US3670755A

US3670755A - Fluid flow control device

Info

Publication number: US3670755A
Authority: US
Inventors: Giancarlo Nardi
Original assignee: Italiana Westinghouse Freni e Segnali SpA
Current assignee: Compagnia Italiana Westinghouse Freni e Segnali; Italiana Westinghouse Freni e Segnali SpA
Priority date: 1968-12-06
Filing date: 1969-09-17
Publication date: 1972-06-20
Anticipated expiration: 1989-06-20
Also published as: FR2025509A1; GB1247426A; DE1961206A1

Abstract

A fluid flow control device in which a housing is provided with a flat chamber having two parallel sides, a supply passage communicating with one end of the chamber and dimensioned to pass between the parallel sides of the chamber a stream of fluid in a substantially laminar flow condition to an aligned output passage on the opposite chamber end, the stream contacting the two flat sides to form a fluid diaphragm and dividing the chamber into two lateral chambers, each communicating with different control pressure passages for pressuring the two lateral chambers at different static pressure levels to provide a differential pressure gradient acting on the full free length of the fluid stream across the chamber, bending the stream an amount determined by the pressure gradient to deliver a portion of the stream to a second output passage adjacent the first output passage.

Description

United States Patent 1 June 20, 1972 Nardi [54] FLUID FLOW CONTROL DEVICE [72] Inventor: Giancarlo Nardi, Pisa, Italy [73] Assignee: Compagnia Italiana Westinghome Freni E Segnali, Torino, ltaly [22] Filed: Sept. 17, 1969 [21] Appl. No.2 858,651

[30] Foreign Application Priority Data Dec. 6, 1968 Italy ..54202 A/68 [52] U.S.Cl ..l37/81.5 [51] Int. Cl. ..Fl5c 1/04 [58] Field otsearch ..137/81.5

[56] References Cited UNITED STATES PATENTS 3,362,421 1/1968 Schaffer..............................137/81.5 3,362,422 1/1968 Toma ..137/81.5

3,405,225 10/1968 Fox ..137/8l.5 3,405,736 10/1968 Reader et al ..137l81.5

Primary Examiner-Samuel Scott Attorney-Adelbert A. Steinmiller and Ralph W. Mclntire, Jr.

[57] ABSTRACT A fluid flow control device in which a housing is provided with a flat chamber having two parallel sides, a supply passage communicating with one end of the chamber and dimensioned to pass between the parallel sides of the chamber a stream of fluid in a substantially laminar flow condition to an aligned output passage on the opposite chamber end, the stream contacting the two flat sides to form a fluid diaphragm and dividing the chamber into two lateral chambers, each communicating with different control pressure passages for pressuring the two lateral chambers at different static pressure levels to provide a differential pressure gradient acting on the full free length of the fluid stream across the chamber, bending the stream an amount determined by the pressure gradient to deliver a portion of the stream to a second outputipassage adjacent the first output passage.

FLUID FLOW CONTROL DEVICE BACKGROUND OF INVENTION This invention relates to the field of fluid flow control devices in general and particularly as it relates to pure fluid devices for controlling the fluid input to other apparatus associated therewith.

Heretofore, in those instances where fluid control devices are utilized for controlling fluid flow to apparatus such as chemical reactors or a device for mixing fluids where the amount of controlled fluid is critical, and particularly where the controlled fluid is of a corrosive type, fluid flow control devices having movable parts are inefficient because of inexact metering and because of their subjection to corrosive damage. Pure fluid proportional amplifiers eliminate the need for relatively movable parts, but are inexact in their control function because of the turbulence induced in the main fluid stream by the shock applied laterally to the main fluid stream by the control jet stream or streams.

SUMMARY OF INVENTION It is the object of the present invention to provide a fluid flow control device for delivering at an output a portion of a substantially laminar stream of supplied fluid in an amount in accordance with static fluid pressure differential across the laminar stream.

In the construction of the apparatus comprising the present invention, it has been found that, by the injection of a liquid stream in a substantially laminar flow condition in a path parallel with and between a pair of substantially parallel flat surfaces closely eorrelatively disposed, the liquid stream joins the two flat surfaces along the path to form with respect to the flat sides a liquid diaphragm. It has further been found that by applying laterally to the liquid diaphragm a pneumatic pressure gradient along its free length so as not to induce turbulence in the fluid stream, it is possible to bend the stream in the direction of the applied pressure gradient, in the manner, for example. that a beam fixed at one end is bent under the application of a laterally applied load.

