US3408050A - Apparatus for mixing fluids - Google Patents

Description

2 Sheets-Sheet l mm N@ wm w m t ww INVENTOR.

HTTOP/VEY h' JOHN J/Icos HZ Oct. 29, 1968 J. JACOBS nl APPARATUS FOR MIXING FLUIDS Filed Jan. 13, 1966 OC- 29, 1968 .1..1AcoBs APPARATUS FOR MIXING FLUIDS 2 Sheets-Sheet 2 Filed Jan. 13,

R@ mm mw r VA Lr mJ on@ m J W Y B u United Stas Patent O 3,408,050 APPARATUS FR MIXING FLUIDS John Jacobs III, Darien, Conn., assignor to Sonic Engineering Corporation, Norwalk, Conn., a corporation of Connecticut Filed llan. 13, 1966, Ser. No. 527,637 1 Claim. (Cl. 259-4) ABSTRACT F THE DISCLOSURE An in-line uid mixing device comprises an orifice and a blade-like vibratory element xed at one end and disposed in line with said orifice so that the free end of said vibratory element is disposed opposite and closely spaced from said orifice. The free end of the vibratory element is dimensioned so as to be substantially the same as the orifice dimension on the downstream face side thereof so that as fluid moves through said orifice the vibratory element is caused to vibrate and as the free end of the vibratory element comes opposite and in line with the orilice ow therethrough tends to be interrupted.

This invention relates to apparatus for mixing fluids, and more particularly relates to an improved apparatus lbased upon the oscillation of a cantilevered blade in a uid jet.

Devices exist which employ a lluid jet to cause a cantilevered blade to oscillate, the oscillation of the blade then causing high intensity mixing of the uid jet. The principle of operation of such devices is popularly known as the liquid whistle principle, and involves two separate aspects. The first aspect -is the rapid oscillation at its resonant frequency of a cantilivered blade when exposed to a fluid jet of the proper kind which impinges on its free edge. The second aspect is the turbulence, high vorticity, and cavitation produced by such a blade in the impinging stream, resulting in high intensity mixing of the iiuids constituting the uid jet.

The liquid whistle device has been highly successful as a homogenizer or high intensity mixer. The conditions under which it is most advantageously operated have however rendered it less satisfactory -in certain uses where these conditions do not exist. The prior art liquid whistle devices are high pressure devices, so that line pressure boosters are generally necessary for their use. Moreover, while they produce high intensity mixing efliciently, they are less efficient in the production of lower intensity mixing, and introduce a larger pressure drop (power consumption) than can usually be tolerated (or than is available) in typical lower intensity mixing requirements, such as for in-line mixers.

The present invention provides a device that employs only the rst aspect of the liquid whistle principle, i.e., the excitation of a blade at its resonant frequency by a fluid jet. The present invention utilizes the blade oscillation to provide uid shear which effects the lower intensity mixing or blending with which the invention is especially concerned. Since all, or essentially all, cavitation is eliminated (the aforesaid second aspect of the fluid whistle principle) the high pressure requirement and the large power consumption (pressure drop) heretofore associated with liquid whistle mixers are eliminated, thus rendering the present invention particularly suitable to in-line mixing, among other uses. The devices which may be constructed according to the principles of the present invention have been collectively designated as iiuid intermixers, or simply as intermixers.

It is an object of the present invention to provide an improved apparatus for agitating uid.

Another object of the invention is to provide a fluid 3,408,050 Patented Oct. 29, 1968 ice intermixer employing a fluid powered cantilevered blade to mix the fluid primarily by means of shear forces thereon.

Another object of the invention is to provide an improved apparatus for intermixing u'ids under conditions of relatively low line pressure.

Another object of the invention is to provide apparatus for intermixing fluids so as to produce relatively low line pressure drop.

Another object of the invention is to provide apparatus for employing self-excited fluid interruption by means of a fluid powered oscillating cantilevered blade to produce high shear forces for mixing the liuid.

Another Vobject of the invention is to provide continuous intermixing of iiuids or uid carried substances while in a liquid stream.

