Multiphase mixing apparatus using acoustic resonance

A multiphase mixing apparatus using acoustic resonance. The apparatus can induce a pressure difference between fluids to be mixed so that a resonance and an acoustic energy are generated, thereby shattering the fluids and effectively mixing them. The shattered gas fluid penetrating into the liquid fluid goes along a swirl flow so that the gas fluid stays in the liquid fluid for a relatively long time. In addition, the acoustic energy perturbs the fluids, a mass transfer resistance decreases. The fluids can be effectively agitated not only by an acoustic energy of a resonance generated between the mixed fluids flow and a resonance volume portion but also by a resonance generated by a mixed swirl flow formed by a circular

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a mixing apparatus for mixing materials
 having different phases such as liquid and gas by using acoustic
 resonance.
 2. Description of the Prior Art
 In general, mixing devices have been used to mix materials having different
 phases such as liquid-gas or liquid-solid in fermenters such as for beer
 and microorganisms and waste water disposal processes. To effectively mix
 the materials, it is proper to maximize a contact area between the
 materials and perturb the equilibrium state therebetween so as to narrow
 an interface layer thickness therebetween. Particularly, when the gas to
 be mixed with the liquid is dispersed, the contact area therebetween
 widens so that the gas and liquid are effectively mixed with each other.
 Note should be made of the fact that a mixing apparatus using vibration is
 disclosed in U.S. Pat. No. 3,108,749 entitled "Vibratory apparatus for
 atomizing liquids" and in U.S. Pat. No. 3,917,233 entitled "Vibrator".
 FIGS. 1 and 2 also show a mixing apparatus for dispersing gas by narrowing
 thruholes through which gas passes. Assuming the mixing apparatus is
 utilized in a waste water dispersing plant, the mixing apparatus will be
 explained below.
 FIG. 1A is a perspective view of a conventional mixing apparatus and FIG.
 1B is a sectional view taken along line III--III shown in FIG. 1A.
 Referring now to FIGS. 1A and 1B, pressurized air from a compressor (not
 shown) is supplied into a pipe 11 through a connecting portion 14 and a
 joint 13. Pipe 11 is made of ceramic or polyethylene, is formed with a
 plurality of fine holes 11a and is placed in waste water. The air supplied
 into pipe 11 is dispersed through holes 11a while passing through pipe 11
 and penetrates into the waste water, thereby fermenting microorganisms
 contained in the waste water.
 In the above mixing apparatus, the amount of air supplied into the waste
 water is determined size by the hole formed at pipe 11. However, there may
 be a lower limit in fining the hole size, so it cannot be always satisfied
 by a client.
 Also, since underwater plants which inhabit in the waste water sometimes
 block the fine holes, the pipe must be cleaned periodically.
 FIG. 2A is a sectional view of another conventional mixing apparatus and
 FIG. 2B is a plan view of the apparatus shown in FIG. 2A.
 Referring to FIGS. 2A and 2B, pressurized air is supplied into a housing 21
 through an inlet portion 21a by a compressor (not shown). The air then
 passes through an intermediate net 22 and a cover net 23 so as to disperse
 the air into the waste water. At this time, balls 24 float in housing 21
 so as to collide with the inflowing air and also disperse the air.
 However, the above mixing apparatus is also restricted in the fineness of
 the net meshes, so mixing efficiency is not satisfactory.
 SUMMARY OF THE INVENTION
 The present invention is intended to overcome the above-described
 disadvantages. Therefore, it is an object of the present invention to
 provide a material mixing apparatus which can disperse materials to be
 mixed by using an acoustic resonance therebetween, thereby improving
 mixing efficiency.
 In order to achieve the above object of the present invention, there is
 provided a multiphase material mixing apparatus using acoustic resonance.
