US3441236A - Airfoil - Google Patents

Description

April 29, 1969 E ARNHOLDT 3,441,236

AIRFOIL Filed Jan. 16, 1967 CONTROL [/61 51 '55 Magus \5 50 m 55 31 5c 15d 55 R1 7 a II 52/6 flew/mar ATTORNEYS United States Patent 3,441,236 AIRFOIL Eric Arnholdt, 7108 Seacliff Road, McLean, Va. 22101 Filed Jan. 16, 1967, Ser. No. 609,431 Int. Cl. 1864c 21/02, 3/00; B64d 15/02 US. Cl. 244-42 Claims ABSTRACT OF THE DISCLOSURE An apparatus for providing lift in a fluid medium having an adjustable slot-like passage extending from the underneath pressure surface tothe upper suction surface for providing additional high velocity fluid flow over the latter. A deicing system channeling heated air chordwise along the passage and through its discharge nozzle is positioned within the airfoil.

The present invention relates to improvements in airfoils and, more particularly, relates to improvements in airfoils having a lift modifying passage formed therein.

In my prior US. patent application, Ser. No. 425,853, filed Jan. 15, 1965, entitled, Airfoil, now US. Patent 3,298,636, issued I an. l7, 1967, there is provided an improved airfoil having an upper suction surface formed in an undulating fashion with relatively spaced crests and valleys for enhancing the lift-to-drag ratio. As explained in this earlier patent this desired result is accomplished by providing a passage through the airfoil extending substantially parallel to the fluid flow from the underneath pressure surface to the upper suction surface. This passage terminates in a restricted nozzle to cause a high velocity stream of fluid to be expelled tangentially of said valley thereby causing the fluid flow to follow the curvature of the valley as well as the crest in a fashion to materially improve the lift and reduce the drag, and to thus enhance the lift-to-drag ratio.

The present invention is concerned with the provision of structure used to control the flow of air through this type of lift modifying passage and thus a main objective is to thereby provide a means for efficiently controlling the velocity and mass flow of air through the passage and into the boundary layer region of the slipstream over the lift or suction surface. Broadly speaking, the apparatus of the present invention is not limited to use with the specific airfoil disclosed and claimed in this previous patent, but can be utilized for the control of the fluid flow through similar passages in conventional airfoils, which are primarily designed to prevent premature separation of the fluid flow and thus a reduction in the drag coeflicient, for example, as shown in the US. patent to Grant, No. 2,649,265, issued Aug. 18, 1953.

It is an additional objective of the present invention to provide an airfoil with a passage of the type described having a novel deicing arrangement, which is effective to prevent the undesirable build-up of ice in the passage.

Briefly, the apparatus of the present invention includes a passage in the airfoil which is formed of opposed inner wall members, the inner Wall members being spaced to form an enlarged mouth opening at the pressure surface and a restricted nozzle opening at the suction surface. At least one of the wall members is movable, and preferably the upper wall member is formed of a series of articulated sections which are capable of being selectively moved toward and away from the opposed or lower wall member. With this construction, the cross sectional area of the passage may be easily adjusted to vary the mass flow of fluid through the passage, and thereby vary the velocity and effectiveness of the lift modifying stream of fluid exiting through the nozzle and tangentially onto the "ice suction surface. Also, of importance is the provision of an extensible join-t in said upper wall member, which allows a maximum adjustable range of movement of said wall member. As a result of this feature, the forwardmost articulated sections may assume in one limit position, a closing relationship across the mouth of the passageway to cut off the flow of fluid through the passage, and at the other limit of movement, the mouth is allowed to be wide open for maximum flow through the passage, as desired. Thus, in accordance with the present invention, the lift modifying passage may be fully opened for maximum mass flow during periods when high lift is required, such as during take off and landing; then the passage can be adjusted to assume an intermediate position for normal flight; and finally the passage can be fully closed whenever the lift modifying effect is not desired.

