US3104680A - Supersonic nozzle - Google Patents

Description

Sept. 24, 1963 Filed Jan. 19, 1962 W. J. ORLIN SUPERSONIC NOZZLE 4 Sheets-Sheet I INVENTOR. WILLIAM J. ORLlN ATTORNEY AGENT Sept. 24, 1963 w. J. ORLlN SUPERSONIC NOZZLE Filed Jan. 19, 1962 4 Sheets-Sheet 2 NJ *LIL Y Q INVENTOR.

WILLIAM J.0RLIN ATTORNEY Mm fl x,

AGENT Se t. 24, 1963 w. J. ORLIN 3,104,680

SUPERSONIC NOZZLE Filed Jan. 19, 1962 4 Sheets-Sheet 5 \=QIN\ #3 d a I 2 4 :21 A 3 8 4 Q w fi g m S O m INVENTOR. WILLIAM J. ORLIN ATTORNEY AGENT Sept. 24, 1963 w. J. ORLIN SUPERSONIC NOZZLE Filed Jan. 19, 1962 4 Sheets-Sheet 4 INVENTOR. WILLIAM J. ORLI N AGENT United States Patent 3,104,680 SUPERSONIC NOZZLE William J. Orliu, Box 871, Dayton, Ohio Filed .l'an. 19, 1962, Ser. No. 167,369 9 (Ilaims. (Cl. 138-45) This is a continuation-in-part application of my copending patent application, Serial No. 595,549, filed July 2, z195 6. This invention relates to supersonic nozzles and, more particularly, to nozzles suitable for use in wind tunnels for controlling the flow Mach number variation to produce uniform, shock free flow at supersonic speeds in such tunnels.

Examination of the prior art establishes the fact that a great diversity of supersonic nozzle configurations have existed for many years. However, all of these devices for converting the thermal energy of a gas into flow energy at supersonic velocity have evolved from a single basic concept-that of providing flow boundary Walls compatible with the requirements of theoretical gas dynamics. The aforementioned well known theory predicates a converging flow passage in which there are smooth contour boundaries extending from the highest pressure region to a minimum area section (designated as the throat) and continuing downstream therefrom as a di vergent passage in such manner that the cross section area continuously increases to a maximum value at the exit, while simultaneously providing the necessary boundary contour shape to properly'cancel all disturbances arising from this flow expansion process. Thus, a supersonic nozzle will be useful for Wind tunnel application only insofar as it succeeds in accomplishing the process just described, thereby providing a gas stream in the test region of uniform velocity, pressure, and temperature. A number of mathematical and graphical methods have been applied to the design of such passages or channels and these have resulted in numerous mechanical arrangements to achieve the calculated aerodynamic boundaries. The generalized solutions fall into two main categories designated two-dimensional or three-dimensional and characterized respectively by expansion of the flow downstream of the throat in one plane only (x, y) or spatially (x, y, z coordinates); the former is illustrated by square or rectangular nozzles having a pair of plane parallel opposite Walls while the latter is illustrated by conical or pyramid shaped nozzles (usually of square or round cross section). Further, both main categories may be subdivided into variable or fixed types depending on whether or not provisions are incorporated in the design to adjust the flow passage areas and hence obtain a series of aerodynamically correct nozzle shapes with a single mechanical contrivance; examples of three-dimensional variable nozzles include cylindrical rubber sleeves which are contorted to the desired shape by means of multiple screw-jacks or tension bands, and plug designs which axially translate a rigid contoured body to alter the flow area; two-dimensional variable nozzles are exemplified by contoured walls comprising combinations of rigid and flexible segments ranging from entirely flexible (or spring) walls formed to shape by jacks, to entirely rigid contours which are either pivoted or translated with respect to each other.

Heretofore, variable supersonic nozzles, both automatic and manual, have been employed in wind tunnel facilities for some time. Two important advantages of such nozzles, multiple Mach number testing with a given test setup and greatly increased facility utilization, quickly ofiset the relatively high initial cost of the adjustable nozzle installation. However, it is apparent there can be no significant compromise with either reliability of operation or aerodynamic quality of flow.

The two types of adjustable nozzles used in major wind tunnel facilities are the asymmetric sliding block nozzles and the completely flexible wall nozzles. In the former type, Mach number variation is obtained by changing the relative position of two fixed contours. The wall shapes of the fixed contours are correct for two Mach numbers only, although experimental results indicate that satisfactory flow may be obtained at intermediate values and, also, slightly above and considerably below the design range. However, this type of nozzle is very much longer than symmetrical nozzles because all expansion waves originate on one Wall and all cancellation is accomplished on the other wall. Also, a formidable problem is introduced in free jet application because of jet exit dissymmetry resulting from translation of the nozzle block.