 The apparatus comprises: a housing for guiding first and second fluids to
 form a swirl flow, the housing having a side, upper and bottom walls so as
 to form a chamber having a cylindrical shape therein, being immersed
 within the first fluid, being formed at the side wall thereof with a
 helical guide portion, and being formed with a guide post extending from
 the lower wall thereof toward the outlet portion, the guide post being
 tapered to converge toward the upper wall of the housing; an inlet portion
 for introducing the second fluid into the chamber at a predetermined
 pressure and allowing the second fluid to form the swirl flow, the inlet
 portion including an inlet port formed at the side wall of the housing;
 and an outlet portion having an outlet port formed at the upper wall of
 the housing for expelling the swirl flow through a circumferential end
 portion thereof and allowing the first fluid to flow into a center portion
 of the swirl flow through a corresponding center portion thereof, a
 resonance being generated by the expelling swirl flow and the inflowing
 first fluid thereby generating an acoustic energy and mixing the first and
 second fluids.
 The second fluid has a gas phase and the first fluid has a liquid phase. A
 resonant frequency is in a range of 2000 Hz to 3000 Hz.
 A height of the chamber H, a diameter D1 of the chamber, a diameter D3 of
 the inlet port, an inlet pressure P.sub.in of the second fluid passing
 through the inlet port and an outlet pressure P.sub.out of mixed first and
 second fluids are designed as:
EQU H/D1.apprxeq.0.5.about.2, D1/D3.apprxeq.5.about.8, .DELTA.P(P.sub.in
 -P.sub.out).ltoreq.2 bar.
 Also, there is provided a multiphase mixing apparatus using acoustic
 resonance, the apparatus comprising: a housing forming a passage therein
 for allowing a first fluid and a second fluid to be mixed with the first
 fluid to flow therethrough, the housing being immersed within the first
 fluid; and a resonance volume portion for generating a resonance by
 interacting with a mixture of the first and second fluids being expelled
 through an outlet port of the passage, the resonance volume portion being
 located adjacent to the outlet port so as to be communicated therewith.
 The passage includes an inlet port being smaller than the outlet port in
 size, and the resonance volume portion is formed with an opening which is
 communicated with the outlet port and oriented in parallel with a
 streamline along which the mixture flows.
 The passage includes an inlet passage and an outlet passage which meet at a
 right angle, and a circular rod is provided within and along the inlet
 passage for allowing the mixture to form a swirl flow therealong.
 An annular space is formed between the circular rod and the inlet passage.
 A plate is provided at a distal end of the inlet passage for colliding with
 the mixed first and second fluids.
 A screw is provided at the outlet port for adjusting an opened portion of
 the outlet port.
 The first and second fluids have liquid and gas phases respectively, and in
 a case where an inlet pressure of the second fluid is in ranges of 0.1 bar
 to 2 bar and a flowrate of 100 to 500 l/min, a resonant frequency is
 within a range of 1000 Hz to 5000 Hz.
 The mixing apparatus can induce a pressure difference between fluids to be
 mixed so that resonance and acoustic energy are generated, thereby
 dispersing the fluids and effectively mixing them.
 Also, the dispersed gas fluid penetrating into the liquid fluid goes along
 the swirl flow so that the gas fluid stays in the liquid fluid for a
 relatively long time. In addition, since the acoustic energy perturbs the
 fluids, a mass transfer rate increases.
 In addition, the fluids to be mixed can be effectively agitated not only by
 an acoustic energy of resonance generated between the mixed fluids flow
 and the resonance volume portion but also by resonance generated by the
 mixed swirl flow formed by the circular rod.

DETAILED DESCRIPTION OF THE INVENTION
 Hereinafter, material mixing apparatuses using acoustic resonance of
 various embodiments will be explained in more detail with reference to the
 accompanying figures.
 All the embodiments will be described by assuming that they are utilized in
 a waste water disposal plant.
 Embodiment 1
 FIG. 3A is a perspective view of a mixing apparatus of a first embodiment
 and FIG. 3B is a sectional view taken along line III--III of FIG. 3A.
