Abstract:
A force-generating device employing a flared body and a surrounding shroud to define a duct of axially diminishing flow area defining a nozzle for accelerating and directing the discharge of a fluid at a cambered vane, a pressure dam depends from the bottom surface of the vane to entrap a portion of the fluid flowing chordwise along the bottom surface of the vane. A deflector formed on the enlarged end of the flared body and extending into the duct fluid outlet deflects the fluid stream to increase its velocity and direct it toward the vane. In another embodiment, a second deflector formed on the rim of the shroud and projecting into the duct deflects the discharge stream to further increase the velocity of the fluid stream and increase the angle of attack of the fluid stream impinging on the vane. In an alternative embodiment, the first shroud is enclosed in a second shroud to form a second duct of axially diminishing flow area defining a nozzle. The second duct directs its discharge against the bottom surface of the vane, thereby increasing the volume of fluid impinging against the pressure dam. The cumulative effect of these features is to increase and augment the lifting force produced by the vane, and at the same time enhance the efficiency, dynamic stability and directional control of the device.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention is related generally to apparatus for producing a force, and in particular to devices that employ ducted fluids flowing over an airfoil-shaped structure to generate lift, induce motion, or produce power. Still more particularly, it is concerned with methods and means for increasing the efficiency and enhancing the utility of such devices. 
     2. Description of the Prior Art 
     The use of shaped ducts for directing the flow of air, water, or other fluids over wing-like structures to generate or enhance lift is well known. A variety of designs embodying combinations of shaped ducts and airfoils have been proposed. Typical examples are illustrated by U.S. Pat. Nos. 2,812,980, 3,276,723, 3,297,228, 3,365,149, 3,489,374, 3,612,445, 3,785,592, 4,117,992, 4,235,397, and 5,170,963. Although promising on paper, few if any of these devices have proven successful in operation, much less commercially useful. Among their many deficiencies, most commonly three, namely, limited performance, low efficiency, and inherent dynamic instability, preclude them from serving a useful purpose. 
     Heretofore, as exemplified by the cited examples, conventional wisdom called for the use of ducts having axially expanding flow area. By definition, such ducts are diffusers and slow the flow of fluid discharged from them. U.S. Pat. No. 5,155,992, in which I am a co-inventor, discloses an alternative method and means employing a shaped duct and an annular cambered vane for generating a force. The patented invention utilizes a flared body enclosed in a shroud to form a duct terminating in an outlet of axially diminished flow area. A fan or impellor drives a fluid stream through the duct. Having a reduced fluid outlet, the duct defines a nozzle. Precisely opposite from a diffuser, a nozzle serves to accelerate the fluid discharge. The device is designed to direct the discharge over a cambered vane or wing positioned in the duct fluid outlet. 
     Tests have demonstrated the successful operation of the invention and confirmed its utility. I have discovered that by incorporating certain improvements, features and refinements in the patented device, I can greatly enhance its performance, efficiency and stability. The present disclosure relates to methods employing those improvements, features and refinements, to a force-producing apparatus embodying them, and to mechanisms, such as vehicles, employing. 
     SUMMARY OF THE INVENTION 
     The subject invention, or some of its features, may be applicable to other prior art devices, but it is intended primarily as an improvement in devices embodying the teachings of U.S. Pat. No. 5,155,992 to generate lift, induce motion, or produce power. Such devices serve a variety of applications. By way of example, they can be used to achieve vertical lift in VTOL/STOL aircraft, or to propel the rotor blades that provide lift for helicopters. Immersed, they can provide propulsion for surface or sub-surface vessels. 
