Control Of Fluid Dynamics In Spiraling Gas Streams

Abstract

Spin rate and volume flow rate of spiraling gas streams are regulated to control the fluid dynamics thereof. At constant supply pressure, either the spin rate or the volume flow rate of the spiraling stream can be changed without altering the other rate. Should the supply pressure change, both rates can be maintained constant. In addition, the spin rate can be increased even if the static pressure is lowered and can on the other hand be decreased if the static pressure is raised. These effects are accomplished by regulating the spin rate and the volume flow rate of a spiraling gas stream independently of one another.

Description

BACKGROUND OF THE INVENTION

A flowing stream of gas can be formed into a spiraling stream in order to better utilize the kinetic energy of the stream. For instance, the turbulence and shearing actions which occur within spiraling gas streams enhances mixing and reaction with another fluid, e.g. the mixing of air and a fluid fuel in a combustion process. In other cases, the momentum of the gaseous spiral is imparted to still another material for the processing thereof, e.g. centrifugal separation of entrained solids or liquids, or fluid energy grinding of entrained solids. Also, the momentum of a spiraling gas stream can be transferred to an even larger body of gas for imparting a spiraling or swirling motion thereto, e.g. a process as described in U.S. Pat. No. 3,301,639.

Heretofore, the average spiraling velocity (spin rate) and volume flow rate of spiraling gas streams have been interdependent since it has not been readily possible to alter one without directly affecting the other. Thus, at constant supply pressure, the volume flow rate of a gas spiral could not be lowered without lowering the spin rate. On the otherhand, if supply pressure changed, the volume flow rate and the spin rate could not be maintained at preestablished conditions. Furthermore, the spin rate could not be increased when the supply pressure was reduced, and the spin rate could not be reduced when the supply pressure was increased. As a consequence, the kinetic energy potential of a spiraling gas stream could not be developed and utilized to the desired extent in many cases.

SUMMARY OF THE PRESENT INVENTION

It is therefore an object of the present invention to control the spin rate and the volume flow rate of a spiraling gas stream independently of one another.

It is another object of the present invention to provide control over the fluid dynamic conditions of a spiraling gas stream.

In accordance with the present invention independent means are therefore provided for regulating both the spin rate and the volume flow rate of a spiraling gas stream. The spiraling gas stream can be produced by introducing the gas tangentially into a cylindrical chamber or barrel. The barrel can, for instance, have an elongated circumferential wall with a closure at one end and a discharge outlet at the other end, and it can be provided with a gas inlet located at a distance far enough upstream of the outlet to permit adequate formation of the spiraling stream as the gas traverses the length of the barrel. The gas which is shaped into a spiral can then be fed into the barrel by means of a gas supply conduit which communicates with the aforesaid inlet.

For controlling the spin rate and the volume flow rate of spiraling gas stream, a dual gated valve can be placed in the gas supply conduit and located proximal to the gas inlet of the aforesaid barrel. Both of the valve gates should be movable in crosswise relation to each other and in a direction which is transverse in relation to the normal direction of gas-flow through the valve. More particularly, one gate can be movable at angle which is about 90.degree. in relation to the direction in which the other gate is moved. When constructed in such a fashion, the valve can be arranged in the gas supply conduit so that one gate moves transversally and the other axially in relation to the longitudinal axis of the barrel.

When using the above-identified arrangement, the transversally movable gate of the valve can be positioned so that the gas inlet is partially obstructed, thus forcing the gas stream to enter predominately to one side of the barrel, i.e. tangentially, and form a spiral therein. At the same time the axially movable gate is positioned to establish a passageway in the valve of sufficient open area to permit a desired volume flow rate at the existing supply pressure. At any given supply pressure, the axially movable valve gate can be repositioned to alter the volume flow rate of gas in the spiraling stream without materially affecting the spin rate. On the otherhand, the transversally movable gate may be repositioned to alter the spin rate, i.e. the smaller the opening created by closure of the gate the faster the spin, and vice versa. At constant pressure this also has the effect of lowering volume flow rate, but this can be compensated for by further opening of the axially movable gate, thus increasing the total open area of the passageway through the valve. It will nonetheless be appreciated that this repositioning of the axially movable gate primarily alters the volume flow rate of the spiral and does not materially effect the spin rate thereof.

It will be understood that the control means just described can also be employed to maintain a desired volume flow rate or spin rate by repositioning of the valve gates upon change in the supply pressure. Thus, at a given setting of the two gates the desired spin rate can be maintained by opening or closing the first gate as the pressure decreases or increases, respectively. In the same fashion, the desired volume flow rate can be maintained by opening or closing the second gate as the supply pressure decreases or increases, respectively.