The latter type of nozzle offers the possibility of obtaining the required nozzle contours at all Mach numbers and under all flow conditions. In this type the plate thickness and jack spacing are fixed by the maximum allowable slope between jack stations consistent with the required flow quality. If the number of jacking points and hence mechanical complexity are kept to a minimum, the flexible plate must he thick, with the result that the minimum allowable bending radius (and therefore nozzle length) is increased. Manufacturing, control and calibration problems associated with the completely flexible nozzle are complicated; the possibility of mechanical or electrical failure leading to permanent distortion of the flexible Wall is ever present. It is also possible that considerable loss of operating time might result because of minor control system difliculties. It is apparent, therefore, that the former type of nozzle is characterized by compromising aerodynamics and simple control, while the latter type of nozzle presents complicated control and good aerodynamics.

The purpose of the present invention is to provide a symmetrical, supersonic nozzle that offers combining of good flow quality, i.e., Mach number and flow direction, and simple control.

The supersonic nozzle constructed according to the present invention is further adapted to be employed in connection with supersonic wind tunnels for free jet testing of air breathing engines, and is, also, adapted to provide continuous and rapid variation of Mach number for transient testing over a broad range.

The present invention further provides a nozzle with a symmetrical nozzle exit configuration at all Mach numbers to avoid jet boundary disturbances in the region of the air breathing engine inlet and with a short nozzle length to permit angle of attack variation which is especially necessary because of the impracticability of pitching the test engine to high angles of attack.

The present invention specifically relates to two-dimensional variable nozzles and, more paiticularly, to the type which employs 'com'b-ined rigid and flexible Walls to attain flo-w passage area variations. There is presented a completely new principle of operation and mechanism for attainment thereof. Said principle utilizes a contour generating unit (movable Wall) consisting of a formed rigid upstream portion (designated as scoop inlet segment) and an integrally attached flexible plate downstream portiton arranged in such manner that as the scoop inlet segment moves in circular arc motion about a fixed pivot point, thereby changing the throat area, the flexible plate automatically elastically deforms in accordance with the required aerodynamic cancellation shape. The aforementioned arrangement refers to the pivot point location and flexible plate end conditions (both upstream and downstream extremities) which are exactly defined by the design methods of this invention and therefore not amenable to arbitrary disposition. Thus, variation of exit Mach number is achieved solely by rotation of the scoop inlet segment about a fixed center without any requirement for screw-jacks or other complicated positioning devices on the flexible plate. For simplicity of ex )lanation, the above description or" the operating principle of the present invention mentions only one contour gen erating unit since a nozzle may be so constructed (having -a third plane Wall perpendicular to the two plane parallel opposite walls); however, it is to be clearly understood that the invention primarily relates to a configuration employing two identical con-tour generating units symmetrically disposed about a centerplane and moving simultaneously toward and away from each other; this latter configuration is solely referred to in the invention application since, in view of the above, it also embraces the reflection plane (single contour generating unit) design.

The nozzle of the present invention is also characterized by its symmetry of flow for the possibility of flow angularity deviation is minimized since geometric symmetry is maintained throughout the operating range, and is further characterized by its minim-um length since the flexible wall section or plate origin-ates at or downstream of the inflection point of the nozzle wall curvature and therefore the throat section curvature and initial expansion are dictated by aerodynamic considerations only.

Also, the present invention provides a supersonic nozzle in which the pivot point location of the rigid walls and the flexible wall section end conditions may be obtained by several convenient papa-meters that optimize the nozzle wall contours during calibration.

The nozzle of the present invention is further characterized by its simplicity of control which is obtained solely by symmetrical rotation of the scoop inlet segments about their pivot by a single power actuator or mechanism connected thereto.

These and other features of the present invention are described in detail below in connection with the accompanying drawings in which;

FIG. 1 is a diagrammatic showing of a contour generating unit of the type utilized with the invention;

FIG. 2 is a diagrammatic showing of a nozzle embodying the present invention;

FIG. 3 is a longitudinal sectional view partly in elevation showing a nozzle embodying the present invention positioned in a wind tunnel section;

FIG. 4 is a schematic top plan view of the nozzle of FIG. 3;

FIG. 5 is a fragmentary enlarged transverse section of the nozzle taken substantially on line 55 of FIG. 3; and

FIG. 6 is an enlarged end elevation of the nozzle of FIG. 3.