     For illustrative purposes, several preferred embodiments of the invention will be described in conjunction with a force-generating device in which the vane and shroud embody the generally circular plan form shown in U.S. Pat. No. 5,155,992. In this configuration, the flared body is preferably generally conical, that is, radially symmetrical, in shape, and coaxial with the shroud. The lower end of the flared body extends into and overlaps the flared end of the annular shroud and with the overlapping portion of the shroud forms an annular duct of axially diminishing flow area. The converging walls of the duct define an annular nozzle. The vane, in this design a generally horizontally disposed annular cambered wing, is mounted to the duct in the path of fluid discharged radially outwardly from the nozzle. 
     In one of the preferred embodiments shown here, the invention comprises a first deflector in the form of an annular skirt mounted to the enlarged upper end of the flared body. This deflector extends outwardly of the flared body into the duct fluid outlet. A second deflector in the form of an annular flange mounted to the lip of the shroud and extending radially inwardly of the shroud (i.e., in the direction of the flared body) into the duct fluid outlet; and a structural feature that I call a “pressure dam” in the form of a flange depending generally normally from the bottom surface of the vane at or near its trailing edge. At least one of the purposes of the pressure darn is to entrap a portion of the fluid flowing chordwise along the bottom surface of the vane. 
     In another preferred embodiment of the invention, the shroud of the first embodiment is enclosed in a second shroud that, with the first shroud, forms a second, outer, annular duct (like the first duct a nozzle of upwardly diminishing flow area). The stream of fluid discharged by the annular fluid outlet of this outer duct is directed toward the bottom surface of the vane. 
     I am not certain as to the precise fluid-dynamic principles called into play by the invention, however, based on my test data, it appears that three functions are in operation: One, served by the first deflector, involves the compression of the fluid discharge and the resulting increase in the velocity of the fluid exiting the duct nozzle. Another, associated with the second deflector, involves the exercise of control over the angle of attack and distribution of the flow of the accelerated fluid mass under and over the cambered vane. The third, influenced if not determined by the pressure dam, has to do with the chordwise location of the region of impact of the fluid discharge against the lower surface of the vane. Individually, these functions offer marginal overall improvement in the operation of the patented device. Collectively, they produce a marked increase in the lift force generated by the device, noticeable improvement in its efficiency, and demonstrably enhanced stability and controllability. The provision of the second shroud appears to increase, and augment the control of, the flow of fluid across the bottom surface of the vane. 
     It will be understood that the subject invention, though illustrated and described in connection with an annular duct and vane, is readily adaptable for use with a force-generating device of other than annular configuration. By way of example, rather than conical, the flared body may be rectilinear in cross-section with the shroud or shrouds taking the form of curved sheets or surfaces spaced convergently or divergently from its flared wall or walls. FIG. 3 of U.S. Pat. No. 5,155,992 is illustrative of one such non-annular embodiment of the invention. The shape of the vane in such a device would be defined by the configuration of the shroud or shrouds and the flared body. In the non-conical variation of the invention shown in FIG. 3 of U.S. Pat. No. 5,155,992, a pair of straight vanes are positioned in the outlets formed at either side of the bilaterally symmetrical flared body. The pressure dam and first and second deflectors, of course, would conform to the configuration of the vane, the flared body, and the shroud or shrouds, respectively. 
     A principal object of the subject invention is to provide a method and means for maximizing the force produced by the cambered vane of a device of the type described in my earlier patent. 
     Another object is to provide a method and means, for use in a device of the type described, for directing the fluid exiting the duct nozzle efficiently under and over the cambered vane. 
     A further object is to provide a method and means, for use in a device of the type described, in which the velocity of the discharged fluid is increased as well. 
     Another object is to provide a method and means, for use in a device of the type described, incorporating a pressure dam for increasing the force generated by the fluid impinging on the lower surface of the cambered vane. 
     Still another object is to provide a method and means, for use in a device of the type described, in which the acceleration and directional control of the fluid are achieved by adjusting the configuration of the duct and its fluid outlet. 
     A still further object is to provide such a method and means in which the configuration of the duct and fluid outlet are established by a combination of deflectors mounted to the flared body and its surrounding shroud and extending into the duct fluid outlet. 