As previously indicated, the present invention can also be utilized for increasing the spin rate of a spiraling stream even when the stream supply pressure is lowered; or, on the other hand, to decrease the spiraling rate when the supply pressure is raised. To increase spin rate after reduction in the supply pressure, the transversally movable valve gate is closed further than before, and the axially movable gate can be repositioned to establish a desired volume flow rate. A reverse procedure is employed for reducing the spin rate when the supply pressure increases, i.e. the transversally movable valve gate is opened further than before and the axially movable gate can be repositioned to establish a desired volume flow rate.

Each component of the previously described control system should be sized large enough, of course, to permit accomplishment of desired spin velocities and flow rates at the available gas stream supply pressures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration, mostly in section, of one form of apparatus, which can be employed in the practice of the invention.

FIG. 2 is a sectional view along the lines 2--2 of FIG. 1.

FIG. 3 is a sectional view along the lines 3--3 of FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENT

The present invention will be described with particular reference to a spiral mixer-burner which can be employed in the formation and ignition of combustion mixtures, but it will be understood that the invention can be employed for controlling the dynamic characteristics of any spiraling gas stream.

FIG. 1 depicts a cylindrical mixing barrel assembly having an elongated circumferential wall with a closure plate 2 at one end, a discharge outlet 3 at the other end, and a gas inlet 4 substantially upstream of the discharge outlet. The end closure plate 4 is affixed to the barrel by means of a flange 5 and fasteners 6.

For feeding a gaseous component of a fuel mixture into the barrel, a gas supply conduit 7 intercommunicates with the inlet 4 through a valve, generally represented at 8. For supplying a second gaseous or liquid component of the combustion mixture, a conduit 9 passes through a guide 10 affixed to plate 2 and extends axially into the barrel. The conduit 9 can be provided with an atomizing nozzle or gas distributor 11 at the tip end thereof.

In the illustrated case, the mixer barrel assembly is shown attached to a burner block 12 which is constructed of a high-temperature refractory and wherein ignition of the combustible mixture can be initiated. The burner block can, of course, be located in the wall of a furnace chamber wherein ignition of the mixture can be either initiated or carried forward thereafter. Alternately, the circumferential wall 1 of the barrel can be constructed of a refractory material when it is desirable to initiate and carry on combustion therein.

The valve, generally represented at 8, is provided with a first gate 13 which is movable transversally with respect to the longitudinal axis 14 of the barrel, and a second gate 15 which is movable axially with respect to the axis. Other components of the valve are end plates 16a and 16b, whereby the valve assembly is attached to the gas supply conduit 7 and the gas inlet 4, respectively; sealing gaskets 17a, 17b, and 17c; and spacers 18a and 18b, whereby the valve is made gastight while providing means for guided movement of the gates. The valve assembly is held together by means of fasteners 19. Thus, the aforementioned end plates, gaskets and spacers of the valve form a casing when all are securely fastened together, the purpose of the casing being to retain the gas within the system while holding the gates in place. Accordingly, the gaskets and spacers bound channels, or seats, for guiding movement of the gates within the casing while also forming a relatively tight seal with the edges of the gates. In the illustrated case the gates are rectangular plates, but it will be understood that even other shapes can be adapted to the purpose, e.g. circular discs.

The transversally movable gate 13 can be positioned and retained in location by means of a threaded screw 20 in a threaded member 21, the latter of which is affixed to the plate 13. The outer end of the screw 19 is provided with a crank 22. The screw 19 is stablized with a mounted bearing affixed to a support plate 24. The axially movable gate 15 is equipped with equivalent positioning means, generally represented at 25.

As can be seen from the drawings, and especially FIG. 3, the valve gates 13 and 15 are arranged to move transversally with respect to normal flow of a fluid through the valve while also being arranged to move crosswise in relation to each other. Arranged thus, a fluid passageway 26 in the valve is established by opening and/or closing the gates, and the open area and configuration of the passageway is thus dependent upon positioning of the gates in relation to one another. With respect to the longitudinal axis 14 of the barrel, gate 13 thus controls the width of the inlet 4, while gate 15 controls the length thereof.

It will be appreciated that closing of the gate 13 so that it extends inwardly beyond the longitudinal axis of the barrel creates a passageway 26 which provides tangential injection of gas into the barrel. The further gate 13 is closed, the faster will be the spiraling velocity, at any given volume flow rate, of the gaseous spiral within the barrel. As previously pointed out, closure of gate 13 also has the effect of reducing volume flow, but this can be reestablished by opening ate 15. Thus, both the volume flow rate and the velocity of the gas which passes through the valve can be finely controlled by means of the dual gates. Advantageously, the gates can be arranged, as illustrated, to cross at about a right angle, but it will be appreciated that equivalent effects can be obtained with other angles.

