US3472255A - Fluidic device - Google Patents

Description

H. L. FOX ETAL FLUIDIC DEVICE y oct. 14,1969

2 Sheets-Sheet 'l Filed April 20, 1967 .w ,.6 NMN Ww l Nwww m @I ,QW /////////V/////// ZUM W, w www ,AMW HM k @l wb @Mq m W VW///wmv A KVVNM//V/V//V/V/M m QANXNWMWQ.. ML NN M @Y @Q wv mw@ yy m /4, Mm QN ,l{ W N* ,II l WQN MN NN WW NNNM NWN, QN J NM Oct. 14, 1969 H. L. Fox ETAL 3,472,255

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United States Patent O M 3,472,255 FLUIDIC DEVICE Harold L. Fox and Gale H. Thorne, Salt Lake City, Utah,

assignors, by mesne assignments, to I-T-E Imperial Corporation, Chicago, Ill., a corporation of Delaware Filed Apr. 20, 1967, Ser. No. 632,280 Int. Cl. F15c 1/04 U.S. Cl. IS7-81.5 15 Claims ABSTRACT F THE DISCLOSURE A high pressure luidic oscillator having spaced, aligned supply and receiver nozzles with an outlet port on the side of the receiver nozzle toward the supply nozzle, the sizes of the nozzles, the pressure of the supply iiuid, and the axial spacing between the nozzles being such that a stationary nodal pattern in the supply nozzle jet causes pressure buildup in the receiver nozzle resulting in the establishment of a shock wave near the supply nozzle aspirating the outlet port which snaps toward the receiver nozzle after a predetermined reduction in the receiver pressure thereby pressurizing the outlet port.

BACKGROUND OF THE INVENTION The present pure fluid device falls within the broad group of uidic elements, i.e. fluid devices without moving parts, experiencing rapid technological and commercial growth in the last decade.

Most of the tiuidic devices thus far developed may be classified in one of the following categories: wall attachment devices, turbulence amplifiers, jet deflection or stream interaction devices, vortex devices and impact modulators. The wall attachment devices utilize the Coanda eiiect and generally have a digital output. The operation of this amplifier requires a supply or power stream passing through a restricted nozzle which serves to convert the major portion of the streams static pressure into velocity head. At either side of this power nozzle are channels for directing control streams to deflect the direction of the main supply jet. The jet is switched from one output to the other by introducing the control jet suliiciently to overcome the entrainment capability of the jet adjacent one side wall causing it to attach to the other side wall.

The turbulence amplifier is a slow, low pressure device consisting of precisely aligned power iiow tubes introduced into a vented cavity with one or more input signal tubes generally perpendicularly related to the main tube axis. The power stream is introduced into the cavity from one power tube at a speed which will allow it to ow without turbulence to the other power tube, being the output. It one or more of the control flows are introduced, the power stream is excited suiiiciently to become turbulent. The power stream then misses the output power tube. These devices must be operated in a narrow range of Reynolds number to avoid the instability of the supply iiow.

The jet deliection or stream interaction amplifier is a proportional device based upon the difference of pressure or momentum flux between opposed control streams causing deflection of a power jet more into one output receiver than another.

The vortex device utilizes the tangential admission of a control flow into a cylindrical chamber to create a vortex restricting the flow of a supply fluid into the chamber and thus varying the output characteristics in a centrally located output duct.

The impact modulator amplifiers utilize the axial impacting position of two opposed supply jets. An output collector adjacent one of the supply nozzles provides an 3,472,255 Patented Oct. 14, 1969 output dependent upon the difference in intensity of the two supply jets. The essential operating characteristic of the impact modulator is that the power streams establish a jet balance system where the equilibrium point or impact point is located where the momentum flux of the two impacting streams is equal. The impact point and thus the output is varied by controlling the intensity of one of the supply streams. The operation of the impact modulators usually requires an absolute pressure ratio (ie. supply pressure over ambient pressure), of less than two, and thus is practically limited to operation below a supply pressure of about 30 p.s.i.