Referring now in detail to the drawings wherein like numerals designate like parts throughout the several views, there is generally illustrat d at 1d the contour gencrating-unit of the invention which unit includes several distinct components which in their specific relationship define an improved composite unit forming the basis of the invention, and when taken together with an actuation meohanism (hereinafter described) comprises a completely new automatic supersonic nozzle system. Thus referring to FIG. 1, the airflow surface of the contour generating unit It consists of an 'aerodyna-mically shaped rigid portion or scoop inlet segment 12 and a flexible portion or flexible plate 18 shown integrally formed from a solid block of metal (since this is desirable from the structural viewpoint). Securely attached to the scoop inlet segment 12 are the pivot arm 54 with sidewise projecting shaft 56 and wiper seal 86 while at the downstream end of the flexible plate 18, slidable support means are provided at 58. The overall nozzle configuration, therefore, consists of two such. contour generating unit assemblies as shown in FIG. 2 symmetrically arranged about the centerplane AA and which may be contained in a box-like structure (as will be described hereinafter) so that there is minimum clearance between the movable walls (constituting segments 1") and the two plane parallel opposite side walls which, as previously discussed, are

characteristic of the two-dimensional type nozzle; also it is to be noted here that the box enclosure is pressure-tight and that the top and bottom of said enclosure also serve as mounting bases for mechanism components which engage the flexible slidable support means 58 and the wiper seal 86. The method of operation by which the contour generating units or movable Wall assemblies generate rethe flexible plate juncture point P. However, the down 1 stream extremity of the flexible plate 13 is constrained to move in an axial direction only (parallel to centerpl'ane AA), and, therefore, the slope and ordinate will remain unchanged. Now, it can be shown by mathematical analysis that (for small deflections within the elastic theory) the slope and ordinate at both ends of a flexible plate are sufflcient to completely define the generated smooth curve. The present invention utilizes this natural plate bending property through selection of the geometrical parameters of pivot point location (which determ nes motion of point P) and length of flexible plate 13 in such manner as to obtain coincidence between the generated elastic shape and the required aerodynamic contour throughout the operating range. The necessity for slidably supporting the downstream end of flexible plate 18 at 58 is apparent since point P is displaced axially when moving in a circular are about the pivot, and the projected length of the lexible plate is dependent upon the generated curve; the combined effect is to cause the flexible plate end at 58 to move in a downstream direction as the throat is closed (i.e., scoop inlet segment rotates toward centerplane). Further, the wiper seal 35 acts as an essential component of the movable wall assemb-ly since it serves in conjunction with a mating member of the enclosed box structure) to prevent high pres sure air leakage into the region behind the flexible plate, irrespective of the angular position of the scoop inlet segment 12. In the diagrammatic view of FIG. 2, the nozzle box frame 2? is shown with one side wall removed and with the symmetrical pair of contour generating units at 12 in a high Mach number operating position; it is evident that additional angular motion would cause the upper and lower scoop inlet segments 12 to come into contact at the centerplane A-A thereby closing the throat, while rotation in the opposite direction effects a progressively open throat reaching a limit of operation cone spending to a straight flexible plate condition (utilized for the lowest design Mach number).

Referring to the drawings and in detail to the several components of the inventive contour generating unit 10', thEIE 'EllIC described herein certain additional important features which are essential to the overall operation of the invention. The component constituting the scoop inlet segment 12 for-ms the rigid upstream portion of the inventive contour generating unit It} and extends across the full width of the air passage perpendicular to the plane parallel opposite walls of the box frame 28 mounting said contour generating unit 19. One of said walls is illustrated at 23 in FIG. 2-; said component 'isfreely movable between said parallel walls having its edges in the closest possible proximity thereto without actual rubbing contact. The airflow surface of the scoop inlet segment 12 is contoured in such manner as to provide a gradual, loss-free transition from the very low subsonic entrance velocity of the gas stream to the supersonic Each angular position of the scoop velocity at the start of the flexible plate 18; thus, as shown in FIG. 2, all angular positions (identical for upper and lower scoop inlet segments since these are synchronized by an external drive system) will resu t in simultaneous formation of a convergent passage 1-!- and a divergent passage 16. Although not specifically limited thereto, the aforementioned airflow contour of the scoop inlet segment 12 is generally a continouus composite curve consisting of a circular arc upstream lip, an ellip tical segment which extends to the vicinity of the throat region, and a downstream portion defined by a cubic (or higher order) equation. This latter portion of the surface contour of segment 12 is of particular importance in the design method since the supersonic expansion waves originate thereon and consequently determine the flexible plate bending curves necessary for complete uniform flow at the exit; two distinct design variations are herein presented and, in constnuctin a nozzle embodying the subject invention, the selection of one or the other will be established by the desired Mach number operating range. If the desired range includes sonic velocity (Mach number 1.0) and does not exceed approximately Mach number three, the optimum design configuration would be one in which the curve defined by the cubic (or higher order) equation extends to the downstream tip of the scoop inlet segment 12, having zero curvature at this point (point P, FIG. 1) and being convex to the flow along its entire length; the flexible plate originates at this tip (matching ordinate and slope at the airflow surface) and, for values of Mach number greater than unity, would present a concave airflow surface thereby causing an inflection point to exist at the juncture of scoop inlet segment 12 and flexible plate 21$. The second design variation applies when the desired Mach number range is entirely supersonic, and results in an optimum configuration for which the expansion curve terminates at a definite distance (depending on the design range) upstream of the flexible plate originagain, the expansion curve is arranged so that the curvature is zero at the terminal point and the surface is convex to the flow upstream therefrom; however, in this instance, an additional cubic (or higher order) curve (determined by theoretical supersonic flow characteristics methods) is provided between said terminal point and the downstream tip of the scoop inlet segment 12, disposed in manner directly opposite to the first curve but continuous therewith (i.e., matching slope and ordinate, concave to the airflow, and having zero curvature at its upstream end) thereby causing an inflection point to exist on the surface of the rigid contour at the merging point of the aforementioned curves; the flexible plate will originate at point P (FIG. 1), matching the slope and ordinate of the terminal curve just described, and will thus present a continuous concave airflow surface downstream of the inflection point. In summary, the airflow surface contour of the scoop inlet segment 12 as well as the general overall proportions of the contour generating unit it) are fundamentally established by the intended Mach number range of the nozzle. Utilization of the scoop inlet configuration of this invention provides excellent subsonic airflow velocity distribution in the contraction region l t thereby contributing significantly to achievement of uniform, shock free supersonic gas flows; the projecting upstream lips or" the scoop inlet segments 12 allow favorable streamline adjustment and attachment of the approaching airflow, thus avoiding possible separation and other undesirable effects normally associated with intake of the thick boundary layer existing on the plenum inlet walls. An additional very important advantage is realized as a consequence of the symmetrical angular movement of the scoop inlet segments 12 since, as the opposing airflow contours approach one another (throat closing), the minimum area plane continuously relocates in an upstream direction to provide a longer supersonic 6 expansion region as is inherently required by gas dynamics theory.