It should be noted that the adjustable lift modifying effect of the airfoil of the invention is gained without a change in the camber of the wing or a change in the rearward sweep of the wing, as has been proposed in the past, and the airfoil of the invention is accordingly of much simpler design for savings in cost and weight, which factors are of utmost importance in craft of this type. Furthermore, since the cross section and the position of the wing remain unchanged in the airfoil of the present invention, it is considered to be more reliable and not subject to the costly maintenance problems usually associated with these prior art variable shaped or variable sweep wing constructions.

In accordance with the other but related aspect of the present invention, the airfoil is provided with means for preventing the build-up of ice in the passage, thus insuring efficient operation of the apparatus under adverse weather conditions. Preferably, the working medium for the deicing system is supplied by the hot air exhaust or compressor bleed from the aircrafts engines and this air is directed first along the inside surfaces of the wall members forming the passage and then directed into the restricted nozzle of the passage where icing conditions are more prevalent. With this arrangement, it has been found that maximum ice prevention is obtainable along the entire length of the passage with a minimum amount of adverse turbulence being introduced into the stream of fluid passing through the passage. Furthermore, flap valves are provided on the orifices which introduce the heated air into the restricted nozzle to allow the proper proportioning of the heated fluid with the high velocity stream of air for maximum acceleration of said stream resulting from the mixing of the fluids.

In a modification of the deicing system of the present invention, continuous passageways are provided along the inside of the wall members forming the passage to confine the floW of heated air adjacent said wall member for maximum heat transfer. On the upper wall member, which, it will be remembered, has articulated sections in the preferred embodiment illustrated, this passageway is preferably formed by a series of articulated parallel deflectors interconnected to said sections by links for adjustable movement therewith.

Still other objects and advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description, wherein I have shown and described only the preferred embodiments of the invention, simply by way of illustration of the best modes contemplated 'by me of carrying out my invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modification in various obvious respects, all Without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.

In the drawings:

FIGURE 1 is a cross-sectional view of a preferred embodiment of the airfoil of the present invention having a lift modifying passage shown in the normal open mode of operation for normal lift modifying and anti-icing effects;

FIGURE 2 is a cross-sectional view of the airfoil of FIGURE 1 illustrating the closed mode of operation for no-lift modifying and maximum deicing efiects;

FIGURE 3 is a cross-sectional view of the airfoil of FIGURE 1 showing the operating mode for maximum lift effect on the airfoil;

FIGURE 4 is a detailed cross-sectional view taken along line 44 of FIGURE 3 showing the sealing arrangement at the edges of the wall members; and

FIGURE 5 illustrates a modification of the airfoil of the invention having continuous heated air passageways along the upper and lower wall members of the passage.

Referring now specifically to FIGURE 1 of the accompanying drawing, there is illustrated an airfoil having a leading edge 11 and a trailing edge 12; it being understood that said trailing edge 12 may lead to a valley of an undulating type airfoil such as shown in my previous patent or may terminate in a conventional trailing edge, as desired. In any case, the airfoil 10 has a conventional upper suction surface 13 and a lower pressure surface 14 extending between the leading and trailing edges 11, 12.

Any number of vertical ribs 15 (only one being shown in the drawing) are provided to afford stability to the airfoil construction, and if desired conventional lightening holes 16 may be incorporated in the interior areas, as illustrated. Bounded on the sides by adjacent ones of these ribs 15 is a slot-like passage 17, which extends substantially parallel to the flow of the slipstream across the airfoil 10 from a mouth 18 formed in the pressure surface 14 to an egress opening 19 formed in the suction surface 13. For ease of discussion, the passage 17 itself may be defined as having a forward accelerating section, generally designated by the reference numeral 20, and a restricted nozzle, generally designated by the reference numeral 21. As will be realized, during the operation the fluid entering the mouth 18 is accelerated over the lentgh of the forward section 20 and ejected at a high velocity through the nozzle 21 into the boundary layer region of the fluid flowing over the airfoil 10 for improving the lift on the airfoil 10.

The forward section 20 of the passage 17 is formed by an upper wall member 25, which in the preferred embodiment shown includes any number of articulated sections 25a-25d connected together by pivot hinges 26 and a lower wall member 27 which in the embodiment illustrated is fixed. It is contemplated that other types of movable wall structures could be utilized in lieu of the wall member 25 if desired in accordance with the broader teachings of the present invention, and that the fixed wall 27 could, if required, also be made to be adjustable.