In accordance with one application of the present invention, a body member having a chamber comprised of at least two spaced parallel flat sides therein includes a fluid supply passage communicating with the open end of the chamber to provide across the chamber, in a path disposed between and parallel with the flat sides, a fluid stream in a laminar flow condition, which stream joins the two sides along the path to form a liquid diaphragm dividing the chamber into a pair of pressure chambers on opposite sides of the fluid stream along its free length. Control pressure passages communicating with each of the pressure chambers are subjected to a pressure differential to provide in the pressure chamber along the free length of the fluid stream a fluid pressure gradient for bending the fluid stream away from a normally straight path, which stream normally communicates with a first outlet passage at the other end of the chamber. The fluid stream is deflected or bent by an amount depending upon the pressure gradient thereacross, toward a second outlet passage disposed adjacent to the first outlet passage. By connecting apparatus to the second outlet passage. the quantity of fluid delivered thereto progressively increases with the bending or deviation of the fluid stream away from the straight path, that is, in accordance with the applied pressure gradient. Conversely, by connecting an apparatus to the first outlet passage, the input to such apparatus will decrease with the increase in the pressure gradient.

This and other objects of the invention will become more readily apparent in the following description, taken in conjunction with the drawing, in which:

FIG. 1 is an elevational view of a fluid flow control device, with the cover removed, showing my invention;

FIG. 2 is a sectional view of the fluid flow control device of FIG. 1, taken along the line 22 of FIG. 1;

FIG. 3 is a partial sectional view of the central portion of FIG. 2, showing a fluid stream therein;

FIG. 4 is a diagram of the principal of the invention, showing fluid path deviation within the flow control device of FIG. 1; and

FIG. 5 is a second embodiment of the flow control device, showing my invention.

Referring now to FIGS. 1 and 2 of the drawing, there is shown a fluid flow control device, generally indicated at 10 comprising a housing structure basically similar to that of the well-known pure fluid amplifier, that is, a wafer comprising a flat base 11, to which is attached in any suitable manner, not shown, a cover plate 12. The base and cover plate may be composed of any suitable material such as plastic, or ceramic, or other material.

The cover plate 12 is omitted from FIG. 1 to show the inner surface of base 11 which is provided with a depression which forms with the cover plate a flat chamber 13 having a flat bottom 14 of uniform depth below the upper face. The periphery of the chamber may be oval, elliptical or circular, as desired. In its present embodiment, the opposite ends 15. 16 of the chamber are semi-circular.

At the chamber end 16 there is provided an inlet or supply passage 17 for supplying a stream of fluid which passes directly across the chamber in the direction of the arrow to the chamber end 15 to an outlet passage 18 aligned with the supply passage 17. Both passages 17 and 18 have flat bottoms in the plane of the fiat bottom 14 of the chamber 13. The sides of passages 17 and 18 are preferably perpendicular to the respective bottoms.

A second outlet passage 19 is disposed adjacent the aforementioned passage 18, and exits from chamber 13 in a manner divergent to passage 18. The two passages 18 and 19 join the chamber 13 in such manner that one vertical wall of each passage meets with the other to form the opposite sides of a stream splitter 20. Passage 19 also has a flat bottom in the plane of the bottom 14 of chamber 13, with the sides thereof perpendicular to the bottom.

In the operation of the flow control device, as thus far described, a liquid is continuously supplied to the inlet or supply passage 17 from a reservoir 21 by a conventional pump 22 preferably of the rotary type. The inlet portion 23 of passage 17 has a cross-sectional area larger than the outlet portion of passage 17 so that, in accordance with the wellknown principles of fluid dynamics, the fluid completely fills the outlet of supply passage 17 and crosses chamber 13 as a compact fluid stream 24, as shown in FIG. 3, in a substantially laminar flow condition.

Under the aforesaid conditions, the stream 24 flows across chamber 13 toward aligned outlet passage 18 in continuous contact with the bottom 14 of chamber 13 and the inner face of cover plate 12. Thus, the fluid stream 24 forms in chamber 13 a fluid diaphragm which divides main chamber 13 into two

sub-chambers

25 and 26, as shown in FIG. 1, the path of which stream remains unaltered from a straight line to outlet 18v so long as the static pressures P1 and P2 in sub-chambers 2S and 26, respectively, are the same.

Referring to FIG. 3 of the drawing, it will be noted that a static pressure gradient applied upon stream 24 by a pressure gradient in

sub-chambers

25 and 26 will necessarily deflect or deviate the fluid stream from a straight path.

Referring now to the diagram of FIG. 4, there is illustrated the manner in which the desired path deviation can be achieved.

In the diagram, L is the free length of stream 24 between

passages

16 and 18 across the chamber 13 as shown in FIG. 1. Provided that the speed V of the stream is constant, and that a static pressure gradient P P =AP is applied to the fluid stream along its entire free length, the fluid stream will assume a path along the arc of a circle, the radius R of which is given by the equation:

R DWV /P 1 l in which D is the density of the fluid and W is the effective cross-sectional area of the 'inlet passage 17. Accordingly, the deviation X of the fluid stream is determined as:

It is therefore evident, by suitably changing the A P gradient, there will be produced a corresponding deviation X of fluid stream 24 from its original straight path to such a degree that a corresponding portion 27 of the stream will be separated from the main fluid stream by means of stream splitter to enter outlet passage 19.