The flexible plate components 18 of this invention are arranged to automatically bend (within the elastic range of the metal) in such manner as to provide identical but opposite (mirror images about the centerplane A-A) continuous concave airflow surfiace contours compatible with each value of the throat height (and hence nozzle exit Mach number, since the exit height remains constant), said required airflow surface contours for each Mach number being determined by well known theoretical graphical-analytical methods. Automatic bending of the flexible plates 18 is accomplished solely by rotation of the scoop inlet segments 12 about the pivot shaft centers 56, thus completely eliminating the need for jacks or other devices affixed to said plates intermediate of their ends. As noted previously, each flexible plate 18 is rigidly attached at its upstream end to the respective scoop inlet segment (preferably machined integral therewith) forming a smooth continuation of the airflow surface thereon; hence, angular displacement of the scoop inlet segment 12, which is constrained to move in a circular path by the pivot arm 54 securely attached thereto, results in the flexible plate origin point P (FIG. 1) describing a portion of a circular arc with radius equal to the distance between point P and the center of respective pivot shaft 56. Further, the downstream end of the flexible plate has an integral rigid block formed thereto, as indicated at 18a, said block being slidably supported to move parallel to the centerplane A-A only as by means of slidable support means 58, thereby causing the slope and ordinate (distance from the centenpl ane AA) of the downstream extremity of the flexible portion of plate 18 to remain fixed while allowing unhindered longitudinal mo tion (of this extremity) as the scoop inlet segments -12 pivot on the shafts 56. Now, by applying the theory for elastic bending of thin, constant thickness plates, it is found that the above-described arrangement for restraint of the ends of flexible plate 18 will result in continuous curves, everywhere concave to the air stream and properly shaped, as required by the aerodynamic design, providing the length of flexible plate 18 and scoop inlet segment pivot point location are properly selected; exact selection of these parameters is dictated by the desired Mach number operating range of the nozzle. In general, the pivot point must be located so that the flexible plate 18 will be straight (and parallel to the centerplane A-A) for the lowest value of Mach number in the design range and, further, must be longitudinally confined to the middle third of the flexible plate length; this latter condition is theoretically necessary to prevent occurrence of an inflection point intermediate of the flexible plate ends. In the above description, the flexible plate was assumed to be of constant thickness throughout its length and such configuration has been found to be entirely satisfactory in practice; however, this restriction is not required since the design method can be extended to include longitudinally tapered (and other) plates when some advantage might accrue. Referring again to the constant thickness design, the actual value employed will be determined by the maximum operating pressure level and the allowable yield stress of the metal. In summary, the flexible plate 18 of this invention is rigidly attached to the downstream tip of the scoop inlet segment 12, contains an integral block 18a at its downstream extremity which is slidably supported at 58 from the nozzle box enclosure, and is completely devoid of jacking or other I positioning devices intermediate of its ends; the exact overall length and thickness are determined by the operating requirements (principally, Mach number range and maximum pressure). Said flexible plate 18 is caused to bend elastically solely by controlled angular displacement of the scoop inlet segment 12 about the pivot 55; proper location of said pivot center results in elastic bending curves which precisely match the required theoretical aerodynamic contours. Further, as discussed hereinafter, the pivot shafts 56 serves an additional primary function of structural aspect, being the means of transmitting the very high longitudinal pressure forces (which exist on the adjustable surfaces of all variable nozzles) into the enclosing box structure; since the pivot shafts 56 are mounted in high capacity anti-friction bearings, the contour positioning actuation mechanism to be utilized therewith is completely relieved of loading from the aforementioned source.