These and other objects and advantages of the invention will appear more fully as a detailed description of one presently preferred but merely illustrative embodiment thereof is set forth hereinbelow, in connection with the drawings, in which:

FIG. l is a plan view of an apparatus according to the invention with the cover thereof partially broken away to show internal details of construction;

FIG. 2 is an elevational section view of the apparatus shown in FIG. 1 taken along plane 2--2 therein;

FIG. 3 is a section view through the apparatus shown in FIG. 1 and taken along plane 3-3 therein;

FIG. 4 is a section view of the apparatus shown in FIG. 2 and taken along plane 4-4 therein; and

FIG. 5 is an exploded detail perspective view of certain of the internal parts shown in FIGS. 1-4 inclusive.

Referring now to the figures, an apparatus 10 according to the invention includes a generally cylindrical housing 11 provided at opposite ends with end- fittings 12, 13 respectively. The materials employed in an apparatus according to the invention generally need not be capable of resisting high pressures since it is contemplated that the invention will be employed primarily as an in-line mixing device not requiring a pressure booster on its upstream side. However, the device may also be employed for higher pressure ranges, and for such employment the various parts may be fabricated in high tensile materials such for example as stainless steel, and otherwise adapted to high pressure use. In any event it is desirable in general that the parts be fabricated from corrosion-resistant materials.

Each of end- ttings 12, 13 includes a circular liange portion 12a, 13a, which divides the respective end-fitting between a tapered, externally threaded portion 12b, 13b, and a cylindrical portion 12e, 13o. Each end-fitting is provided with a longitudinal passageway 12d, 13d respectively. Flange portions 12a, 13a, each includes a plurality of peripherally spaced apertures 12e, 13e respectively. End-fitting 12 is mated to a housing end face 11a and end-fitting 13 is mated to the opposite housing end face 11b, so that the respective cylindrical portions 12C, 13C are closely coaxially fitted within cylindrical bore 11e of housing 11, and flange portions 12a, 13a are abutted against end faces 11a, 11b respectively. Endfitting 12 is secured to housing 11 by a plurality of machine screws 14 which pass through each of the plurality of fiange apertures 12e for threaded engagement within a corresponding plurality of apertures 11d in housing 11, and end-fitting 13 is similarly secured by a plurality of machine screws 15 threadedly engaged in a plurality of apertures 13e in housing 11. End-fitting cylindrical portions 12C, 13e are provided with an annular recess 123, 13j, and O-rings 16, 17 are carried therein respectively to seal the interface of end- fittings 12, 13 with housing 11.

The generally cylindrical outline of housing 11 is modified at the central portion thereof, to a generally troughlike outline. Specifically, housing 11 is, for a short longitudinal distance inward of end faces 11a, 11b, cylindrical in outline, but is, at the aforesaid intermediate portion, approximately semicylindrical in outline, as is best seen in FIGS. 3 and 4. The major part 11f of this portion extending from transverse face 11g to stepped portion 11h is precisely semicylindrical (FIG. 3), and the balance extending from stepped portion 11h to transverse face 11i is slightly less than semicylindrical (FIG. 4).

A cylindrical cover is slidably fitted over housing 11 thus enclosing in cooperation with housing 11 'a chamber 11j intermediate the end- fittings 12, 13. Flange portion 13a of end-fitting 13 has a diameter which is slightly greater than the diameter of housing 11, while flange portion 12a of end-fitting 12 has a diameter equal to that of housing 11. Cover 20 may accordingly be slipped on and removed from housing 11 at the end thereof mated with end-fitting 12, and will abut against flange 13a. Cover 20 is removably retained axially and rotationally by the action of a set screw 21 against a fiat 11m on housing 11 in cooperation with the aforesaid action of fiange 13a. Intermediate each of housing faces 11a and 11b and chamber 11j is, respectively, an annular recess 11p, 11g, and carried respectively therein are annular O-ring gaskets 22, 23, which serve to seal the interface of housing 11 and cover 20.

