US2696110A - Variable-constriction nozzle - Google Patents

Description

Dec. 7, 1954 Q JR I 2,696,110

VARIABLE-CONSTRICTION NOZZLE Filed May 2, 1952 I INVENTOR. ALFRED J eaamgm.

BY jl f romvn's turbulence.

United States Patent '0 256965110 v VARIABLE-CONS'IRICTION. Nozzrn Alfred J". Eggers, Jr.,' LosAlt0s,

I Application May2, 1952 S'erial No.. 285,782.

' 4 ch. 13-141 (Granted-under. Title 35,1 S..Code}(,1952),1sec. 266) This: invention relates. to nozzles adapted for developing: high supersonic" speeds: with; particular-application to use in wind tunnels where the characteristics of bodies subjected to airflow are to be determined.

In winrhtunneli use. flexibility and adaptability to various speed requirements. is often-of. highest; importance. Not only is it desirable that air speed changes be readily made, but it.ise;aIso important that thesechanges be made easily andiquicklyand with maintenance ofi'economy of operation.

In methods heretoforev in use modification oftunnel air flow has been obtained by usecof fixed or variable geometry nozzles including an effuser located upstream from: the.- nozzle test section in which the highest supersonic air. speeds are secured: and'a diffuser located downstream of the test section. In the case of fixed; geometry nozzles it becomes necessary to replace one nozzle by another of different design, a procedure which is time consuming and aerodynamically inefficient due to the excessively high power required to start and operate the tunnel. In the case of variable geometry nozzles of prior use the operator is hindered by the complexity of the adjusting mechanism. 7

The objects of this invention therefore include the provision of nozzle construction which is simple in form, which is easily manipulated to modify air flow speed, and which operates efficiently to establish and maintain the required high supersonic air speeds.

Other objects and features of the invention will become apparent on consideration of the following description of an embodiment of the invention taken with the accompanying drawings, in which Fig. 1 is a schematic flow diagram of the nozzle and related equipment;

Fig. 2 is a diagrammatic showing of the movable nozzle sections and adjusting mechanism;

Fig. 3 is a detail view of typical nozzle adjustment structure; and

Fig. 4 is a section of the nozzle showing the sealing means.

Referring to the schematic flow diagram of Fig. 1, the wind tunnel unit includes the air compressor 8, the high pressure reservoir 9, the valve 10, nozzle 12, evacuated tank 13 and vacuum pumps 14. A settling chamber may be placed between the valve and nozzle 12 to reduce These units are all connected in series, as named, so that pronounced air flow may be developed through the nozzle, in the direction as indicated by the arrow.

The nozzle is divided into three sections, the effuser 15 to produce air acceleration with gain of kinetic energy and loss of pressure energy, the test section 16 for insertion of models and test of their aerodynamic characteristics. and the diffuser 17 for converting the kinetic energy of air flow back into pressure for discharge into the tank 13 or atmosphere. Throat restrictions 18 and 19 are thus formed respectively at the effuser and diffuser.

In order to secure variation in the effuser-diffuser dimensions and outline and thus control speed condition in the test section, the nozzle is constructed of four main parts, including stationary parallel wall sections 20, 21 (Fig. 4) and movable nozzle sections 22 and 23 positioned between the wall sections. As illustrated in Fig. 4 this arrangement produces a rectangular cross section so that on movement of the movable nozzle sections a linear variation in cross sectional area results, lending itself to.

easy control of air flow. Each nozzle section 22, 23

one form; of nozzlesection: adjusting mechanism.

2,696,110 Patented, Dec. 7, 1.954

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iszshaped allochirally on facing areas to obtain the etfuserdifiuser contour desired for formation of the test nozzle. Section 16., as shown in Fig. 2', has movable support means, diagrammatically indicated by strap attachments 25, 26-, 27', andi28, employed to shift these nozzle sectionsbctween thelimits illustrated, for example, by the fuli'anci broken outlines 311 and 31 of the nozzle face; and, to this end, each strap attachment is connected to themovable sections- 22 and23 by pivot pins 29. It is particularly pointed out that constriction 18 has mini? mum crosssectional area at the extreme down stream end thereofwith the up stream contour of the constriction diverging. Since the adjacent pivot is upstream from this smallest area, as shown in Fig, 2, any outward movement of power-element 26 will enlarge thearea of both the down. stream. and up stream constrictions and, thus, both: constrictions maybe modified in the same sense by asingle power element adjacent the down stream end of the nozzle.

Since the supports 2528 may be adjusted separately or simultaneously by manualor motor means; it is evident. that a widerange of settings may be made for the movable nozzle sections, thus securing high flexibility inair' speed: control.

