Ultrasonic atomization frequency conversion nozzle and design method thereof

Abstract

The application provides an ultrasonic atomization variable-frequency nozzle and a design method, which comprises third, second, terbium-dysprosium-iron hollow rods, first amplitude rods, matching blocks and pressing blocks arranged in sequence; wherein first, second, third, fourth and fifth electrode sheets, first, second, third, fourth and fifth piezoelectric ceramics are sequentially arranged from right to left between the matching block and the first amplitude rod; the coil is wound outside the terbium-dysprosium-iron hollow rod; after the first, second, third, fourth and fifth electrode sheets are connected to an alternating power supply, the fourth, third, second and first piezoelectric ceramics convert electric energy into mechanical energy through the inverse piezoelectric effect, the vibration amplitude is amplified through the first, second and third amplitude rods, and the micron-sized mist droplets are formed through the surface tension wave and cavitation effect acting on the liquid medicine.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of plant protection atomizing nozzles, and in particular to an ultrasonic atomizing variable-frequency nozzle and a design method thereof. BACKGROUND

[0002] At present, the plant protection atomizing nozzles on the domestic market adopt traditional atomizing modes such as pressure atomization and centrifugal atomization, and the droplet size is relatively large. Different categories of pests and diseases, growth periods and severity should correspond to different optimal spray particle sizes. Especially in the face of complex agricultural spraying operations, different types of nozzles need to be frequently replaced. The amplitude rod has a fixed resonance frequency after being manufactured and cannot be adjusted. However, in the actual operation process, the resonance frequency of the amplitude rod will be affected by factors such as load, temperature and wear and will deviate, resulting in a decrease in the working efficiency of the transducer. The current method to solve this problem is to use a sweep signal to excite the ultrasonic transducing system in operation, and then use a laser vibration meter to obtain the image of the amplitude of the working end surface changing with the resonance frequency, to obtain the current resonance frequency. The impedance analyzer can also be used to calculate the current resonance frequency. Finally, the excitation power of the ultrasonic generator is adjusted to ensure that the transducing system works in the resonance state. However, the working frequency obtained by this method is not equal to the design frequency of the transducing system, which will change the displacement node and make the flange not at the displacement node. This further leads to an increase in the amplitude of the flange, an increase in the heat generation, a decrease in the service life of the amplitude rod and a decrease in the transmission efficiency.

[0003] In addition, when the working environment changes, the operation task also changes. For example, when performing plant protection operation tasks, agricultural workers will use different pesticides according to different plants and their categories of pests and diseases, and each category of pests corresponds to a droplet size that has the best control effect, i.e. the optimal biological control particle size. The droplet size obtained by ultrasonic atomization is related to the resonance frequency of the ultrasonic vibration system. Therefore, the ultrasonic atomization system can be adapted to different pesticide application scenarios by replacing amplitude rods with different resonance frequencies. However, this will lead to the need to equip too many amplitude rods with different resonance frequencies for replacement, reducing the convenience of operation.

[0004] In summary, the existing plant protection nozzles have the problems of difficulty in forming small droplet sizes and inability to adjust the droplet size in real time, especially the inability to dynamically and real-time adjust the spray particle size to carry out precise spraying operations, and the inability to implement fine droplet microenvironment diffusion spraying according to individual crop microenvironments to improve the coverage rate of droplets on the plant surface, resulting in low leaf coverage density, low uniformity of coverage and low utilization rate of pesticides. SUMMARY

[0005] To solve the above problems, the application discloses an ultrasonic atomization variable frequency nozzle and a design method thereof.

[0006] To achieve the above object, the technical scheme of the application is as follows:

[0007] An ultrasonic atomization variable frequency nozzle comprises, from right to left, a third amplitude rod, a second amplitude rod, a terbium-dysprosium-iron hollow rod, a first amplitude rod, a matching block and a compression block; first to fifth electrode sheets, first to fourth piezoelectric ceramics and the matching block are sequentially arranged between the first amplitude rod and the matching block from right to left; the terbium-dysprosium-iron hollow rod is made of a terbium-dysprosium-iron alloy; a coil is wound outside the terbium-dysprosium-iron hollow rod; after the first to fifth electrode sheets are connected to an alternating power supply, the fourth to first piezoelectric ceramics convert electric energy into mechanical energy through the inverse piezoelectric effect, and then the vibration amplitude is amplified through the first, second and third amplitude rods, and micron-sized droplets are formed through the action of surface tension waves and cavitation effect on the liquid medicine.

[0008] Further, the first amplitude rod body is a circular truncated cone, and a first through hole is arranged along the center line thereof; second and first stepped shafts are arranged at the two ends of the first amplitude rod respectively; one end of the first stepped shaft sequentially penetrates the first to fifth electrode sheets, the first to fourth piezoelectric ceramics and the matching block from right to left, and is finally connected with the compression block.

[0009] Further, a first thread is arranged on the shaft shoulder of the first stepped shaft; and the compression block is fixed on the first stepped shaft through the first thread.