As can be seen in FIG. 1, the geometrical axis of outlet passage 19 is a bent one, such axis corresponding to the extension of fluid path 27 under the condition of total deviation of the fluid stream 24 from outlet passage 18 to outlet passage 19.

Under the existent pressure gradient, as described above, a part of the fluid stream 24 will return to the reservoir 21 through a bypass line 28, while the remaining part 27 will be delivered through a pipe 29 to the device 30, which may comprise apparatus such as a proportionally controlled liquid mixer. By increasing the pressure gradient, the apparatus 30 will be supplied with increasing quantities 27 of the fluid stream 24. Alternatively, if the apparatus is connected to outlet passage 18, and if outlet 19 is connected to bypass 28, it follows that increase in the pressure gradient will correspondingly decrease the quantity of fluid delivered to the apparatus.

From the foregoing description of the apparatus and the operation thereof, it is apparent that the present invention is based upon principles completely different from those involved in the well-known pure fluid amplifier having moving parts. The Coanda effect relied upon in many pure fluid devices to achieve desired results, is deliberately avoided in the present invention. In any case, prior pure fluid amplifiers control the main fluid stream by the moment of force of a control jet acting on a limited length of the main fluid stream. The present invention eliminates the Coanda effect" and utilizes a static pressure gradient, rather than a jet, applied to the entire full length L of a fluid stream to control its flow path. In the present invention, the application of a control jet to the fluid stream 24 would produce turbulence to thereby destroy or at least substantially modify the laminar flow necessary for the operational efficiency of the present invention.

In accordance with the present invention, the control system for the hereinbefore-described laminar stream 24, includes at least one of the sub-chambers and 26 and at least one fluid pressure control passage by which a fluid is provided in the one sub-chamber, the dimension and location of which control passage are such as to provide the formation of a desired static pressure gradient, as distinguished from a jet, between the sub-chambers and across the fluid stream 24.

In the device of FIG. 1, it is desired to provide in subchamber 25 a static pressure larger than that present in subchamber 26. To this end, there is provided in the side of chamber 13 opening to sub-chamber 25, a control passage 31, preferably enlarged at the inlet end 32 so that the kinetic energy of the control fluid, in this instance, a gas, will transform itself into static pressure energy within sub-chamber 25, without applying to the fluid stream 24 in this instance a liquid, a jet shock concentrated on a portion of the stream 24. Therefore, as the pressure in sub-chamber 25 increases, acting upon the entire free length L of the stream, the fluid stream 24 will correspondingly deviate towards the outlet passage 19. That portion of the stream 24 which flows through outlet passage 18 will carry along therewith a portion of the control gas applied by passage 31, forming an emulsion.

In order to facilitate the discharge of the emulsion and to avoid an undesired resistance to the liquid flow through passage 18, there is provided a cross-sectional enlargement 33 in a portion of passage 31 remote from the intersection of passage 31 with sub-chamber 25.

In order to compensate for the amount of gas which leaks from sub-chamber 25 to outlet passage 18, and to avoid undesired fluctuation of the pressure gradient A P between

subcharnbers

25 and 26, the diameter of control pressure passage 31 upstream of portion 32 is made suitably larger than the diameter of the outlet passage 18, preferably at a ratio of 1.5 to I.

In the device of FIG. 1, there are provided two additional

control pressure passages

34 and 35 opening to sub-chamber 26 substantially opposite control pressure passage 31. The

control pressure passages

34 and 35 are utilized to provide in sub-chamber 26 a predetermined pressure P2, no larger than pressure P1 in sub-chamber 25, for effecting better control of fluid stream 24.

The

control pressure passages

34 and 35 demonstrate that the static pressure in sub-chamber 26 may be controlled by more than one variable pressure acting in the same or opposite directions. Thus, a lower pressure P2 produced in subchamber 26 through one of the two

control pressure passages

34 or 35 may be altered by means of the pressure in the other of the two passages.

Passages

34 and 35 each are provided with a diameter larger than that of outlet passage 19, preferably by a ratio of 1.5 to l, and are provided with enlarged outlets for the same reason control pressure passage 31 is enlarged relative to outlet passage 18. Similarly, outlet passage 19 is provided with an enlarged portion 36 remote from the intersection of passage 19 with sub-chamber 13.

It is clear from the foregoing, that in the simplest construction, the stream 24 of FIG. 1 can be controlled by applying a control pressure in control passage 31, and connecting

passages

34 and 35 to atmosphere. In any case, it is preferable to proportion the parameters W and V in formula l) and to chose a control A P such that with a maximum A P only a portion of the stream 24 flows to outlet passage 19, so that some of the stream 24 flows to the outlet 18.