IPassageway 12d of end-fitting 12 is closed off within chamber 11]' by an orifice fitting 25, best seen in FIGS. 2, 4 and 5. Orifice fitting 25 includes a lower portion 25a having a semicircular outline adapted to closely conform to the inner diameter surface 11c of housing 11. The side surfaces 25b and 25e of orifice fitting 25 are parallel and tangential to semicircular surface 25a and extend upwardly to upper curved surface 25d, which is circularly curved for alignment with the outer surface of housing 11 and the inner surface of cover 20 mated therewith. A portion 25e of orifice fitting 25 is formed as a cylindrical extension thereof coaxial with semicircular surface 25a. An annular recess 25]c is formed in portion 25e, and an O-ring gasket 27 is carried therein thereby sealing the interface of housing 11 and orifice fitting 25.

Orifice fitting 25 includes a bore 25g of the same diameter as bore 12d of end-fitting 12. Orifice fitting 25 and endfitting 12 are abutted within the bore of housing 11, and a machine screw 30 is employed to secure orifice fitting 25 to housing 11 by threaded engagement through stepped recess 25i and into an adjacent one of apertures 11, which aperture 11d extends completely through housing 11 between faces 11a, 11i thereof, so that machine screw 30 and one of machine screws 14 both occupy it from opposite ends thereof. Bore 25g of end-fitting 25 is terminated by wall 25m, and a slot orifice 25p is formed in wall 25m along a diameter of bore 25g aligned with the upper faces 11s of semicircular housing portion 11f. As will appear hereinafter, other orifice 25p configurations may be employed, the long narrow slot configuration being advantageous but not necessary to the practice of the invention. When end-tting 12 is connected to a fluid conduit (not shown) by means of threaded portion 12b, fiuid may be introduced into passageway 12d for movement in the direction indicated by the arrow shown in FIG. 2, so as to enter bore 25g and be forced through orilice 25p and emitted into chamber 11j as a fluid jet.

As is best shown in FIGS. 1-3, a blade structure indicated generally at is held in place within chamber 11j in a specific orientation relative to orifice 25p. Blade structure, 40 includes a bracket portion 40a formed of relatively thick and structurally rigid stock, a blade 40C formed integrally with bracket portion 40a, and a tip member 40b terminating the cantilevered end of blade 40C remote from bracket portion 40a. Bracket portion 40a includes a pair of apertures 40d, 40e and tip member 40b includes Ia blunted (i.e., relatively flat or normal to the blade 40g; axis) end face 40j opposed to orifice 25p, and

4. a pair of spaced lateral faces 40g, 40h, normal to and contiguous with face 40j. Blade 40C is preferably tapered from the end adjacent bracket 40a to the end adjacent tip portion 40h, for a purpose to appear hereinafter, and face 40j will often, under typical design conditions, be of greater depth than the thickness of the adjacent portion of blade 40C, thus necessitating a thickened tip portion 40b, as is illustrated in the figures by a bar configuration.

The blade structure 40 is held in place by an adjustable bracket 45 and a plate 55. Adjustable bracket 45 includes a pair of threaded apertures 45a, 45b spaced on the same centers as apertures 40d, 40e of blade bracket 40a. A rectangular recess 45C is formed in the underside of adjustable bracket 45, and is of a depth and width suliicient to accommodate a portion of the thickness of blade bracket 40a. A pair of slotted apertures 45d, 45e are spaced outwardly from threaded apertures 45a, 45b and receive respectively a pair of screws 50, 51 which are threadedly engaged in apertures 11t, 11u of housing 11. Plate 55 includes a pair of apertures 55a, 55b spaced on the same centers as apertures 40d, 40e of blade bracket 40a. A pair of screws 60, 61 pass through plate 55 and blade bracket 40a for threaded engagement within apertures 45a, 45b thereby clamping blade structure 40 between plate 55 and adjustable bracket 45. The spacing of blade end face 45j from orifice 25p may thereby be adjusted by moving adjustable bracket 45 relative to housing 11, at the slotted apertures 45d, 45e.

