US3403691A

US3403691A - Vortex vent for fluid amplifiers

Info

Publication number: US3403691A
Application number: US412478A
Authority: US
Inventors: Hayes William Frederick; Ashikian Baruir; Kwok Clyde Chi Kai
Original assignee: Aviation Electric Ltd
Current assignee: Aviation Electric Ltd
Priority date: 1964-10-02
Filing date: 1964-11-19
Publication date: 1968-10-01
Anticipated expiration: 1985-10-01

Description

OCtl 1968 w. F. HAYES ETAL 3,403,691

VORTEX VENT FOR FLUID AMPLIFIERS Filed Nov. 19, 1964 5 Sheets-Sheet 1 Oct. 1, 1968 w. F. HAYES ETAL 3,403,691

VORTEX VENT FOR FLUID AMPLIFIERS Filed Nov. 19, 1964 3 Sheets-Sheet 2 FLUID FLOW FLUID FLOW SOURCE l LOAD FLUID FLW SINK HWS-rgis Oct. l, 1968 w. F. HAYES ETAL 3,403,691

VORTEX VENT FOR FLUID MPLIFIERSv Filed Nov. 19, 1964 5 Sheets-Sheet 3 United States Patent O z C1aims.(ci. 137-815) This invention relates to fluid operated 'systems wherein the fluid flow characteristics are influenced solely by fluid means. Such systems provide fluid operated units which can fulfill many functions analogous to electrical oscillators, amplifiers, etc.

Devices of this type have been described in the literature, notably in an article entitled, Fluid Computers, by Wood and Fox in the International Science and Technology periodical of November 1963, as well as an article entitled, New Shapes for Fluid Flip Flops, by Russ Henke in the periodical, Machine Design, dated Mar. 14, 1964. Patents of interest in this connection include U.S. Patents Nos. 3,004,547 and 3,001,539 to Hurvitz; U.S. Patent No. 3,016,066 to Warren; U.S. Patent No. 3,107,850 to Warren et al.; and U.S. Patents Nos. 3,122, 165 and 3,137,464 t-o Horton.

Many devices have been developed in recent years in which a fluid stream is influenced 4by means of a much smaller fluid control stream. For example, devices have been constructed which enable control of the rate of mass transfer, pressure, or pressure fluctuations, and the like by means of a relatively low power control fluid jet. By the use of t-he feed back principle oscillators can be constructed which are quite analogous to electric oscillators.

Typically, devices of this type include a fluid power jet discharging through an orifice into a plurality of outlet passages spaced from the orifice. One or more control jets substantially normal to the direction of the power jet provide a means of influencing the direction of the power jet and thus to determine the proportion of the power jet entering eac-h outlet passage. For example, an oscillator might be constructed of a power jet discharging through an orifice leading into an interaction chamber and then into two outlet passages separated -by a divider. A portion of the output from the outlet jet is fed back into control jets located near the power jet aperture and the resulting interaction between the control jets and the power jet produces oscillations which can be employed for various purposes.

In this art, the term power fluid interaction refers to an operation in which fluid flows interact directly with each other to perform a desired function. The power fluid control device is a device utilizing these principles to obtain a control function.

One of the pro'blems encountered in the use of devices of this type is an inherent instability under certain conditions of power input jet pressure, outlet passage construction and shape, and in particular, load factors. Normally, in the ideal case where the outlet passages lead to an area of ambient pressure such as to the atmosphere no such problems yare encountered. However, in actual use one or more of the outlet passages will include constrictions, sharp turns, variable loads, and other elements which may lead to upsetting of the operation of the power jet under the influence of the control jets because of back pressures and reflected pressure pulses in one or more of the outlet passages.

The practice yof the present invention provides an improvement in such devices in which the effects of load fluctuations, reflected pulses and the like are minimized or eliminated.

This invention also provides a convenient means of bleeding the output in combinations of this type of device in which it is desired to avoid cumulative increments in throughput of fluid resulting from the repeated addition of fluid by control jets.

It is known to provide the output passages of these devices with bleeders. By means of these bleeders it is possible to operate a series of similar units in some form of series such as a cascade and still avoid upsetting the designed pressure ratios across the individual power jet orifices. The 4usual design of the device entails a bleed passage usually at an obtuse angle to the output flow in a region of high velocity. The angle of the bleeder and the momentum of t-he output stream inhibit flow into the 'bleed passage in the absence of any appreciable :back pressure in the Ioutlet passage. A back pressure or reverse pulse will result in active flow through the bleeder which will inhibit a rise in pressure in the jet interaction zone. This, of course, will reduce or eliminate the chances of upsetting the desired flow characteristic which should be determined solely lby the control jet and other design characteristics.

