Variable frequency atomizing nozzle based on giant magnetostrictive material and droplet size control method

Abstract

The application provides a frequency conversion atomizing nozzle based on giant magnetostrictive material and a droplet size regulation method, the nozzle comprising, in sequence, a pressing block, a second matching block, a terbium-dysprosium-iron hollow rod, a first matching block, a fourth piezoelectric ceramic, a third piezoelectric ceramic, a second piezoelectric ceramic, a first piezoelectric ceramic, a first amplitude transformer and a second amplitude transformer; wherein a fifth electrode sheet, a fourth electrode sheet, a third electrode sheet and a second electrode sheet are sequentially arranged on the fourth piezoelectric ceramic, the third piezoelectric ceramic, the second piezoelectric ceramic and the first piezoelectric ceramic; a first electrode sheet is arranged on the first amplitude transformer; wherein the outer surface of the terbium-dysprosium-iron hollow rod is wound with a coil; and the terbium-dysprosium-iron hollow rod is made of terbium-dysprosium-iron alloy. The nozzle can change the external magnetic field of the nozzle, adjust the working frequency in real time, accurately control the droplet size and solve the problem that the particle size of the traditional ultrasonic atomizing nozzle is difficult to adjust in real time.

Description

Technical Field

[0001] This invention relates to the field of atomizing nozzles for plant protection, and more particularly to a frequency conversion atomizing nozzle based on a super magnetostrictive material and a method for controlling droplet size. Background Technology

[0002] An ultrasonic amplitude transformer, also known as an ultrasonic speed transformer or ultrasonic energy concentrator, is typically a variable cross-section bar and is an important component of an ultrasonic vibration system. During operation, the vibration amplitude generated by the ultrasonic transducer's radiating surface is relatively small; at frequencies within the 20kHz range, the amplitude is only a few micrometers. However, in many high-intensity ultrasonic applications such as ultrasonic machining, ultrasonic welding, ultrasonic tinning, ultrasonic cell destruction, and ultrasonic metal forming, amplitudes ranging from tens to hundreds of micrometers are required. Because the vibration amplitude directly output from the transducer is far from meeting the requirements of practical applications, an amplitude transformer is necessary to amplify the displacement and velocity of the mechanical vibrating particles and concentrate the ultrasonic energy over a smaller area, creating an energy-concentrating effect.

[0003] After manufacture, the amplitude transformer's resonant frequency is fixed and cannot be adjusted. However, during actual operation, the resonant frequency of the amplitude transformer can shift due to factors such as load, temperature, and wear, leading to reduced transducer efficiency. Current methods to address this issue include: using a swept-frequency signal to excite the ultrasonic transducer system during operation, and then using a laser vibrometer to obtain an image of the amplitude change at the working end face with the resonant frequency to determine the current resonant frequency. Alternatively, an impedance analyzer can be used to calculate the current resonant frequency. Finally, the excitation power supply of the ultrasonic generator is adjusted to ensure the transducer system operates in a resonant state. However, the operating frequency obtained in this way is not equal to the design frequency of the transducer system, which will lead to a change in the displacement node, causing the flange to be outside the displacement node. This, in turn, results in increased flange amplitude, increased heat generation, reduced amplitude transformer lifespan, and decreased transmission efficiency.

[0004] Furthermore, the tasks change when the working environment changes. For example, when performing plant protection operations, agricultural workers use different pesticides depending on the plant and its pests and diseases. Each pest and disease corresponds to a droplet size that provides the best control effect, i.e., the optimal biological control droplet size. The droplet size obtained through ultrasonic atomization is related to the resonant frequency of the ultrasonic vibration system. Therefore, the ultrasonic atomization system can be adapted to different application scenarios by replacing the amplitude transformer with one of different resonant frequencies. However, this would require equipping too many amplitude transformers with different resonant frequencies for replacement, reducing the convenience of the operation. Summary of the Invention

[0005] To address the aforementioned issues, this invention discloses a variable frequency atomizing nozzle based on a giant magnetostrictive material and a method for controlling droplet size. This nozzle can adjust its operating frequency in real time by changing the external magnetic field, thereby precisely controlling the droplet size and solving the problem of difficulty in real-time adjustment of droplet size in traditional ultrasonic atomizing nozzles.

[0006] A variable frequency atomizing nozzle based on terbium-dysprosium-iron magnetostrictive material includes a first amplitude rod, a second amplitude rod, a first electrode plate, a second electrode plate, a third electrode plate, a fourth electrode plate, a fifth electrode plate, a first piezoelectric ceramic, a second piezoelectric ceramic, a third piezoelectric ceramic, a fourth piezoelectric ceramic, a first matching block, a second matching block, a clamping block, a terbium-dysprosium-iron hollow rod, and a coil.

