a pivot axis  20 , as will be described in greater detail below. 
         [0027]      FIG. 2  illustrates an alternative embodiment of a flow guide  11 . The flow guide of  FIG. 2  has a leading edge  13  and a trailing edge  15 , the leading edge being semi-bulbous (having a rounded side and a flat side) and the flow guide  11  tapering to the trailing edge. The flow guide  11  has a convex surface  17  and a substantially flat surface  19 . 
         [0028]    The embodiments illustrated here are for the purposes of describing the invention. Other shapes capable of dividing an air flow into a higher pressure flow and a lower pressure flow may be suitable if given an appropriate angle of orientation relative to the air flow. 
         [0029]    For example, a symmetric vane  110  as shown in  FIG. 3 , having a bulbous nose  112  and tapered tail  114  and convex curves on both side  116 ,  118  may be suitable.  FIG. 4 , shows a circular arc shaped vane  210  having convex curvatures on both sides  216 ,  218 , with a tapered nose  212  and tapered tail  214 .  FIG. 5  shows another alternative vane  310  having a bulbous nose  312  and tapered tail  314 , with concave curvatures on both sides  316 ,  318 . 
         [0030]    A flow guide may be incorporated in another flow control device, such as a fairing that encloses part of the gap between the leading and trailing vehicle. A flow control device of the invention may be formed or mounted at the trailing edge of the fairing. Alternatively, a cab side fairing may be formed with the shape of the flow guide of the invention. 
         [0031]    According to another aspect of the invention, a flow guide of the invention may include vortex generating devices formed or mounted at the trailing edge of the flow guide. Vortices in the air flow contacting the trailing vehicle surface help reduce drag.  FIG. 6  shows a perspective section view of a trailing end  14  of flow guide  10  according to  FIG. 1  including vortex generators  26  at the trailing edge  14 . The vortex generators  26  are illustrated as triangular wedges rising from the surface  16  of the flow guide  10 . Vortex generators may have other shapes as is known in the art. 
         [0032]      FIG. 7  is a schematic top view of an arrangement of the flow guide apparatus on a vehicle  30  connected to a trailing vehicle  40 . The vehicle  30  may be a tractor truck and the trailing vehicle  40  may be a trailer as is known in the tractor-trailer combination. The vehicle  30  alternatively may be a leading trailer in a tandem or triple trailer combination. A trailer connected to the leading trailer would be the trailing vehicle  40 . The leading vehicle  30  and connected trailing vehicle  40  are spaced longitudinally so that a gap  42  between the vehicles is provided. The gap  42  accommodates relative movement between the vehicles, as for turning or road risings and fallings, to avoid contact between the vehicles. 
         [0033]    As seen in  FIG. 7 , a flow guide  10 , illustrated here as the flow guide of  FIG. 1 , is mounted at the trailing edge  32  of the vehicle  30  by way of a bracket assembly  24  or similar arrangement. The bracket arrangement  24  mounts the flow guide  10  in a vertical orientation relative to the vehicle  30 , that is, with the leading edge  12  of the flow guide substantially parallel to a trailing edge  32  of an outer lateral surface  34  of the vehicle. it should be noted that the flow guide  10  extends for substantially the entire height of the trailing edge  32  of the vehicle  30 , or as may be accommodated at the trailing edge of the vehicle. The flow guide  10  is positioned with a space  36  between a gap side  18  of the flow guide and the outer lateral surface  34  of the lead vehicle  30 . Preferably, the space  36  is provided so that the flow guide divides a boundary layer from the main body of the air flowing along the vehicle lateral side surface  34 . 
         [0034]    As may be seen by the arrows depicting air flow, the flow guide  10  divides the air flow departing the outer lateral surface  34 . The flow guide is positioned and oriented so that the air flow is divided into a higher pressure flow on the gap side  18  of the flow guide  10  and a lower pressure flow on the outward facing surface  16  of the flow guide, The divided flow joins at the trailing edge  14  of the flow guide. The higher pressure flow on the gap side is believed to help prevent the air flow departing the outer lateral surface  34  of the vehicle from entering the gap  42 , and thus avoid creating turbulence in the gap. The leading edge  12  of the flow guide  10  is positioned relative to the trailing edge  32  of the vehicle  30  so to divide the boundary layer of the air flow detaching from the lateral surface  34  of the vehicle. This may be at, ahead, or behind the trailing edge  32  as appropriate for the flow characteristics generated by the outer lateral surface  34  of the vehicle. 
         [0035]    The bracket assembly  24  may include an upper bracket and a lower bracket at opposite top and bottom ends of the flow guide  10 . Alternatively, additional brackets between an upper and lower bracket may be provided as need to prevent bending or flexing of the flow guide  10 . 
         [0036]    According to an embodiment of the invention, the bracket assembly  24  mounts the flow guide  10  for pivotal movement on a vertically oriented pivot axis  20 , which may be an axis parallel or substantially parallel to the outer lateral surface  34  of the vehicle, or an axis perpendicular to a horizontal plane defined by the wheel axles of the vehicle  30 . The pivot axis  20  is located forward of the center of pressure of the flow guide for stability of the flow guide  10  in moving air. 
         [0037]    The flow guide  10  may be mounted freely pivotal on the bracket assembly  24  to self-adjust an angle of the flow guide relative to the longitudinal direction of the vehicle to accommodate the air flow characteristics at different vehicle speeds. In such an embodiment, the bracket assembly  24  may include a rod coincident with the pivot axis on which the flow guide mounted, or an upper and lower pin arrangement, or other arrangement as will occur to those skilled in the art. In addition, stops may be provided to limit the angular range of motion. 
         [0038]    Alternative to being freely pivotal, the bracket assembly may include an actuator for adjusting and controlling the angle of the flow guide  10 . The actuator may be a linear actuator mounted to the vehicle  30  and connected to the flow guide  10  or a rotary actuator connected on the bracket assembly  24 . The actuator may be controlled responsive to a vehicle speed. Alternatively, the actuator may be controlled responsive to air pressure readings from sensors on the gap side surface and outward facing surface of the flow guide so that a desired higher air pressure is present on the gap side surface. 
         [0039]    According to yet another alternative, the flow guide may be oriented at a fixed angle optimized for a particular vehicle speed and generated air speed, for example for a highway truck combination that operates for extended periods at a particular speed. 
         [0040]      FIG. 8  shows an alternative arrangement of the flow guide  10  mounted on the bracket assembly  24 . In this arrangement, the concave surface  18  of the flow guide  10  is on the gap side and the convex surface  16  is on the outward facing side. Either of the arrangements of  FIG. 4  and  FIG. 5  may be used depending on which provides the most favorable flow characteristics in terms of a pressure difference between gap side and outward facing side and in terms of the direction and turbulence avoidance ability of the flow joining at the trailing edge of the flow guide. 
         [0041]    Any flow guide embodiment, including those shown in  FIGS. 1 through 5 , may be used in the arrangements illustrated in  FIG. 7  and  FIG. 8 , and the descriptions of  FIG. 7  and  FIG. 8  should be understood to be inclusive of different embodiments of the flow guide. 
         [0042]    The invention has been described in terms of preferred embodiments and components; however, those skilled in the art will understand that substitutions for those things described here may be made without departing from the scope of the invention as defined by the appended claims.