[0010] Further, the second amplitude rod body is a stepped shaft, a first threaded hole is arranged at the end with a larger diameter of the second amplitude rod, and a second through hole is arranged along the center line of the second amplitude rod; the second amplitude rod is threadedly connected with the first amplitude rod through the first threaded hole.

[0011] Further, the third amplitude rod body is a stepped shaft with a conical transition, a second threaded hole is arranged at the end with a larger diameter of the third amplitude rod, and the second threaded holes of the second and third amplitude rods are threadedly connected, so that the terbium-dysprosium-iron hollow rod is arranged between the second and third amplitude rods.

[0012] Further, the center lines of the first amplitude rod, the second amplitude rod, the terbium-dysprosium iron hollow rod, the third amplitude rod, the first piezoelectric ceramic, the second piezoelectric ceramic, the third piezoelectric ceramic, the fourth piezoelectric ceramic, the matching block and the pressing block are on the same straight line.

[0013] A design method of an ultrasonic atomization variable frequency nozzle, specifically comprising the following steps:

[0014] Step 1: After the third amplitude rod is threadedly connected with the second amplitude rod through the second threaded hole, the terbium-dysprosium iron hollow rod is pressed, so as to provide a pre-stress for the terbium-dysprosium iron hollow rod, the terbium-dysprosium iron hollow rod is externally wound with a coil, and the coil is externally connected with a circuit with a variable resistor. By adjusting the current input to the coil, the size of the magnetic field generated by the coil is changed; when the magnetic field around the terbium-dysprosium iron hollow rod changes, the elastic modulus of the terbium-dysprosium iron hollow rod also changes, thereby changing the resonant frequency of the terbium-dysprosium iron hollow rod; and the natural frequency of the longitudinal vibration of the two-end free thin rod is:

[0015]

[0016] In formula 1, E is the elastic modulus of the thin rod, p is the density of the thin rod, l is the length of the thin rod, and n is a positive integer, when n = 1, is the fundamental frequency of the free longitudinal vibration, and the natural frequency of the free longitudinal vibration of the thin rod is a positive integer multiple of the fundamental frequency;

[0017] Step 2: Based on the frequency equation: assuming that the variable cross-section rod is composed of uniform and isotropic material, and there is no mechanical loss; when the lateral size of the rod is much smaller than the wavelength of the longitudinal wave, it can be determined that the plane longitudinal wave moves along the axial direction of the rod, and the stress distribution is uniform on the cross section of the rod; the tensile stress of any variable cross-section rod on a small volume element (the interval defined by x, x+d) is According to Newton's law, the dynamic equation can be written as

[0018]

[0019] In formula 2, S = S(x) is the cross-sectional area function of the rod; and ξ = ξ(x, t) is the displacement function of the mass point, is the stress function.

[0020] In the case of simple harmonic vibration, formula 2 can be expressed as:

[0021]

[0022] Formula 3 is the wave equation of the longitudinal vibration of the variable cross-section rod. Wherein k is the circular wave number, and ω is the circular frequency, is the propagation speed of the longitudinal wave in the thin rod.

[0023] Step 3: design a simplified uniform bar, S1 is the cross-sectional area of the thicker end of the second stepped shaft of the first amplitude bar, respectively represent the force and velocity of the input end of the second stepped shaft of the first amplitude bar, respectively represent the force and velocity of the output end of the second stepped shaft of the first amplitude bar. By using the method of separation of variables, the particle displacement function ξ(x, t) of the second stepped shaft of the first amplitude bar can be decomposed into the product of a spatial function and a time function, i.e.

[0024] ξ(x, t) = U(x)Y(t) (4)

[0025] In formula 4, U(x) is the mode function of the second stepped shaft of the first amplitude bar, representing the longitudinal vibration state of the second stepped shaft of the first amplitude bar, and Y(t) represents the vibration law of a point on the second stepped shaft of the first amplitude bar. Substituting ξ(x, t) = U(x)Y(t) and into formula 3, the solution of formula 3 can be obtained as:

[0026] U(x) = [A1 cos(kx) + B1 sin(kx)] (5)

[0027]

[0028] In formula 5, formula 6, E1 is the elastic modulus of the second stepped shaft of the first amplitude bar, A1 and B1 are undetermined coefficients, which depend on the boundary conditions

[0029] The boundary conditions are:

[0030]

[0031] Under the resonance condition, the vibration velocity and the displacement are different by π / 2 radians, so we can get:

[0032]

[0033] Substituting formula 11 into formula 7, formula 8, we can get:

[0034]

[0035] Substituting A1 and B1 into formula 9, formula 10, we can get

[0036]

[0037] In formula 14, formula 15, Z1 = S1ρ1C1 is the characteristic force impedance of the second stepped shaft of the first amplitude bar, ρ1 is the density of the material of the second stepped shaft of the first amplitude bar, and C1 is the propagation speed of sound in the second stepped shaft of the first amplitude bar.