[0007] The first electrode plate, the first piezoelectric ceramic, the second electrode plate, the second piezoelectric ceramic, the third electrode plate, the third piezoelectric ceramic, the fourth electrode plate, the fourth piezoelectric ceramic, the fifth electrode plate, the second matching block, the terbium-dysprosium hollow rod, the first matching block, and the clamping block are arranged sequentially from right to left.

[0008] The first amplitude rod has a first through hole at its center line, a first stepped shaft at the end with a larger diameter, a second stepped shaft at the end with a smaller diameter, and an external thread on the shoulder of the first stepped shaft.

[0009] The clamping block is provided with a second through hole, which is a threaded hole.

[0010] The first stepped shaft of the first amplitude rod passes through the first electrode plate, the first piezoelectric ceramic, the second electrode plate, the second piezoelectric ceramic, the third electrode plate, the third piezoelectric ceramic, the fourth electrode plate, the fourth piezoelectric ceramic, the fifth electrode plate, the second matching block, the terbium-dysprosium hollow rod, the first matching block, and the clamping block from right to left, and is connected to the second through hole of the clamping block by a thread.

[0011] The second amplitude rod is provided with a third through hole, and the end of the second amplitude rod with a larger diameter is provided with a first blind hole. The first blind hole is a threaded hole, and the second stepped shaft of the first amplitude rod and the first blind hole of the second amplitude rod are connected by threads.

[0012] The coil is wound around the outside of the terbium-dysprosium hollow bar and provides a bias magnetic field for the terbium-dysprosium hollow bar.

[0013] The center lines of the first amplitude transformer, the second amplitude transformer, the terbium-dysprosium hollow rod, the first piezoelectric ceramic, the second piezoelectric ceramic, the third piezoelectric ceramic, the fourth piezoelectric ceramic, the first matching block, the second matching block, and the clamping block are all on the same straight line.

[0014] A method for controlling droplet size in a frequency-converting atomizing nozzle based on a giant magnetostrictive material includes the following steps:

[0015] Step 1: The second matching block and the first matching block are pressed together by the pressure of the clamping block to provide pre-stress to the hollow terbium-dysprosium iron rod. A coil is wound around the outside of the hollow terbium-dysprosium iron rod, and a circuit with a variable resistor is connected to the coil. By adjusting the current connected to the coil, the magnitude of the magnetic field generated by the coil is changed. When the magnetic field around the hollow terbium-dysprosium iron rod changes, the elastic modulus of the hollow terbium-dysprosium iron rod also changes, thereby changing the resonant frequency of the hollow terbium-dysprosium iron rod. The natural frequency of the longitudinal vibration of the free thin rods at both ends is:

[0016] (1)

[0017] In Equation 1, E is the elastic modulus of the thin rod. Let be the density of the thin rod, l be the length of the thin rod, and n be a positive integer. hour, 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.

[0018] Step 2: Based on the frequency equation: Assume the variable cross-section bar is made of homogeneous, isotropic material with no mechanical loss; when the transverse dimension of the bar is much smaller than the wavelength of the longitudinal wave, it can be assumed that the plane longitudinal wave moves along the axis of the bar, and the stress distribution is uniform on the cross-section of the bar; for any variable cross-section bar, 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 dynamic equations can be written.

[0019] (2)

[0020] In Equation 2, Let be the cross-sectional area function of the rod; Let be the displacement function of the particle. This is the stress function.

[0021] In the case of simple harmonic motion, equation 2 can be expressed as:

[0022] (3)

[0023] Equation 3 is the wave equation for the longitudinal vibration of a variable cross-section rod. Wherein... k is the circular wave number. It is the angular frequency. Let be the propagation speed of the longitudinal wave in the thin rod.

[0024] Step 3: Design the simplified uniform cross-section bar. For the cross-sectional area of ​​the second matching block, , These represent the force and velocity at the input of the second matching block, respectively. , These represent the force and velocity at the output of the second matched block, respectively. The displacement function of the mass point of the second matched block can be obtained using the method of separation of variables. It can be decomposed into the product of a space function and a time function, i.e.

[0025] (4)

[0026] In Equation 4, Let be the mode shape function of the second matched block, characterizing the longitudinal vibration state of the second matched block. Characterize the vibration pattern at a point on the second matching block. Substituting into equation 3, we obtain the solution to equation 3 as follows:

[0027] (5)

[0028] (6)

[0029] In equations 5 and 6, The elastic modulus of the second matching block. , These are undetermined coefficients, which depend on the boundary conditions.

[0030] The boundary conditions are:

[0031] (7)

[0032] (8)

[0033] (9)

[0034] (10)

[0035] Under resonance conditions, the vibration velocity differs from the displacement. Therefore, we can conclude that:

[0036] (11)

[0037] Substituting equation 11 into equation 7 and equation 6 into equation 9, we get:

[0038] (12)

[0039] (13)

[0040] Substituting equations 12 and 13 into equations 6 and 11, we can obtain the distribution expressions for force and vibration velocity.