The blade structure 40 is oriented so that it is axially aligned with orifice 25p when 'blade 40e is in the rest position, thereby placing end face 40f in direct opposition to orifice 25p. The end face 40jc has the same configuraf tion and area as the orifice 25p, and is spaced from orifice 25p by a very small distance. The result is that a near blocking of orifice 25p Iby end face 40,1c is effected when blade 40a` is in the illustrated rest position. From the standpoint of fluid shear alone, the end face 40f should be as close as possible to orifice 25p, jbut in practice it has been found that there is a limit to the closeness of spac ing which can be achieved while preserving self-excitation of the blade structure 40 `by the fluid jet. The closest spacing is limited by the viscosity of the fluid in question, and in general, the blade 40e will be self-excited by the fiuid jet, i.e., will be started oscillating, if the spacing of end face 40f from orifice 25p z's at least about 0.004 inch for water. For more viscous liquids, the spacing must, as a minimum, be somewhat greater than 0.004 inch, generally 'between 0.004-0.008 inch minimum spacing. It is a feature of the invention that under such conditions the jet emanating from orifice 25p will excite the blade 40e into oscillations up to itsresonant frequency. The pet impinging on surface 40f will excite blade 40e into oscillation even when there is very little turbulence and vorticity present therein, i.e., even when the jet is stable.

As 'blade 40C oscillates, the end face 40] swings through repeated cycles from one side of orifice 25p to the other, so that full Iblocking occurs only during two brief intervals of each cycle. At the extremes of the oscillatory movement, the end face 40f preferably just clears the orifice 25p entirely. The overall action constitutes a constant interruption of the flow from the jet so that great fluid shear is imposed thereon at each passage of tip portion 40b from an unblocked position into a blocked position. The very high shear forces which are thus developed constitute the preponderant mechanisms 'by which the fluid in the jet is mixed or blended according to the invention. It is a feature of the invention that this mixing or blending may be accomplished at lower jet pressures than has been heretofore possible with liquid whistle type mixing apparatus, and additionally it is a feature of the invention that the pressure drop through the liquid whistle apparatus is much lower in the configuration according to the invention than in prior art configurations. As has previously been mentioned, these advantages make the device according to the invention very desirable in those classes of use where regular inline mixing of relatively thorough but low intensity is required, and where no special pumping to high pressure for the purpose of mixing is `desired and where substantial pressure drops cannot be tolerated. Such classes of use constitute common occurrences in industrial fiow processes, and accordingly the invention is deemed to be a distinct advance in yallowing the many advantages of liquid whistle type mixers to be adapted to such use conditions.

While the orifice 25p need not, in Iaccordance with the present invention, be so dimensioned as to produce an unstable jet, it is nevertheless preferable that the orifice 25p assume the proportions of a rectangular slot as illustrated. Thus, while other configurations may be adopted, such a long and narrow slot is desirable because it induces higher frequency in the oscillations of blade 40e with correspondingly lower amplitude of travel of end face 40f. lIt is desirable that this amplit-ude be diminished and the frequency increased so that maximum fluid shear is attained per unit time and accordingly per unit fiow. Since it is the repeated intrusion of end face 40jc into the fluid jet which causes this iiuid shear, optimum movement of en-d face 40f would constitute movement in one direction until all of end face 401 has barely cleared orifice 25p, followed yby immediate return movement through the blocking position and onward in the opposite direction until once again all of end face 40)c has barely cleared orifice 25p, followed by immediate return movement through the blocking position and onward in the opposite direction until once again all of end face 40f has barely cleared orifice 25p, and so forth in repeated cycles. Such an optimum mode of motion will yield the highest density of fiuid shear per unit time. For this reason a long narrow slot is preferable, although the invention maybe operated with other orifice configurations together with other corresponding blade tip configurations.