The wiper seal 36 provides a gas seal in the chamber of the inventive nozzle at the nozzle inlet in order to prevent application of the high pressure therein to the underside of the flexible plate 18. Said seal is rigidly attached to the underside of the scoop inlet segment 12 and extends full width thereof and contains a smooth, curved downstream face 86:: which is a portion of a circular arc having its center coincident with that of the pivot shaft 56. Engaging this seal face 36a is a wiper plate 88 (with suitable pressure packing material in its upstream edge) fastened to the nozzle box enclosure 28 and extending fully between the opposite parallel side walls thereof. The seal thus formed is independent of the angular position of the scoop inlet segment 12 during actuation thereof about the pivot center 56. An equally important function of the wiper seal component 86 is associated with its effect on aerodynamic forces as follows: The contour generating unit 14? is subjected to pressure forces induced by the airflow; the pressure in the flow passage 14-46 decreases continuously from the scoop inlet lip to the nozzle exit, whereas the reverse side of the contour generating unit ltl experiences the highest system pressure in the region upstream of the wiper seal face She and a very low value downstream therefrom. Integration of these surface pressures over the entire perimeter of the contour generating unit it) yields a resultant force and moment at the pivot shafts 56; the force is transmitted directly to the nozzle box enclosure 28; however, the moment resulting therefrom is applied to the actuation mechanism. The desirability of minimizing said moment throughout the operating range is obvious, and this can be effectively accomplished by judicious longitudinal location of the wiper seal 86 and related wiper plate 83.

The previously-referred to actuating mechanism may include an external drive mechanism for actuating the scoop inlet segments 12 in symmetrical motion toward and away from one another thereby generating the required supersonic nozzle airflow passages. It is evident that numerous such mechanisms can be utilized. For example, separate hydraulic cylinder actuators (one for each contour generating unit) could be attached between the underside of the scoop inlet segment 12 (adjacent to the seal plate) and the nozzle box enclosure 28, being operated synchronously by suitable controls. Again, actuation might be accomplished solely through the pivot shafts 56 by having said shafts extend through one of the box enclosure side walls and affixing thereon a synchronized power driven gear system. Thus, the specific choice of actuating mechanism will depend largely on the particular nozzle application. However, a precise micro-adjusting type system, suitable for high pressure nozzle operation, is described in detail hereinafter and forms part of the subject invention. It is important to note here that said mechanisms all reflect the inherent simplicity of the contour generating unit operating principle of angular motion about a fixed center; as a consequence, and especially in view of the pressure balancing action of the wiper seal 86, a supersonic nozzle constructed according to this invention will permit extremely rapid traverse of the Mach number range, thereby providing transient test capabilities not heretofore available.

FIGS. 3 and 4 illustrate a practical stnuctural arrangement of the supersonic nozzle embodying the present invention, wherein the nozzle has been mounted in a test chamber of a wind tunnel for operation. The contour generating units 10 of the nozzle are arranged in vertically.

spaced relation between two fixed side plate Walls 22, 23 having parallel surfaces. A top plate Wall 24 and a bottom plate wall 2% extending between and connectcdto the side walls 22, 23 form a rigid box frame 28 for supporting the contour generating units 10 in the test section 29.

At the upstream end of the box frame 28, the side plate walls 22 and 23 are formed with curved end edges and are further arranged to abut fairing plates 30 mounted in the wind tunnel test section 20 and rigidly held in place by base plates 32 bolted to the fairing plates 30' and to the walls of the test section 20 as by bolts 36 as shown in FIG. 3. At the downstream end, the box frame 28 is arranged to extend through an opening 38 in a bulkhead 4% of the test section 29, and on which hulkhead 4% the box frame 28 is pivotally mounted by pins 4-2 extending through lugs 44 and pivotally engaging the or decreasing the angle of attack of the nozzle, particularly useful in testing jet engines or the like. The top and bottom walls 24 and 26 of the box frame 28 are further provided with seal blocks 48, which blocks 48 are aligned with the bulkhead opening 38 and are formed with a curved surface 54 arranged to engage seal plates 52' attached to the bulkhead 49 thereby sealing off the test section 2i) and, therefore, preventing any fluid flow through the opening 38 around the outer surfaces of the box frame 28 to spoil the fluid flow at the exit of the nozzle.