[0041] (14)

[0042] (15)

[0043] in, It is the characteristic force impedance of the second matching block. The density of the second matching block material, The speed at which sound propagates in the second matching block.

[0044] Will Substituting into equations 14 and 15, we can obtain

[0045] (16)

[0046] (17)

[0047] From equations 16 and 17, the transmission matrix of the second matching block can be derived as follows:

[0048] (18)

[0049] In Equation 18, , , ,

[0050] To simplify the model, the first electrode plate, the first piezoelectric ceramic, the second electrode plate, the second piezoelectric ceramic, the third electrode plate, the third piezoelectric ceramic, the fourth electrode plate, the fourth piezoelectric ceramic, and the fifth electrode plate can be regarded as a whole and called the piezoelectric oscillator group.

[0051] Since the terbium-dysprosium hollow rod, the first matching block, the piezoelectric vibrator assembly, the larger diameter end of the second stepped shaft of the first amplitude transformer, the larger diameter end and the smaller diameter end of the second amplitude transformer are all approximately equal-section rods, and the analysis process is similar to that of the second matching block, the transfer matrix of the terbium-dysprosium hollow rod can be obtained as follows:

[0052] (19)

[0053] In Equation 19, , , , , The characteristic force resistance of a terbium-dysprosium hollow bar. Let be the cross-sectional area of ​​the terbium-dysprosium hollow rod. The density of the terbium-dysprosium hollow rod material. Let be the speed of sound propagation in a terbium-dysprosium hollow rod. The length of the terbium-dysprosium hollow rod;

[0054] The transfer matrix of the first matching block is:

[0055] (20)

[0056] In Equation 20, , , , , The characteristic force impedance of the first matching block, Let be the cross-sectional area of ​​the first matching block. The density of the first matching block material, The speed at which sound travels in the first matching block. The length of the first matching block;

[0057] The transmission matrix of the piezoelectric oscillator group is:

[0058] (twenty one)

[0059] In Equation 21, , , , , The characteristic force impedance of the piezoelectric oscillator assembly. Let be the cross-sectional area of ​​the piezoelectric resonator assembly. The average density of the piezoelectric oscillator assembly material. The average speed of sound propagation in the piezoelectric oscillator array. is the length of the piezoelectric oscillator assembly.

[0060] The transmission matrix of the larger diameter end of the second stepped shaft of the first amplitude transformer (11) is:

[0061] (twenty two)

[0062] In Equation 22, , , , , The characteristic force impedance is the end of the second stepped shaft of the first amplitude transformer with the larger diameter. The cross-sectional area is the larger diameter end of the second stepped shaft of the first amplitude transformer. The density of the material at the end of the second stepped shaft of the first amplitude transformer with the larger diameter. The propagation speed is the larger diameter end of the second stepped shaft of the first amplitude transformer. The length of the end with the larger diameter of the second stepped shaft of the first amplitude rod.

[0063] The transmission matrix at the larger diameter end of the second amplitude transformer is:

[0064] (twenty three)

[0065] In Equation 23, , , , , The characteristic force impedance is at the end of the second amplitude transformer with the larger diameter. This refers to the cross-sectional area of ​​the larger diameter end of the second amplitude rod. The density of the material at the larger diameter end of the second amplitude rod. The propagation speed is the larger diameter end of the second amplitude rod. This is the length of the end with the larger diameter of the second amplitude rod.

[0066] The transmission matrix at the smaller diameter end of the second amplitude transformer is:

[0067] (twenty four)

[0068] In Equation 24, , , , , The characteristic force impedance is at the smaller diameter end of the second amplitude transformer. This refers to the cross-sectional area of ​​the smaller diameter end of the second amplitude rod. The density of the material at the smaller diameter end of the second amplitude rod. The propagation speed is the smaller diameter end of the second amplitude rod. It is the length of the end with the smaller diameter of the second amplitude rod.

[0069] Step 4: Design the simplified variable cross-section bar of the first amplitude transformer. The diameter of the left side of the first amplitude rod body is [missing information]. The diameter of the right side of the first amplitude rod body is [missing information]. , These represent the force and velocity at the input end of the first amplitude transformer, respectively. , These represent the force and velocity at the output end of the first amplitude transformer, respectively. The cross-sectional area on the left side of the main body of the first amplitude transformer is... Let be the cross-sectional area of ​​the right side of the first amplitude transformer main body. The area function of the first amplitude transformer main body is:

[0070] (25)

[0071] (26)

[0072] In equations 25 and 26, , The length of the main body of the first amplitude transformer;

[0073] 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 transformer into Equation 3, the solution to Equation 3 can be obtained as follows:

[0074] (27)

[0075]

[0076] (28)

[0077] In equations 27 and 28, , These are undetermined coefficients, depending on the boundary conditions;

[0078] The boundary conditions are:

[0079] (29)

[0080] (30)

[0081] (31)

[0082] (32)

[0083] in, The elastic modulus of the main material of the first amplitude rod;

[0084] Under resonance conditions, the vibration velocity differs from the displacement. Therefore, we can conclude that:

[0085] (33)

[0086] Substituting equation 33 into equation 29 and equation 28 into equation 30, we get:

[0087] (34)

[0088] (35)

[0089] Substituting equations 34 and 35 into equations 28 and 33, we can obtain the distribution expressions for force and vibration velocity.