[0038] And formula 14, formula 15 can be represented with the equivalent T-shaped network with concentrated parameters, by Kirchhoff voltage / current law can obtain

[0039]

[0040] With the undetermined coefficient method to compare formula 14, formula 15, formula 16 and formula 17, the expression of the equivalent impedance of the equivalent T-shaped network of the second stepped shaft of the first amplitude transformer can be obtained as follows:

[0041]

[0042] In formula 18, formula 19, Z1=S1ρ1C1 represents the characteristic force impedance of the second stepped shaft of the first amplitude transformer, S1 represents the cross-sectional area of the second stepped shaft of the first amplitude transformer. ρ1 represents the material density of the second stepped shaft of the first amplitude transformer. C1 represents the propagation speed of sound in the second stepped shaft of the first amplitude transformer. l1 represents the length of the second stepped shaft of the first amplitude transformer.

[0043] Since the second amplitude transformer, the terbium dysprosium iron hollow rod, the larger diameter end of the third amplitude transformer and the smaller diameter end of the third amplitude transformer all belong to the equal cross-section rod, the analysis process is similar to the second stepped shaft of the first amplitude transformer, so the equivalent impedance of the second amplitude transformer, the terbium dysprosium iron hollow rod, the larger diameter end of the third amplitude transformer and the smaller diameter end of the third amplitude transformer can be represented as:

[0044]

[0045] In formula 20, formula 21, Z i =S i ρ i C i (i=2,3,4,5) respectively represent the characteristic force impedance of the second amplitude transformer, the terbium dysprosium iron hollow rod, the larger diameter end of the third amplitude transformer and the smaller diameter end of the third amplitude transformer, S i (i=2,3,4,5) respectively represent the cross-sectional area of the second amplitude transformer, the terbium dysprosium iron hollow rod, the larger diameter end of the third amplitude transformer and the smaller diameter end of the third amplitude transformer. ρ i (i=2,3,4,5) respectively represent the material density of the second amplitude transformer, the terbium dysprosium iron hollow rod, the larger diameter end of the third amplitude transformer and the smaller diameter end of the third amplitude transformer. C i (i=2,3,4,5) respectively represent the propagation speed of sound in the second amplitude transformer, the terbium dysprosium iron hollow rod, the larger diameter end of the third amplitude transformer and the smaller diameter end of the third amplitude transformer. l i (i=2,3,4,5) respectively represent the length of the second amplitude transformer, the terbium dysprosium iron hollow rod, the larger diameter end of the third amplitude transformer and the smaller diameter end of the third amplitude transformer.

[0046] Step 4: design the first amplitude transformer body simplified variable cross-section rod, is the first amplitude transformer body left side diameter, is the first amplitude transformer body right side diameter, respectively represent the force and velocity of the first amplitude transformer body input end, respectively represent the force and velocity of the first amplitude transformer body output end. is the first amplitude transformer body left side cross-sectional area, is the first amplitude transformer body right side cross-sectional area, and the area function of the first amplitude transformer body is:

[0047]

[0048] In formula 22, formula 23, l6 is the first amplitude transformer body length;

[0049] By using the separation of variables method to process the displacement function, and substituting the area function of the first amplitude transformer body into formula 3, the solution of formula 3 can be obtained as:

[0050]

[0051] In formula 24, formula 25, A6, B6 are undetermined coefficients, which depend on the boundary conditions;

[0052] The boundary conditions are:

[0053]

[0054] wherein E6 is the elastic modulus of the material of the first amplitude transformer body;

[0055] And under the resonance condition, the vibration velocity and the displacement are different by π / 2 radians, so:

[0056]

[0057] Substituting formula 30 into formula 26, formula 27, we can get:

[0058]

[0059] Substituting formula 31, formula 32 into formula 28, formula 29, we can get the expressions of the forces on the two end faces about the end face velocities:

[0060]

[0061] In formula 33, formula 34, is the characteristic force impedance of the first amplitude transformer body input end, ρ6 is the characteristic force impedance at the output end of the first amplitude transformer body, C6 is the material density of the first amplitude transformer body, l6 is the sound propagation speed of the first amplitude transformer body, and l6 is the length of the first amplitude transformer body.

[0062] By comparing Equations 33, 34, 16, and 17 using the method of undetermined coefficients, the equivalent impedance expression of the equivalent T-shaped network of the first amplitude transformer body can be obtained as follows:

[0063]

[0064] Since the conical transition section of the third amplitude transformer is a conical bar, the analysis process is similar to that of the main body of the first amplitude transformer (5). Therefore, the equivalent impedance of the equivalent T-type network of the conical transition section of the third amplitude transformer can be expressed as:

[0065]

[0066] In equations 38, 39 and 40, The characteristic force impedance of the conical transition section of the third amplitude transformer is... ρ7 is the characteristic force impedance at the output end of the conical transition section of the third amplitude transformer, C7 is the material density of the conical transition section of the third amplitude transformer, and l7 is the sound propagation speed in the conical transition section of the third amplitude transformer.

[0067] The vibration model of the amplitude transformer can be compared to: Figure 2 The circuit model, when the two ends of the amplitude transformer are free, F out =F in =0, the impedance value of the equivalent circuit

[0068]

[0069] in,

[0070] When the system resonates, the equivalent circuit reactance is 0, therefore

[0071]

[0072] Simultaneous equations 43 and ω=k i C, ω=2πf, The expression for the resonant frequency f can be obtained as follows:

[0073]

[0074] The resonant frequency f i Arranged from smallest to largest, f1 is the first resonant frequency, also known as the fundamental frequency, and the other resonant frequencies are positive integer multiples of f1.

