CN117993250A - Reactor sound insulation device optimization method considering noise reduction and heat dissipation dual optimization - Google Patents
Reactor sound insulation device optimization method considering noise reduction and heat dissipation dual optimization Download PDFInfo
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Abstract
A reactor sound insulation device optimization method considering noise reduction and heat dissipation double optimization comprises the following steps: step 1, constructing a three-dimensional electromagnetic-structure-sound field and flow field-temperature field coupling simulation model of an air-core reactor, and obtaining simulation results of the sound field and the temperature field of the reactor under the condition of adding and not adding a sound insulation device; step 2, analyzing the distribution characteristics of the sound field and the temperature field of the reactor under the added and non-added sound insulation devices, and determining the structural optimization parameters of the sound insulation devices of the reactor; step 3, adopting a Latin square test design and finite element simulation combined method to obtain simulation results of a reactor sound field and a temperature field under sound insulation devices with different structural parameters; and 4, constructing an approximate model according to experimental data, and obtaining the optimal structural parameters of the sound insulation device by adopting a multi-island genetic optimization algorithm. The invention considers the influence of the sound insulation device on the noise suppression and heat dissipation performance of the reactor, so that the optimization result achieves the effect of reducing noise and temperature rise.
Description
Technical Field
The invention relates to the technical field of reactors, in particular to a method for optimizing a sound insulation device of a reactor by considering noise reduction and heat dissipation double optimization.
Background
The air-core reactor is used as important equipment in a power system, and plays roles in limiting short-circuit current of a power grid, filtering out higher harmonics and the like. However, in actual operation of the converter station, it is the source of acoustic pollution. At present, the main measure of noise reduction in engineering is to install a sound insulation device around the reactor, however, after installing the sound insulation device, the heat convection between the reactor and surrounding fluid is inevitably restrained, so that the heat dissipation capacity of the reactor encapsulated coil is obviously reduced. Therefore, in order to simultaneously reduce noise and improve the heat dissipation capacity of the encapsulated coil, it is important to develop optimization research of the reactor sound insulation device.
In terms of optimizing the reactor sound insulation device: studies summarize the audible noise spectrum characteristics of dry air-core reactors and propose the use of sound-insulating panels to reduce noise; the sound insulation effect is improved by additionally arranging a perforated plate in the sound insulation cover of the dry type air reactor by utilizing the resonance sound absorption principle; on the basis of considering that the sound-proof cover is restrained by noise reduction and heat dissipation, the influence of the structural shape parameters of the sound-proof cover on the temperature rise of hot spots is studied and optimized. The method reduces noise and temperature rise to a certain extent, but fails to consider the influence of the sound insulation device on the noise suppression and heat dissipation performance of the reactor at the same time, and has certain limitations.
Disclosure of Invention
The invention aims to solve the technical problem of providing an optimization method of the reactor sound insulation device, which considers the dual optimization of noise reduction and heat dissipation, and simultaneously considers the influence of the sound insulation device on the noise suppression and heat dissipation performance of the reactor, so that the optimization result achieves the effect of reducing noise and temperature rise.
In order to solve the technical problems, the invention adopts the following technical scheme: a reactor sound insulation device optimization method considering noise reduction and heat dissipation double optimization comprises the following steps:
Step 1, constructing a three-dimensional electromagnetic-structure-sound field and flow field-temperature field coupling simulation model of an air-core reactor, and obtaining simulation results of the sound field and the temperature field of the reactor under the condition of adding and not adding a sound insulation device;
Step 2, analyzing the distribution characteristics of the sound field and the temperature field of the reactor under the added and non-added sound insulation devices, and determining the structural optimization parameters of the sound insulation devices of the reactor;
step 3, adopting a Latin square test design and finite element simulation combined method to obtain simulation results of a reactor sound field and a temperature field under sound insulation devices with different structural parameters;
and 4, constructing an approximate model according to experimental data, and obtaining the optimal structural parameters of the sound insulation device by adopting a multi-island genetic optimization algorithm.