In the preferred embodiment illustrated, each of the sections 25b, 25c, 25d is adjustably operated by any number of hydraulic cylinder units 30, 31, 32 (only one each being shown) that are connected in any suitable manner to the airfoil structure, as by a cross bar 33 carrier between the ribs 15. As shown, the forwardmost section 25a is preferably shorter than the remaining sections 25b25d and performs the important function of varying the width of the mouth 18. For example, note the position of the section 25a in the plane of the mouth 18 in FIGURE 1, thus limiting the cross sectional size of the same to that shown by the reference indicia M in this figure. Also, it should be noted that the forwardmost section 25a does not include aseparate operating cylinder and thus is operated as a follower, i.e. movement of section 25a is gained from the combined operation of the hydraulic cylinders 30, 31 to properly position the pivot hinges 26, as shown in the drawing. The hydraulic cylinders 30-32 are provided with suitable control means 34, which is interconnected by hydraulic lines 35, 36, 37 to the respective cylinders; said control means being capable of selectively positioning each section 25b-25d as required. The position of the wall member 25 as shown in FIGURE 1 can be considered to be the normal flight position with increased lift being provided by the airfoil 10 from the flow of fluid through the passage 17 as noted by the flow arrows in this figure.

As can best be seen in FIGURE 2, the rearwardmost section 25d includes an extensible joint, generally designated by the reference numeral 40, which allows the wall member 25 to expand whereby the passage 17 may be closed at the mouth 18 by deployment of the articulated sections 25a, 25b as shown. This position of the wall member 25 thus represents a limit position in the direction toward the fixed wall member 27 and is utilized when the lift modifying effects of the stream of fluid afforded by the passage 17 are not desired. At any intermediate position between the positions of FIGURES 1 and 2, a reduced amount of fluid flows through the passage 17 for reduced velocity in the nozzle 21 and a corresponding reduction in lift effect along the suction surface 13.

As shown in FIGURE 3, the control means 34 can, on the other hand, be effective to increase the lift effect by moving the wall member 25 to the full open position shown in FIGURE 3, wherein the maximum amount of fluid is scooped into the passage 17 for discharge at increased velocity through the nozzle 21. As shown, the forwardmost or follower section 25a is, in this position, removed from the plane of the mouth 18 thus increasing the size of the mouth 18 by an amount indicated by the reference indicia X so as to be coordinated with the increase in size of the passage 17. Thus, with this arrangement it can be seen an infinitely variable mass flow of fluid can be received, accelerated and directed through the restricted nozzle 21 for any desirable velocity flow from the egress orifice 19.

As best shown in FIGURES 3 and 4, the extensible joint 40 preferably takes the form of a reduced tongue 41 integrally formed with the rear half of the section 25d, which tongue works in a slot 41a formed in the forward half of said section 25d. Sealing strips 42 of molded nylon or other suitable material may be provided along the entire length of the edges of the articulated wall member 25 for cooperation with the adjacent rib 15 (note FIGURE 4) so as to confine the stream of fluid to the passage 17, as desired.

With reference once again to FIGURE 1 of the drawing, the deicing system for the leading edge 11 and the lift modifying passage 17 of the present invention will now be described. Thus, a blast nozzle 50 is positioned on the underneath side of the upper surface 13 and directed chordwise around the interior of the airfoil 10 so as to direct a flow of heated air in the direction shown by the flow arrows in this figure. The flow of air from the nozzle 50 may be regulated as desired by a suitable valve 52 which serves to interconnect the nozzle 50 with a suitable source of heated air 53, which for example, may be gained from the exhaust system of a piston engine, compressor bleed from a turbine engine, bleed from the aircrafts pneumatic system or any other suitable means carried by the aircraft. After the flow of heated air has passed over the entire surface of the wall member 25, it is received by a deflector horn 55 carried by the rear half of the section 25d and then directed through a fixed transfer passageway 56 and out a discharge orifice 57, which is located immediately upstream of the nozzle 21.