     Another object is to provide a method and means, for use in a device of the type described, which incorporates a second annular duct nozzle for increasing the velocity of and directing the discharged fluid impinging on the bottom of the cambered vane. 
     An additional object is to provide methods and means of the type described for use in force generating devices of other than annular configuration. 
     Yet a further object is to provide a method and means, for use in a device of the type described, that utilize in combination the configuration of the fluid-containing duct, fluid deflectors associated with a tapered central body and its enclosing shroud, and a pressure dam on the bottom surface of the vane, for maximizing the force generated by, and improving the stability, directional control, and efficiency of, such a device. 
     Still another object is to provide a method and means, for use in a device of the type described, for generating a force that overcome the deficiencies inherent in the prior art shaped-duct lift-generating devices. 
    
    
     For a fuller understanding of the invention and the manner and means by which it achieves these and other objects and advantages which will become apparent to those skilled in the art, reference is made to the following detailed description of the preferred embodiments illustrated in the accompanying drawings, in which: 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of a force-generating device in accordance with the subject invention with portions of the device cut away to show its internal construction; 
     FIG. 2 is a side sectional view of an alternative embodiment of the invention illustrated in FIG. 1; 
     FIG. 3 is a diagrammatic side view of one half of the embodiment of the invention illustrated in FIG. 2, illustrating the dimensions employed in defining a mathematical model of the invention; and 
     FIG. 4 is a diagrammatic side view of one half of an alternative embodiment of the invention illustrated in FIGS.  2  and  3 . 
    
    
     Wherever practicable, the same numeral is used to identify identical or substantially similar features appearing in the several figures. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates the subject invention embodied in a device of the type described in my U.S. Pat. No. 5,155,992 as it might be used to provide lift for a VTOL/STOL aircraft. The device comprises a flared, in this instance generally conically-shaped, body  11  and a contoured, similarly flared annular shroud  12 . The concentrically mounted body  11  and shroud  12  define an annular duct  13  having a fluid inlet  14  and a fluid outlet  15 . The device is constructed with the inlet flow area of fluid inlet  14  substantially greater than the flow area of the duct fluid outlet  15  at the outlet of duct  13 . 
     For comparative purposes, the inlet flow area is defined as πD 2 /4, where D is the diameter of fluid inlet  14 . The outlet flow area is equal to C 15 W, where C 15  is the length of the fluid outlet (the circumference of fluid outlet  15  in the annular embodiment shown here) taken at the midpoint of the outlet, and W is the width of the outlet (in this instance, the width of the opening measured from the outer edge of deflector  22  to the lip  24  of deflector  21 . It will be noted that the flow area of a fluid duct, for example, annular duct  13 , is not the same as the cross-sectional area of the duct. 
     Energized fluid, here air, from a source such as compressor  16 , is further compressed and accelerated as it passes through duct  13 . The high-velocity discharge from nozzle fluid outlet  15  impinges on the leading edge of concentrically mounted annular cambered vane  17 , thereby producing upwardly directed lift. 
     The subject invention comprises three components: a first deflector  21  in the form of an annular skirt mounted to the upper end of the flared body  11 , a second deflector  22  mounted to the upper edge of shroud  12 , and a pressure dam, here in the form of a flange  23  mounted rigidly to the lower surface of vane  17  at or near its trailing edge. Deflector  21  extends radially outwardly of the flared body  11  into the duct fluid outlet  15 , effectively acting upon the fluid stream so as to change its flow direction and further accelerate the discharged fluid virtually at the point of its impingement with vane  17 . It should be pointed out that while the first deflector  21  is shown extending normally of the surface of body  11 , the desired effect can be achieved by mounting deflector  21  to body  11  by means of a cap (not shown in FIG. 1) from which the deflector  21  depends vertically, rather than normally of the surface of the flared body  11 , the significant factor being the spatial location of the lip  24  which defines the effective aperture of fluid outlet  15 . This alternative arrangement is depicted in FIG.  2 . 
