Fluid handling – Processes – With control of flow by a condition or characteristic of a...
Reexamination Certificate
1999-07-27
2001-06-26
Hepperle, Stephen M. (Department: 3753)
Fluid handling
Processes
With control of flow by a condition or characteristic of a...
C137S890000, C137S892000
Reexamination Certificate
active
06250324
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a venturi tube apparatus.
BACKGROUND
Venturi tubes are well known in the art for introducing a second fluid into a first fluid. Typically, the inlet of the venturi tube is attached to a conduit for the first fluid, and the second fluid is introduced through a second inlet, hereafter called an aspirator inlet, so that the combined fluid exits through the venturi's outlet. In operation, the gas or liquid to be introduced is sucked into the venturi through the aspirator inlet, as the fluid flows through the venturi tube. For a given venturi tube, the aspiration rate depends on the flow rate of the fluid which passes through the venturi inlet and the viscosity of the fluids.
One of the major problems associated with conventional venturi tubes is that any single tube can only operate over a narrow range of fluid flow rates. This is in part because back pressure produced within the venturi increases greatly with increases in the fluid flow rate. It is known that this problem can be overcome by connecting an external bypass system to the fluid conduit, in parallel to a venturi tube, so that a portion of the fluid flow stream flowing through the conduit bypasses the venturi by flowing through the bypass system. Conventional bypass systems have several limitations including being costly, bulky and requiring complex plumbing which hinders easy installation in association with an existing fluid conduit.
There exists a need for a simple venturi tube apparatus which can be added easily to an existing fluid carrying conduit and which can operate over a wider range of fluid flow conditions.
SUMMARY OF THE INVENTION
The invention provides for the insertion of a venturi tube directly within a fluid flow stream. A broad aspect of the invention provides an apparatus for use within a conduit for a fluid flow stream comprising a venturi tube having an inlet, an aspirator inlet and an outlet; and supporting means for supporting said venturi tube within said conduit in such a manner that said venturi tube is aligned axially in the direction of said flow stream with the aspirator inlet not in contact with the fluid flow stream.
Another aspect of the invention provides a fluid flow control means which divides the fluid flow stream into a first stream which flows through the venturi tube and a second stream which flows around the venturi tube. The fluid flow control means is adapted to allow the back pressure within the venturi tube (which increases as the fluid flow rate increases) to force an increasing proportion of the flow stream to flow around the venturi tube in order to maintain a relatively constant aspiration rate within the venturi tube. This permits a relatively constant and consistent operation of the venturi tube over a wider range of fluid flow rates by increasing the flow rate of the second stream rather than increasing the flow rate of the first stream as the rate of the fluid flow stream increases.
In another aspect, the invention provides means for inducing a vortex in the second stream, preferably at or near the venturi tube outlet. This induced vortex produces a surprising increase in the venturi effect and reduces backpressure at any given fluid flow rate. In addition, the vortex increases the mixing action of the first and second streams. The induced vortex permits more constant flow rates in the first stream, yielding a satisfactory venturi effect over a wider range of fluid flow rates.
Another aspect of the invention provides for reduced pressure at the venturi tube outlet by means of an increased pipe diameter at that point relative to the diameter of the fluid flow inlet pipe. Preferably, this increased pipe diameter persists over a distance of about 1 to about 4 pipe diameters extending from the venturi outlet; even more preferably, over a distance of about 2 to about 3 diameters from that point.
In another aspect the invention is directed to an aspirator inlet having, at its point of intersection with the venturi tube, a diameter selected so as to achieve a desired flow velocity (or range of flow velocities) as the second fluid is introduced into the first fluid. Preferably, the inner diameter of the aspirator inlet will be selected so as to achieve, in conjunction with the other components of the invention as described herein, high flow velocities, which may be subsonic, sonic or hypersonic, over at least a portion of the operating range of fluid flow rates for a given system.
In a preferred embodiment of the invention the in-line venturi comprises vortex inducing means and increased fluid flow outlet diameter relative to the fluid flow inlet pipe diameter. In a particularly preferred embodiment, the aspect ratio is adjusted so as to provide for optimal vortex formation under the particular flow conditions of the system, and the aspirator inlet comprises an aspirator tube.
In a preferred embodiment of the invention the supporting means comprises a plate or disc inserted within the conduit (or integral therewith). The fluid flow control means comprises first passage means through said plate or disc for allowing said first stream to flow through said venturi tube and second passage means, preferably in the form of at least one aperture, through said plate or disc, for allowing said second stream to flow. The aspiration rate of the venturi tube, for a given fluid flow rate, is determined by the cross sectional area of the venturi tube relative to the cross sectional area of the second passage means. The cross section of the second passage means can therefore be preset for a given venturi tube to be used within a fluid flow stream having a given flow rate, in order to achieve a desired aspiration rate.
Preferably said fluid flow control means further comprises adjusting means for adjusting the flow rate of the second stream, typically by adjustably blocking (or unblocking) said second passage means, in order to maintain a relatively constant flow rate through the venturi tube. Thus the total cross sectional area of the at least one aperture of the second passage means, relative to the cross sectional area of the venturi tube, can be adjusted by varying the extent the apertures of the second passage means are blocked. This allows for a greater range of flow rates of the fluid flow stream to be used with a given venturi tube to produce a desired aspiration rate.
In one embodiment, the adjusting means allows for adjustment of the extent to which the second passage means is blocked.
In another embodiment, the adjusting means includes regulating means, responsive to changes in the fluid flow rate for regulating the flow rate of the second stream. In one such embodiment, the regulating means comprises a blocking means which is biased towards the plate (or disc) by some resilient means, so as to block the second passage means. The blocking means is moved away from the second passage means, against the bias of the said resilient means, by the fluid flow stream as the flow rate (and resulting pressure) increases. Furthermore, both such adjusting means can be utilized together, if desired.
In some applications (for example in cases of high back pressure downstream from the venturi tube), it is desirable to increase the pressure drop across the venturi tube. This acts to increase the aspiration rate of the venturi tube. Consequently, another aspect of the invention provides for an optional constriction means for reducing the pressure at the venturi tube outlet, by constricting the flow of the second stream, in the vicinity of the venturi tube outlet.
In another embodiment, the invention comprises a venturi support body having, at the fluid inflow end, a concave face which acts to direct the incoming fluid stream toward a central aperture and therethrough into a venturi tube which is partly integral to the venturi support body and partly a separate tube held in close apposition against a mating surface on the venturi support body, in which the separate venturi tube further comprises one or more flow directors which cause the formation
Bowman Gerald Earl
Conrad Helmut Gerhard
Conrad Wayne Ernest
Phillips Andrew Richard Henry
Phillips Richard Stanley
Hepperle Stephen M.
Wixon Henry N.
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