Preferably, in the step 1, the three-dimensional electromagnetic-structure-acoustic field coupling simulation model of the air-core reactor is built by using COMSOL simulation software according to structural parameters of the air-core reactor, and the specific process is as follows:
Under the excitation of time-varying current, the air-core reactor is driven by the electromagnetic force under the combined action of the time-varying current and the magnetic field, so that the reactor encapsulation generates forced vibration, and noise is generated to the surrounding environment; the method is based on a magnetic-solid coupling mode, electromagnetic force vibration unfolding numerical calculation is performed on the air-core reactor, and sound field distribution of the reactor is obtained;
The current of the air-core reactor mainly depends on the inductance matrix of the encapsulated coils, wherein the current distribution of each encapsulated coil of the reactor meets the impedance matrix, as shown in a formula (1);
（1）
In the method, in the process of the invention, For/>Equivalent resistance of layer winding,/>For/>Self-inductance of individual encapsulated coil windings,/>For/>Layer and/>Mutual inductance between individual encapsulated coils,/>Is angular frequency;
under normal working state of the reactor, the current flowing through the winding generates an alternating magnetic field around the coil, wherein the magnetic field calculation equation is as follows:
（2）
Wherein: Is angular frequency,/> For conductivity,/>Is magnetic sagittal,/>Is relative permeability,/>Is relative permeability,/>Is coil current density;
When the air-core reactor winding passes through the current, the current flowing through the winding can generate a magnetic field inside and outside the reactor, and the magnetic field acts on the current-carrying winding in turn to generate magnetic field force on the winding; when the passing current alternates with time, the magnitude and direction of the magnetic field also change, so that the magnetic field force borne by the winding wire changes, and the winding vibrates; for the coil of the air core reactor, the magnetic field intensity and the magnetic induction intensity are unevenly distributed on the winding of the reactor, so that the magnetic field force born by each winding and each coil is different, but the stress of each point is always in direct proportion to the current of the point and the magnetic induction intensity of the point. The magnetic induction intensity is in direct proportion to the current generating the magnetic field, so that the magnetic field force acting on each coil winding for the current with single frequency can be expressed by the formula (3);
（3）
In formula (3) Representing the integrated coefficient, as determined by geometry and magnetic permeability, and current/>Is independent of the size and frequency of (a);
Setting current By expanding equation (3-3) using the half-angle equation, it can be obtained that the frequency is/>Magnetic field force/>, formed by single-frequency sinusoidal currentAs shown in formula (4);
（4）
Wherein the vibration component is represented by the following formula;
（5）
（6）
Wherein: -a current magnitude function; /(I) -Square of the amplitude of the current; /(I)The frequency of the force of the oscillating magnetic field,，/>Is the current frequency. From the above, it can be obtained: frequency/>Single current/>Generating a static magnetic field force (/ >) corresponding to the pre-application) And a main vibration frequency/>Amplitude/>；
The time-varying electromagnetic force exerted by the encapsulated coil windings is a major source of noise; therefore, the acoustic field distribution around the encapsulated coil is obtained by coupling the electromagnetic force with the acoustic field; in the simulation process, a solid mechanical module is selected, and a structural force field solving domain equation set is shown as a formula (7);
（7）
In the method, in the process of the invention, Is a quality matrix; /(I)Is a damping coefficient matrix; /(I)Is a rigidity matrix; /(I)Is a displacement vector;
Selecting a pressure acoustic module in sound field analysis, wherein the variable solved by the pressure sound field module is sound pressure ; Solving a domain sound pressure fluctuation equation:
（8）
In the method, in the process of the invention, Is sound velocity,/>For sound pressure, the relationship between sound pressure and velocity is described as follows:
（9）
The conversion of sound pressure to sound pressure level can be represented by the following formula:
（10）
In the method, in the process of the invention, Is air density/>Is sound pressure level,/>Is the pressure.
Preferably, in the step 1, a flow field-temperature field three-dimensional simulation model of the air-core reactor is built by using COMSOL simulation software according to structural parameters of the air-core reactor, and specifically includes:
(1) Heat source
The loss of the reactor envelope coil consists of resistive loss and eddy current loss.
The resistance loss of the reactor envelope can be calculated by formula (11):
（11）
Wherein, For/>Number encapsulated Joule thermal Power,/>、/>、/>、/>Respectively is/>Envelope current, turns, diameter and conductor cross-sectional area,/>Is the conductivity of the metal conductor.
The eddy current loss can be calculated from equation (12).
（12）
In the method, in the process of the invention,Is angular velocity (rated frequency is 50 Hz),/>For the envelope radial width,/>Is the axial height of single turn,/>As the axial component of the magnetic induction,/>Is a radial component of the magnetic induction.
