US3405907A - Venturi arrangement - Google Patents

Description

1968 L. T. KAYSER VENTURI ARRANGEMENT Filed May 7, 1965 INVENTOR ZQ7'JLZr ATTORNEY FIG. 4

United States Patent ABSTRACT OF THE DISCLOSURE A venturi arrangement for control of fluid passing therethrough substantially independent of pressure variations downstream of the venturi arrangement in which fluid fed in axial direction of the venturi is deflected at the end of the inlet in direction substantially normal to the axis and passed through a radially outwardly extending annular gap which has a length and width so that its peripheral cross section gradually increases in radially outward direction to a cross section several times larger than its smallest cross section so that the fluid cavitating and partly evaporating in the region of the smallest cross section of the gap will recondense in the latter to produce thereby a constant fluid flow through the venturi arrangement independent of pressure variations downstream of the gap.

In the field of control and measurement of fluid flow, as well as in the field of hydraulic control arrangements, control means are necessary in which the amount of fluid flow passing through the control means is completely or at least nearly independent from the fluid pressure downstream of the control means. Throttle valves, regulating pumps and complicated regulating arrangements have been used for this purpose, however, the above stated requirements have only to a limited degree been satisfied with such arrangements.

Lately, cavitating venturi tubes, comprising a convergent tube portion and a coaxial divergent tube portion joined to the smallest cross section of the convergent tube portion and diverging at a very small acute angle, have been used for controlling the flow of liquids substantially independent of the pressure downstream of the control arrangement.

In such known venturi tubes the velocity of the flow of the liquid therethrough increases until the static pressure of the liquid is equal to the vapor pressure of the liquid, whereby the liquid starts to cavitate with the result to limit the amount of liquid flowing through the venturi tube to a maximum value. The amount of flow of liquid through the venturi tube becomes independent from the pressure downstream of the venturi tube due to this hydrodynamic effect.

To change the amount of fluid flow per time unit passing through such an axial venturi tube it is necessary to change the smallest cross section of the passage, which may for instance be accomplished by a conically tapering axial movable control mandrel coaxially arranged with the venturi tube and movable in axial direction into and out of the smallest cross section of the tube. The practical construction of such arrangement is, however, rather difficult, especially in venturi tubes of small dirnensions in which the central mandrel has to be exactly I guided which due to the necessarily close tolerances will result in an expensive construction. Furthermore, it is practically impossible to produce with such a construction a change of the throughput of liquid which is in linear relationship to the axial movement of the mandrel. In addition, the relationship of upstream fluid pressure to the "ice maximum allowable downstream fluid pressure will in such a venturi tube not be constant over the whole control range, but this relationship will depend to a great degree on the smallest cross section which is open at any time. Furthermore, the necessary sealing of the movable mandrel complicates such a construction and creates also undesired maintenance problems.

It is an object of the present invention to overcome these difliculties and disadvantages of known control means of the aforementioned kind, especially of venturi tubes with axial in and out flow.

It is an additional object of the present invention to provide a venturi arrangement operating according to the principle of a cavitating venturi tube, which is usable as a regulating valve and which is simple in construction so it can be manufactured at very reasonable cost and will stand up trouble free under extended use.

It is an additional object of the present invention to provide a venturi arrangement of the aforementioned kind in which all sealing problems are eliminated.

With these objects in view, the venturi arrangement of the present invention basically comprises housing means having an axial inlet passage means for feeding a fluid, for instance liquid under pressure into the housing means, and wall means defining an annular gap extending in radia1 outward direction from the inlet passage means. Deflector means are also provided which extend substantially normal to the axis of the inlet passage means and which are arranged opposite and spaced from the inner end thereof for deflecting the axial stream of fluid passing through the inlet passage means in radial outward direction and the wall means defining the annular gap extend from the space between the inner end of the inlet passage means and the deflector means in radial outward direction to guide the fluid in a sheet-like annular stream in radial outward direction. The adiabatic evaporation taking place in the smallest cross section of the annular gap will produce such an increase of the specific volume of the fluid passing therethrough that the amount of fluid passing per time unit through the arrangement will be substantially constant and substantially independent from the fluid pressure downstream of the arrangement while the downstream fluid pressure is less than the inlet fluid pressure. Thereby it is important the the cross section of the annular gap downstream of the smallest cross section thereof increases gradually so that the condensation of the mixture of saturated vapor passing therethrough can take place during a sufliciently long time and in a stable manner. The logitudinal cross section of the annular gap has therefore to be formed accordingly in such a manner that the peripheral flow cross section of the annular gap increases gradually in radial outward direction to a cross section which is several times larger than the smallest peripheral cross section.