[0075] The expression of the amplification coefficient is:

[0076]

[0077] Compared with the prior art, the application has the beneficial effects that:

[0078] 1. By adjusting the coil current, the magnetic field around the TbDyFe hollow rod is changed, so that the elastic modulus of the TbDyFe reaches a given value, and the real-time frequency adjustment of the transducer is realized, so that the nozzle can change the droplet diameter online to meet different application scenarios.

[0079] 2. The TbDyFe magnetostrictive material has a fast response speed (microsecond level), and can quickly realize frequency adjustment of the transducer.

[0080] 3. The TbDyFe magnetostrictive material has a significant ΔE effect, so that the frequency adjustment range of the amplitude rod is large, and more biological optimal particle diameters can be met to realize more complex operation tasks.

[0081] 4. Since the TbDyFe is externally wound with a multi-turn coil, placing the TbDyFe in the middle section of the amplitude rod can make the mass distribution more reasonable, the required torque of the nozzle rotation is smaller, and the energy consumption is lower; the magnetostrictive value of the TbDyFe magnetostrictive material (TbxDy1-xFe2) at room temperature can reach 1.5 ‰, which is 8-10 times larger than the currently widely used piezoelectric ceramic, and the energy density is 20-30 times larger. BRIEF DESCRIPTION OF DRAWINGS

[0082] Figure 1 The equivalent T-type network circuit diagram of the second stepped shaft (5A) of the first amplitude rod (5) described in the application.

[0083] Figure 2 The equivalent T-type network circuit diagram of the variable frequency transducer described in the application.

[0084] Figure 3 The structure schematic diagram of the variable frequency transducer described in the application.

[0085] Figure 4 The structure schematic diagram of the first amplitude rod in the variable frequency transducer described in the application.

[0086] Figure 5 The structure schematic diagram of the second amplitude rod in the variable frequency transducer described in the application.

[0087] Figure 6 The structure schematic diagram of the variable frequency transducer described in the application. Figure 5 The cross-sectional structure schematic diagram of B-B.

[0088] Figure 7 The structure schematic diagram of the third amplitude rod in the variable frequency transducer described in the application.

[0089] Figure 8 The resonant frequency adjustment principle of the variable frequency transducer described in the present application is shown in the figure. Figure 7 The cross-sectional structure diagram at A-A in the figure.

[0090] Figure 9 The resonant frequency adjustment principle of the variable frequency transducer described in the present application is shown in the figure. DETAILED DESCRIPTION

[0091] The present application will be further clarified by the following description and specific embodiments, which should be understood as merely illustrative of the present application and not limiting the scope of the present application. It should be noted that the words "front", "back", "left", "right", "upper" and "lower" used in the following description refer to the directions in the figures, and the words "inner" and "outer" refer to the directions towards or away from the geometric center of a particular component.

[0092] As shown in the figure, Figure 3 The intelligent variable frequency nozzle provided by the present application is a high adaptability nozzle with real-time adjustable working frequency. The nozzle comprises a first amplitude rod 1, a terbium dysprosium iron hollow rod 2, a coil 3, a second amplitude rod 4, a third amplitude rod 5, a first electrode sheet 6, a second electrode sheet 7, a third electrode sheet 8, a fourth electrode sheet 9, a fifth electrode sheet 10, a matching block 11, a pressing block 12, a fourth piezoelectric ceramic 13, a third piezoelectric ceramic 14, a second piezoelectric ceramic 15, and a first piezoelectric ceramic 16.

[0093] The terbium dysprosium iron hollow rod 2 is made of terbium dysprosium iron alloy, which has fast response speed (microsecond level) and significant ΔE effect, that is, when the magnetic field around the material changes, the range of its Young's modulus also changes greatly. By adjusting the size of the magnetic field around the terbium dysprosium iron hollow rod 2, the Young's modulus of the terbium dysprosium iron hollow rod 2 is changed, and then the stiffness of the transducer is changed, finally the real-time adjustment of the working frequency of the terbium dysprosium iron hollow rod 2 is realized.

[0094] The coil 3 is wound outside the terbium dysprosium iron hollow rod 2, and the size of the magnetic field around the terbium dysprosium iron hollow rod 2 is changed by controlling the current of the coil 3.

[0095] The coil 3 provides a bias magnetic field for the terbium dysprosium iron hollow rod 2 and adjusts the Young's modulus of the terbium dysprosium iron hollow rod 2. According to the ΔE effect of the terbium dysprosium iron hollow rod 2, the resonant frequency of the terbium dysprosium iron hollow rod 2 can be adjusted according to the required optimal biological particle size of the use scene, so that the formed mist droplet particle size reaches the required optimal biological particle size.

[0096] Figure 9 As shown in the figure,

[0097] There are two main hypotheses for the mechanism of ultrasonic atomization: capillary wave hypothesis and cavitation hypothesis.