According to the current of the reactor coil and the distribution condition of the surrounding magnetic field, the total loss of different encapsulated coils can be obtained, and the total loss can be calculated by a formula (13); in a simulation model, taking the obtained total loss of each encapsulated coil as a heat source of each coil;
（13）
(2) Control equation
When the air core reactor works, heat can be transferred to the surrounding environment through three modes of heat conduction, heat convection and heat radiation;
Heat conduction: in the solid region of the reactor, heat is transferred from the hot region to the cold region mainly by heat conduction, and the heat conduction control equation is shown in formula (14);
(14)
Wherein t is temperature, phi is heat generated by unit volume of the encapsulated coil, lambda is the heat conductivity coefficient of the encapsulating material, and x, y and z are lengths along the directions of all coordinate axes respectively;
Thermal convection: thermal convection is the primary heat exchange means in the fluid region of the reactor and the surface of the encapsulated coil. We can describe this process using continuity, momentum and energy equations, as shown in equation (15);
(15)
Wherein ux, uy and uz are components of fluid velocity in x, y and z directions respectively, fx, fy and Fz are components of volume force in x, y and z directions respectively, p is pressure of fluid, ρ is density of fluid, v is kinematic viscosity of fluid, and cp is constant pressure specific heat capacity of fluid;
Heat radiation: for the innermost and outermost surfaces of the encapsulated coil, heat radiation is also a primary heat sink. Wherein the heat radiation control equation can be represented by formula (16);
（16）
wherein: ψ is the heat flux, ε is the object surface emissivity, S is the radiating area, δ is the Boltzmann constant, T is the coil temperature, and Tair is the ambient temperature.
Preferably, in the step 1, the method further includes boundary conditions and mesh subdivision setting:
(1) Boundary conditions
Boundary conditions of the sound field model are set as follows: the sound field adopts four modules of magnetic field, circuit, solid mechanics, pressure acoustics and frequency domain; the electromagnetic force applied by the encapsulated coil is used as a body load condition of the structural field; the star-shaped frame has the reinforcing effect on the encapsulated coil, so that the upper and lower boundaries of the star-shaped frame are set to be fixed and restrained, namely the vibration displacement is zero; considering that engineering is actually an open boundary, setting an external boundary of a calculation domain as a plane wave radiation condition for absorbing sound waves on the boundary;
the boundary conditions of the temperature field model are set as follows: the model uses laminar flow and fluid heat transfer modules; the surfaces of the encapsulation coil and the sound insulation cover are static wall surfaces, and no sliding occurs; the bottom surface of the calculation area is an inlet of outside air, the other surfaces are outlets, and the initial speed and static pressure are all zero; the surface emissivity of the innermost and outermost surfaces of the encapsulated coil was 0.9 in view of heat radiation; the initial temperature and the ambient temperature of the reactor are set to be 20 ℃;
(2) Mesh subdivision
The density of the grid directly influences the simulation calculation precision of the temperature field, and in order to ensure the calculation precision, a free split method is used for grid subdivision of the model in consideration of the calculation speed; a fine mesh is used in the area of the encapsulated coil and a coarsened mesh is used in the other air area.
Preferably, in the step 2, the structural optimization parameter of the sound insulation device of the air-core reactor is a rain hat height x1, a radius x2 of the rain hat, a distance x3 between the outermost packaging coil and the outer side of the sound insulation device, a distance x4 between the rain hat and the sound insulation cover, and a distance x5 between the top end of the sound insulation cover and the top end of the coil; in order to meet the actual insulation requirement of the reactor, the following ranges should be selected for each parameter: x1 ranges from 0.1m to 0.3m, x2 ranges from 0.4m to 0.7m, x3 ranges from 0.1m to 0.4m, x4 ranges from 0.1m to 0.3m, and x5 ranges from 0.1m to 0.3m.
The invention provides an optimization method of a reactor sound insulation device considering noise reduction and heat dissipation double optimization, which has the following beneficial effects:
1. The invention considers the influence of the sound insulation device on the noise suppression and heat dissipation performance of the reactor, so that the sound insulation device reduces the noise and simultaneously reduces the temperature rise;
2. according to the neural network model established by the Latin square test design table, the optimal structural parameters of the sound insulation device are obtained by combining a multi-island genetic algorithm, the sound pressure level of the measuring point of the reactor is reduced by 7.6dB under the optimal parameters, the highest temperature is reduced by 6.5 ℃, and the effect is obvious.