The deflector means may comprise a flexible membrane forming part of the wall means defining the aforementioned annular gap, which membrane is at its outer perighery fixed t0 the housing means. Such an arrangement includes further means engaging substantially central portion of the membrane at the surface thereof facing away from the inner end of the inlet passage means for moving the central portion of the membrane toward or away from the inner end of the inlet passage means to change thereby the axial thickness of the annular gap. The deflector means may also be constituted by an axially movable piston arranged opposite the inner end of the inlet passage means and having preferably a convexly curved surface facing the inner end of the inlet passage means.

The arrangement may also comprise spring means having a characteristic changing according to a linear or square function and acting on a central portion of the membrane or on the piston in a direction opposite to the force imparted thereto by the pressure of the fluid passing into the housing through the inlet passage means and impinging on the membrane or the piston. The arrangement may also include fluid passage means communicating with the inlet passage means and guiding fluid with substantially the same pressure as will reside in the inlet passage means to the surface of a central portion of the membrane or to the movable piston which faces away from the inner end of the inlet passage means so that the same pressure will act on opposite sides of the membrane or the piston, whereby the arrangement will become independent from fluid pressure variations upstream of the venturi arrangement.

The axial adjustment of the central portion of the membrane or of the piston, necessary for the control of the amount of fluid flowing through the arrangement, can also be produced by screw means acting on the rear face of the membrane or the piston. The pitch of the screw thread of the screw means is preferably chosen in such a manner that the total desired adjustment of the axial thickness of the annular gap can be produced with a single revolution of the screw means so that the adjusted axial thickness of the annular gap and therewith the adjusted throughput of fluid can be easily observed, respectively set, by means of a pointer fixed to the screw for rotation therewith and a linear scale cooperating with the pointer.

The venturi arrangement of the present invention differs from the venturi arrangements known in the art in which the inflow as well as the outflow of the fluid occurs in axial direction, in that, that in the venturi arrangement of the present invention only the inflow of the fluid occurs in axial direction, whereas the outflow downstream of the smallest cross section of the annular gap occurs in a sheet like flow in radial outward direction. The axial smallest cross section of the annular gap is preferably arranged radially outwardly of the cylindrical inner surface of the inlet passage means. The inner end of the inlet passage means preferably gradually increases to blend into the smallest cross section of the annular gap.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. 1 is a schematic axial cross section through the venturi arrangement of the present invention;

FIG. 2 is a partial cross section through a venturi arrangement according to the present invention and illustrating a different arrangement for adjusting the position of the membrane;

FIG. 3 is a partial cross section similar to FIG. 1 and differing therefrom mainly by the configuration of the annular gap; and

FIG. 4 is a partial cross section similar to FIG. 3 and showing a further modification.

Referring now to the drawings and more specifically to FIG. 1 of the same, it will be seen that the venturi arrangement according to the present invention comprises housing means including a first member 1 having a central tubular portion 2 defining an inlet passage means for feeding a fluid under pressure into the housing means. The first member 1 includes further an annular plate-shaped portion 3 having preferably an inner frustoconical surface 3' of a cone angle which is only slightly smaller than 180 and the annular plate-shaped portion 3 is integrally joined at its inner periphery to the inner end of the tubular portion 2. At its outer periphery the annular plate-shaped portion 3 is integrally joined to an annular portion 7 defining an annular chamber 7, and

the annular portion 7 has an outer radial flange 9 spaced in axial and radial direction from the annular plateshaped portion 3. The inner surface of the central tubular portion 2 gradually blends into the inner surface of the plate-shaped portion 3 along a curve 4 which may have the shape of a quarter of a circle or a similar configuration so that fluid may pass the inner end of the tubular portion 2 without turbulence.