Another known improvement in this type yof device entails a vortex-inducing cusp 'situated in the wall of the outlet passage. This is of some value in preventing unexpected back pressures in the outlet passage from being transferred back to the jet interaction zone but it is generally of limited usefulness.

The present inventors have found that the provision of a vented vortex cusp in the outlet passage of a fluid amplifier provides unexpected results. The present improvement provides a latched vortex in which a portion of the mass flow of a fluid stream is diverted through an orifice, the axis of which orifice is perpendicular to the mean velocity vector of the fluid stream, and the configuration lof the channel confining the said fluid stream being adapted in the vicinity of the orifice to induce and maintain a fluid vortex or swirl with the rotational axis of the core of the said swirl flow coincident with the axis of the said orifice.

By the use of the present invention is provided a means |of attaining substantially constant rate unidirectional fluid flow in a fluid outlet passage upstream of the latched Vortex vent, such constant flow being largely independent of restrictions and diversions of the fluid flow downstream of the vortex vent. This permits a 4high degree of impedance matching or impedance loading to lbe incorporated in the design of these devices.

The portion of the fluid stream which is diverted or bled out of the vortex vent is determined -by many factors such as the size of the vent orifice and the geometric configuration of the vortex cusp.

The use of the vented vortex cusp also provides a means for enabling the transfer of the fluid flow from a smaller diameter passage to a larger diameter passage with a minimum of turbulence and or pressure loss. This principle -has been applied previously but the present invention provides a greatly improved diffusion characteristic since the vent tends to reduce or eliminate the peeling or shedding of the vortex flow on its way downstream.

By maintaining a permanent impedance load on the outlet passage of a fluid amplifier a latched vortex can -be maintained and a proportion |of all fluid flow bled off through such vent. One of the characteristics of t-he latched vortex is that it can prevent or greatly diminish the effect of a reflected pressure wave travelling upstream in the outlet passages. This reflected pressure wave can cause a reversal of the desired operation of the amplifier and are generally highly undesirable. It is found that these reflected pressure waves are dissipated in being forced to pass through a latched vortex.

As previously mentioned the provision of a vent in such a vortex device prevents the shedding or peeling 01T of the vortex.

Devices incorporating the present invention also provide a convenient means of indicating, under appropriate flow restriction conditions downstream of the latched vortex, the presence and magnitude of a fluid stream upstream of the vortex vent. This is provided by sensing the fluid flow out of the vent orifice. This could be important in feedback or integrated circuits fluid devices in which it is difficult to measure the output because of inaccessibility to test instruments.

The fluid described in this invention can be a liquid or a gas. It can also be a suspension such as liquid or solids suspended in gas, solid particles suspended in a liquid, or some other variation of these phases.

In a latched vortex the vortex is at high pressure and relatively low velocity at its periphery and near the vent orilice the flow has a characteristic of high velocity and relatively low pressure. Thus there is a decreasing pressure gradient across the vortex from the adjacent fluid stream to the vent orifice.

In the drawings forming part of the specification:

FIGURE 1 is a diagrammatical presentation of a generalized fluid bistable element.

FIGURE 2 is a schematic representation of an outlet passage including a latched vortex according to the present invention.

FIGURE 3 shows a section A--A from FIGURE 2.

FIGURE 4 illustrates a semischematic View of a practical embodiment of the present invention.

FIGURE 5 shows a side view of the device shown in FIGURE 4.

FIGURES 6, 7, 8 and 9 show schematically some typical phases in the operation of the device Shown in FIG- UR-ES 4 and 5.