[0090] (36)

[0091] (37)

[0092] Will and Substituting into equations 14 and 15, we can obtain

[0093]

[0094] (38)

[0095]

[0096] (39)

[0097] In Equation 39, , The density of the main material of the first amplitude transformer bar. The speed at which sound travels through the main body of the first amplitude transformer;

[0098] From equations 38 and 39, the transmission matrix of the first amplitude transformer body can be obtained as follows:

[0099] (40)

[0100] In Equation 40, , , , .

[0101] Since the conical transition section of the second amplitude transformer is a conical bar, the analysis process is similar to that of the main body of the first amplitude transformer. Therefore, the transfer matrix of the conical transition section of the second amplitude transformer can be derived as follows:

[0102] (41)

[0103] In Equation 41, , , , .

[0104] Therefore, the transmission matrix of the composite amplitude transformer can be derived as follows:

[0105]

[0106] (42)

[0107] When both ends of the composite amplitude transformer are free, in equation 42, At this point, equation 42 can be written as

[0108] (43)

[0109] Right now (44)

[0110] (45)

[0111] To make any If all of Equation 41 are true, then Solve for the resonant frequency;

[0112] From Equation 45, we can obtain the magnification factor.

[0113] (46)

[0114] 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.

[0115] Compared with the prior art, the beneficial effects of this invention are:

[0116] 1. By adjusting the coil current, the magnetic field around the hollow terbium-dysprosium iron rod is changed, so that the elastic modulus of the terbium-dysprosium iron reaches a given value, realizing real-time frequency modulation of the transducer, enabling the nozzle to change the droplet diameter online to meet different application scenarios.

[0117] 2. Terbium-dysprosium magnetostrictive materials have a fast response speed (microsecond level), enabling rapid transducer frequency modulation.

[0118] 3. Terbium-dysprosium magnetostrictive materials exhibit a significant ΔE effect, enabling a wide frequency adjustment range for the amplitude transformer, which can meet the optimal particle size requirements of more organisms and achieve more complex operational tasks.

[0119] 4. Terbium-dysprosium magnetostrictive material is a brittle material with weak ability to withstand high-frequency vibration. Placing the terbium-dysprosium hollow rod at the end of the piezoelectric unit can reduce the maximum amplitude of the terbium-dysprosium hollow rod, reduce the risk of breakage, and improve service life. Attached Figure Description

[0120] Figure 1 This is a schematic diagram of the structure of the frequency converter described in this invention.

[0121] Figure 2 This is a cross-sectional structural diagram of the frequency converter described in this invention.

[0122] Figure 3 This is a schematic diagram of the structure of the first amplitude transformer in the frequency converter of the present invention.

[0123] Figure 4 In the frequency converter described in this invention Figure 2A schematic diagram of the cross-sectional structure at point BB.

[0124] Figure 5 This is a schematic diagram of the structure of the second amplitude transformer in the frequency converter of the present invention.

[0125] Figure 6 In the frequency converter described in this invention Figure 4 A schematic diagram of the cross-sectional structure at point CC.

[0126] Figure 7 This is a schematic diagram illustrating the resonant frequency adjustment principle of the frequency converter described in this invention. Detailed Implementation

[0127] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, and the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0128] like Figure 1 As shown, the intelligent variable frequency nozzle provided by the present invention is a highly adaptable nozzle whose working frequency can be adjusted in real time. The nozzle includes a clamping block 1, a second matching block 2, a terbium-dysprosium hollow rod 3, a first matching block 4, a fifth electrode plate 5, a fourth electrode plate 6, a third electrode plate 7, a second electrode plate 8, a first electrode plate 9, a second amplitude rod 10, a first amplitude rod 11, a first piezoelectric ceramic 12, a second piezoelectric ceramic 13, a third piezoelectric ceramic 14, a fourth piezoelectric ceramic 15, and a coil 16.

[0129] The terbium-dysprosium iron hollow rod 3 is made of terbium-dysprosium iron alloy. Terbium-dysprosium iron alloy has a fast response speed (microsecond level) and a significant ΔE effect, meaning that its Young's modulus changes significantly with changes in the surrounding magnetic field. By adjusting the magnitude of the magnetic field around the terbium-dysprosium iron hollow rod 3, the Young's modulus of the terbium-dysprosium iron hollow rod 3 is changed, thereby altering the stiffness of the transducer and ultimately achieving real-time adjustment of the operating frequency of the terbium-dysprosium iron hollow rod 3.