SUMMARY OF THE INVENTION In accordance with the present uidic device large pressure `diiierentials may be supported, heretofore not possible with prior art devices in this lield. A supply nozzle is provided mounted coaxially and spaced from a receiver nozzle with an outlet port immediately adjacent the receiver nozzle on the side thereof toward the supply nozzle. If the appropriate relation of nozzle diameter, supply nozzle to receiver nozzle spacing, outlet port configuration, and supply pressure is established, oscillation will result. A jet of iiuid leaving the supply nozzle impinges on the receiver nozzle causing the pressure within a receiver (a closed volume connected to the receiver nozzle) to rise. When the pressure in the receiver has reached a value which is a significant fraction of the supply fluid pressure there is a sudden change in flow direction through the receiver nozzle. Flow from the receiver expels against the liow from the supply nozzle accompanied by the formation of a strong shock wave between the two opposing flows. This shock wave moves toward. the supply nozzle until arrested by a high pressure-high density zone in the supply jet outside the outlet port decreasing the pressure therein. As the receiver pressure decreases due to the loss of fluid therein, the shock wave moves toward the receiver nozzle until it is adjacent the receiver nozzle when there occurs an audible snap and a change of iiow direction in the receiver nozzle resulting in an increase in pressure in the outlet port.

This effect may be distinguished from the Hartmann generator phenomena as described in Sonics, T. F. Hueter and R. H. Bolt, John Wiley and Sons, New York, 1955, pages 286 to 288, in that the latter generator oscillation is dependent upon acoustic phenomena (where mean flow=0) whereas the former is a volume dependent effect where mean flow is not zero. Furthermore, the present oscillation effect is quite different from the buzz phenomena described in Supersonic Inlet Ditusers, An Introduction To Internal Aerodynamics, R. Herman, Honey- Well Corp., Minneapolis, Minn. 1956, the latter being associated with unstable supersonic iiow attaching and detaching from a surface.

The operation of the present oscillator is dependent upon the supply pressure being large enough and the supply nozzle being designed to establish a diamondshaped -wave pattern.

When in a sonic nozzle the absolute pressure ratio of supply pressure to ambient pressure exceeds two, using air as the liuid media, the onset of a nodal wave formation appears in the liuid jet issuing from the nozzle. As this pressure ratio increases the diamond-shaped nodal wave formation becames more clearly defined; an effect visible on a Schlieren apparatus (a device well known for viewing tiuid tiow phenomena). The diamond-shaped patterns represent soft shock waves produced by an underexpanded jet of fluid issuing from a nozzle. Now there is a significant cyclical axial pressure variation in the jet moving away from the nozzle outlet. This pressure variation, as will appear below, contrtbutes to the formation and stability of a strong shock wave, necessary for operation of the present device.

As the pressure ratio increases there is produced in the fluid jet issuing from a convergent nozzle a plurality of wave patterns beginning immediately adjacent the nozzle outlet where an initial expansion of the jet occurs. In the rst wave pattern an extremely strong shock wave effect referred to as the Reimann shock occurs and the pressure gradient across this -wave may be as high as 150 p.s.i. or even higher. The present device advantageously employs the Reimann shock in one mode of operation for controlling the position of the strong shock wave although other high pressure-high particle density areas or zones in the supply jet may be used for the same purpose.

According to the present invention when one of the nodal patterns is properly positioned with respect to the receiver nozzle, the above noted increase in pressure in the receiver eventually causes backiiow from the receiver nozzle and the propagation of the strong shock wave. This relationship is discussed more specifically below.

The present invention while shown incorporated in an axi-syrnmetric device in the present specification should be understood to iind application in planar fiuidic devices.

BRIEF DESCRIPTION O-F THE DRAWINGS FIG. 1 is an elevation view partly in cross section of the present fiuidic device;

FIG. 2 is an enlarged fragmentary view of the nozzles shown in FIG. l;

FIG. 3 is a graph showing the variation in dynamic pressure with axial distance from the present supply nozzle for a given supply pressure;

FIG. 4 is a curve showing the output signal in the present device as a function of time for one exemplary construction;

FIG. 5 is a curve showing the receiver pressure as a function of the same time base employed in the curve of FIG. 4; and

FIG. 6 is a diagrammatic view of the nozzle portions of the present oscillator under operating conditions.

While we have shown and shall hereinafter describe one embodiment of the invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as defined in the appended claims.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings and particularly FIGS. l and 2, a iiuidic oscillator 10 is shown consisting of a housing 11 containing the various nozzles and ports and a closed volume chamber 12 connected to the housing by suitable tubing 14. It should be understood that the volume chamber 12j might be formed integrally within the housing 11 where practical, although the required size of the chamber 12 may not permit this. A source of supply fluid, such as air, under pressure shown diagrammatically at 16 supplies fiuid to the housing 11 through conduit 18. Regulator valve 20 is provided in conduit 18 for regulating the pressure of supply fluid to housing 11 from zero p.s.i.g. to approximately ten times the ambient pressure, although this level of pressure is not required for sonic operation of the present oscillator. The main elements contained in the housing 11 are a supply nozzle 22, a receiver nozzle 23 and a divider 24 defining an annular outlet port 26 between the divider and the forward end of the receiver nozzle 23.