[0098] Capillary wave hypothesis is that under the action of continuous external oscillation, very uniform surface capillary waves are formed on the surface of the liquid film. The surface capillary wave is composed of wave crest and wave trough. When the oscillation intensity increases to a certain amplitude, the wave crest position of the surface capillary wave will be separated from the liquid, and atomization occurs.

[0099] In the cavitation hypothesis, it is assumed that in a vibration system with high frequency and high power, when the liquid film is affected by sound waves, bubbles will be formed in the cavities. These bubbles grow and oscillate with the change of sound pressure, causing the increase of internal pressure. At a certain time, when the bubbles reach the surface of the liquid, due to the huge internal and external pressure difference, they will break and produce strong impact, causing the surrounding liquid to be ejected from the liquid film and atomized.

[0100] The empirical formula of the average diameter of the sub-liquid droplets in the capillary wave hypothesis is:

[0101]

[0102] In formula (1), f is the excitation frequency of the ultrasonic generator, σ is the surface tension of the liquid, and ρ is the density of the liquid.

[0103] After the type of pesticide is selected, the surface tension σ and the density ρ of the pesticide solution are determined values, so in order to change the average diameter of the sub-liquid droplets, the excitation frequency of the ultrasonic generator can be adjusted.

[0104] The relationship between the resonance frequency f of the system and the mass and stiffness is:

[0105]

[0106] In formula (2), k is the stiffness of the system, and m is the mass of the system.

[0107] For a cylinder, the expression of the stiffness k of the system is:

[0108]

[0109] In formula (3), E is the Young's modulus of the system, A is the cross-sectional area, and L is the length.

[0110] When the magnetic field or stress acting on the terbium-dysprosium iron changes, the Young's modulus of the terbium-dysprosium iron will change, and the mathematical expression of the ΔE effect of the terbium-dysprosium iron is:

[0111]

[0112] In formula (4), ΔE is the change amount of the Young's modulus of the material, σ is the normal stress acting on the material, ε σ is the elastic strain of the material, and ε m0 is the magnetoelastic strain of the material under the action of the initial bias magnetic field.m1 The magnetic strain of the material under the changed magnetic field.

[0113] The Young's modulus E is expressed as:

[0114]

[0115] In formula (2), L is the length before deformation of the material, and Delta L is the elongation after deformation.

[0116] The elastic modulus E is a function of the magnetic field strength H and stress, which can only be measured by experiments at present and obtained by interpolation method.

[0117] The formula of the magnetic field strength H is:

[0118]

[0119] In formula (6), N is the number of turns of the exciting coil, I is the current through the exciting coil, and Le is the effective magnetic path length.

[0120] Therefore, the experimental data can be functionally fitted to obtain the fitting function of the Young's modulus E of terbium dysprosium iron with respect to the coil current I, so that the Young's modulus can be actively controlled in an open loop by controlling the current size.

[0121] The inverse piezoelectric effect: after an external electric field is applied to the piezoelectric crystal, the internal polarization state of the piezoelectric crystal will change accordingly, and a strain proportional to the strength of the applied electric field will be generated. The expression of the inverse piezoelectric effect in the thickness direction of the piezoelectric sheet is:

[0122]

[0123] In formula (7), S is the expansion strain in the thickness direction; g is the piezoelectric constant in the thickness direction; U is the voltage applied in the thickness direction; and t is the thickness of the piezoelectric sheet.

[0124] And the super-magnetostrictive material (terbium dysprosium iron) is installed on the amplitude-changing rod, the elastic modulus of the amplitude-changing rod can be adjusted by changing the magnetic field around the super-magnetostrictive material, and then the stiffness of the amplitude-changing rod is adjusted, a nozzle with variable resonance frequency is obtained, and finally the real-time adjustment of the droplet size is realized.

[0125] The first amplitude-changing rod 5 is provided with a second stepped shaft 5A and a first stepped shaft 5B at both ends, a first through hole 5D is arranged on the center line of the first amplitude-changing rod 5, and a first thread 5C is arranged on the shoulder of the first stepped shaft 5B.

[0126] The first electrode sheet 6, the first piezoelectric ceramic 16, the second electrode sheet 7, the second piezoelectric ceramic 15, the third electrode sheet 8, the third piezoelectric ceramic 14, the fourth electrode sheet 9, the fourth piezoelectric ceramic 13, the fifth electrode sheet 10, the matching block 11 and the compression block 12 are sequentially arranged from right to left.

[0127] As shown in the figure, Figures 3-8 The first stepped shaft 5B of the first amplitude horn 5 sequentially passes through the first electrode sheet 6, the first piezoelectric ceramic 16, the second electrode sheet 7, the second piezoelectric ceramic 15, the third electrode sheet 8, the third piezoelectric ceramic 14, the fourth electrode sheet 9, the fourth piezoelectric ceramic 13, the fifth electrode sheet 10, the matching block 11 and the compression block 12 from right to left.

[0128] The compression block 12 is fixed to the first stepped shaft 5B of the first amplitude horn 5 by the thread 5C.

[0129] As shown in the figure, Figure 2 , Figure 3 , Figure 4 The second amplitude horn 4 is provided with a first threaded hole 4B at the larger diameter end, and a second through hole 4A is arranged on the center line of the second amplitude horn 4. The second amplitude horn 4 is threadedly connected with the first amplitude horn 5 through the threaded hole 4B.