[0130] The coil 16 is wound around the outside of the terbium-dysprosium hollow rod 3, and the magnitude of the magnetic field around the terbium-dysprosium hollow rod 3 is changed by controlling the current of the coil 16.

[0131] The coil 16 provides a bias magnetic field for the terbium-dysprosium hollow rod 3 and adjusts the Young's modulus of the terbium-dysprosium hollow rod 3. Based on the ΔE effect of the terbium-dysprosium hollow rod 3, the resonant frequency of the terbium-dysprosium hollow rod 3 can be adjusted according to the optimal biological particle size required for the application scenario, so that the formed droplet particle size reaches the requirement of the optimal biological particle size.

[0132] There are two main hypotheses regarding the mechanism of ultrasonic atomization: the capillary wave hypothesis and the cavitation hypothesis.

[0133] The capillary wave hypothesis states that under the influence of continuous external oscillations, highly uniform surface capillary waves are formed on the surface of a liquid film. These surface capillary waves consist of crests and troughs. When the oscillation intensity increases to a certain amplitude, the crests of the surface capillary waves will separate from the liquid, resulting in atomization.

[0134] The cavitation hypothesis posits that in a high-frequency, high-power vibrating system, bubbles form within the cavity when a liquid film is affected by sound waves. These bubbles grow and oscillate with changes in sound pressure, leading to an increase in internal pressure. At a certain point, when the bubbles reach the liquid surface, they rupture due to the significant internal and external pressure difference, generating a powerful impact that causes the surrounding liquid to be ejected from the liquid film and atomized.

[0135] The empirical formula for the average diameter of the subdroplet in the capillary wave hypothesis is:

[0136] (1)

[0137] In equation (1), f is the excitation frequency of the ultrasonic generator. The surface tension of the liquid, The density of the liquid.

[0138] Once the type of pesticide is selected, the surface tension of the pesticide solution... ,density Since these are all fixed values, the excitation frequency of the ultrasonic generator can be adjusted to change the average diameter of the subdroplets.

[0139] The relationship between the system's resonant frequency f and its mass and stiffness is as follows:

[0140] (2)

[0141] In equation (2), k is the stiffness of the system and m is the mass of the system.

[0142] For a cylindrical material, the expression for stiffness k is:

[0143] (3)

[0144] In equation (3), E is the Young's modulus of the material, A is the cross-sectional area of ​​the material, and L is the length of the material.

[0145] When the magnetic field or stress on terbium-dysprosium iron changes, its Young's modulus will change. The mathematical expression for the ΔE effect of terbium-dysprosium iron is:

[0146] (4)

[0147] In equation (4), This represents the change in the Young's modulus of the material. The normal stress on the material, For the elastic strain of the material, The magnetoelastic strain of the material under the action of the initial bias magnetic field. The magnetoelastic strain of the material under the action of a changed magnetic field.

[0148] The expression for Young's modulus E is:

[0149] (5)

[0150] In equation (2), L is the length of the material before deformation. It is the elongation after deformation.

[0151] The elastic modulus E is a function of the magnetic field strength H and stress. Currently, it can only be measured experimentally, and empirical formulas are derived through interpolation.

[0152] The formula for magnetic field strength H is:

[0153] (6)

[0154] In equation (6), N is the number of turns of the excitation coil, I is the current through the excitation coil, and Le is the effective magnetic circuit length.

[0155] Therefore, the experimental data can be fitted with a function to obtain the fitting function of the Young's modulus E of terbium-dysprosium iron with respect to the coil current I, thereby enabling active open-loop control of the Young's modulus by controlling the current magnitude.

[0156] Inverse piezoelectric effect: When an external electric field is applied to a piezoelectric crystal, the internal polarization state of the crystal changes accordingly, resulting in strain proportional to the applied electric field strength. The expression for the inverse piezoelectric effect in the thickness direction of the piezoelectric sheet is:

[0157] (7)

[0158] In equation (7), S is the tensile strain along the thickness direction; g is the piezoelectric constant along the thickness direction; U is the voltage applied along the thickness direction; and t is the thickness of the piezoelectric sheet.

[0159] By adding a giant magnetostrictive material (terbium-dysprosium iron) to the amplitude transformer, the elastic modulus of the amplitude transformer can be adjusted by changing the magnetic field around the giant magnetostrictive material, thereby adjusting the stiffness of the amplitude transformer, obtaining a nozzle with a variable resonant frequency, and ultimately achieving real-time adjustment of droplet size.

[0160] like Figure 3 , Figure 4 As shown, the first amplitude rod 11 has a first stepped shaft 11A and a second stepped shaft 11B at both ends, a first through hole 11E is provided on the center line of the first amplitude rod 11, a first thread 11D is provided on the shoulder of the first stepped shaft 11A, and a second thread 11C is provided at the end of the second stepped shaft 11B.