The supply nozzle 22 is a convergent nozzle (without a divergent section) and therefore of the sonic type. While the present device will operate with supersonic nozzles, the results thus far have been more desirable with sonic nozzles having only convergent sections. Nozzle 22 is cylindrical and pressed into through bore 28 in housing 11 so that the nozzle exit of the cylindrical throat or orifice 29 projects somewhat into a recess or slot 33 in the housing 11 intersecting through bore 28. Fitting 34 threaded in the left end of bore 28 connects supply line 18 to the supply nozzle 22.

The pressure in supply line 18 is regulated by valve 20 so that air is supplied to nozzle 22 at a pressure above twice the ambient pressure, thus producing the onset of the nodal wave formation, described above, in the supply jet exiting from nozzle 22 toward the receiver nozzle 23.

The curve in FIG. 3 illustrates the pressure Pr in the receiver nozzle 23 resulting from varying the axial spacing between the supply and receiver nozzles 22 and 23. It also represents (disregarding the rapidly oscillating portions 70, 71 and 72) the apparent pressure along the centerline of jet 36 issuing from the supply nozzle 22. It should be understood that the apparent pressure is the velocity head, such as would be obtained by moving a Pitot tube along the jet centerline, and not the total pressure. The nodal pattern of the ow issuing from jet 22 is diagrammatically represented below the curve in FIG. 3 and includes individual diamond-shaped nodal patterns 40, 41, 42, etc., connected together at nodal points 44, 45. Disregarding for the moment the rapidly oscillating portions of the curve in FIG. 3 (which are produced only when the receiver nozzle 23 is interposed as a proper location along the supply jet) it may be seen that the velocity head in the nodes increases and decreases as we proceed through the nodes away from the supply nozzle 22 such that each diamond-shaped nodal pattern is seen to have a high pressure-high density portion near the center or widest portion of the nodal pattern and low pressurelow density pattern near the nodal points. The nodal patterns 40 and 41 in FIG. 3 are approximately correctly aligned with the apparent pressure curve so that the apparent centerline pressure in these nodes may be found by projecting a line upwardly to the intersection of the curve PR. An increase in the supply pressure to nozzle 22 results in increased aring of the fiuid jet from the nozzle accompanied by a lengthening of the nodal individual patterns and increases in the sizes of the vertex angles. It is possible through the proper design of the supply nozzle 22 and sufficient supply pressure to achieve ten or more nodal patterns.

The first nodal pattern 52 is not always diamond-shaped as the others. With suitably high pressures (i.e. pressure ratio S5) it has a strong standing shock wave 53 referred to as the Reimann shock.

The receiver nozzle 23 is provided for receiving the supply jet from nozzle 22 and expelling a portion of this fiuid to create the present strong shock wave. Receiver nozzle 23 is annular in configuration and press fitted into bore 28 coaxially aligned with the nozzle 22. It includes a cylindrical throat section or orifice 55 and a diverging section 56. A suitable fitting 58 connects the receiver nozzle 23 with the volume chamber 12 through tube 14. Thus the receiver nozzle 23 communicates with a closed volume. Hereinafter the term receiver will be used to refer to the interior of nozzle 23, the portion of bore 28 communicating therewith, tube 14 and the chamber volume 12. The size of volume chamber 12 determines the period or frequency of oscillations of the present device, since it determines the time for a predetermined pressure rise and decay in the receiver nozzle 23 as will appear more clearly hereinbelow.

The relationship between supply nozzle pressure, axial distance between the supply nozzle 22 and receiver nozzle 23, and the diameters of throat sections 29 and 55 are important in the proper establishment of oscillations in the outlet port 26. The sufficient buildup of pressure within the chamber 12 and the nozzle 23 depends upon the relationship of the receiver throat 55 with respect to one of the nodal patterns. The device will operate with the throat 55 positioned adjacent any one of a number of nodal patterns in the supply jet but operation adjacent the second diamond-shaped nodal pattern 41 has been found preferable as shown in FIG. 3. Since the shape of the individual nodal patterns depends on the variables of supply nozzle diameter and supply pressure, the proper axial distance between the supply nozzle 22 and the receiver nozzle 23 will depend on these variables.