 A housing 100 immersed within a first fluid which has a liquid phase and
 forming a chamber 110 therein is provided. Housing 100 includes side wall
 120, and upper and lower walls 140 and 130 opposite each other for forming
 chamber 110 therebetween.
 Housing 100 is formed at side wall 120 with an inlet portion 125 having an
 inlet port 125a. A second fluid having a gas phase is supplied into
 chamber 110 through inlet portion 125 by a compressor (not shown). Inlet
 portion 125 is directed tangentially into chamber 110 so that the second
 fluid forms a swirl flow along side wall 120 and ascends to be expelled.
 Upper wall 140 of housing 100 is opened to form an outlet portion 145
 having an outlet port 145a. That is, the second fluid flowing into chamber
 110 through inlet port 125a is mixed with the first fluid and expelled
 through outlet port 145a. In detail, the second fluid supplied into
 chamber 110 by the compressor with a pressure P.sub.in forms a swirl flow
 along side wall 120 of housing 100, and is mixed with the first fluid
 received in chamber 110 and is thereafter expelled through outlet portion
 145. At this time, the center portion of the mixed swirl flow has a lower
 pressure than that of the circumferential end portion so that the first
 fluid which surrounds housing 100 flows into the center portion of the
 expelled flow.
 In particular, the expelled mixed flow and the inflowing first fluid are
 again mixed and there is generated a resonance by the pressure difference
 therebetween. At this time, the second fluid having a gas phase is
 dispersed and penetrates into the first fluid, thereby accomplishing an
 effective mixing.
 The resonance generates an acoustic energy which facilitates penetration of
 the second fluid into the first fluid. In more detail, the acoustic energy
 disperses the second fluid, thereby increasing the contact area between
 the first and second fluids. Also, the dispersed second fluid penetrating
 into the first fluid goes along the swirl flow so that the second fluid
 stays in the first fluid for a relatively long time. In addition, as the
 acoustic energy perturbs the fluids, the mass transfer resistance
 decreases.
 Preferably, housing 100 has a cylindrical shape. This can decrease a form
 drag force while the mixed fluids form a swirl flow along side wall 120.
 The resonant frequency F1 is evaluated by the following equation:
 ##EQU1##
 K is an experimental parameter indicating a rotational speed drop of the
 second fluid by a friction with the side wall of the chamber, C is a sound
 speed in the medium of the second fluid, D1 is a chamber diameter,
 P.sub.in is an inlet pressure of the second fluid flowing into the
 chamber, and P.sub.out is an outlet pressure of the mixed fluids expelled.
 In a waste water disposal plant, since the air is the medium, C is
 approximately 340 m/s.
 At this time, since the resonant frequency is in a proper range when it is
 between 2000 Hz to 3000 Hz, housing 100 can be designed to met above
 requirement.
 For example, when the height of chamber 110 is H, the diameter of inlet
 port 125a is D3 and the flowrate of the air is in the range of 100-500
 l/min, housing 100 can be designed such that H is 30 mm, D1 is 20 mm,
 .DELTA.P (P.sub.in -P.sub.out) is below 2 bar, and the ratio of D1 to D3
 (D1/D3) is in the range of 5-8. Then the resonant frequency F1 is settled
 in the range of 2000-3000 Hz. Preferably, D3 is designed to be 6 mm
 approximately.
 By using housing 100 designed as above, the mass transfer efficiency of the
 second fluid increases to be approximately 30 percent greater than with a
 conventional mixing apparatus.
EQU Mass transfer efficiency=(penetrated gas mass per time)/(supplied gas mass
 per time) (2).
 Embodiment 2
 FIGS. 4A and 4B are sectional views of a mixing apparatus of a second
 embodiment.
 The mixing apparatus of the second embodiment has the same construction as
 that of the first embodiment except that the diameter D2 of outlet port
 145a is smaller than the diameter D1 of chamber 110. Thus, a pressure
 difference is induced between the mixed fluids expelled through outlet
 port 145a and the inflowing first fluid, thereby improving the mixing
 efficiency.
