CN101829531B - Variable cross-section standing wave ultrasonic reactor - Google Patents

Abstract

The variable cross-section standing wave ultrasonic reactor of the present invention relates to a device for treating liquid by using ultrasonic cavitation effect. It includes a tank containing the liquid to be processed, at least one ultrasonic transducer (10), and an ultrasonic transducer drive circuit. The cross-sectional area of the standing wave sound field in the above box changes periodically with the position of the cross-section. At the position where the sound pressure amplitude is zero (sound pressure nodal surface), the cross-section of the sound field is the smallest; At the position of maximum (sound pressure anti-nodal plane), the cross section of the sound field is the largest; between adjacent sound pressure nodal planes and anti-nodular planes, the cross-section of the sound field transitions from minimum to maximum linearly or nonlinearly. The utilization rate of the sound field energy of the ultrasonic reactor is improved by increasing the volume of the liquid near the anti-nodal surface of the sound pressure and reducing the volume of the liquid near the nodal surface of the sound pressure.

Description

Variable Cross Section Standing Wave Ultrasonic Reactor

technical field

The variable cross-section standing wave ultrasonic reactor of the present invention relates to a device for treating liquid by using ultrasonic cavitation effect.

Background technique

The ultrasonic reactor uses the local high temperature and high pressure (~5000K, ~2000atm) generated by the ultrasonic cavitation effect to treat liquids such as water. Structurally, the ultrasonic reactor system includes a tank, the liquid to be processed in the tank, an ultrasonic transducer for applying ultrasonic waves to the liquid to be processed, and a drive circuit for the ultrasonic transducer. It is used in disinfection and sterilization of drinking water, decomposition of carcinogens in drinking water, disinfection and sterilization of wastewater, decomposition of organic matter in wastewater, physical catalysis of chemical synthesis and crystallization process, acceleration of fermentation process, production of biomass gas and liquid fuel, etc. It has great application prospect. The working principle of the existing ultrasonic reactor, as described in references (T.J.Mason, J.P.Lorimer, Applied Sonochemistry, Wiley-VCH, Weinheim, 2002), mainly utilizes the standing wave ultrasonic field in the processed liquid to cause the acoustic cavitation effect . In this way, the sound pressure amplitude of the ultrasonic field is not uniform in space, and there are sound pressure nodal planes and anti-nodal planes. The sound pressure amplitude is zero on the sound pressure nodal plane, and the sound pressure amplitude is maximum on the sound pressure anti-nodal plane. For this reason, there occurs a phenomenon that the liquid near the acoustic pressure anti-nodal surface is excessively sonicated, and the liquid near the acoustic pressure nodal surface is not sufficiently processed. This leads to problems of uneven sound treatment and low utilization of sound energy.

Contents of the invention

In order to overcome the problems of uneven sonication and low utilization rate of sound energy in existing ultrasonic reactors, the patent of the present invention provides a new ultrasonic reactor, which uses a relatively uniform ultrasonic field to sonicate the liquid in it to Improve the uniformity of the acoustic treatment of the acoustic reactor and the utilization rate of the acoustic energy in the acoustic reactor.

The first variable cross-section standing wave ultrasonic reactor is characterized in that: it includes a box containing the liquid to be processed, an ultrasonic transducer installed on the second wall of the box, and the first wall as a reflecting wall on the box. The distance between the acoustic radiation surfaces of the ultrasonic transducers is an odd multiple of a quarter wavelength, and the bottom surface of the box is curved, folded or wavy; the curved, folded or wavy shape of the bottom of the box makes the bottom of the box and the liquid The distance between the surfaces changes periodically with the distance from the sound radiation surface; where the distance from the sound radiation surface m c/(2f), the distance between the bottom of the box and the liquid surface is the minimum; the distance from the sound radiation surface (2m+1)c/(4f), the distance between the bottom surface of the tank and the liquid surface is the maximum value; where m is a natural number greater than or equal to 0, c is the sound velocity of the liquid to be processed, and f is the ultrasonic transducer working frequency.