It has been found that when blade 40's employs the illustrated tapered thickness (and/ or width) from a thick (and/or wide) fixed end to the thin (and/or narrow) free end adjacent the 'bar 40h, a higher resonant frequency and a greater maximum defiection may be attained without undue stress, as compared to a blade having uniform thickness (and/or width). Frequency is important, as already explained, Ibecause it directly relates to rate of fluid shear. Amplitude is important to the extent of fully unblocking the orifice twice in each cycle so that shear and flow are mutually maximized. While such tapered blades are for these reasons preferred, the invention is fully operable with untapered blades.

The provision of slotted apertures 45d, 45e allows both initial and subsequent adjustment of the position of end face 40jc relative to orifice 25p. In the initial assembly operation, the spacing therebetween may be set by use of a feeler gauge, for example, so that normal parts tolerances can be obviated and the spacing can be accurately set. YIf, for example, the device is to be employed to mix a liquid comprising basically water, the spacing will be set to about 0.004 inch. As aforesaid, although greater shear density can be attained with closer spacing for water, the important self-exciting feature will be lost or at least rendered sporadic. Also as aforesaid, when a more viscous liquid is to be employed, the minimum spacing should be increased out to about 0.008 inch at the furthest for viscous liquids. Liquid shear falls off rapidly with increased spacing, and spacings of greater than about 0.025 inch are not efficacious for introducing substantial liquid shear mixing and Iblending according to the invention. Whenever the liquid employed with the device is to Ibe materially changed with respect to viscosity, the cover 20 may be drawn away and the blade structure 40 may lbe adjusted relative to orifice 25p by first loosening and then retightening screws 50, 51. Since the selfexcitation feature relates only to start-up, variations in viscosity after start-up are not critical to operation.

The fluid emanating from orifice 25p is subjected to alternating applications of blocking and shearing. The line pressure developed at the upstream side, i.e., upstream of orifice 25p, is thereby varied in oscillatory fashion between the pressure representative of the unblocked orifice 25p and the pressure represented by the blocked orifice 25p (it being understood that total blocking is never actually attained). The overall result is that mixing or blending in the 10W intensity to medium intensity range is effected at low line pressures (e.g., 30 p.s.i.) and with low power consumption (e.g., 10 p.s.i.), neither of which was possible with liquid whistle devices of the cavitation type. In-line uses thus may have the benefits of a mixer or blender of the general liquid whistle type, but without line pressure boosters. While it is primarily contemplated that the present invention will be particularly advantageous in this class of uses, it may also be employed at high line pressures with suitable changes in materials and jacketing configuration to accommodate such higher pressures.

The invention has been described with reference to an illustrative, but not limiting, embodiment thereof. Those skilled in the art will readily perceive how the parts may be modified in form and arrangement to provide countless other embodiments of the invention, all equally partaking of the inventive principles.

I claim:

1. A fiuid mixer comprising an orifice adapted to form a stream of fluid into a jet, a cantilevered vibratory element having a free end and a fixed end arranged so that the free end thereof is disposed spaced from and opposite the ldownstream side of said orifice, said free end having a blunted end face provided by a transverse bar fixed to the leading edge of the free end of said vibratory element, said transverse bar being dimensioned so as to substantially block said orifice when in direct opposition thereto and wherein said vibratory element ha's at least one lateral dimension tapered from a larger dimension at the fixed end thereof to a smaller dimension adjacent said transverse bar at the free end thereof.

References Cited UNITED STATES PATENTS 944,717 12/ 1909 Caul 259-20 XR 2,693,944 11/ 1954 Fowle. 2,792,804 5/ 1957 Bouyoucos et al. 259-1 XR 3,212,756 10/ 1965 Hutton. 3,251,576 5/1966 Horsley 259-4 3,321,283 5/1967 Ewald 259-8 XR 3,333,826 8/1967 Kessler 259-8 2,657,021 10/ 1953 Cottell et al. 259-1 3,169,013 2/1965 Jones 259-4 3,176,964 4/1965 Cottell et al. 259-1 WALTER A. SCHELL, Prm'ary Examiner.

JOHN M. BELL, Assistant Examiner.

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