[0130] As shown in the figure, Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 The third amplitude horn 1 is provided with a second threaded hole 1B at the larger diameter end, and a third through hole 1A is arranged on the axis of the third amplitude horn 1. The third amplitude horn 1 is threadedly connected with the second amplitude horn 4 through the second threaded hole 1B.

[0131] After the first electrode sheet 6, the second electrode sheet 7, the third electrode sheet 8, the fourth electrode sheet 9 and the fifth electrode sheet 10 are connected to an alternating power supply, the fourth piezoelectric ceramic 13, the third piezoelectric ceramic 14, the second piezoelectric ceramic 15 and the first piezoelectric ceramic 16 convert electrical energy into mechanical energy through the inverse piezoelectric effect, then the vibration amplitude is amplified through the first amplitude horn 5, the second amplitude horn 4 and the third amplitude horn 1, and then the surface tension wave and cavitation effect act on the liquid medicine to form micron-sized droplets.

[0132] When the magnetic field strength continues to increase, the elastic modulus of the giant magnetostrictive material no longer decreases, and the magnetic field strength at this time is called the saturation magnetic field strength.

[0133] The current size of the adjusting coil 3 is adjusted to obtain 0, 0.25, 0.5, 0.75 and 1 times of the saturated magnetic field strength, respectively, the resonant frequency of the transducer under 0, 0.25, 0.5, 0.75 and 1 times of the saturated magnetic field strength is measured by the impedance analyzer, and recorded as f0, f0.25, f0.5, f0.75 and f1, respectively, and the current is recorded as I0, I0.25, I0.5, I0.75 and I1, respectively. Then the interpolation function f=f(I) is obtained by using the four times spline interpolation method, and the relationship between the resonant frequency of the transducer and the current size is fitted by using the function. In the execution of the drug application task, the working resonant frequency of the transducer is calculated according to the optimal biological particle size and the seed particle size empirical formula of the target plant, and the required current is obtained according to the interpolation function, and then the current size of the circuit is adjusted. Then the resonant frequency of the transducer at this time is measured by using the impedance analyzer, and then the excitation frequency of the ultrasonic generator is adjusted, as shown in Figure 7

[0134] The technical means disclosed in the scheme of the present application is not limited to the technical means disclosed in the above-mentioned embodiments, but also includes the technical scheme composed of any combination of the above technical features.​

Claims

1. An ultrasonic atomizing frequency conversion nozzle, characterized in that: The system includes, from right to left, a third amplitude transformer (1), a second amplitude transformer (4), a terbium-dysprosium hollow rod (2), a first amplitude transformer (5), a matching block (11), and a clamping block (12); wherein, between the matching block (11) and the first amplitude transformer (5), from right to left, are arranged a first electrode plate (6), a first piezoelectric ceramic (16), a second electrode plate (7), a second piezoelectric ceramic (15), a third electrode plate (8), a third piezoelectric ceramic (14), a fourth electrode plate (9), a fourth piezoelectric ceramic (13), and a fifth electrode plate (10); the terbium-dysprosium hollow rod (2) is made of terbium-dysprosium alloy; and a coil (3) is wound around the outside of the terbium-dysprosium hollow rod (2). After the first electrode (6), second electrode (7), third electrode (8), fourth electrode (9), and fifth electrode (10) are connected to an alternating power supply, the fourth piezoelectric ceramic (13), third piezoelectric ceramic (14), second piezoelectric ceramic (15), and first piezoelectric ceramic (16) convert electrical energy into mechanical energy through the inverse piezoelectric effect. Then, the vibration amplitude is amplified by the first amplitude transformer (5), second amplitude transformer (4), and third amplitude transformer (1), and the surface tension wave and cavitation effect act on the liquid medicine to form micron-sized droplets. The first amplitude transformer (5) is a frustum, and a first through hole (5D) is provided along its center line. The two ends of the boom (5) are respectively provided with a second stepped shaft (5A) and a first stepped shaft (5B); one end of the first stepped shaft (5B) passes through the first electrode plate (6), the first piezoelectric ceramic (16), the second electrode plate (7), the second piezoelectric ceramic (15), the third electrode plate (8), the third piezoelectric ceramic (14), the fourth electrode plate (9), the fourth piezoelectric ceramic (13), the fifth electrode plate (10) and the matching block (11) from right to left, and finally connects with the clamping block (12); the shoulder of the first stepped shaft (5B) is provided with a first thread (5C); the clamping block (12) is fixed to the first stepped shaft by the first thread (5C). (5B) The second amplitude rod (4) is a stepped shaft with a first threaded hole (4B) at its larger diameter end and a second through hole (4A) on its center line; the second amplitude rod (4) is threaded to the first amplitude rod (5) through the first threaded hole (4B); the third amplitude rod (1) is a stepped shaft with a conical transition and a second threaded hole (1B) at its larger diameter end and a third through hole (1A) on its center axis; the third amplitude rod (1) and the second amplitude rod (4) are threaded to each other through the second threaded hole (1B).