     The second deflector  22  plays a significant though not vital role in the performance of the invention. For convenience, if desired it can be omitted. When deflector  22  is included, it appears to serve two functions: first, it accelerates the flow of fluid through the fluid outlet nozzle and over vane  17  as previously described in connection with deflector  21 . Secondly, in deflecting the fluid toward the center of shroud  12 , it effectively increases the angle of attack of the flowing fluid with respect to vane  17 . The result is to increase the lift produced by the vane  17 . 
     The pressure dam created by flange  23  appears to increase substantially the lift generated by vane  17 . I assume it does so by entrapping at least a portion of the air mass impacting the lower surface of vane  17  and thereby creating an overpressure acting upwardly against that surface. Unlike the numerous well-known conventional aircraft wing flaps, the pressure dam does not appear to rely on an increase in the camber or outer surface area of vane  17  for its enhancement of the lift provided by vane  17 . 
     In the embodiment of FIG. 2, a force-generating device of the type illustrated in FIG. 1 is provided with a second contoured shroud  32  mounted (by conventional means not shown) to the first shroud  12 . The two shrouds  12 ,  32  effectively define a second duct  33  having a fluid inlet  34  of greater flow area than the fluid outlet  35  at the outlet of duct  33 . 
     Fluid inlet  34  is operatively connected to a source of fluid under pressure, preferably the same source, compressor  16 , supplying pressurized fluid to fluid inlet  14  of the first duct  13 . Fluid outlet  35  is configured and oriented to direct the stream of high-velocity fluid discharged from duct  33  against the bottom surface of vane  17 , thereby increasing the overpressure accumulated in front of flange  23 . 
     As noted earlier, first deflector  21 ′ is mounted to flared body  11  by means of an annular cap  36 . In this construction, the deflector  21 ′ is vertical, rather than inclined as in the embodiment of FIG.  1 . Since the lip  24 ′ of deflector  21 ′ is in the same spatial position with respect to body  11  as the lip  24  in the construction of FIG. 1, the function and effect of deflector  21 ′ are precisely the same as those of deflector  21 . What I believe are the principal airflow paths  34  for the two embodiments are depicted diagrammatically in FIGS. 1 and 2. 
     From test data, I have been able to synthesize a mathematical model representing a successful design embodying the subject invention. The model is defined by a series of dimensional relationships, which are independent of scale and are equally valid for large as well as small craft. 
     Referring to FIG. 3, the mathematical model design assumes the annular vane  17  is a circular wing disposed on a horizontal plane  41  containing the leading edge  42  of the wing airfoil. The particular airfoil is a matter of choice and forms no part of the invention. The center of circular vane  17  is the vertical centerline  43  of the model. For the most part, the pertinent dimensions are taken from horizontal plane  41  and vertical centerline  43  and encompass a range of values for each parameter. 
     For modeling purposes, I base the wing area on a target wing diameter. Conveniently, the wing aspect ratio may be from about 10 to about 20 and preferably, for this example, 17.8. Given a design wing diameter and the aspect ratio for the selected wing, the wing area can be readily calculated using conventional aerodynamic principles, equations, and formulas. 
     The wing radius  44  is measured from the center  45  of the wing chord to the model centerline  43 . 
     The inlet radius  51  of the fluid inlet  14  of inner shroud  12  is equal to or greater than the radius  44  of vane  17 . The depth of duct  13  from the fluid inlet  14  to the narrowest region, throat  18 , is about 1.25 times the inlet radius  51  of fluid inlet  14 . The inlet radius  52  of the fluid inlet  34  of the outer shroud  32  is greater than inlet radius  51  of inner shroud  12 , the difference being dependent at least in part on the volume of fluid flow desired in the second duct  33 . 