The desired pressure rise in the receiver during the` receipt of fluid from jet 36 issuing from the supply nozzle 22 appears to result from the blockage of reverse flow through the throat orifice 55 by the nodal pattern, e.g. pattern 41, adjacent thereto. This seems reasonable because portions of the diamond-shaped patterns represent high density and high pressure areas in the fluid power supply jet. Thus, for example, when the maximum diameter portion 65 of nodal pattern 41 is positioned slightly Within the throat 55, as seen in FIG. 3, it effectively prevents continuous reverse flow of fluid from the nozzle 23 resulting in an increase in pressure in the chamber 12 and nozzle 23.

The extent of the pressure rise in the receiver necessary to establish a reverse flow in the throat 55 and the desired strong shock wave permits some variation in the axial position of the nozzle 23 with respect to the selected nodal pattern adjacent thereto, e.g. pattern 41, so that supply pressure may vary within certain limits, nozzle sizes may vary within certain limits, and the axial spacing between supply nozzle and receiver nozzle may vary within certain limits and the fluidic element will still produce the desired oscillations in outlet port 26. Note in this regard that the nodal patterns have a greater diameter than the receiver orifice or throat 55 due to the normal expansion of fluid issuing from nozzle 22 even when the diameters of the throats 29 and S5 are equal.

The device will operate with the receiver orifice positioned approximately just over the wide portion of most of the well defined diamond-shaped nodal patterns. At supply pressures below 50 p.s.i., of which the curve PR in FIG. 3 is representative, the device will oscillate only when the receiver tip, the left hand side of throat 55, is spaced from approximately one third the nodal length (from one nodal point to the adjacent nodal point) from the trailing nodal point to approximately one half of the nodal length from the same trailing nodal point of the nodal pattern under consideration. Above 50 p.s.i. supply pressure the receiver may have a greater range of axial positions with respect to the considered nodal pattern and still produce oscillations.

Operation on the second diamond-shaped nodal pattern is preferred, and it may be expressed approximately in terms of the axial spacing X between the supply nozzle 22 and the receiver nozzle 23 as X=2w where w is the nodal length. This relationship is limited to sonic flow. Thus, viewing the diagrammatic showing in FIG. 3, if the supply pressure were reduced or the axial spacing between nozzles increased such that the maximum diameter portion 65 of the nodal pattern `41 were shifted outside the orifice nozzle to the left, fluid would continually escape in the direction of arrow 69 in FIG. 3 establishing a steady state condition preventing a sufficient pressure rise Within the nozzle 23 from the necessary shock wave to produce oscillations. Oscillations will continue to be produced, however, if the nodal pattern is shifted to the right iwith respect to the orifice 55, i.e. further into the orifice, but when the maximum diameter portion 65 goes Within the nozzle 23 past the throat continuous backllow again precludes the production of a strong shock wave and oscillation.

The effect of varying one of the variable parameters is shown by the curve PR, the receiver pressure, in FIG. 3. Thus, it is seen that only for certain axial spacings between nozzles, being represented on the abscissa by X, does oscillation occur. The rapidly oscillating portions 70, 71 and 72 of the receiver pressure curve PR represent axial spacings of the nozzles which will produce oscillations for given supply pressure and nozzle diameters. It is thus apparent that there are spacings or axial positions of the nozzles which will not produce the desired oscillations such as when the end of the receiver nozzle is positioned iadjacent one of the nodal points, a low pressure area. It has also been found that as the supply pressure increases, a greater range of axial spacings at each nodal pattern is possible and still produce oscillations. Note in FIG. 3 that oscillating portion 70 on the graph is taken when receiver nozzle 23 is positioned adjacent nodal pattern 40, and oscillating portion 71 is taken when nozzle 23 is positioned adjacent nodal pattern 41, etc.