2. The ultrasonic atomizing frequency conversion nozzle according to claim 1, characterized in that: The outer lengths of the first amplitude rod (5), the second amplitude rod (4), and the third amplitude rod (1) are equal.

3. The design method of an ultrasonic atomizing frequency conversion nozzle according to any one of claims 1-2, characterized in that: Includes the following steps: Step 1: After the third amplitude rod (1) and the second amplitude rod (4) are threaded together through the second threaded hole (1B), the terbium-dysprosium hollow rod (2) is pressed to provide pre-compression stress to the terbium-dysprosium hollow rod (2). A coil (3) is wound around the outside of the terbium-dysprosium hollow rod (2), and a circuit with a variable resistor is connected to the outside of the coil (3). By adjusting the current connected to the coil (3), the magnitude of the magnetic field generated by the coil (3) is changed. When the magnetic field around the terbium-dysprosium hollow rod (2) changes, the elastic modulus of the terbium-dysprosium hollow rod (2) will also change, thereby changing the resonant frequency of the terbium-dysprosium hollow rod (2). The natural frequency of the longitudinal vibration of the free thin rods at both ends is: In Equation 1, E is the elastic modulus of the thin rod, ρ is the density of the thin rod, l is the length of the thin rod, and n is a positive integer. When n = 1, The fundamental frequency of free longitudinal vibration is the natural frequency of the free longitudinal vibration of the thin rod, which is a positive integer multiple of the fundamental frequency. Step 2: Based on the frequency equation: Assume the variable cross-section rod is made of homogeneous, isotropic material with no mechanical loss; when the transverse dimension of the rod is much smaller than the wavelength of the longitudinal wave, it can be assumed that the plane longitudinal wave moves along the axial direction of the rod, and the stress distribution is uniform on the cross-section of the rod; for any variable cross-section rod, its axis of symmetry is the x-axis, and the tensile stress on any small volume element (the interval defined by x, x+d) is... According to Newton's laws, the equations of motion can be written. In Equation 2, S = S(x) is the cross-sectional area function of the rod; ξ = ξ(x,t) is the displacement function of the mass. The stress function; In the case of simple harmonic motion, equation 2 can be expressed as: Equation 3 is the wave equation for the longitudinal vibration of a variable cross-section rod; where k is the circular wave number, and ω is the angular frequency. The propagation speed of the longitudinal wave in the thin rod; Step 3: Design a simplified constant cross-section bar, where S1 is the cross-sectional area of ​​the thicker end of the second stepped shaft (5A) of the first amplitude-changing bar (5). These represent the force and velocity at the input end of the second stepped shaft (5A) of the first amplitude transformer (5), respectively. These represent the force and velocity at the output end of the second stepped shaft (5A) of the first amplitude transformer (5), respectively; Using the method of separation of variables, the particle displacement function ξ(x,t) of the second step shaft (5A) of the first amplitude rod (5) can be decomposed into the product of a spatial function and a time function, i.e. ξ(x,t)=U(x)Y(t) (4) In Equation 4, U(x) is the mode shape function of the second stepped shaft (5A) of the first amplitude transformer (5), representing the longitudinal vibration state of the second stepped shaft (5A) of the first amplitude transformer (5), and Y(t) represents the vibration law of a certain point on the second stepped shaft (5A) of the first amplitude transformer (5); ξ(x,t)=U(x)Y(t) and Substituting into equation 3, we obtain the solution to equation 3 as follows: U(x)=[A1 cos(kx)+B1 sin(kx)] (5) In Equations 5 and 6, E1 is the elastic modulus of the second step shaft (5A) of the first amplitude transformer (5), and A1 and B1 are undetermined coefficients that depend on the boundary conditions. The boundary conditions are: Under resonance conditions, the vibration velocity differs from the displacement by π / 2 radians, therefore we can obtain: Substituting equation 11 into equations 7 and 8, we get: Substituting A1 and B1 into equations 9 and 10 respectively, we get... Equations 14 and 15, Z1 = S1ρ1C1 is the characteristic force impedance of the second step shaft (5A) of the first amplitude rod (5), ρ1 is the density of the material of the second step shaft (5A) of the first amplitude rod (5), and C1 is the propagation speed of sound on the second step shaft (5A) of the first amplitude rod (5). Equations 14 and 15 can be represented by an equivalent T-shaped network with lumped parameters, which can be obtained from Kirchhoff's voltage / current law. By comparing Equations 14, 15, 16, and 17 using the method of undetermined coefficients, the expression for the equivalent impedance of the equivalent T-shaped network of the second step shaft (5A) of the first amplitude transformer (5) can be obtained as follows: In Equations 18 and 19, Z1 = S1ρ1C1 represents the characteristic force impedance of the second stepped shaft (5A) of the first amplitude transformer (5); S1 represents the cross-sectional area of ​​the second stepped shaft (5A) of the first amplitude transformer (5); ρ1 represents the material density of the second stepped shaft (5A) of the first amplitude transformer (5); C1 represents the propagation speed of sound on the second stepped shaft (5A) of the first amplitude transformer (5); and l1 represents the length of the second stepped shaft (5A) of the first amplitude transformer (5). Since the larger diameter end of the second amplitude transformer (4), the terbium-dysprosium hollow rod (2), and the smaller diameter end of the third amplitude transformer (1) are