Fig. 31 illustrates a practical structural arrangement of Intermediate the side plates 20 and 21 andadjacent the top edges: thereof is secured fi xedl'y a cross block 40 centrally apertured to receive a shaft 41. The shaft is grooved near: one end, as at- 42, and aball bearing race way including rings 43 andand bearings 45 secured" to the grooved? shaft section and the inner face. of the block aperture. top of the block aperture to hold bearing ring 44 in place.

At the upper end of the shaft above the block 40 a drive wheel 47 is mounted; and to side plate 20 a re versible motor unit 48 having a power shaft 49 terminating in a pulley 50 is secured, pulley belt 51 providing power drive connection between the pulley wheels 50 and 47. Usual control means (not shown) are provided to connect and control the supply of power to the motor 48; or, alternatively, manual means may be used in place of the motor unit.

The shaft 41, as supported for rotation on block 40, is formed with an external screw thread 55 at its inner or lower end, as shown in Fig. 3. Adapted for threaded engagement of this shaft end 55 is a block 56 having pivot pins 57 fixed thereto on two opposite sides, as by lock pins 58, and extending into pin bearing apertures 59 formed in side support 60 and 61. These side blocks, in turn, are fixed to the side walls 62 and 63 of the U- shaped upper movable nozzle section 22, so that the center block 58 which receives the screw shaft 41 has pivoted movement with reference to the nozzle section 22. Since this adjustment mechanism is placed at both ends of the nozzle section. it is apparent that either end may be adjusted independently of the other and hence successive or simultaneous adjustment may be made.

The apparatus of Fig. 3 is exemplary of independent control at one end only of a movable nozzle section. However, the motor connections may be arranged to actuate simultaneously a similar control unit at the adjacent end of the other nozzle section. This may readily be done by roviding an extension of the motor shaft to 'the under edge of side plate 20 for connection to the opposite pulley system.

In order to prevent air leakage between the side plates 20 and 21 and the sides 62, 63 of a nozzle section there is embedded in a lengthwise groove on either side of the section adjacent the outer edges thereof square rubber tubes which frictionally engage the inner surfaces of side plates 20 and 21.

In operation, the starting nozzle blocks 22, 23 are positioned as shown in Fig. 2 in broken lines with the area of the second throat 19 sufliciently large to pass the transient shock system which precedes the supersonic flow as it is established progressively further downstream in the nozzle. The valve 10 is then opened and the effuser expands the high pressure air to supersonic speeds in the test section where it remains approximately constant. Beyond the test section the air is recompressed in the An annular strip 46 is insertedat the diffuser to a lower supersonic speed and downstream of throat 19 there is a slight expansion followed by a normal shock system and subsequent difiusion from subsonic velocities to a state of rest.

The air supersonic speed thus attained in the nozzle is relatively low due to the displaced sections at throat 18. The nozzle is now adjusted to a more constricted throat area as shown in full lines in Fig. 2, thus producing a high supersonic speed value. By starting in this way at a low supersonic speed and hence a low starting compression ratio, and then increasing the speed to high supersonic values, there is obtained a considerable saving in power, and this factor with the simplicity of structure and flexibility of use combine to make this nozzle of considerable importance in wind-tunnel equipment.

While specific mechanism and arrangements have been described to set forth the substance of the invention, it is apparent that modifications may be made subject to limitations imposed by the claims as hereto appended.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. A wind tunnel nozzle comprising an elongated tube having at least two successive constrictions therein spaced by an enlarged recess, a movable section in said nozzle including joined peripheral segments of said constrictions and recess, support elements adjacent each constriction for supporting each end of said movable section, said support elements each having a pivot connection to said section, the up stream constriction having the point of smallest cross-sectional area down stream from the transverse plane including the pivot connection, and a single power mechanism connected to the down stream section pivot for changing the cross-sectional area of both of said constrictions.

\ eluding said pivot connection,

2. A wind tunnel nozzle comprising an elongated tube having at least two successive constrictions therein spaced by an enlarged recess, a movable section in said nozzle including joined peripheral segments of said constrictions and recess, a support element adjacent the upstream constriction having a pivot connection to said section, the upstream constriction having the point of smallest crosssectional area downstream from the transverse plane inand a single power device for moving said section on said pivot connection, said power device being connected to said section at a point displaced from said pivot connection.

3. The wind tunnel nozzle as defined in claim 2,

with said power device attached to said movable section adjacent the down stream end thereof, the power movement of the device at the point of attachment to said section being transverse to the nozzle axis.

4. The wind tunnel nozzle as defined in claim 2,

. said upstream constriction smoothly diverging upstream at a uniform rate from the point of minimum cross-sectional area.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Hypersonic Research Facilities at the Ames Aeronautical Lab., Journal of Applied Physics, vol. 21, 11,

'Nov. 1950, pp. 1150-1155.

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