The arrangement includes further, a second annular substantially disc-shaped member 11 having a central cylindrical flange 15 extending in axial direction away from the central tubular portion 2 of the first member 1 and an outer flange 17 arranged opposite the flange 9 of the first member. A flexible membrane 10 overlays the inner surface of the second member 11 and the membrane 10- has an outer peripheral portion tightly clamped between the outer flanges 9 and 17 of the first and second member. A plurality of screws 16, only two of which are shown in FIG. 1', extend through appropriate bores in the flange 9 and in the outer periphery of the membrane 10 and are screwed with their ends into threaded bores of the flange 17 to press the flanges 9 and 17 against each other so as to tightly clamp the outer peripheral portion of the membrane 10 between these flanges. Outlet passage means 8 in form of a tube extending fluid-tightly connected to the transverse wall of the annular portion 7 communicates with the chamber means 7 formed by the annular portion 7 of the first member 1. The inner surface 3' of the annular plate-shaped portion 3 of the first member 1 forms with the inner surface of the membrane 10 facing the surface 3' an elongated annular gap 6 having its narrowest cross section at 5 and the annular gap 6 in the embodiment illustrated in FIG. 1 gradually increases in thickness towards the annular chamber 7'.

To change the cross section of the annular gap 6 the arrangement according to the present invention preferably also comprises adjusting means and such adjusting means may include a piston 12 guided for movement in axial direction in the cylindrical flange 15 of the second member 11. The piston 12 engages with its preferably convexly curved end wall 13 a central portion of the flexible membrane 10 so that during axial movement of the piston 12 toward the inner end of the inlet passage means 2 the central portion of the membrane 6 may be inwardly deflected to change thereby the narrowest cross section 5 of the annular gap 6. Inward movement of the piston 12 against the pressure of the liquid passing through the inlet passage 2 into the venturi arrangement may be produced by a screw 14 abutting with one end thereof against the transverse wall 13 of the piston 12. The screw 14 threadingly engages a support member 16 connected in any manner, not shown in the drawing, to the housing of the venturi arrangement and a small wheel 18 may be fixedly connected to the outer end of the screw 14 for turning the latter about its axis. The pitch of the screw thread of the screw 14 is preferably chosen in such a way that the total desired axial adjustment of the piston 12 may be obtained with a single revolution of the screw. A pointer 19 is preferably fixedly connected to the screw 14 and the end of the pointer 19 cooperates with a linear scale 20 provided on the support member 16 about the axis of the screw 14 so that the position of the screw and therewith the axial adjustment of the piston 12 can be easily observed and set.

Instead of the adjusting screw 14 a spring abutting with one end against the transverse wall 13 of the piston 12 and with the other end thereof against a support member similar to the member 16 may also be provided to counteract the forces acting on the inner forces of the central portion of the membrane. Such a spring may have any desired predetermined characteristic so that the spring pressure changes in any desired manner with the change of the axial position of the piston 12 and the spring pressure may also be adjusted by compressing the spring to varying degree by changing the position of the support member against which one end of the spring abuts.

A slightly modified arrangement is partly shown in FIG. 2 in which the cylindrical flange 15 of the member 11 is closed at its outer end and in which passage means 21 are provided which communicate at one end thereof with the inlet passage means 2 and at the other end thereof with the space between the piston 12 and the outer closed end of the cylindrical portion 15'. Such a passage 21 may be used in an arrangement in which the piston 12 is pushed inwardly by a rod 22 to which a variable force is applied in axial direction and in which it is desired to change the axial position of the piston 12 and therewith the axial cross section of the annular gap 6 in dependence on the variable force applied against rod 22. The passage means 21 will assure that in this case the axial position of the piston 12 is not influenced by variations of the pressure of the fluid passing through the inlet passage means 2, since the passage means 21 will equalize the pressure acting on opposite sides of the central portion of the membrane 10, so that the axial position of the piston 12 and therefore the position of the central portion of the membrane will depend only on the force applied onto the rod 22.

While FIG. 1 illustrates an arrangement in which the axial thickness of the annular gap 6 gradually increases in radially outward direction, FIG. 3 shows anarrangement in which the inner surface 3" of the plate-shaped portion of the member 1 is parallel to the opposite surface of the second member 11 so that the axial thickness of the annular gap 6 is constant throughout its length. FIG. 4 shows a further arrangement in which the inner surface 3 of the member 1" is inclined in the direction opposite to that shown in FIG. 1 so that the axial width of the annular gap 6" decreases gradually in radially outward direction. Instead of connecting the outer flanges 9 and 17 of the two members together by screws 16, as shown in FIG. 1 it is also possible to Weld the two flanges 9 and 17 and the outer peripheral portion of the membrane 10 together as shown at 23 in FIGS. 3 and 4.