Similarly, the lower wall member 27 is provided with a suitable blast nozzle 60 for directing hot air along the same with a fixed transfer passageway 61 located adjacent a discharge orifice 62. These orifices 57, 62 are provided with suitable flap valves 63, 64, respectively, which are pivoted on the upstream side of their respective orifices so as to operate in response to the differential in pressure between the high velocity fluid stream in passage 17 and the pressure of the heated air exiting through the orifices 57, 62. These flaps valves 62, 64 allow the proper proportioning of the mixing fluids for maximum efliciency and are effective to maintain the desired laminar flow of fluid through the nozzle 21. This is so since, as shown by the flow arrows in FIGURE 3, the flap valves 63, 64 form an interface between the streams at the orifices 57, 62 so that when they join in the nozzle 21 they are both traveling substantially parallel to the longitudinal axis of said nozzle 21. It will be realized that the heated air entering the nozzle 21 not only serves the important function of preventing and/or removing the formation of ice along said nozzle 21, but also serves to give additional mass flow and velocity to the lift modifying stream of fluid exiting through the egress opening 19.

As shown in FIGURE 2, when the articulated wall member 25 is positioned in the lower limit position, the flow of fluid into the mouth 18 and the accelerating section 20 of the passage 17 will be cut off thereby allowing the flap valves 63, 64 to open to their full open position to cause the maximum flow of heated air through the nozzle 21. In this mode of operation the heated air will be effective to free the nozzle 21 of ice formations in the event that such should develop at any time during operation. After the nozzle 21 has been freed of ice in this position, the wall member 25 can be moved to the normal position of FIGURE 1 whereby maximum flight efliciency can be resumed.

During any mode of operation it may be desirable to terminate the flow of heated air to the nozzles 50 by closing the valves 52 whereupon the flap valves 63, 64 will assume their fully closed position (note dotted line position of FIGURE 3) thus allowing the maximum flow of unheated air from the pressure surface 14 to the suction surface 13.

In the modification of the deicing system shown in FIGURE 4, continuous passageways 70-, 71 are formed from the blast nozzles 50, 60, respectively, to channel the heated air immediately adjacent the respective surfaces 25, 27. Thus, the passageway 70 is preferably formed by an articulated series of deflector members 75a.- 75d corresponding to the articulated sections '25a25d with the sections being constrained for movement with the wall member 25 by provision of connecting links 76, which interconnect pivot pins 77 of the deflector member 75 with the corresponding pivot pins 26 of the wall member 25. Similarly, the blast nozzle 60 is connected to the transfer passageway 61 by a continuous deflector wall 78, as shown in this figure.

It should now be apparent to those skilled in this art that an adjustable lift modifying passage 17 has been provided with an efficient deicing system wherein a maximum amount of deicing is obtained with a minimum amount of disturbance of the laminar flow of fluid in the passage 17. Further, since the heated air is introduced directly into the nozzle 21, the maximum amount of deicing etfect can be obtained in this critical area. Also, of course, as pointed out above, the introduction of the heated air into the nozzle tends to increase the velocity and mass flow of the fluid thereby improving the overall operation of the lift modifying passage 17.

In this disclosure, there is shown and described only the preferred embodiments of the invention, but, as aforementioned, it is to be understood that the invention is capable of various changes or modifications within the scope of the inventive concept.

I claim:

1. In an airfoil having leading and trailing edges and relatively fixedly spaced suction and pressure surfaces extending between said edges, the improvement comprising a passage in said airfoil extending substantially parallel to the fluid flow relative to said surfaces of said airfoil, said passage being formed by opposed inner. wall members in said airfoil, said wall members being spaced to form an enlarged mouth opening through said pressure surface and a restricted nozzle opening through said suction surface so as to form a high velocity stream of fluid and direct the same tangentially along said suction surface whereby to cause said fluid flow to follow said suction surface, at least one of said wall members being movable toward and away from the other wall member and means for selectively moving said one wall member whereby the cross sectional area of said passage may be adjusted to vary the mass flow of fluid through said passage and the velocity of said stream exiting through said nozzle, said wall members being located at all times wholly between said relatively fixedly spaced surfaces, and one of said wall members being disposed for movement into and from closing relation with respect to said mouth opening.