 Outlet port 145a of FIG. 4A is convergingly formed, and outlet port 145a of
 FIG. 4B converges upwardly and then goes straight.
 Embodiment 3
 FIG. 5 is a sectional view of a mixing apparatus of a third embodiment.
 The mixing apparatus of the third embodiment is different from that of the
 second embodiment in that, referring to FIG. 5, a helical guide portion
 115 is formed at the inside wall of housing 100. Guide portion 115
 includes a groove or a projection formed at the inside wall which guides
 the second fluid flowing through inlet portion 145 and the mixed fluids to
 easily form a swirl flow. Thus, in the third embodiment, the flow
 resistance is decreased by the guide portion.
 Embodiment 4
 FIG. 6A is a sectional view of a mixing apparatus of a fourth embodiment
 and FIG. 6B is a sectional view taken along line III--III shown in FIG.
 6A.
 The mixing apparatus of the fourth embodiment is different from that of the
 first embodiment in that, referring to FIG. 5, housing 100 is formed at a
 center portion of lower wall 130 thereof with a guide post 135 extending
 toward outlet portion 145. Guide post 135 makes the mixed fluids form a
 swirl flow easily. For reducing the flow resistance, guide post 135 has an
 oval crosssection and converges toward outlet portion 145 so as to allow
 the first fluid to easily flow into housing 100 through outlet port 145a.
 In designing housing 100 of the fourth embodiment, when the height of
 chamber 110 is H, the diameter of inlet port is D3, the diameter of
 chamber is D1, the inlet pressure of the second fluid P.sub.in and the
 outlet pressure of the mixed fluids is P.sub.out, and the flowrate is in
 the range of 100 to 500 l/min, housing 100 is designed as:
EQU H=30 mm, D1=20 mm, .DELTA.P.ltoreq.2 bar and D1/D3.apprxeq.5-8.
 In this case, the resonant frequency F1 is in the range of 2000-3000 Hz and
 the mass transfer rate of the second fluid increases to be up to 150
 percent greater than with a conventional mixing apparatus. Preferably, D3
 is designed to have a diameter of approximately 6 mm.
 The mixing apparatus may have a cylindrical Helmholtz resonator which
 generates a resonance of a unique resonant frequency, or the mixing
 apparatus may be of an air jet type having a nozzle. The Helmholtz
 resonator is adequate for an inlet pressure lower than 1 bar and a
 flowrate lower than 300 l/min. The air jet resonator is adequate for an
 inlet pressure lower than 3 bar and a flowrate lower than 300 l/min.
 Embodiment 5 FIG. 7A is a sectional view of a mixing apparatus of a fifth
 embodiment and FIG. 7B is a perspective view showing an inner structure of
 the mixing apparatus of FIG. 7A.
 Referring to FIGS. 7A and 7B, a housing 200 is formed therein with a
 passage 210 for the first and second fluids which have liquid and gas
 phases respectively, and is immersed within the first fluid. Housing 200
 includes a body 200a forming passage 210 and a couple of side plates 200b
 attached to respective sides of body 200a. Housing 200 is formed at a
 portion therein adjacent to an outlet portion 213 of passage 210 with a
 resonance volume portion 220 which communicates with passage 210.
 Resonance volume portion 220 has a cylindrical shape and is excited by
 interacting with mixed fluids, thereby generating a resonant acoustic
 energy. The acoustic energy disperses the first and second fluids and
 mixes them. Thus, the mass transfer rate between the first and second
 fluids increases.
 Outlet portion 213 of passage 210 below which resonance volume portion 220
 is located is narrower than an inlet portion 215. Opening 223 of resonance
 volume portion 220 is formed in parallel with the stream line of the mixed
 fluids expelled through outlet portion 213. This is for setting a state
 where the mixed fluids are excited with resonance volume portion 220.
 Preferably, a width b1 of opening 223 is identical to a width b of outlet
 portion 213.