The second variable cross-section standing wave ultrasonic reactor is characterized in that: it includes a box containing the liquid to be processed, an ultrasonic transducer installed on the second wall of the box, and the first wall as a reflecting wall on the box is connected to the first wall of the box. The distance between the acoustic radiation surfaces of the ultrasonic transducers is an odd multiple of a quarter wavelength, the bottom surface of the box and the top surface of the box are curved, folded or wavy, and the treated liquid is filled with the ultrasonic reactor box; The shape of the bottom surface of the above-mentioned box body and the top surface of the box body makes the distance between the bottom surface of the box body and the top surface change periodically with the distance from the sound radiation surface; The distance between the bottom surface and the top surface is the minimum value; the distance between the sound radiation surface (2m+1)c/(4f) and the distance between the bottom surface of the box and the liquid surface are the maximum value; where m is greater than or equal to 0 The natural number of , c is the sound velocity of the liquid being processed, and f is the working frequency of the ultrasonic transducer.

The third variable cross-section standing wave ultrasonic reactor is characterized in that: it includes a box body containing the liquid to be processed, an ultrasonic transducer installed on the bottom surface of the box body, and the liquid surface or top surface on the box body as a reflective wall surface is in contact with the The distance between the acoustic radiation surfaces of the ultrasonic transducers is an odd multiple of half the wavelength, and at least one box wall in at least one of the two sets of opposite walls is curved, folded or wavy; the above box The curved folded or wavy shape of the wall makes the distance between the group of opposite walls periodically change with the distance from the sound radiation surface; the distance between the relative walls of the position m c/(2f) away from the sound radiation surface is the smallest value; where the distance from the sound radiation surface (2m+1)c/(4f), the distance between the relative walls is the maximum value; where m is a natural number greater than or equal to 0, c is the sound velocity of the liquid to be processed, and f is the ultrasonic The working frequency of the transducer.

The above-mentioned standing wave ultrasonic reactor utilizes an immersed flat panel ultrasonic transducer, or an inserted Langevin ultrasonic transducer with a flat radiating surface.

The cross-sectional area of the standing wave sound field in the standing wave ultrasonic reactor changes periodically with the position of the cross-section, and the position where the sound pressure amplitude is zero (sound pressure nodal plane) is the distance from the sound radiation surface m c/(2f) [where m=0, 1, 2, 3..., c is the speed of sound of the liquid being processed, f is the position of the operating frequency of the ultrasonic transducer, the cross section of the sound field is the smallest; at the position where the amplitude of the sound pressure is the largest (Sound pressure anti-nodal surface) is the distance from the sound radiation surface (2m+1)c/(4f) [where m=0, 1, 2, 3..., c is the sound velocity of the liquid being processed, f is the ultrasonic transducer At the position of the operating frequency of the instrument, the cross section of the sound field is the largest. Between adjacent sound pressure nodal planes and anti-nodal planes, the cross-sectional area of the sound field transitions linearly or nonlinearly from minimum to maximum. With the above-mentioned three types of box structures, the volume of liquid near the anti-nodal surface of the sound pressure will be greater than the volume of liquid near the nodal surface of the sound pressure. As a result, the utilization rate of the acoustic field energy in the acoustic reactor and the uniformity of the acoustic treatment are increased.

The performance of the ultrasonic reactor in terms of sonication uniformity and sound energy utilization can be expressed by the non-uniformity index NU1 of the sound field:

${\mathrm{<span\; class="notranslate">\; NU</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; am</span>}}}\sqrt{\frac{{<span\; class="notranslate">\; \&Integral;</span><span\; class="notranslate">\; \&Integral;</span><span\; class="notranslate">\; \&Integral;</span>}_{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Pa</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; am</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; dV</span>}}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Where p _a is the sound pressure amplitude at the field point, p _am is the spatial average of p _a , and V ₀ is the volume of the sound field. The smaller the non-uniformity index NU ₁ of the sound field, the better the performance of the ultrasonic reactor in terms of sound treatment uniformity and sound energy utilization. The NU ₁ of the traditional standing wave ultrasonic reactor is 0.447. The finite element theoretical calculation (COMSOL MULTIPHYSIC5) shows that the patent of this invention can reduce the NU ₁ index to 0.2.

Description of drawings

Fig. 1: the structural diagram of the variable cross section standing wave ultrasonic reactor of embodiment 1; Wherein Fig. 1 (a) is the sectional view of ultrasonic reactor, Fig. 1 (b) is the top view of ultrasonic reactor.