[0161] like Figure 1 , Figure 2 As shown, the first electrode plate 9, the first piezoelectric ceramic 12, the second electrode plate 8, the second piezoelectric ceramic 13, the third electrode plate 7, the third piezoelectric ceramic 14, the fourth electrode plate 6, the fourth piezoelectric ceramic 15, the fifth electrode plate 5, the first matching block 4, the terbium-dysprosium hollow rod 3, the second matching block 2, and the clamping block 1 are arranged sequentially from right to left.

[0162] like Figure 1 , Figure 2 As shown, the first stepped shaft 11A of the first amplitude rod 11 passes through the first electrode plate 9, the first piezoelectric ceramic 12, the second electrode plate 8, the second piezoelectric ceramic 13, the third electrode plate 7, the third piezoelectric ceramic 14, the fourth electrode plate 6, the fourth piezoelectric ceramic 15, the fifth electrode plate 5, the first matching block 4, the terbium-dysprosium hollow rod 3, the second matching block 2, and the clamping block 1 from right to left.

[0163] like Figure 1 , Figure 2 As shown, the clamping block 1 is fixed to the first stepped shaft 11A of the first amplitude rod 11 by thread 11C.

[0164] like Figure 5 , Figure 6 As shown, the larger diameter end of the second amplitude rod 10 is provided with a first blind hole 10B, and the center line of the second amplitude rod 10 is provided with a second through hole 10A.

[0165] like Figure 3 , Figure 6 As shown, the second amplitude rod 10 is threadedly connected to the second stepped shaft 11B of the first amplitude rod 11 through the threaded hole 10B.

[0166] After the first electrode plate 9, the second electrode plate 8, the third electrode plate 7, the fourth electrode plate 6, and the fifth electrode plate 5 are connected to an alternating power supply, the first piezoelectric ceramic 12, the second piezoelectric ceramic 13, the third piezoelectric ceramic 14, and the fourth piezoelectric ceramic 15 convert electrical energy into mechanical energy through the inverse piezoelectric effect. The vibration amplitude is then amplified by the first amplitude transformer 11 and the second amplitude transformer 10, and then acts on the liquid medicine through the capillary wave effect and cavitation effect to form micron-sized droplets.

[0167] When the magnetic field strength continues to increase, the elastic modulus of the supermagnetostrictive material no longer decreases. The magnetic field strength at this point is called the saturation magnetic field strength.

[0168] The current in coil 16 was adjusted to obtain saturated magnetic field strengths of 0, 0.25, 0.5, 0.75, and 1 times the saturated magnetic field strength. The resonant frequencies of the transducer under these conditions were measured using an impedance analyzer and recorded as f0, f0.25, f0.5, f0.75, and f1, respectively. The currents were also recorded as I0, I0.25, I0.5, I0.75, and I1. The interpolation function, f = f(I), was then used to fit the relationship between the transducer resonant frequency and the current. During pesticide application, the transducer's operating resonant frequency was calculated based on empirical formulas for the optimal biomass size and sub-particle size of the target plant. The required current was then derived from the interpolation function, and the circuit current was adjusted accordingly. The transducer's resonant frequency was measured again using an impedance analyzer, and the excitation frequency of the ultrasonic generator was adjusted accordingly. Figure 7 As shown.

[0169] The technical means disclosed in this invention are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features.

Claims

1. A variable frequency atomizing nozzle based on a giant magnetostrictive material, characterized in that: The nozzle includes, in sequence, a clamping block (1), a second matching block (2), a terbium-dysprosium hollow rod (3), a first matching block (4), a fourth piezoelectric ceramic (15), a third piezoelectric ceramic (14), a second piezoelectric ceramic (13), a first piezoelectric ceramic (12), a first amplitude transformer (11), and a second amplitude transformer (10); wherein the fifth electrode plate (5), the fourth electrode plate (6), the third electrode plate (7), and the second electrode plate (8) are sequentially disposed on the fourth piezoelectric ceramic (15), the third piezoelectric ceramic (14), the second piezoelectric ceramic (13), and the first piezoelectric ceramic (12). The first electrode plate (9) is disposed on the first amplitude rod (11); wherein the outer surface of the terbium-dysprosium hollow rod (3) is wound with a coil (16); the terbium-dysprosium hollow rod (3) is made of terbium-dysprosium alloy; the main body of the first amplitude rod (11) is a frustum, and a first through hole (11E) is provided on the center line; a first stepped shaft (11A) is provided at the end of the first amplitude rod (11) with a larger diameter, and a second stepped shaft (11B) is provided at the end of the first amplitude rod (11) with a smaller diameter; a first thread (11D) is provided on the shoulder of the first stepped shaft (11A); the second The stepped shaft (11B) is provided with a second thread (11C) at its end; the first stepped shaft (11A) passes through the first electrode plate (9), the first piezoelectric ceramic (12), the second electrode plate (8), the second piezoelectric ceramic (13), the third electrode plate (7), the third piezoelectric ceramic (14), the fourth electrode plate (6), the fourth piezoelectric ceramic (15), the fifth electrode plate (5), the first matching block (4), the terbium-dysprosium hollow rod (3), and the second matching block (2) from right to left, and is connected to the second through hole on the clamping block (1) through the second thread (11C); the second amplitude The main body of the rod (10) is a stepped shaft with a conical transition. The end with the larger diameter is provided with a first blind hole (10B). The center line of the second amplitude rod (10) is provided with a second through hole (10A). The second amplitude rod (10) is threadedly connected to the second stepped shaft (11B) of the first amplitude rod (11) through the first blind hole (10B). The center lines of the first amplitude rod, the second amplitude rod, the terbium-dysprosium hollow rod, the first piezoelectric ceramic, the second piezoelectric ceramic, the third piezoelectric ceramic, the fourth piezoelectric ceramic, the first matching block, the second matching block and the clamping block are all on the same straight line.