In FIGURE 1 fluid bistable element shown generally at 10 includes a power input passage 11 leading to a power orifice 12 into a interaction zone 13. Right and left control inputs 14 and 1S lead to right and left input orifices 16 and 17 respectively. Right and

left output passages

18 and 19 lead away from interaction zone 13. In operation a fluid power input 11 through power inlet passage 11 passes through power jet orifice 12 into interaction zone 13. Initially, the fluid jet will emerge from the element either through right output passage 18 or left output passage 19 or a combination of the two. However, if the design interaction area 13 is so designed the fluid jet will lock-0n to one of the other of

walls

20 or 21 as a result of entrainment of the fluid between the jet and one or the other of the

walls

20 or 21 and resulting lower pressure region which then swings the jet to one side or the other. When, for example, the jet is locked-on to wall 20 and is thus emerging substantially entirely from output passage 18 a relatively small controlled jet injected through right control inlet 14 through right control orifice 16 will result in destruction of the low pressure region causing the lock-on. A further application of right control jet pressure will by momentum considerations result in the swing of the output jet over to the left outlet passage 19. One jet will then adhere to the passage of wall 21 as a result of a lock-on. There are many variations of this type of device as outlined in the literature listed above.

FIGURE 2 shows a latched vortex vent incorporated into an outlet passage such as outlet passage 18 in FIG- URE l. The fluid stream leaving the upstream interaction region 13 referred to in FIGURE l forms a vortex upon reaching the vortex cusp 31. A portion of the vortex flow is vented through vent orifice 32. In the embodiments shown in FIGURE 2 the passage 33 downstream of the vortex cusp is of greater diameter than passage 30. The transfer of the fluid stream from the smaller passage 30 to the larger passage 33 is effected smoothly and with a minimum of turbulence by virtue of the vortex flow. Also it is found that with the vented vortex flow of the present invention little or no shedding of the vortex occurs and the diffusion to the larger passage is much improved over prior devices. The flow of the Vortex is shown schematically in FIGURE 3 in which it is clearly shown that some of the fluid in the vortex is bled off through Ivent orifice 32.

The latched cusp vortex of the present invention while normally used Within the power fluid control device itself rnay also be located in a conducted passage between fluid elements even at a point remote from the interaction region of these elements.

FIGURE 4 illustrates a plan view embodiment of a pure fluid latched vortex vent in accordance with the present invention where 41 indicates a housing formed by four

flat plates

42, 43, 44 and 45.

Plates

43 and 44 are positioned between

plates

42 and 45 and are sealed between these plates by machine screws 55. These plates may be composed of a metallic, plastic, ceramic or other suitable material. FIGURE 5 illustrates the side view of the pure fluid latched vortex vent shown in FIGURE 4.

The configuration cut from plate 44 provides a fluid flow channel 46 and a swirl chamber 47 located adjacent to the fluid flow channel 46. A circular orifice 48 cut from plate 43 is located with its axis coincident with the centre of the swirl chamber 47. The term orifice as used herein, includes orifices having parallel, converging or diverging walls.

Bores

49 and 50 formed in plate 45 are threaded to receive

tubes

60 and 61 respectively. The end of tube 60 extending from plate 45 is attached to a source of fluid under positive pressure relative to a datum reference pressure indicated by reference 51. The end of tube 61 extending from plate 45 is attached to a fluid flow load or restriction indicated by reference 52. Bore 53 formed in plate 42 is threaded to receive tube 56. The end of tube 56 extending from plate 45 is attached to a fluid sink maintained at constant datum reference pressure indicated by reference 54.

When fluid from the input source 51 flows via the channel 46 into a high positive impedance or high flow resistant load 52 substantially no flow occurs within the swirl chamber 47 or through the vent orifice 48 as indicated in FIGURE 6.

When fluid from the input source 51 flows via the channel 46 into a high positive impedance or high low resistant load 52 a portion of the input fluid flows through the vent orifice 48 -into the fluid sink l54 via a swirling motion within the swirl chamber 47 as indicated in FIGURE 7. It may be seen that in this case of a high flow resistant load, a segment of the outer periphery of the fluid swirl flow which is exposed to the fluid flow in channel 46 forms, in effect, a moving wall for the diffusion process applied to the portion of the fluid flowing into the load thereby ensuring eflicient pressure recovery in the channel 46 downstream of the vent.

When fluid flow from the input source 51 flows via channel 46 into an infinite impedance or complete flow blockage load, all of the input fluid flows through the vent orifice 48 into the fluid sink 54 via a swirl flow within the swirl chamber 47 as indicated in FIGURE 8.