The inner surface of the membrane 10 and/ or the inner surface 3', 3" or 3" may be roughened to provide for a pressure drop in the fluid passing between these surfaces.

The venturi arrangement above described may be used for control of fluid (amount of flow and mixture ratio of fuel and a combustion agent) independent of the pressure downstream of the venturi arrangement for rocket engines or other combustion engines, for feed control independent of the load acting on the feed mechanism in hydraulic devices, especially in machine tools. By use of metal membranes of appropriate material, it is possible to control and adjust the flow of aggressive or very hot liquids, for instance also the flow of molten metals. This is especially possible with the venturi arrangement according to the present invention in which no sealing means which would be attacked by such liquids are necessary and in which the members forming the housing of the venturi arrangement may be welded together. The venturi arrangement of the present invention can be used as a regulating valve which is independent from pressure variations downstream of the valve in all such cases Where a simple throttle valve is unsuitable or where axial cavitating venturi tubes, control pumps or other control arrangements would be too expensive or not be suitable in view of the characteristics of the fluid medium to be controlled.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of venturi arrangements differing from the types described above.

While the invention has been illustrated and described as embodied in a venturi arrangement having an axial inlet passage and means to deflect the flow of fluid in a sheet like annular stream in radial outward direction, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a venturi arrangement for controlling flow of fluid, especially liquid, therethrough, in combination, housing means having an axial substantially cylindrical inlet passage means for feeding a fluid under pressure into said housing means, said inlet passage means having an inner end; and wall means defining an annular gap, said gap having a radial length which is a multiple of its maximum axial thickness, said annular gap having its smallest peripheral cross section in the region of said inner end of said passage means and said peripheral cross section gradually increasing in radially outward direction to a peripheral cross section which is several times larger than said smallest peripheral cross section, said gap constituting means for causing cavitation and partial evaporation of the fluid in said smallest peripheral cross section and subsequent recondensation of the fluid during radial outward flow thereof for thereby producing a constant fluid flow through the arrangement substantially independent of pressure variations downstream of said gap while the downstream fluid pressure is less than the inlet fluid pressure.

2. In a venturi arrangement as set forth in claim 1, and including deflector means extending substantially normal to the axis of said inlet passage means and arranged opposite and spaced from said inner end thereof for deflecting an axial stream of fluid passing through said inlet passage means in radially outward direction, said annular gap extending in radial outward direction from the space between said inner end of said inlet passage means and said deflector means to guide the fluid in a sheet-like stream in radially outward direction.

3. In a venturi arrangement as set forth in claim 2, and including means for changing the axial thickness of said gap.

4. In a venturi arrangement as set forth in claim 2, wherein the axial thickness of said annular gap gradually increases from the radially inner to the readily outer end of said gap.

5. In a venturi arrangement as set forth in claim 4, wherein the shape of the longitudinal cross section of said annular gap corresponds to the desired speed of condensation of the fluid passing therethrough.

6. In a venturi arrangement as set forth in claim 2, wherein the axial thickness of said annular gap gradually changes from the radially inner to the radially outer end of said gap.

7. In a venturi arrangement as set forth in claim 6, wherein the relation of the cross section of said inlet passage means to that of said narrowest portion of said annular gap is such that when gas at a given pressure is fed through said inlet passage means into said housing means, said gas will reach sonic speed at said narrowest portion of said gap to limit thereby the amount of gas flowing through the venturi arrangement substantially independent of pressure variations downstream of said gap.

8. In a venturi arrangement as set forth in claim 2, and including annular chamber means coaxially arranged about said inlet passage means, said annular gap extending from the space between said inner end of said inlet passage means in radially outward direction to said annular chamber means, and outlet passage means communicating with said annular chamber means.

9. In a venturi arrangement as set forth in claim 8, wherein said wall means are arranged and constructed so that said annular gap has a uniform axial thickness.

10. In a venturi arrangement as set forth in claim 8, wherein said Wall means are arranged and constructed so that said annular gap has an axial thickness gradually increasing toward said annular chamber means.

11. In a venturi arrangement as set forth in claim 8, wherein said wall means are arranged and constructed so that said annular gap has an axial thickness gradually decreasing toward said annular chamber means.

12. In a venturi arrangement as set forth in claim 8, and including adjusting means operatively connected to said deflector means for adjusting the axial position thereof in order to vary the smallest cross section of said gap to change thereby the flow of fluid through the venturi arrangement.