2. The method for controlling droplet size of a variable frequency atomizing nozzle based on a giant magnetostrictive material according to claim 1, characterized in that: Includes the following steps; Step 1: The second matching block (2) and the first matching block (4) press the terbium-dysprosium hollow rod (3) together under the pressure of the clamping block (1), providing pre-compression stress to the terbium-dysprosium hollow rod (3). A coil (16) is wound around the outside of the terbium-dysprosium hollow rod (3), and a circuit with a variable resistor is connected to the coil (16). By adjusting the current connected to the coil (16), the magnitude of the magnetic field generated by the coil (16) is changed. When the magnetic field around the terbium-dysprosium hollow rod (3) changes, the elastic modulus of the terbium-dysprosium hollow rod (3) will also change, thereby changing the resonant frequency of the terbium-dysprosium hollow rod (3). The natural frequency of the longitudinal vibration of the free thin rods at both ends is: (1) In Equation 1, E is the elastic modulus of the thin rod. Let be the density of the thin rod, l be the length of the thin rod, and n be a positive integer. hour, 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 bar is made of homogeneous, isotropic material with no mechanical loss; when the transverse dimension of the bar is much smaller than the wavelength of the longitudinal wave, it can be assumed that the plane longitudinal wave moves along the axis of the bar, and the stress distribution is uniform on the cross-section of the bar; for any variable cross-section bar, 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: Write the dynamic equations based on Newton's laws. (2) In Equation 2, Let be the cross-sectional area function of the rod; Let be the displacement function of the particle. The stress function; In the case of simple harmonic motion, equation 2 can be expressed as: (3) Equation 3 is the wave equation for the longitudinal vibration of a variable cross-section rod; where k is the circular wave number. It is the angular frequency. The propagation speed of the longitudinal wave in the thin rod; Step 3: Design the simplified uniform cross-section bar. For the cross-sectional area of ​​the second matching block (2), , These represent the force and velocity at the input of the second matching block (2), respectively. , These represent the force and velocity at the output of the second matching block (2), respectively. The displacement function of the second matching block (2) can be obtained by using the method of separation of variables. It can be decomposed into the product of a space function and a time function, i.e. (4) In Equation 4, The mode shape function of the second matching block (2) characterizes the longitudinal vibration state of the second matching block (2). Characterize the vibration pattern of a point on the second matching block (2); Substituting into equation 3, we obtain the solution to equation 3 as follows: (5) (6) In equations 5 and 6, The elastic modulus of the second matching block (2) is , These are undetermined coefficients, depending on the boundary conditions; the boundary conditions are: (7) (8) (9) (10) Under resonance conditions, the vibration velocity differs from the displacement. Therefore, we can conclude that: (11) Substituting equation 11 into equation 7 and equation 6 into equation 9, we get: (12) (13) Substituting equations 12 and 13 into equations 6 and 11, we can obtain the distribution expressions for force and vibration velocity. (14) (15) in, It is the characteristic force impedance of the second matching block (2). The density of the material of the second matching block (2) The speed at which sound propagates in the second matching block (2); Substituting into equations 14 and 15, we can obtain (16) (17) From equations 16 and 17, the transmission matrix of the second matching block (2) can be obtained as follows: (18) In Equation 18, , , , To simplify the model, the first electrode (9), the first piezoelectric ceramic (12), the second electrode (8), the second piezoelectric ceramic (13), the third electrode (7), the third piezoelectric ceramic (14), the fourth electrode (6), the fourth piezoelectric ceramic (15), and the fifth electrode (5) are considered as a whole and called the piezoelectric oscillator group. Since the terbium-dysprosium hollow rod (3), the first matching block (4), the piezoelectric vibrator group, the larger diameter end of the second stepped shaft (11B) of the first amplitude transformer (11), the larger diameter end of the second amplitude transformer (10), and the smaller diameter end are all approximately equal cross-section rods, and the analysis process is similar to that of the second matching block (2), the transfer matrix of the terbium-dysprosium hollow rod (3) can be obtained as follows: (19) In Equation 19, , , , , The characteristic force resistance of the terbium-dysprosium hollow rod (3); The cross-sectional area of ​​the terbium-dysprosium hollow rod (3) is given by [reference to the cross-sectional area]. The density of the terbium-dysprosium hollow rod (3) material, Let be the speed of sound propagation in the terbium-dysprosium hollow rod (3). The length of the terbium-dysprosium hollow rod (3) is given. The transmission matrix of the first matching block (4) is: (20) In Equation 20, , , , , The characteristic force impedance of the first