When fluid flow from the input source y51 flows via the channel 46 into a negative impedance or reverse flow load, all of the input fluid plus all of the load fluid flows through the yvent orifice 48 into the fluid sink 54, lthe load fluid being induced into the swirl flow through viscous entrainment as illustrated in FIGURE 9. The resistance to `flow of fluid at vent orifice 48 is dependent upon the pressure drop across the swirl -flow within the swirl chamber 47 from the adjacent fluid stream in channel 46 to the vent orifice 48. This swirl flow pressure drop results from two fluid flow phenomena within the swirl chamber; namely the pressure drop due to viscous drag and turbulent flow energy dissipation; and the pressure drop associated `with increasing fluid flow tangential velocity towards the vent orifice resulting from flow angular momentum considerations. Thus the greater the degree of swirl of the uid ow within the swirl chamber 47, the greater the resistance to uid ow through the vent orice 48 to the fluid sink 54. It can be seen that the degree of swirl of the tluid -ow within the swirl chamber 47 is dependent on thediameter of the vent orilice 48 relative to the diameter of the swirl chamber 47.

When a step function is superimposed on a steady state flow input from the fluid source 51 to the channel 46 a pressure wave is generated and propagated at the local speed of sound, through the fluid in the channel. The swirl ow in the swirl chamber 47 rotating in the direction of propagation of the pressure wave does not inhibit the passage of the pressure wave downstream thereof. Discontinuities in the fluid ow channel, such as right angle turns, open ended passages and blocked passages reflect pressure waves. The swirl flow in the swirl chamber 47 rotating in a direction opposite to the direction of propagation of the reflected pressure waves has been shown to inhibit or attenuate these reected pressure waves, thus reducing or eliminating their disturbing influence on, for example, a uid interaction region 13 of a uid element upstream.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a pure fluid control device the combination of:

(a) `a uid inlet jet;

(b) a control jet;

(c) a jet interaction region into which the fluid inlet jet and the control jet are arranged to discharge;

(d) an outlet passage arranged to receive fluid discharged from the fluid inlet jet which has passed through the jet interaction region;

(e) a circular vortex chamber disposed for the most part to one side of the outlet passage but having part of its periphery extending into that passage;

(f) a cusp formed by the intersection of the vortex chamber and the outlet passage; and

(g) a centrally disposed fluid outlet vent from the vortex chamber, the axis of this outlet vent lying laterally to one side of the outlet passage.

2. The control device according to claim 1, in which:

(a) a Wall of the outlet passage intersects a wall of the vortex chamber to form the cusp at a side of the vortex chamber towards` which fluid from the jet interaction region flows;

(b) a continuation of the said Wall of the outlet passage also intersects the wall of the vortex chamber;

(c) the continuation of the said wall is parallel to the said wall; and

(d) the continuation of the said wall is displaced laterally from the said wall towards the axis of the outlet vent.

References Cited UNITED STATES PATENTS 2,841,182 7/1958 Scala 138-37 2,894,703 7/ 1959 Hazen 137-815 3,185,166 5/1965 Horton 137-815 3,194,512 7/ 1965 Saunders 137-815 3,209,774 10/ 1965 Manion 137-815 3,225,780 12/ 1965 Warren 137-815 3,232,095 1/ 1966 Symnoski 137-815 3,238,960 3/1966 Hatch 137-815 3,329,152 7/1967 Swartz 137-815 M. CARY NELSON, Primary Examiner.

Claims

1. IN A PURE FLUID CONTROL DEVICE THE COMBINATION OF: (A) A FLUID INLET JET; (B) A CONTROL JET; (C) A JET INTERACTION REGION INTO WHICH THE FLUID INLET JET AND THE CONTROL JET ARE ARRANGED TO DISCHARGE; (D) AN OUTLET PASSAGE ARRANGED TO RECEIVE FLUID DISCHARGED FROM THE FLUID INLET JET WHICH HAS PASSED THROUGH THE JET INTERACTION REGION; (E) A CIRCULAR VORTEX CHAMBER DISPOSED OF THE MOST PART OF ONE SIDE OF THE OUTLET PASSAGE BUT HAVING PART OF ITS PERIPHERY EXTENDING INTO THE PASSAGE; (F) A CUSP FORMED BY THE INTERACTION OF THE VORTEX CHAMBER AND THE OUTLET PASSAGE; AND (G) A CENTRALLY DISPOSED FLUID OUTLET VENT FROM THE VORTEX CHAMBER, THE AXIS OF THIS OUTLET VENT LYING LATERALLY TO ONE SIDE OF THE OUTLET PASSAGE.