Fig. 2: the structural diagram of the super cross section standing wave ultrasonic reactor of embodiment 2; Wherein Fig. 2 (a) is the sectional view of ultrasonic reactor, Fig. 2 (b) is the top view of ultrasonic reactor.

Label names in the figure: 1. Box body, 2. Liquid to be processed, 3. Liquid surface, 4. Improved standing wave sound field, 5. Bottom surface of box body, 6. First wall surface, 7. Second wall surface, 8. Nodal surface of sound pressure, 9, nodal surface of sound pressure, 10, ultrasonic transducer, 11, sound radiation surface, 12, top surface of box body.

specific implementation plan

The variable cross-section standing wave ultrasonic reactor of Embodiment 1 is shown in FIG. 1 .

The ultrasonic reactor rectangular metal box with a curved flat bottom is filled with treated water 2 . The ultrasonic transducer 10 is an immersion-type flat-panel ultrasonic transducer, which is fixed on the second wall 7 of the box. The distance between the acoustic radiation surface 11 and the opposite reflective wall surface, that is, the first wall surface 6, is an odd multiple of a quarter wavelength, so there is a gap between the acoustic radiation surface 11 and the first wall surface 6 when the acoustic reactor works. Standing wave sound field.

The size of the immersed flat panel ultrasonic transducer is 30cm (height)×12cm (width)×1cm (thickness), the working frequency f is 20kHz, and the working voltage is 65Vrms. The length of the rectangular metal box is 10.375cm, and the width is 13cm. The distance h between the bottom surface of the curved plate and the liquid surface 3 changes periodically with the distance from the sound radiation surface. At the positions of 1.875cm, 5.625cm and 9.375cm away from the sound radiation surface, h is equal to its maximum value of 45cm; at the positions of 0cm, 3.75cm and 7.5cm away from the sound radiation surface, h is equal to its minimum value of 30cm.

In this embodiment, according to the finite element calculation (COMSOL MULTIPHYSICS), the theoretical value of the non-uniformity index NU ₁ of the ultrasonic field is 0.2, which is much smaller than the NU ₁ (=0.447) of the traditional standing wave ultrasonic reactor. In the finite element calculation, the harmonic analysis function (Harmonics Analyzes, Acoustics Module) in the acoustics module of the software is used; the absorption coefficient of the sound field is 1.0×10 ^-5 1/m; the ultrasonic field is assumed to be a linear field. This shows that increasing the sound field cross-sectional area near the standing wave anti-nodal surface while reducing the sound field cross-sectional area near the standing wave nodal surface can effectively improve the uniformity of the ultrasonic reactor's sonication and the utilization of sound energy.

The variable cross-section standing wave ultrasonic reactor of Example 2 is shown in FIG. 2 .

The ultrasonic reactor rectangular metal box with a curved flat bottom surface and a curved flat top surface is filled with treated water. The submerged flat-panel ultrasonic transducer is fixed on the second wall 7 of the box. The distance between the acoustic radiation surface 11 and the opposite reflective wall surface, that is, the first wall surface 6, is an odd multiple of a quarter wavelength, so there is a standing wave between the acoustic radiation surface and the reflective wall surface when the acoustic reactor is working. sound field.

The size of the immersed flat panel ultrasonic transducer is 30cm (height)×12cm (width)×1cm (thickness), the working frequency f is 20kHz, and the working voltage is 65Vrms. The length of the rectangular metal box is 10.375cm, and the width is 13cm. The distance h between the bottom surface and the top surface of the curved plate varies periodically with the distance from the sound radiating surface. At the positions of 1.875cm, 5.625cm and 9.375cm away from the sound radiation surface, h is equal to its maximum value of 60cm; at the positions of 0cm, 3.75cm and 7.5cm away from the sound radiation surface, h is equal to its minimum value of 30cm.