The walls 10 of the nozzle are further provided with arms 54 attached to the scoop inlet segments 12 pivotally mounted on the side walls 22, 23 as at 56 for pivotally supporting the scoop inlet segments 12 for rotational movement to various positions, for example, such a position as shown by the dotted line in FIG. 3, for obtaining Mach number variations. The flexible wall sections 18 of the contour generating unit 10 are slidably supported by rollers 58 at the downstream ends thereof, which rollers 53 engage tracks 66 provided on the inner sides of the top and bottom walls 24, 26, respectively, of the box frame 28, as shown in FIGS. 3 and 6.

It is apparent, therefore, that longitudinal flexing of the flexible wall sections or plates 18 is obtained by the simple rotational movement of the scoop inlet segments 2 about the fixed pivot centers 56, while the free ends of the flexible wall sections '18 are slidably guided by the rollers 58 in the tracks 60.

Rotation of the nozzle walls 10 about their pivot centers 56 for a simultaneous positioning thereof to a wide range of settings for continuous Mach number variation control is obtained by a single power actuator 62 consisting of a pair of drive lead screws 64 mounted on the outer side of the side plate walls 22 and 23 as shown in FIGS. 4 and 5. As shown in detail in FIG. 5, each lead screw 64 formed with an upper right hand and a lower left hand threaded portion is arranged to be driven by either manual means (not shown) or by a motor 66 through a gearing system 68 arranged in any well known manner.

Each drive lead screw 64 is further provided with a pair of internally threaded slides 70 arranged for simultaneous movement toward and from one another by rotation of the drive lead screw 64. The slides 70 are further connected to a pair of slide blocks 72 by pins 74 extending through openings 76 in the side wall 22 for movement of the slide blocks 72 with the lead screw slides 70. The slide blocks 72 slidably arranged between the side walls 22 are connected to their respective scoop inlet segments 12, for movement therewith by pins 78 extending through openings in the slide blocks 72 and through openings in arms 80 fixedly attached to the scoop inlet segment 12 as shown in FIG. 5. The lead screws 64 are, also, synchronized by idler gears 82 only one of which is shown as in FIG. 5.

In order to prevent air leakage from the sides of the nozzle, the edges of the contour generating unit abutting the fixed side plate walls 22, 23 and the fairing side plates are formed with grooves that function as labyrinth seals 84 providing minimum clearance with the inner surfaces of the side walls 22, 23 and the fairing plates 30. In addition, the wiper seals 86 attached to the contour generating unit similarly employ labyrinth seals along their. edges and provide minimum clearance on the inner surfaces of the fairing plates 30. Also, the wiper seals frictionally engage seal plates 88 attached to the upstream edges of the side plate walls 22, 23 as shown in FIG. 3. Air leakage is therefore prevented by sealing along all the moving parts of the nozzle as just set forth above. Also, the nozzle walls 10 may be provided with side spacing rollers 90 mounted on the sides of the scoop inlet segment 12 as shown in FIG. 3.

The specific mechanism and arrangements have been described above for purposes of illustration only and the present invention is not intended to be limited by this description or otherwise except as defined in the appended claims.

I claim:

1. A symmetric supersonic nozzle comprising a pair of walls arranged in spaced relation defining a fluid flow passageway, said walls each having a rigid section incorporating a scoop inlet and a pivot center extending from a point adjacent the upstream end of said passageway downstream to a flexible section integrally formed at its upstream end with said rigid section and terminating in a slidably supported downstream end, said walls having predetermined curvatures each characterized by an inflection point formed upstream of the juncture between said rigid and flexible sections and forming a subsonic contraction and a supersonic expansion section in said passageway, and a single power mechanism connected to said rigid wall sections for simultaneously moving said walls toward and from one another for varying the crosssectional area of said sections thereby controlling the Mach number variation of the fluid flow, said single power mechanism comprising a pair of drive lead screw elements integrally formed in spaced relation to each other and incorporating, respectively, right hand and left hand threaded portions, an internally threaded slide element in adjustable engagement on each of said pair of screw elements for simultaneous movement toward and from each other on rotation of said drive screw elements, a slide block element pin-connected to each of said slide elements for movement therewith and an arm element affixed to each of said walls and pin-connected to each of said slide block elements for movement of said walls towards and from one another on simultaneous operation of said pair of drive lead screw elements.