The outlet port 26 is defined by a generally conical space between the divider 24 and the forward reduced end of receiver nozzle 23. The divider 24 is generally cup-shaped and press fitted within bore 28 in a similar manner to the nozzles 22 and 23. Formed on the divider is a depending annular flange portion 78 closely fitted on a reduced cylindrical portion 79 on nozzle 23. A cylindrical orifice 81 is formed centrally in the divider 24 aligned with the orifices in nozzles 22 and 23. The orifice 81 is larger than the orifice 29 of nozzle 22 so that it does not disturb the underexpanded jet issuing from the nozzle. Extending awa-y from the orice 81 is a conical wall 83 diverging slightly with respect to conical surface 84 on the outside of nozzle 23. The relative spacing of the walls 83 and 84 has a significant effect on the shape of the output pressure wave form as well as the sensitivity of the device to high and low downstream output impedances.

The port 26 communicates with a threaded outlet fitting bore 87 through aligned bores 85 and 86 in the flange portion 78 and housing 11, respectively. The total volume of the outlet ducting including the outlet port 26, passages 85, 86, bore 87 and any tubing (not shown) connected thereto is less than the total volume of the receiver including the interior of nozzle 23, the communieating portion of Ibore 28, tubing 14 and chamber volume 12.

The operation of the device as thus far described will be related to the diagrammatic view shown in FIG. 6. Nozzle 22 is connected to a suitable source of air regulated to supply fluid under -a pressure of at least twice ambient, e.g. pressure ratio of 2-l approximately 30 p.s.i. The convergent nozzle 22 will thus produce the repeating nodal pattern described above with reference to FIG. 3. The axial spacing of the receiver nozzle 22 is adjusted to produce the desired pressure rise within the receiver 23 clearly described above. The objective of the device, of course, is to provide two stable states necessary for alternately filling and emptying the outlet port 26, creating an oscillatory output. If the fluid used is air at normal room temperature, setting the supply pressure to the value calculated from the operating pressure Iratio for the zero load condition will result in optimum operating conditions. Should the supply fluid be at some different temperature a slight adjustment of the supply pressure may be necessary to achieve optimum operating conditions. The influx of flow by the -fluid jet 36 into the nozzle 23 and the capacitive volume 12 causes a pressure rise within the receiver when the proper relationship is achieved with the nodal pattern in the supply jet. Thus, the pressure rise occurs as a result of filling an effectively closed chamber. This pressure rise continues apparently until the pressure Within the orifice of nozzle 23 equals the pressure in the fluid jet at the side of the divider adjacent slot 33 (communicating with atmosphere). This results in a reversal of flow in the receiver orifice 55 creating an unstable condition which causes the formation of a new strong shock wave moving to the left in vent slot 33 and stopping approximately at position 96 shown in FIG. 6. At this time all th-e nodal patterns in jet 36 from the shock wave 96 to the right in FIG. 6 (downstream nodal patterns) disintegrate. The strong shock Wave stops at position 96 apparently because of the resistance offered by a high pressure zone in the first nodal pattern.

Once the new strong shock wave at 96 has been established, a much lower pressure can maintain it substantially in that position. Thus, reverse fiow from the nozzle 23 and the divider orice 81, possible as a result of the pressure buildup during the period of infiux of iiuid into the receiver nozzle 23, maintains the strong shock approximately at position 96 although there may be some slow, rightward movement of the shock from position 96 toward the divider orifice 81 as the receiver pressure PR decreases.

With the reverse flow continuing from nozzle 23 and issuing from divider orifice 81 the pressure in the outlet port 26 is reduced below ambient condition through aspiration caused by fiow through a smaller diameter orifice of receiver nozzle 23 into a larger diameter orifice 81 in the divider 24.

This reverse fioW from the nozzle 23 will continue until the pressure and flow are insufficient to maintain the strong shock near location 96 in the slot vent 33. At this time the strong shock will snap within the divider orifice 81 reestablishing the original nodal pattern in jet 36 as well as reversing flow through the receiver throat 55 again providing infiux of ow into the receiver. With the reestablishment of the supply jet into the receiver nozzle 23 the pressure in outlet port 26 rises rapidly to a high value.

After the initial rise in outlet port pressure as shown in FIG. '4 there exists a further increase in pressure but at a much slower rate. One explanation for this is that there is a shock wave established in this state immediately outside the receiver orice approximately in the position shown at 98 in FIG. 6. This causes spill-over of the sup ply jet around the shock wave (as indicated by arrow 99) into the outlet port. Thus, in this state the receiver orifice acts more like a divider for the supply jet flow. As discussed `below the outlet port configuration has a signicant affect on the shape of the outlet wave form.