Drawings
The invention is further illustrated by the following examples in conjunction with the accompanying drawings:
FIG. 1 is a flow chart of the method of the present invention;
figure 2 is a block diagram of the air core reactor of the present invention;
FIG. 3-1 is a diagram of simulation results of a reactor sound field without a sound insulation device at 50Hz according to the present invention;
FIG. 3-2 is a diagram of simulation results of a sound field of a reactor with a sound insulation device at 50Hz according to the present invention;
FIG. 3-3 is a graph of simulation results of a sound field of a reactor without a sound insulation device at 100Hz according to the present invention;
FIGS. 3-4 are graphs of simulation results of a sound field of a reactor with a sound insulation device at 100 Hz;
FIGS. 3-5 are graphs of simulation results of a reactor sound field of the invention without a sound insulation device at 150 Hz;
FIGS. 3-6 are graphs of simulation results of a sound field of a reactor with a sound insulation device at 150 Hz;
FIG. 4 is a diagram of the air core reactor noise measurement point arrangement of the present invention;
FIG. 5-1 is a graph of simulation results of a reactor temperature field without a sound insulation device according to the present invention;
FIG. 5-2 is a graph of simulation results of a reactor temperature field with a sound insulation device added to the invention;
FIG. 6 is a flowchart of the multi-island genetic algorithm optimization of the present invention;
FIG. 7-1 is a diagram of simulation results of a reactor sound field under optimal parameters of the present invention;
fig. 7-2 is a graph of simulation results of a reactor temperature field under the optimal parameters of the present invention.
Detailed Description
As shown in fig. 1, the method for optimizing the design of the reactor sound insulation device by considering noise reduction and heat dissipation double optimization comprises the following steps:
Step 1: and constructing a three-dimensional electromagnetic-structure-sound field and flow field-temperature field coupling simulation model of the air-core reactor, and obtaining simulation results of the sound field and the temperature field of the reactor under the condition of adding and not adding a sound insulation device.
Step 2: and analyzing the distribution characteristics of the sound field and the temperature field of the reactor under the added and un-added sound insulation devices, and determining the structural optimization parameters of the sound insulation devices of the reactor.
Step 3: and a method of combining Latin square test design with finite element simulation is adopted to obtain simulation results of a sound field and a temperature field of the reactor under the sound insulation devices with different structural parameters.
Step 4: and constructing an approximate model according to experimental data, and obtaining the optimal structural parameters of the sound insulation device by adopting a multi-island genetic optimization algorithm.
In step 1, the air-core reactor prototype used comprised three coaxial coils connected in parallel in a circuit. The adjacent coils are separated by air passages and used for isolation and cooling, and each coil is composed of a plurality of parallel circular leads. The electrical parameters of the air core reactor are as follows: the rated inductance is 17.1mH and the rated current is 107.3A. The reactor has the following structural parameters: the reactor is composed of three encapsulated coils, wherein the height of the encapsulated coil 1 is 1.2m, the height of the coil 2 is 1.18m, the height of the coil 3 is 1.19m, the width of an air passage is 0.02m, the inner radius and the outer radius are respectively 0.325m and 0.402m, the thickness of an insulating layer is 0.01m, and the encapsulation quantity is 3.
The rain hat is arranged at the top of the reactor and is supported by the insulating support column, the sound-proof housing is of a cylindrical structure, and is arranged around the sealing coil at the outermost layer of the reactor and provided with an opening in the center of the upper bottom surface and the lower bottom surface. The rain hat parameters are as follows: the diameter is 0.75m, the height is 0.05m, and the distance from the top of the encapsulated coil is 0.27m, and the encapsulated coil is made of polyester film. The specification of the sound-proof cover is 1.8m high, the upper and lower apertures are 0.5m, the thickness is 0.1m, and the sound-proof cover is made of thermoplastic polyester. The overall structure of the air core reactor is shown in fig. 2.
The three-dimensional electromagnetic-structure-sound field coupling simulation model of the air-core reactor is built by using COMSOL simulation software according to the structural parameters of the air-core reactor. The principle is as follows.
Under the excitation of time-varying current, the air-core reactor is driven by the electromagnetic force under the combined action of the time-varying current and the magnetic field, so that the reactor encapsulation generates forced vibration, and noise is generated to the surrounding environment. The method is based on a magnetic-solid coupling mode, electromagnetic force vibration unfolding numerical calculation is performed on the air-core reactor, and sound field distribution of the reactor is obtained.
The current of the air-core reactor is mainly dependent on the encapsulated coil inductance matrix, wherein the current distribution of each encapsulated coil of the reactor satisfies the impedance matrix as shown in formula (1).
（1）
In the method, in the process of the invention,For/>Equivalent resistance of layer winding,/>For/>Self-inductance of individual encapsulated coil windings,/>For/>Layer and/>Mutual inductance between individual encapsulated coils,/>Is the angular frequency.