2. A variable nozzle suitable for producing uniform, shock free fluid flow at supersonic speeds comprising a pair of fixed parallel walls, a pair of movable rigid walls of preshaped contour arranged in spaced relation, defining with said fixed walls a fluid flow passageway of varying cross section, said rigid walls each incorporating an inflection point and being of preshaped contour forming upstream curved inner surfaces, and a pair of flexible walls extending from said rigid walls from a point originating at or a predetermined distance downstream from the inflection point, said rigid Walls arranged for pivotal movement toward and from one another, and said flexible walls integrally formed with, and as a continuation of, said rigid walls, said flexible walls each terminating in a downstream end portion slidably positioned relative to said fixed parallel walls and accordingly arranged for automatic flexing compatible with pivotal movement of said rigid walls thereby forming downstream flow surfaces with a reverse curvature with respect to the upstream flow surfaces for achieving uniform fluid flow in said nozzle and control means for effecting pivotal movement of said rigid walls towards and from one another thereby simultaneously automatically flexing said flexible walls, said control means comprising a pair of oppositely threaded relatively elongated power-actuated main control elements arranged for simultaneous movement in opposite directions, pin-connected interconnecting elements operatively connected between each of said pair of main control elements and each of said pair of walls for effecting simultaneous pivotal movement of said walls towards and from each other, said variable nozzle adapted for mounting within a wind tunnel having fixed, parallel side wall surfaces, and top and bottom wall surfaces extending therebetween and interconnected with said side wall surfaces to form a rigid box-like structure housing said nozzle in supported relation therewithin, additional pivot means at the downstream end of the wind tunnel pivotally mounting the downstream end of said box-like structure, and means for pivoting said box-like structure and the nozzle carried therewithin to a variety of angularly related positions corresponding to a plurality of angles of attack.

3. A variable transonic nozzle having a pair of fixed and parallel side walls enclosed within top and bottom walls, said nozzle comprising a pair of spaced rigid walls housed within said fixed walls defining the fluid flow passageway, said rigid walls having a curved inlet section and an outlet section of similar curvature forming a continuous convex surface, a pair of flexible walls integrally attached to said rigid walls forming a concave downstream extension thereof and establishing a point of inflection at the juncture of the rigid and flexible walls, said rigid walls incorporating integrally attached arms pivotally supporting said rigid walls on said fixed walls at pivots located in predetermined manner intermediate of the ends of said flexible walls, and said flexible walls slidably supported at the downstream ends thereof on said fixed walls, whereby said rigid walls may be rotated for movement toward and from one another thereby flexing said flexible walls to form the desired aerodynamic curvature, and power actuated means for moving said combined rigid and flexible walls pivotally toward and from one another.

4. A variable supersonic nozzle having a pair of fixed and parallel side walls enclosed within top and bottom walls, said nozzle comprising a pair of spaced rigid walls housed within said fixed walls defining the fluid passageway, said rigid walls having a curved inlet section and an outlet section of reverse curvature with respect to said curved inlet section forming a point of inflection therebetween, a pair of flexible walls integrally attached to said rigid walls forming a downstream extension thereof beginning at a point originating a predetermined distance downstream of the point of inflection, said rig-id walls incorporating integrally attached arms pivotally supporting said rigid walls on said fixed walls at pivots located in predetermined manner intermediate of the ends of said flexible walls, and said flexible walls slidably supported at the downstream ends thereof on said fixed walls, whereby said rigid walls maybe rotated for movement toward and from one another thereby flexing said flexible walls to form the desired aerodynamic curvature, and power actuated means for moving said combined rigid and flexible walls pivotally toward and from one another.

5. A two-dimensional variable supersonic nozzle including a contour generating unit comprising a rigid scoop inlet segment, a pivot arm rigidly attached to the downstream end of said scoop inlet segment, transversely extending pivot shaft means pivotally supporting the end of said pivot arm for pivotal movement of said scoop inlet segment about a fixed center, a flexible plate rigidly attached at the upstream end thereof as a continuation of said scoop inlet segment, and slidably supported rigid block means on the downstream end of said flexible plate for movement in a direction parallel to the centenplane of said nozzle, said contour generating unit having a box enclosure for supporting said pivot shaft means in fixed relation thereto, a Wiper plate aflixed to said nozzle box enclosure and extending transversely between opposite side walls thereof and wiper seal means aflixed to the underside of said scoop inlet segment and incorporating a smooth downstream face portion constituting a portion of a circular arc having its center of radius coincident with that of said pivot shaft means and in continual, pressure-sealing contact with said Wiper plate independent of the angular position of said contour generating unit to thereby prevent application of high pressure upstream thereof to the underside of said flexible plate, said scoop inlet segment and wiper seal arrangement constituting means, through proper longitudinal positioning of said wiper seal means, for balancing aerodynamic loads on said contour generating unit.

6. A two-dimensional variable nozzle comprising a pair of contour generating units each including a scoop inlet upstream portion, a flexible, relatively elongated downstream portion atlixed to saidscoop inlet portion and terminating in a slida bly supported end, a box-type enclosure for supporting said contour generating unit in pressure-sealed relation, transversely-disposed pivot means afiixed between opposite side walls of said enclosure incorporating pressure sealed plate means extending fully thereacross, interconnecting pivot arms aflixed to said transversely-disposed pivot means and aflixed at the upstream end thereof to the downstream end of said scoop inlet portion, and means for simultaneously moving said scoop inlet portions in an are about said first-named pivot means to move the point of juncture between said scoop inlet portion and said flexible portion constituting the origin of said flexible portion in a circular are about said pivot means, and wiper seal means affixed to the underside of said scoop inlet portion in continuous transverse relation thereacross and incorporating an arcuate surface having a radius whose center is at the pivot means in continuous, pressure-sealing relation with said pressure sealed plate means for all angular positions of said contour generating unit.