The spiraling gas stream that is produced in the mixing barrel has been generally depicted at 27 in the drawings. Upon discharge from the end of the barrel, or the burner block 12, the gas stream will have a predominate momental direction which is to one side of the axis of the barrel, and can thus be employed as described in U.S. Pat. No. 3,301,639 for imparting a spiral to the gaseous contents of a furnace. It will also be appreciated that the conduit 9 can be positioned axially within the barrel so as to effect mixing of the second fluid component with spiraling gas stream, either within the barrel, beyond it, or at the discharge outlet thereof.

In operation at fixed gas supply pressure, the movable gate 13 is positioned to lend a width to the passageway 26 which will impart a desired spiraling velocity to the gas stream which enters the barrel through the inlet 4. Narrowing the width of the passageway forces the gas stream to flow in a more proximal relationship with the circumferential wall 1, thus increasing the average rotational velocity of the stream. As the width of the passageway is increased by opening gate 13, the average rotational velocity of the gas stream is reduced since it is permitted to occupy a larger part of the cross-sectional area of the barrel. The spiraling stream can thus be visualized as an annulus, the "eye" of which is increased and decreased in size by transversal movement of the first gate.

Volume flow to the spiraling stream is regulated by axial movement of gate 15 which controls the length of passageway 26. Once the desired rotational velocity of the stream has been established by positioning the transversally movable gate, the axially movable gate is positioned to effect the desired volume flow rate. Should the gas pressure change in conduit 7, the gates can be repositioned to maintain the desired spin and volume flow rates.

The present invention can also be employed to either increase the spin rate of the spiraling stream upon reduction in the gas supply pressure, or to reduce the spin rate when the pressure is increased, by positioning of gate 13 to control the spin rate.

Advantageous use of the present invention mixing process will be further described. Air, at a relatively constant pressure, can be supplied to the barrel assembly by means of a blower or compressor. Either a gaseous or a liquid fuel can be supplied through conduit 9. The atomizing nozzle or gas distributor can be positioned within the barrel to effect mixing therein followed by initiation of combustion in the burner block 12. When it becomes desirable to reduce the input of air, i.e. to turn down the burner, the mixing pattern can become considerably altered unless the spin velocity is maintained or even increased. By means of the present invention, the mixing pattern can thus be finely regulated by maintaining or increasing spin rate at reduced volume flow rate or supply pressure. Furthermore, the momentum of the spiraling stream, as is valuable for instance in imparting a spiraling or motion to an even larger body of gas, can be more closely controlled. Conversally, spin rate and momentum of the spiraling stream can be reduced when desired by means of the gate 13, since the spiral formation will gradual diminish as this gate is progressively opened; and can, in fact, be entirely eliminated if opened substantially beyond the longitudinal axis of the barrel.

While the invention has been described with reference to particular materials, apparatus and process conditions, it will be understood that still others may be employed without departing from the spirit or scope of the invention as expressed in the appended claims.

Claims

Therefore, what is claimed is:

1. Apparatus for regulating the fluid dynamic characteristics of a spiraling gas stream comprising:

a. a barrel wherein a gas stream flows as a spiraling stream,

b. a flow control valve through which said gas stream is supplied to said barrel, said valve having:

1. a casing, at least a portion of the casing being in a plane substantially tangent to the barrel,

2. a first gate seated within said casing and guidedly positionable therein transversally with respect to normal flow of gas through the valve and also transversally with respect to a plane through the longitudinal axis of said barrel to the gate, the gate abutting said portion of the casing when the gate is closed,

3. a second gate seated within said casing and guidedly positionable therein transversally with respect to normal flow of gas through the valve and parallel with respect to the longitudinal axis of the barrel so that each of the gates is movable transversally to the movement of the other,

4. a gas passageway which is established in said valve when both of said gates are partially open and from which said gas stream is directed tangentially into said barrel at controlled cross-sectional width and length dependent upon the relative position of said gates to one another,

5. means connected to the gates for positioning each gate within said casing and for retaining the gates in location after the positioning thereof.

2. The apparatus of claim 1 wherein the width of said passageway is dependent upon the position of said first gate in said casing and the length of said passageway is dependent upon the position of said second gate in said casing.

3. The apparatus of claim 1 wherein said barrel is the mixing barrel of a burner into which air is fed through said valve, and further comprising means for supplying a fluid fuel to the air which flows through said barrel, and means at the discharge end of said barrel for burning the resulting mixture of air and fuel.