 In this embodiments, since the resonant frequency is in a proper range when
 it is between 1000 to 5000 Hz, resonance volume portion 220 of housing 200
 can be designed therewith.
 When the inlet pressure of the second fluid passing through inlet portion
 215 is in the range of 0.1 bar to 2 bar, the flowrate is in the range of
 100 l to 500 l, and the resonant frequency F2 is in the range of 1000 Hz
 to 5000 Hz, the mixing apparatus of the fifth embodiment is remarkably
 improved in the mass transfer rate.
 In the fifth embodiment, the resonance is more likely to occur in the
 pressure range of 0.1 bar to 1.5 bar.
 Embodiment 6
 FIG. 8 is a sectional view of a mixing apparatus of a sixth embodiment.
 Only the differences from the fifth embodiment will be explained.
 Referring to FIG. 8, a passage 210 having a circular cross-section includes
 an inlet portion 210a and an outlet portion 210b which meet at a right
 angle. At the crossing portion between inlet and outlet portions 210a and
 210b, a circular rod 230 extends toward inlet portion 210a which makes the
 mixed fluids form a swirl flow. At this time, an annular space is formed
 between inlet portion 210a and circular rod 230, which makes it easier to
 form a swirl flow. Also, since circular rod 230 and inlet portion 210a
 have circular crosssections, they do not create flow resistance.
 On the other hand, the size of outlet portion 213 is adjusted by a screw
 250 which can protrude into outlet portion 213 by a variable distance X.
 At the recessed portion adjacent to the crossing portion of passage 210, a
 plate 240 is provided so as to collide with the mixed fluids and urge them
 to flow toward outlet portion 210b.
 The resonant frequency F3 of the resonance generated by the collision
 between the mixed fluids and the plate 240, the sound speed in the medium
 of the second fluid C, the pressure difference .DELTA.P between the first
 and second fluids, the height H1 of a resonance portion, the diameter Dres
 of the resonance portion, the diameter Dr of the water passage through
 which the swirl flow develops, and the distance L1 between the outlet and
 an opening of the resonance portion are correlated by the following
 equation:
 ##EQU2##
 In particular, the diameter Dr is the diameter of the circular rod. And,
 since the mixing apparatus is utilized in the waste water disposal plant,
 C is approximately 340 m/s.
 At this time, since the resonant frequency is in the proper range when it
 is between 1000 to 5000 Hz, resonance volume portion 220 and housing 200
 can be designed to meet the above requirement. When the inlet pressure of
 the second fluid passing through inlet portion 215 is in the range of 0.1
 bar to 2 bar, the flowrate is in the range of 100 l to 500 l, and the
 resonant frequency F2 is in the range of 1000 Hz to 5000 Hz, the mass
 transfer rate of the mixing apparatus of the sixth embodiment is
 remarkably improved.
 In the sixth embodiment, the resonance by the air injection is more likely
 to happen in a pressure below 3 bar, and the resonance by resonance volume
 portion 220 is more likely to happen in a pressure below 2 bar. Thus, the
 mixing apparatus can be well utilized even when there is a pressure
 fluctuation from high to low or from low to high pressure.
 As described above, the mixing apparatus can induce a pressure difference
 between fluids to be mixed so that a resonance and an acoustic energy are
 generated, thereby dispersing the fluids and effectively mixing them.
 Also, the dispersed gas fluid penetrating into the liquid fluid goes along
 the swirl flow so that the gas fluid stays in the liquid fluid for a
 relatively long time. In addition, since the acoustic energy perturbs the
 fluids, the mass transfer rate increases.
 In addition, the fluids to be mixed can be effectively agitated not only by
 the acoustic energy of the resonance generated between the mixed fluids
 flow and the resonance volume portion but also by the resonance generated
 by the mixed swirl flow formed by the circular rod.
 Although the preferred embodiments of the invention have been described, it
 is understood that the present invention should not be limited to these
 preferred embodiments, but various changes and modifications can be made
 by one skilled in the art within the spirit and scope of the invention as
 hereinafter claimed.