all rods with uniform cross-sections, the analysis process is similar to that of the second stepped shaft (5A) of the first amplitude transformer (5). Therefore, the equivalent impedance of the larger diameter end of the second amplitude transformer (4), the terbium-dysprosium hollow rod (2), and the smaller diameter end of the third amplitude transformer (1) can be expressed as: In Equations 20 and 21, Z i =S i ρ i C i (i = 2, 3, 4, 5) represent the characteristic force resistances of the larger diameter end of the second amplitude transformer (4), the terbium-dysprosium hollow rod (2), and the smaller diameter end of the third amplitude transformer (1), respectively. i (i = 2, 3, 4, 5) represent the cross-sectional areas of the larger diameter end of the second amplitude transformer (4), the terbium-dysprosium hollow rod (2), the third amplitude transformer (1), and the smaller diameter end of the third amplitude transformer (1), respectively; ρ i (i = 2, 3, 4, 5) represent the material densities of the larger diameter end of the second amplitude transformer (4), the terbium-dysprosium hollow rod (2), the third amplitude transformer (1), and the smaller diameter end of the third amplitude transformer (1), respectively; C i (i = 2, 3, 4, 5) represent the propagation speeds of sound at the larger and smaller ends of the second amplitude transformer (4), the terbium-dysprosium hollow rod (2), and the third amplitude transformer (1), respectively; l i (i=2,3,4,5) represent the lengths of the larger diameter end of the second amplitude rod (4), the terbium-dysprosium hollow rod (2), the third amplitude rod (1), and the smaller diameter end of the third amplitude rod (1), respectively; Step 4: Design the simplified variable cross-section bar of the first amplitude bar (5). The diameter of the left side of the main body of the first amplitude rod (5) is... The diameter of the right side of the main body of the first amplitude rod (5) is... These represent the force and velocity at the input end of the first amplitude lever (5), respectively. These are respectively represented as the force and velocity at the output end of the main body of the first amplitude rod (5); The cross-sectional area on the left side of the main body of the first amplitude rod (5) is... Let be the cross-sectional area on the right side of the main body of the first amplitude transformer (5). The area function of the main body of the first amplitude transformer (5) is: In equations 22 and 23, l6 is the main body length of the first amplitude rod (5); By using the method of separation of variables to process the displacement function, and substituting the area function of the main body of the first amplitude rod (5) into Equation 3, the solution of Equation 3 can be obtained as follows: In Equations 24 and 25, A6 and B6 are undetermined coefficients that depend on the boundary conditions; The boundary conditions are: Among them, E6 is the elastic modulus of the main material of the first amplitude rod (5); Under resonance conditions, the vibration velocity differs from the displacement by π / 2 radians, therefore we can obtain: Substituting equation 30 into equations 26 and 27, we get: Substituting equations 31 and 32 into equations 28 and 29, we can obtain the expressions for the forces on both ends with respect to the velocities on the ends: In equations 33 and 34, The characteristic force impedance of the main input end of the first amplitude transformer (5) is... ρ6 is the characteristic force impedance of the output end of the first amplitude rod (5), ρ6 is the material density of the first amplitude rod (5), C6 is the sound propagation speed of the first amplitude rod (5), and l6 is the length of the first amplitude rod (5). By comparing Equations 33, 34, 16, and 17 using the method of undetermined coefficients, the equivalent impedance expression of the equivalent T-shaped network of the main body of the first amplitude transformer (5) can be obtained as follows: Since the conical transition section of the third amplitude transformer (1) is a conical bar, the analysis process is similar to that of the main body of the first amplitude transformer (5). Therefore, the equivalent impedance of the equivalent T-type network of the conical transition section of the third amplitude transformer (1) can be expressed as: In equations 38, 39 and 40, The characteristic force impedance of the conical transition section of the third amplitude rod (1) is... ρ7 is the characteristic force impedance of the output end of the conical transition section of the third amplitude rod (1), ρ7 is the material density of the conical transition section of the third amplitude rod (1), C7 is the sound propagation speed in the conical transition section of the third amplitude rod (1), and l7 is the length of the conical transition section of the third amplitude rod (1). When both ends of the amplitude rod are free, F out =F in =0, the impedance value of the equivalent circuit in, When the system resonates, the equivalent circuit reactance is 0, therefore Simultaneous equations 43 and ω=k i C, ω=2πf, The expression for the resonant frequency f can be obtained as follows: The resonant frequency f i Arranged from smallest to largest, f1 is the first resonant frequency, also known as the fundamental frequency, and the other resonant frequencies are positive integer multiples of f1; The expression for the magnification factor is: Thus, the calculation formulas for the operating frequency f and amplification factor G of the ultrasonic atomizing variable frequency nozzle have been derived. Based on actual usage requirements, the appropriate amplitude transformer material, length, and cross-sectional area function can be selected using the required operating frequency f and amplification factor G to complete the design task of the ultrasonic atomizing variable frequency nozzle.

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