     The total effective area of nozzle fluid outlet  55  is designed to be from about 0.80 to about 1.00, and preferably about 0.89, of the effective area of vane  17 . The (inner) shroud  12  and deflector  21 ′ are configured to position the center  53  of fluid outlet nozzle  55  in the horizontal plane  41  at a radius  54  from centerline  43  defined as from about 0.85 to about 0.95, and preferably about 0.93 of the distance from centerline  43  to the leading edge  42  of vane  17 . The total fluid outlet nozzle opening is calculated from the fluid outlet nozzle area and its radius  54 . 
     The radius  61  of lip  24 ′ of deflector  21 ′ (or lip  24  of deflector  21 ) is from about 0.80 to about 0.90, and preferably about 0.80 of fluid outlet nozzle radius  54 . The end of a line segment  56  drawn from lip  24 ′ through, and an equal distance beyond, the center  53  of fluid outlet  55  defines the location of the lip  57  of inner shroud  12 , or the lip of the second deflector  22 , if this feature of the device is provided (omitted from this embodiment of the invention). In either case, the lip  57  of inner shroud  12  or the lip of the second deflector  22  overlaps, that is, extends radially outwardly of the leading edge  42  of vane  17 . 
     The inner wall  62  of shroud  12  adjacent nozzle fluid outlet  55  is oriented at from about 40° to about 45° and preferably about 40° with the horizontal plane  41 . This is the geometric angle of attack of the vane  17  to the duct airflow. 
     The throat radius  63  of inner shroud  12  is from about 0.60 to about 0.70, and preferably about 0.67, of the radius  64  of shroud lip  57 . 
     The surface  65  of flared body  11  is generally parallel with the inner wall  62  of shroud  12 . The annular duct  66  defined by flared surface  65  and shroud wall  62  has a “depth” or effective opening of from about 1.10 to about 1.5, and preferably about 1.37 times fluid outlet nozzle opening  55 . The depths of deflectors  21  (see FIG. 1) and  21 ′ (of FIG. 2) are defined as percentages of the fluid outlet nozzle opening  55 . The deflectors  21  and  21 ′ have an effective depth (measured along the extended fluid outlet nozzle opening  55 ) of from about 0.25 to about 0.5, and preferably about 0.43 of fluid outlet nozzle opening  55 . From this dimension, the vertical distance from the lip  24 ′ of the deflector  21 ′ to the top surface  67  of flared body  11  can be calculated. 
     The flange  23  depends vertically from the bottom surface trailing edge from about 0.50 to about 0.75, and preferably about 0.50 of the length of the chord of vane  17 . As mentioned earlier, flange  23  serves as a pressure dam positioned directly in the path of fluid exiting the outlet nozzle, e.g.,  55 . The force resulting from the impact of outlet fluid with the flange  23 , or from the pressure differential on opposite sides of flange  23 , or both, demonstrably increases the thrust produced by vane  17 . While the thrust-producing mechanism is not fully understood, it unquestionably contributes significantly to the overall capacity and efficiency of the invention. 
     From the results of my experimentation with deflectors of various configurations, it appears that one, and perhaps the most, significant function of the deflectors  21  (FIG. 1) and  21 ′ (FIGS. 2-3) is the positioning of lips  24  and  24 ′, respectively, with respect to the lip of deflector  22  (FIGS. 1-2) and lip  57  of inner shroud  12 . Lips  24  (FIG. 1) and  24 ′ (FIGS. 2-3) and the lip of deflector  22  (FIGS. 1-2) and lip  57  (FIG.  3 ), respectively, effectively define the size and geometry of nozzle fluid outlets  15  and  55 . 