matching block (4) is... The cross-sectional area of ​​the first matching block (4) is The density of the material of the first matching block (4) The speed at which sound propagates in the first matching block (4), The length of the first matching block (4); The transmission matrix of the piezoelectric oscillator group is: (21) In Equation 21, , , , , The characteristic force impedance of the piezoelectric oscillator assembly. Let be the cross-sectional area of ​​the piezoelectric resonator assembly. The average density of the piezoelectric oscillator assembly material. The average speed of sound propagation in the piezoelectric oscillator array. The length of the piezoelectric vibrator assembly; the transmission matrix of the larger diameter end of the second stepped shaft (11B) of the first amplitude transformer (11) is: (22) In Equation 22, , , , , The characteristic force impedance is the larger diameter end of the second stepped shaft (11B) of the first amplitude rod (11). The cross-sectional area of ​​the larger diameter end of the second stepped shaft (11B) of the first amplitude rod (11) is given. The density of the material at the end with the larger diameter of the second stepped shaft (11B) of the first amplitude rod (11) is... The propagation speed is the larger diameter end of the second stepped shaft (11B) of the first amplitude rod (11). The length of the end with the larger diameter of the second stepped shaft (11B) of the first amplitude rod (11); The transmission matrix of the larger diameter end of the second amplitude transformer (10) is: (23) In Equation 23, , , , , The characteristic force impedance is at the end of the second amplitude rod (10) with the larger diameter. The cross-sectional area of ​​the larger diameter end of the second amplitude rod (10) is... The density of the material at the larger diameter end of the second amplitude rod (10) is... The propagation speed is the larger diameter end of the second amplitude rod (10). The length of the end with the larger diameter of the second amplitude rod (10); The transmission matrix of the smaller diameter end of the second amplitude transformer (10) is: (24) In Equation 24, , , , , The characteristic force impedance of the smaller diameter end of the second amplitude rod (10) is... The cross-sectional area of ​​the smaller diameter end of the second amplitude rod (10) is... The density of the material at the smaller diameter end of the second amplitude rod (10) The propagation speed is the smaller diameter end of the second amplitude rod (10). The length of the end with the smaller diameter of the second amplitude rod (10); Step 4: Design the simplified variable cross-section bar of the first amplitude transformer (11). The diameter of the left side of the main body of the first amplitude rod (11) is... The diameter of the right side of the main body of the first amplitude rod (11) is... , These represent the force and velocity at the main input end of the first amplitude transformer (11), respectively. , These represent the force and velocity at the output end of the first amplitude rod (11), respectively. The cross-sectional area on the left side of the main body of the first amplitude rod (11) is... Let be the cross-sectional area on the right side of the main body of the first amplitude transformer (11). The area function of the main body of the first amplitude transformer (11) is: (25) (26) In equations 25 and 26, , The length of the main body of the first amplitude rod (11); 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 (11) into Equation 3, the solution of Equation 3 can be obtained as follows: (27)； (28) In equations 27 and 28, , These are undetermined coefficients, depending on the boundary conditions; The boundary conditions are: (29) (30) (31) (32) in, The elastic modulus of the main material of the first amplitude rod (11); Under resonance conditions, the vibration velocity differs from the displacement. Therefore, we can conclude that: (33) Substituting equation 33 into equation 29 and equation 28 into equation 30, we get: (34) (35) Substituting equations 34 and 35 into equations 28 and 33, we can obtain the distribution expressions for force and vibration velocity. (36) (37) Will and Substituting into equations 14 and 15, we can obtain (38) (39) In Equation 39, , The density of the main material of the first amplitude rod (11) is, The speed at which sound propagates through the main body of the first amplitude transformer (11); From equations 38 and 39, the transmission matrix of the main body of the first amplitude transformer (11) can be obtained as follows: (40) In Equation 40, , , , ; Since the conical transition section of the second amplitude rod (10) is a conical rod, the analysis process is similar to that of the first amplitude rod (11). The transfer matrix of the conical transition section of the second amplitude rod (10) can be obtained as follows: (41) In Equation 41, , , , . Therefore, the transmission matrix of the composite amplitude transformer can be derived as follows: (42) When both ends of the composite amplitude transformer are free, in equation 42, At this point, equation 42 can be written as (43) Right now (44) (45) To make any If all of Equation 41 are true, then Solve for the resonant frequency; From Equation 45, we can obtain the magnification factor. (46) 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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