7. A two-dimensional nozzle comprising a pair of identically contoured, relatively enlarged contour generating units arranged for angular movement toward and away from a longitudinally extending center-plane, said pair of contour generating units including a pair of scoop inlet segments dis-posed in opposite relation to the centerplane and forming a nozzle throat portion therebetween, a pair of flexible plate portions of predetermined length formed as a downstream continuation of said scoop inlet segments compatible with each change in throat height on opening or closing operation of said scoop inlet segments in relation to the centerplane, said flexible plate portions automatically bending on rotation of said scoop inlet segments, a pair of pivot shafts positioned at a predetermined point downstream of the origin. of said flexible plate portions and pivotally supporting said scoop inlet segments and including interconnecting arm elements aifixed to said pivot shafts and providing constraint for said scoop inlet segments to limit the latter to movement in a circular path about said pivot shafts, rigid means aflixed to the downstream end of said flexible plate portions and disposed on opposite sides of the centerp-lane and ,slidably positioned for movement parallel to the centerplane only to insure proper accommodation of elastic bending of said flexible plate portions in accordance with and matching predetermined aerodynamic contours, and box enclosure means having side wall surfaces enclosing said nozzle and providing support for said pivot shafts.

8. A two-dimensional nozzle as in claim 7, and wiper plate means positioned on and extending rfu-lly across the width of said box enclosure and a pair of Wiper seals attached to the bottom surfaces of said contour generating units adjacent the scoop inlet segments thereof on the upstream end of said nozzle in contacting, pressuresealed relation with said wiper plate means at all angles of adjustment of said scoop inlet segments.

9. A two-dimensional nozzle asin claim 7, and actuating mechanism for simultaneously operating each of a pair of said contour generating units forward and away from the closed and open throat conditions, respectively,

to provide automatic flexing of said flexible plate portions through the respective slidably positioned, rigid means attached to the downstream ends of said flexible plate portions.

References Cited in the file of this patent UNITED STATES PATENTS 2,598,208 Bailey May 27, 1952 2,625,008 Crook Jan. 13, 1953 2,831,505 Menard Apr. 22, 1958 OTHER REFERENCES Agardograph 3A summary of the Techniques of variable Mach Number Supersonic Wind Tunnel Nozzle Design, by J. T. Kcnney and L. M. Webb, October 1954 (TL 500 N6 No. 3), reference pages 4 and 78'79. (Copy in Patent Office Scientific Library.)

Agard (AG 15/ P6), Papers presented at the Fifth Meeting of the Wind Tunnel and Model Testing Panel,. Scheveningen, Netherlands Agard Conference May 3-7, 1954 (TL WS N6p), reference pages and 146. (Copy in Patent Oflice Scientific Lbrary.)

Claims (1)

1. 3. A VARIABLE TRANSONIC NOZZLE HAVING A PAIR OF FIXED AND PARALLEL SIDE WALLS ENCLOSED WITHIN TOP AND BOTTOM WALLS, SAID NOZZLE COMPRISING A PAIR OF SPACED RIGID WALLS HOUSED WITHIN SAID FIXED WALLS DEFINING THE FLUID FLOW PASSAGEWAY, SAID RIGID WALLS HAVING A CURVED INLET SECTION AND AN OUTLET SECTION OF SIMILAR CURVATURE FORMING A CONTINUOUS CONVEX SURFACE, A PAIR OF FLEXIBLE WALLS INTEGRALLY ATTACHED TO SAID RIGID WALLS FORMING A CONCAVE DOWNSTREAM EXTENSION THEREOF AND ESTABLISHING A POINT OF INFLECTION AT THE JUNCTURE OF THE RIGID AND FLEXIBLE WALLS, SAID RIGID WALLS INCORPORATING INTEGRALLY ATTACHED ARMS PIVOTALLY SUPPORTING SAID RIGID WALLS ON SAID FIXED WALLS AT PIVOTS LOCATED IN PREDETERMINED MANNER INTERMEDIATE OF THE ENDS OF SAID FLEXIBLE WALLS, AND SAID FLEXIBLE WALLS SLIDABLY SUPPORTED AT THE DOWNSTREAM ENDS THEREOF ON SAID FIXED WALLS, WHEREBY SAID RIGID WALLS MAY BE ROTATED FOR MOVEMENT TOWARD AND FROM ONE ANOTHER THEREBY FLEXING SAID FLEXIBLE WALLS TO FORM THE DESIRED AERODYNAMIC CURVATURE, AND POWER ACTUATED MEANS FOR MOVING SAID COMBINED RIGID AND FLEXIBLE WALLS PIVOTALLY TOWARD AND FROM ONE ANOTHER.

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