Under normal working state of the reactor, the current flowing through the winding generates an alternating magnetic field around the coil, wherein the magnetic field calculation equation is as follows:
（2）
Wherein: Is angular frequency,/> For conductivity,/>Is magnetic sagittal,/>Is relative permeability,/>Is relative permeability,/>Is the coil current density.
When an air-core reactor winding passes current, the current flowing through the winding can generate magnetic fields inside and outside the reactor, and the magnetic fields in turn act on the current-carrying winding to generate magnetic field force on the winding. When the passing current alternates with time, the magnitude and direction of the magnetic field also change, so that the magnetic field force applied to the winding wire changes, and the winding vibrates. For the coil of the air core reactor, the magnetic field intensity and the magnetic induction intensity are unevenly distributed on the winding of the reactor, so that the magnetic field force born by each winding and each coil is different, but the stress of each point is always in direct proportion to the current of the point and the magnetic induction intensity of the point. The magnetic induction intensity is in direct proportion to the current generating the magnetic field, so that the magnetic field force acting on each coil winding for a single-frequency current can be expressed by the formula (3).
（3）
In formula (3)Representing the integrated coefficient, as determined by geometry and magnetic permeability, and current/>Is independent of the size and frequency of (a).
Setting currentBy expanding equation (3-3) using the half-angle equation, it can be obtained that the frequency is/>Magnetic field force/>, formed by single-frequency sinusoidal currentAs shown in formula (4).
（4）
Wherein the vibration component is shown in the following formula.
（5）
（6）
Wherein: -a current magnitude function; /(I) -Square of the amplitude of the current; /(I)The frequency of the force of the oscillating magnetic field,，/>Is the current frequency. From the above, it can be obtained: frequency/>Single current/>Generating a static magnetic field force (/ >) corresponding to the pre-application) And a main vibration frequency/>Amplitude/>。
The time-varying electromagnetic forces experienced by the encapsulated coil windings are a major source of noise. Therefore, the acoustic field distribution around the encapsulated coil is obtained by coupling the electromagnetic force with the acoustic field. In the simulation process, a solid mechanical module is selected, and the structural force field solving domain equation set is shown as a formula (7).
（7）
In the method, in the process of the invention,Is a quality matrix; /(I)Is a damping coefficient matrix; /(I)Is a rigidity matrix; /(I)Is a displacement vector.
Selecting a pressure acoustic module in sound field analysis, wherein the variable solved by the pressure sound field module is sound pressure. Solving a domain sound pressure fluctuation equation:
（8）
In the method, in the process of the invention, Is sound velocity,/>For sound pressure, the relationship between sound pressure and velocity is described as follows:
（9）
The conversion of sound pressure to sound pressure level can be represented by the following formula:
（10）
In the method, in the process of the invention, Is air density/>Is sound pressure level,/>Is the pressure.
In the step 1, a flow field-temperature field three-dimensional simulation model of the air-core reactor is established by using COMSOL simulation software according to structural parameters of the air-core reactor. In order to ensure the accuracy and duration of the calculation, only the steady-state heat dissipation process is considered in the model.
(1) Heat source
The loss of the reactor envelope coil consists of resistive loss and eddy current loss.
The resistance loss of the reactor envelope can be calculated by formula (11):
（11）
Wherein, For/>Number encapsulated Joule thermal Power,/>、/>、/>、/>Respectively is/>Envelope current, turns, diameter and conductor cross-sectional area,/>Is the conductivity of the metal conductor.
The eddy current loss can be calculated from equation (12).
（12）
In the method, in the process of the invention,Is angular velocity (rated frequency is 50 Hz),/>For the envelope radial width,/>Is the axial height of single turn,/>As the axial component of the magnetic induction,/>Is a radial component of the magnetic induction.
According to the current of the reactor coil and the distribution condition of the surrounding magnetic field, the total loss of different encapsulated coils can be obtained, and the total loss can be calculated by the formula (13). In the simulation model, the resulting total loss of each encapsulated coil is used as the heat source for each coil.
（13）
(2) Control equation
When the air-core reactor works, heat can be transferred to the surrounding environment through three modes of heat conduction, heat convection and heat radiation.
Heat conduction: in the solid region of the reactor, heat is transferred from the hot region to the cold region mainly by heat conduction, and the heat conduction control equation is shown in formula (14).
(14)
Where t is the temperature, φ is the heat generated by the unit volume of the encapsulated coil, λ is the thermal conductivity of the encapsulating material, and x, y and z are the lengths along each coordinate axis.