The cycle then begins to repeat itself as the pressure in the receiver nozzle 23 and capacitive volume 12 increases. As may be seen in FIG. the pressure wave form in the receiver has a smooth saw-tooth shape and may not be reduced to zero p.s.i.g. The minimum lower value or minimum value of pressure possible in the receiver is approximately equal to twice ambient pressure. Thus the pressure differential in the receiver between maximum and minimum levels is quite limited. However, the pressure in the outlet port 26, as seen in FIG. 4, goes below zero p.s.i.g. due to the aspirating effect of reverse flow in receiver nozzle 23. Furthermore, the maximum pressure in the outlet port 26 exceeds the maximum pressure obtainable in the receiver as may be seen by a comparison in the maximum pressure levels in FIG. 4 and FIG. 5. Thus, high pressure differentials may be achieved in the outlet port 26.

The output pressure is a function of both the pressure ratio for which the oscillator is designed as well as the dimensional characteristics of the specic component under consideration. Pressure recoveries (output pressure divided by supply pressure) of as high as 95% for the higher flow rate units and 80% for the low flow rate units have been achieved.

The frequency of oscillation of the present device is dependent upon the volume of the receiver. By varying the size of volume chamber 12 the frequency of oscillation may be varied as desired. It has been found possible to vary the frequency of a single oscillator according to the present invention over a very Wide range with cycle periods varying from one hundred cycles per second to a three minute timing cycle by varying the size of volume chamber 12.

In some applications it is desirable that the output pressure wave as seen in FIG. 4, have a fast rise and fall time as well as an upwardly curved wave form as shown at 100 just behind the trailing or falling part of the wave. The

configuration of the outlet port 26 as defined by the walls 83 and 84 control the rise and fall time of the output pressure wave as well as the wave shape. If the configuration and spacing of these walls is such that a long R-C time constant is provided a pressure wave form to be produced in the outlet port similar in shape to that in the receiver, i.e. a saw-tooth shape. By spacing the receiver orifice 55 very close to the divider orifice S1, i.e. on the order of .002 to .005 of an inch and by matching the resistance to flow of the outlet port moving radially away from the receiver and divider orifices afforded by walls 83 and 84, a fast rise and fall wave form similar to that shown in FIG. 4 may be achieved.

Furthermore, when the divider orifice 81 is close to orifice 55 the device becomes relatively load insensitive. The axial spacing between the divider orifice 81 and the receiver orifice 55 to achieve this load insensitivity varies with the diameter of the supply nozzle orifice. It appears that in the above range of divider to receiver nozzle orifice spacings that the ratio dS/y=3 will achieve the load insensitivity result where as is the supply nozzle orifice diameter and y is the axial spacing between the divider orifice and the receiver nozzle orifice. The device may then operate under either a high or low load impedance.

While it has been found desirable to design the device so that the strong shock wave established by the buildup and pressure in the receiver moves all the way to the first nodal pattern until stopped, it is possible for the device to be designed so that this shock wave moves through only one nodal pattern when moving toward the supply nozzle.

The shock wave propagated by the reverse flow in nozzle 23 moves to the left as shown in FIG. 6 until it meets a wave of sufficient strength to arrest it. It is desirable that this new shock wave has sufficient strength to pass through nodal pattern 40 so that it is not arrested until it reaches the first nodal pattern. The reason for this is that the long movement of the new shock wave gives the highest pressure differential in both the receiver nozzle 23 and the outlet port 26. However, it is possible by varying the axial spacing between the nozzles or the supply pressure to control the new shock wave so that it passes through only one nodal pattern and is arrested by the nodal pattern adjacent to the one within the receiver orifice 55 even though it be a diamond shaped nodal pattern rather than the first nodal pattern (the one adjacent the supply nozzle). Whether the new shock wave jumps through only one nodal pattern or through all the nodal patterns between the receiver and the first nodal pattern adjacent the supply nozzle also depends upon the design of the supply nozzle and the receiver nozzle which affect the shape of the curve PR in FIG. 3.

As mentioned briefly above, the receiver nozzle orifice 55 is slightly smaller than the supply orifice so that in the high pressure state (the state where the fluid supply jet 36 enters the receiver nozzle 23), the supply jet splits somewhat at the orifice due in part to the nodal pattern within the receiver orifice. For sonic nozzles with supply pressure to ambient pressure ratios being in the range of two to five, the ratio of the diameter of the supply nozzle orifice ds to the diameter of the receiver nozzle orifice 55 should be approximately 1.5, i.e., ds/d 15, for best operation.