In this embodiment, according to the finite element calculation (COMSOL MULTIPHYSICS), the theoretical value of the non-uniformity index NU ₁ of the ultrasonic field is 0.3, which is smaller than the NU ₁ (=0.447) of the traditional standing wave ultrasonic reactor. In the finite element calculation, the harmonic analysis function (Harmonics Analyzes, Acoustics Module) in the acoustics module of the software is used; the absorption coefficient of the sound field is 1.×10 ^-5 1/m; the ultrasonic field is assumed to be a linear field. This shows that increasing the sound field cross-sectional area near the standing wave anti-nodal surface and reducing the sound field cross-sectional area near the standing wave nodal surface can effectively improve the uniformity of the ultrasonic reactor's sonication and the utilization of sound energy.

Claims (6)

1. A variable cross-section standing wave ultrasonic reactor, characterized in that: It includes a tank (1) containing the liquid to be treated, an ultrasonic transducer (10) installed on the second wall (7) of the tank, the first wall (6) on the tank as a reflective wall and the ultrasonic transducer The distance between the sound radiation surfaces (11) of (10) is an odd multiple of a quarter wavelength, and the bottom surface of the box (5) is curved, folded or wavy; The curved folded or wavy shape of the above-mentioned box bottom surface (5) makes the distance between the box bottom surface and the liquid surface change periodically with the distance from the sound radiation surface; wherein the distance from the sound radiation surface m c/(2f) , the distance between the bottom surface of the box and the liquid surface is the minimum value; the distance between the bottom surface of the box body and the liquid surface is the maximum value at the position of (2m+1)c/(4f) from the sound radiation surface; where m is A natural number greater than or equal to 0, c is the sound velocity of the liquid being processed, and f is the working frequency of the ultrasonic transducer. 2. The variable-mode cross-section standing wave ultrasonic reactor according to claim 1, characterized in that: the above-mentioned ultrasonic transducer (10) is an immersed flat-panel ultrasonic transducer, or a plug-in Langevin with a flat radiation surface Ultrasonic transducer (Langevin Transducer). 3. A variable cross-section standing wave ultrasonic reactor, characterized in that: It includes a tank (1) containing the liquid to be treated, an ultrasonic transducer (10) installed on the second wall (7) of the tank, the first wall (6) on the tank as a reflective wall and the ultrasonic transducer The distance between the sound radiation surfaces (11) of (10) is an odd multiple of a quarter wavelength, the bottom surface of the box (5) and the top surface (12) of the box are curved, folded or wavy, and the treated The liquid fills the ultrasonic reactor box; The shape of the above-mentioned box body bottom surface (5) and box body top surface (12) makes the distance between the box body bottom surface and the top surface change periodically with the distance from the sound radiation surface; wherein the distance from the sound radiation surface m c/(2f ), the distance between the bottom surface and the top surface of the box is the minimum; where the distance from the sound radiation surface (2m+1)c/(4f), the distance between the bottom surface of the box and the liquid surface is the maximum; Where m is a natural number greater than or equal to 0, c is the sound velocity of the liquid to be processed, and f is the working frequency of the ultrasonic transducer. 4. The variable cross-section standing wave ultrasonic reactor according to claim 3, characterized in that: the above-mentioned ultrasonic transducer (10) is an immersion flat panel ultrasonic transducer, or a plug-in Langevin with a flat radiation surface Ultrasonic transducer (Langevin Transducer). 5. A standing wave ultrasonic reactor with variable cross section, characterized in that: It includes a tank (1) containing the liquid to be treated, an ultrasonic transducer (10) installed on the bottom of the tank, and the acoustic radiation between the liquid surface or the top surface of the tank as a reflective wall and the ultrasonic transducer (10). The distance between the surfaces (11) is an odd multiple of a quarter wavelength, and at least one box wall in at least one of the two sets of opposite walls is curved, folded or wavy; The curved folded or wavy shape of the above-mentioned box wall makes the distance between the group of relative walls periodically change with the distance away from the sound radiation surface; The distance is the minimum value; where the distance from the sound radiation surface (2m+1)c/(4f) is the maximum distance between the opposite walls; where m is a natural number greater than or equal to 0, and c is the sound velocity of the liquid being processed, f is the operating frequency of the ultrasonic transducer. 6. The variable cross-section standing wave ultrasonic reactor according to claim 5, characterized in that: the above-mentioned ultrasonic transducer (10) is an immersion flat panel ultrasonic transducer, or a plug-in Langevin with a flat radiation surface Ultrasonic transducer (Transducer Transducer).

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