     FIG. 4 illustrates an alternative embodiment of the invention that takes advantage of this principle. Here, deflector  21 ″ is a flat, annular ring, mounted to the flared body  11 . Were weight not a consideration in the construction of the device, deflector  21 ″, rather than an annulus, could take the form of a flat, circular plate (not shown) secured to the top of the flared body  11 . In either case, the lip  24 ″ of the deflector  21 ″ is substantially in the plane of the deflector  21 ″, rather than at the periphery of a flange spaced or offset from a plane containing a portion of the deflector as in the embodiments of FIGS. 1-3. Significantly, it will be noted that annular lip  24 ″ at the periphery of deflector  21 ″ is located in the same spatial relationship with the structural elements defining fluid outlet nozzle  55  as lip  24  bears to the elements of nozzle  15  in the embodiment of FIG.  1  and as lip  24 ′ bears to the elements of nozzle  55  in the embodiments of FIGS. 2 and 3. 
     As with the embodiments of FIGS. 1-3, the effective “chord,” i.e., the width or radius of deflector  21 ″, is determined by the configuration of the surface  65  of flared body  11  and its intersection with the adjacent surface of deflector  21 ″ that terminates at lip  24 ″. The dimensions and geometry of deflector  21 ″ define the effective radius  62  of lip  24 ″ in the same manner as previously described in connection with the radii of lips  24  and  24 ′ in the embodiments of FIGS. 1 and 2, respectively (not shown), and the radius  61  of lip  24 ′ in the embodiment of FIG.  3 . 
     Test results strongly suggest that the configuration and angular orientation of the deflectors  21 ,  21 ′,  21 ″, serve several functions bearing on the operation and efficiency of the invention: The first of these is the positioning of the lip  24 ,  24 ′,  24 ″ with respect to the lip of the deflector  22  in the embodiment of FIG. 1 or the associated lip  57  of shroud  12  in the embodiments of FIGS. 2 and 3, respectively. The spacing and spatial relationship of the respective pairs of lips effectively establish the size and geometry of the fluid outlet. In each of the embodiments, by “choking,” i.e., constricting, the fluid outlet, the deflector is employed to define an exit nozzle. The velocity and flow rate (volume) of the fluid exiting the nozzle are determined, and can be selectively controlled by appropriate choice and adjustment of the configuration and orientation of the deflector  21 ,  21 ′,  21 ″. 
     A second function served by the deflectors  21 ,  21 ′,  21 ″ in a manner not fully understood is to enable or cause the fluid stream exiting nozzle  15 ,  55  and flowing over and under the wing  17  to remain attached to the wing surface without separation and stalling over a much greater range of angles of attack, and to a substantially higher angle of attack with respect to the wing chord, than is possible without such deflectors. This feature affords the builder a degree of flexibility in design unknown in prior art devices of this type, and results in an apparatus capable of producing a lifting force much greater than the theoretical maxim calculated or specified for the wing airfoil. 
     A third function is to operate on the fluid in some manner as it exits the nozzle so as to impart to the outflowing fluid an energy and a trajectory that allow it to sustain a higher velocity with resulting noticeably greater wing lift than can be achieved with a similarly sized nozzle without a deflector. 
     Yet another function is to eliminate, or at least substantially reduce the rotational moment induced in the fluid exiting the nozzle. Without deflectors of the type described, the departing fluid stream follows a spiral path or vortex downstream of the nozzle. This result is a substantial reduction in the lift produced by the fluid impacting and flowing over and under the wing. The deflector counteracts this phenomenon and allows the energy that would otherwise be dissipated in the production of the vortex to be translated into lift. The result is greatly enhanced efficiency, with virtually no offsetting deficiency or penalty. 
     The operation and advantages of the invention will be readily apparent from the foregoing description. It should be understood, however, that although the invention has been disclosed in terms of the specific constructions and functions shown in the drawings and described in the specification, it is not to be construed as limited to those embodiments. They are to be regarded is illustrative rather than restrictive. This is particularly true with respect to the geometric configurations depicted in the several figures of the drawings and to the dimensions and dimensional relationships embodied in the aforementioned mathematical model of the invention. The specification is intended to encompass any and all variations and equivalents of the examples chosen for purposes of the disclosure, which do not depart from the spirit and scope of the following claims.