13. In a venturi arrangement as 'set forth in claim 8, wherein said wall means comprises a rigid annular wall integrally joined at the inner and outer periphery thereof to said inner end of said inlet passage means and to said annular chamber means, respectively, and wherein said deflector means comprises a circular membrane having an inner surface facing an inner surface of said rigid annular wall and being spaced a small distance therefrom and 'fluid-tightly joined at its outer periphery to said annular chamber means, said annular gap being formed between said inner surface of said membrane and said inner surface of said rigid annular Wall, and including means engaging that surface of said membrane which faces away from said rigid wall at a substantially central portion thereof in combination, housing means including a first member 1 having a central tubular portion defining an inlet passage means for feeding a fluid under pressure into said housing means, an annular plate-shaped portion extending transverse to the axis of said tubular portion from the inner end of the latter and integrally'joined at its inner periphery to said inner end, and an annular portion defining an annular chamber arranged coaxially with said tubular portion and integrally joined to the outer periphery of said plate-shaped portion, said annular portion defining said annular chamber having an outer radial flange spaced in axial and radial direction from said annular plateshaped portion; a second annular substantially disc-shaped member having a central cylindrical flange extending in axial direction away from said central tubular portion of said first member, and an outer radial flange opposite said outer flange of said first member, said second member having an inner surface axially spaced from an inner surface of said plate-shaped portion of said first member; a flexible membrane overlaying said inner surface of said second member and having an outer peripheral portion tightly clamped between said outer flanges to define with said inner surface of said plate-shaped portion of said first member an annular gap extending from the inner end of said central tubular portion to said annular chamber so that a fluid fed through said tubular portion into said housing means will be deflected in a sheet-like stream passing through said annular gap into said annular chamher, said annular gap having a radial length which is a multiple of its maximum axial thickness and said annular gap having its smallest peripheral cross section in the region of said inner end of said central tubular portion and said peripheral cross section gradually increases in radially outward direction to a peripheral cross section which is several times larger than said smallest peripheral cross section, said gap constituting means for causing cavitation and partial evaporation of the fluid in said smallest cross section and subsequent recondensation of the fluid as it passes toward said annular chamber for thereby producing a constant fluid flow through the arrangement substantially independent of pressure variations downstream of said gap while the downstream fluid pressure is less than the inlet fluid pressure; means for connecting said outer flanges to each other with said outer peripheral portion of said flexible membrane tightly clamped between said outer flanges; a piston member slidably guided in said central cylindrical flange of said second member so as to be movable toward and away from said inner end of said tubular portion, said piston member engaging the outer surface of said membrane at a central portion thereof to change during axial adjustment of the position of said piston member the thickness of said annular gap so as to regulate the amount of fluid passing therethrough; adjusting means operatively connected to said piston member for adjusting the axial position thereof; and outlet passage means communicating with said, annular chamber.

16. In a venturi arrangement as set forth in claim 15, wherein said adjusting means comprise screw means operatively connected to said piston for adjusting the axial position thereof.

17. In a venturi arrangement as set forth in claim 15, and including passage means connecting said central tubular portion of said first member with said central cylindrical flange of said second member at the side of said piston member facing away from said membrane for applying fluid at the same pressure as in said tubular portion to the side of the piston member facing away from said membrane.

18. In a venturi arrangement as set forth in claim 15, wherein said means for connecting said outer flanges comprise weld means for welding said membrane in a fluidtight manner to said outer flanges.

References Cited UNITED STATES PATENTS 234,602 11/1880 Moore 251-282 816,280 3/1906 Tuttle 138-44 1,986,600 1/1935 Pigott 251-124 X 2,918,933 12/1959 Boitnott 251-124 X 3,003,743 10/ 196 1 Sattler 251-282 3,180,360 4/1965 Pavlin 251-124 X 3,283,767 11/1966 Wright 137-815 2,875,977 3/1959 Stone et al. 251-333 X FOREIGN PATENTS 1,155,578 12/1957 France. 1,181,763 1/1959 France. 1,187,832 3/1959 France. 1,227,692 3/1960 France.

842,565 6/ 1952 Germany.

795,192 5/1958 Great Britain.

895,517 5/ 1962 Great Britain.

M. CARY NELSON, Primary Examiner. R. C. MILLER, Assistant Examiner.

Images