The diameter of the divider orifice 81 is greater than both the supply nozzle and receiver nozzle orifice diameters and is preferably approximately 1.5 times the supply nozzle diameter for best operation.

The length of the throats in both the supply nozzle and the receiver nozzle is approximately one half their respective diameter for best operation.

While the present device may be embodied employing a wide range of the basic parameters in accordance with the principles set forth above, the following is an exemplary set of dimensional parameters for an oscillator according to the present invention found to operate satisfactorily along with supply pressure ambient pressure conditions and resulting receiver and outlet pressures:

Pressure in supply nozzle 22 p.s.i.g 30 Pressure in receiver nozzle 23 -p.s.i.g 15-26 Pressure in outlet port 26 p.s.i.g 0-28 Spacing between nozzles 22 and 23 p.s.i.g- 0.071 Diameter of supply nozzle orifice 29 p.s.i.g 0.039 Diameter of receiver nozzle orifice S p.s.i.g- 0.031 Diameter of divider orifice-81 p.s.i.g 0.046 Total receiver volume, approx. cc 286 Total output volume cc-- Ambient pressure p.s.i.g 12.3

We claim:

1. A fluid operable device, comprising: means for establishing a stream of fluid in a predetermined path, means for establishing at least two discontinuous high pressure zones in said stream, receiving means for receiving fluid flow from said stream generally in the direction of flow of said stream and to expel fluid generally in the opposite direction of flow of said stream, said receiving means having a receiver orifice, first port means between one of said high pressure zones and said receiver, said receiving means being positioned so that the other high pressure zone is positioned adjacent the receiver orifice to cause a buildup of pressure within said receiving means, and outlet port means axially adjacent said first port means.

2. A fluid operable device, comprising: means for establishing a fluid jet having a shock pattern with at least two axially spaced high pressure zones, means for receiving at least a portion of said fluid jet and causing a backflow of fluid in a direction generally opposite said jet, said receiving means being positioned so that one of said high pressure zones prevents the continuous escape of fluid from said receiving means thereby causing a pressure rise in said receiving means, said receiving means being constructed such that a sufficient pressure rise is effected therein to establish a shock wave in said jet moving toward and stopping at the other of said high pressure zones, first port means adjacent said receiving means, and second port means adjacent said other high pressure zone, said second port means being isolated from said first port means.

3. A fluid operable device, comprising: means for establishing a fluid jet along a predetermined path including a supply orifice, receiving means in said path for receiving fluid from said jet during a period of time including a receiving orifice, said supply orifice being coaxial with said receiving orifice, first port means along said jet adjacent said jet establishing means, second port means along said jet adjacent said receiving means, and means for selectively reversing flow in said receiving means to cause interaction between the reversing flow and the jet adjacent said first port means to thereby reduce pressure in said second port means, the reversing flow in said receiving means being derived from said fluid jet.

4. A fluid operable device, comprising: a first nozzle adapted to produce an underexpanded jet of fluid having a stationary nodal wave, means for supplying fluid to said nozzle under sufficient pressure to produce at least two nodal patterns and two nodal points in said jet, a receiver nozzle opposing, spaced from and substantially aligned with said first nozzle for receiving at least during a period of time fluid from said first nozzle, said receiver nozzle being spaced from said first nozzle such that one of the nodal patterns in said jet prevents the continuous backflow of fluid from said receiver nozzle, fluid volume means connected to said receiver nozzle, outlet port means adjacent said receiver nozzle along said jet, vent means between said first nozzle and said outlet port means, second fluid volume means connected to said outlet port means, said first fluid volume means being larger than said second fluid volume means, said first fluid volume means being sized such that the pressure rise therein resulting from the fluid jet will be sufficient to break down at least a portion of the nodal wave in said jet and establish a relatively stable shock wave in said jet adjacent said vent means, the breakdown in said nodal pattern being accompanied by a reversal of flow in said receiver nozzle, said first volume means being constructed such that pressure of the reversed flow will decay below that necessary to maintain said shock wave at which time the nodal wave will reappear in said fluid jet, flow will again reverse in said receiver nozzle, and the pressure in said outlet port will increase.