It is also clear from the foregoing and by reference to FIG. 4, that since the pressure gradient is effected by static pressure, the direction of the pressure gradient need not be critical, that is, if desired, the stream 24 may be deviated from its straight path toward either one of the two sides of a straight path in the manner hereinafter described in FIG. 5.

Referring now to FIG. 5, there is shown a flow control device similar to that of FIG. 1 having a base plate 37 and having a chamber 38 divided into two sub-chambers 39 and 40 by a fluid stream 41 supplied to the chamber 38 through a supply passage 42 for normal delivery on a straight path to an aligned outlet passage 43. A pair of

additional outlet passages

44 and 45 are disposed each on a different side of outlet passage 43, each outlet passage being related to outlet 43 in the manner in which the outlet passage 19 relates to outlet 18, as above discussed in FIG. 1.

The static pressures P1 and P2 are applied to the fluid stream 41 via a pair of large ports .46 and 47 disposed in the bottom of sub-chambers 39 and 40, respectively, or disposed at any point of the flat surfaces defining the chamber 38. The fluid stream is deviated towards one or the other of

outlet passages

44 or 45, depending upon the static pressure Pl being larger than P2, or vice versa.

Referring again to FIG. 3 of the drawing, it is to be noted that the planarity of the inner surface of cover plate 12 and the bottom 14 of base plate 11, and also the parallelism therebetween, must be substantially constant for those portions thereof wetted by the liquid stream 41. These portions are generally illustrated in FIG. 5 as that area between the

dotted lines

48 and 49. Beyond the limits of this area, the aforementioned inner surface of the cover plate 12 and the bottom 14 of the bore plate 11 need not be flat or parallel.

The peripheral contour of chamber 13 of FIG. 1 or 38 of FIG. 5 are preferably rounded, as indicated, to eliminate attachment of the liquid stream thereto as resultant from the Coanda effect."

Having now described the invention, what I claim as new and desire to secure by Letters Patent, is:

1. A fluid flow control device, comprising:

a. a housing having a flat chamber therein,

b. said chamber including a pair of flat, parallel sides,

c. an inlet passage in said housing communicating with said chamber and having a configuration and disposition such that, when pressurized by a fluid, will project across said chamber in a straight path a stream of said fluid in a laminar flow condition, said stream joining said two flat parallel sides along said path to form a fluid diaphragm, dividing said chamber into a pair of sub-chambers,

d. a first outlet passage in said housing and communicating with said chamber in alignment with said inlet passage and said fluid stream,

e. a second outlet passage communicating with said chamber adjacent said first outlet passage to one side of said straight path,

fr at least one control passage communicating with one of said fluid stream toward said second outlet,

g. said fluid stream comprises a liquid and said fluid provided through said one control passage comprises a gas.

h. said first outlet passage having a cross-sectionally enlarged area at the outlet end thereof, and

i. the effective minimum cross-sectional area of said one control passage is larger than the effective minimum eross-sectional area of said first outlet passage.

2. A fluid flow control device, as recited in claim 1, in which said sub.chambers which when pressurized by a fl id 10 said effective minimum cross-sectional area of said one convides in said one sub-chamber a static fluid pressure higher than in the other of said pair of sub-chambers to effect a pressure gradient along said path for deviating trol passage is substantially 1.5 times larger than the effective minimum cross-sectional area of said first outlet passage.

Claims

1. A fluid flow control device, comprising: a. a housing having a flat chamber therein, b. said chamber including a pair of flat, parallel sides, c. an inlet passage in said housing communicating with said chamber and having a configuration and disposition such that, when pressurized by a fluid, will project across said chamber in a straight path a stream of said fluid in a laminar flow condition, said stream joining said two flat parallel sides along said path to form a fluid diaphragm, dividing said chamber into a pair of sub-chambers, d. a first outlet passage in said housing and communicating with said chamber in alignment with said inlet passage and said fluid stream, e. a second outlet passage communicating with said chamber adjacent said first outlet passage to one side of said straight path, f. at least one control passage communicating with one of said sub-chambers which when pressurized by a fluid provides in said one sub-chamber a static fluid pressure higher than in the other of said pair of sub-chambers to effect a pressure gradient along said path for deviating said fluid stream toward said second outlet, g. said fluid stream comprises a liquid and said fluid provided through said one control passage comprises a gas, h. said first outlet passage having a cross-sectionally enlarged area at the outlet end thereof, and i. the effective minimum cross-sectional area of said one control passage is larger than the effective minimum crosssectional area of said first outlet passage.

2. A fluid flow control device, as recited in claim 1, in which said effective minimum cross-sectional area of said one control passage is substantially 1.5 times larger than the effective minimum cross-sectional area of said first outlet passage.