2. The combination of claim 1 wherein said one wall member includes articulated sections and an extensible joint whereby said mouth may be closed by at least one of said sections when said one wall member is moved to the limit position toward said other wall member.

3. The combination of claim 2 wherein the forwardmost one of said sections is a follower section positionable in response to the movement of the second in-line section, said follower section being positionable across a portion of said mouth to vary the size thereof in accordance with the adjusted size of said passage.

4. In an airfoil having leading and trailing edges and relatively fixedly spaced suction and pressure surfaces extending between said edges, the improvement comprising a passage in said airfoil extending substantially parallel to the fluid flow relative to said surfaces of said airfoil, said passage being formed by opposed inner wall members in said airfoil, said wall members being spaced to form an enlarged mouth opening through said pressure surface and a restricted nozzle opening through said suction surface so as to form a high velocity stream of fluid and direct the same tangentially along said suction surface whereby to cause said fluid flow to follow said suction surface, at least one of said Wall members being movable toward and away from the other wall member and means for selectively moving said one wall member whereby the cross sectional area of said passage may be adjusted to vary the mass flow of fluid through said passage and the velocity of said stream exiting through said nozzle, said wall members being located at all times wholly between said relatively fixedly spaced surfaces, and one of said Wall members being disposed for movement into and closing relation with respect to said mouth opening, means defining an orifice opening into said passage immediately upstream of said nozzle, means communicating with said orifice for introducing heated air into said nozzle to prevent the formation of ice, a flap valve for cooperating with said orifice to open and close the same, said valve being pivoted at its upstream edge so as to be responsive to the differential in pressure between said heated air and said high velocity stream.

5. The combination of claim 4 wherein said orifice communicates with the interior of said airfoil and said means for introducing heated air includes a blast nozzle positioned in said interior to direct heated air chordwise around the inside of said leading edge and back along said one wall member and deflector means for receiving said heated air and directing the same through said orifice.

6. In an airfoil having leading and trailing edges and relatively spaced suction and pressure surfaces extending between said edges the improvement comprising a passage in said airfoil extending substantially parallel to the fluid flow relative to said surfaces of said airfoil, said passage being formed by opposed inner wall members in said airfoil, said wall members being spaced to form an enlarged mouth opening at said pressure surface and a restricted nozzle opening at said suction surface so as to form a high velocity stream of fluid and direct the same tangentially along said suction surface whereby to cause said fluid flow to follow said suction surface, deicing means for preventing the formation of ice along said Wall members including first and second blast nozzle means on the interior of said airfoil for directing heated air along the inside surfaces of said wall members, first and second orifices formed in the respective wall members immediately upstream of said nozzle for introducing said heated air into said nozzle whereby maximum ice prevention is obtainable along the length of said passage with flow of said heated air in said passage only through said nozzle.

7. The combination of claim 6 wherein are further provided first and second flap valves for cooperating with the respective orifices, said valves being pivoted at their upstream edge so as to be responsive to the difiFerential in pressure between said heated air and said high velocity stream, and means for adjusting the cross section of passage and said mouth to limit said stream and allow increased flow of heated air through said nozzle.

8. The combination of claim 7 wherein said adjusting means includes at least one of said wall members, said one wall member being formed of articulated sections, means for selectively moving said sections of said one wall member toward and away from the other wall member, and an extensible joint in said one wall member, whereby said mouth may be closed by at least one of said sections when said one wall member is moved to the limit position toward said other member.

9. The combination of claim 7 wherein is further provided means for forming first and second continuous passageways along the inside of said one and said other wall members, respectively, to confine the flow of said heated air adjacent said wall members.

10. The combination of claim 8 wherein is further provided means for forming first and second continuous passageways along the inside of said one and said other wall members, respectively, to confine the flow of said heated air adjacent said wall members, said means for forming said first passageway including a series of articulated deflectors connected to said sections for adjustable parallel movement therewith.

References Cited UNITED STATES PATENTS 2,557,829 6/1951 Lavelle 24442 2,678,784 5/1954 Lanier 2444'2 3,326,500 6/1967 Lanier 244-42 MILTON BUCHLER, Primary Examiner. JAMES E. PITTENGER, Assistant Examiner.

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