5. A fluidic oscillator, comprising: first nozzle means adapted to issue a fluid jet having a stationary nodal shock pattern, means for supplying fluid to said first nozzle means at sufficient pressure to establish said nodal pattern, second nozzle means opposed, spaced and generally aligned with said first nozzle means for receiving at least a portion of the fluid from said first nozzle means, vent means between said first and second nozzle means, normally closed volume means connected to said second nozzle means, said second nozzle means being spaced from said first nozzle means and having a size such that the nodal pattern in said fluid jet prevents the continuous escape of fluid from said second nozzle means and said volume means whereby fluid pressure increase in said volume means and said second nozzle means will cause a strong shock wave to be established in said jet adjacent said vent means, outlet port means on the side of said second nozzle means toward said first nozzle means so that `when said shock wave is established fluid jet flow into said second nozzle will be interrupted and pressure will be reduced in said outlet port means, the resulting pressure reduction in said volume means causing reestablishment of the fluid jet flow into said second nozzle means after a predetermined time thereby producing an increase in the pressure in Said outlet port means.

6. A fluidic oscillator as defined in claim 5, wherein said second nozzle means has a flow area smaller than said first nozzle means to assist in preventing the continuous backflow of fluid from said second nozzle means.

7. A fluidic oscillator as defined in claim 5, wherein said first nozzle means has a flow area approximately one and one half times that of the second nozzle means.

8. A fluidic oscillator as defined in claim 5, wherein said vent means and said outlet means are defined in part by a divider having an orifice spaced from both said first nozzle means and said second nozzle means, said orifice being substantially closer to said second nozzle means than to said first nozzle means, the area of said divider orifice being larger than the area of said first nozzle means to prevent interference with said fluid jet.

9. A fluidic oscillator as defined in claim 8, wherein the area of said divider orifice is approximately one and one half times that of the first nozzle means.

10. A fluidic oscillator as defined in claim 5, wherein the pressure orf the supply fluid is greater than twice the ambient pressure in the vent means.

1-1. A fluidic oscillator as defined in claim 5, wherein the pressure of the supply fluid is at least five times the ambient pressure in said vent means, said first nozzle means constructed to produce an underexpanded fluid jet with a stationary Reimann shock wave in the nodal pattern adjacent the first nozzle means, said shock wave being of sufficient strength to pass through the other nodal patterns and stop at said Reimann shock whereby the pressure differential in said outlet port means is increased.

12. A fluidic oscillator as defined in claim 5, wherein said `first nozzle means is constructed to produce a nodal pattern having a plurality of individual diamond-shaped nodal waves connected at low pressure nodal points, said first and second nozzle means `being spaced approximately twice the axial length of an individual nodal wave.

13. The method of operating a fluidic device having a supply nozzle, a generally opposed receiver nozzle communicating with a normally closed chamber, and an outlet port adjacent the receiver nozzle, comprising the steps; supplying fluid to the supply nozzle at sufficient pressure and flow to establish stationary nodal patterns in a supply stream directed at the receiver nozzle, controlling the supply Huid so that one of the nodal patterns is adjacent the receiver nozzle in a position causing a sufcient buildup of pressure in the receiver nozzle to reverse flow in the nozzle and establish a strong shock Wave moving in the direction of the Supply nozzle.

14. The method as deiined in claim 13 wherein said normally closed chamber is continuously closed so that the device operates as an oscillator when the strong shock Wave moves back into the receiver nozzle as the pressure decays in the receiver nozzle and chamber.

15. The method of operating a uidic device having a supply nozzle, a generally opposed receiver nozzle communicating With a normally closed chamber, and an outlet port adjacent the receiver nozzle, comprising the steps; supplying fluid to the supply nozzle at sucient pressure and flow to establish stationary nodal patterns in a supply stream directed at the receiver nozzle, positioning the receiver nozzle axially with respect to the supply nozzle so that one of the nodal patterns is adjacent the receiver nozzle in a position to selectively block reverse ow from the receiver so that pressure in the chamber will increase sufciently to create a strong shock Wave moving in the direction olf the supply nozzle and reversing ow in the receiver nozzle.

References Cited UNITED STATES PATENTS 3,068,880 12/1962 Riordan 137-815 3,128,040 4/1964 Notwood.

3,212,515 10/1965 Zisfein et al 137-815 3,272,215 9/1966 Bjornsen et al. 137-815 3,276,259 10/1966 Bowles et al. 137-815 XR 3,285,263 11/1966 Bjornsen et al. 137-815 3,295,543 1/1967 Zalmanzon 137-815 3,311,120 3/1967 Palmsano 137-815 XR SAMUEL SCOTT, Primary Examiner

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