Thermal convection: thermal convection is the primary heat exchange means in the fluid region of the reactor and the surface of the encapsulated coil. We can describe this process using continuity, momentum and energy equations, as shown in equation (15).
(15)
Where ux, uy and uz are components of fluid velocity in x, y and z directions, fx, fy and Fz are components of volumetric force in x, y and z directions, respectively, p is the pressure of the fluid, ρ is the density of the fluid, v is the kinematic viscosity of the fluid, and cp is the constant pressure specific heat capacity of the fluid.
Heat radiation: for the innermost and outermost surfaces of the encapsulated coil, heat radiation is also a primary heat sink. Wherein the heat radiation control equation can be represented by formula (16).
（16）
Wherein: ψ is the heat flux, ε is the object surface emissivity, S is the radiating area, δ is the Boltzmann constant, T is the coil temperature, and Tair is the ambient temperature.
In step 1, the boundary conditions and mesh subdivision are set as follows,
(1) Boundary conditions
Boundary conditions of the sound field model are set as follows: the sound field adopts four modules of magnetic field, circuit, solid mechanics, pressure acoustics and frequency domain; the electromagnetic force applied by the encapsulated coil is used as a body load condition of the structural field; the star-shaped frame has the reinforcing effect on the encapsulated coil, so that the upper and lower boundaries of the star-shaped frame are set to be fixed and restrained, namely the vibration displacement is zero; considering that engineering is actually an open boundary, setting the boundary outside the calculation domain as a plane wave radiation condition for absorbing sound waves on the boundary.
The boundary conditions of the temperature field model are set as follows: the model uses laminar flow and fluid heat transfer modules; the surfaces of the encapsulation coil and the sound insulation cover are static wall surfaces, and no sliding occurs; the bottom surface of the calculation area is an inlet of outside air, the other surfaces are outlets, and the initial speed and static pressure are all zero; the surface emissivity of the innermost and outermost surfaces of the encapsulated coil was 0.9 in view of heat radiation; the initial temperature of the reactor and the ambient temperature were set to 20 ℃.
(2) Mesh subdivision
The density of the grid has a direct influence on the simulation calculation accuracy of the temperature field. In order to ensure the calculation accuracy while considering the calculation speed, a free-split method is used for mesh dissection of the model. A fine mesh is used in the area of the encapsulated coil and a coarsened mesh is used in the other air area.
According to the above calculation method, the overall sound pressure distribution of the reactor can be obtained.
When the reactor is free of the sound insulation cover, noise generated by electromagnetic force vibration of the reactor is transmitted outwards from the inside of the coil, obvious sound pressure enhancement points and weakening points exist, and the highest sound pressure inside the reactor can reach 10.8Pa.
In step 2, according to the model established in step 1, the simulation results of the reactor sound field with or without the sound insulation device under different frequencies can be obtained, as shown in fig. 3-1 to 3-6.
It can be seen from the figure that the reactor generates electromagnetic force to vibrate under the excitation of coil current according to the theory of electromagnetic-structure-sound field of the reactor without a sound-proof cover. The reactor takes vibration speed as a sound source, air as a propagation medium, sound pressure and sound pressure level are generated inside the reactor, energy is transmitted from inside to outside, and the internal sound pressure level of the innermost coil is sealed to be maximum. The reactor has a maximum sound pressure level of 100Hz and a maximum sound pressure level of 65dB in a low frequency range of 50 to 300 Hz. The sound pressure level of each frequency band under the additional installation sound-proof housing obviously drops, and sound-proof housing and rain cap have certain suppression effect to the noise.
According to the air core reactor noise measurement method, the measurement points are arranged as follows: at the reactor coil height of 1/2H, a position 3m from the soundproof cover is set as a measurement point, as shown in FIG. 4.
Based on the simulation results, the sound pressure level of the 360-degree measuring point of the reactor with the frequency of 100HZ is extracted as shown in table 1.
Table 1 measuring point sound pressure level
| Angle/° | 60 | 120 | 180 | 240 | 300 | 360 |
| Sound pressure level/dB without sound insulation | 67.0 | 68.2 | 67.4 | 68.0 | 68.1 | 67.6 |
| Sound pressure level/dB with sound insulation device | 49.0 | 49.4 | 49.1 | 50.8 | 49.9 | 51.5 |
The sound pressure level of the extracted measurement point is shown in table 2 according to the simulation result.
Table 2 measuring point sound pressure level
| Frequency/Hz | 50 | 100 | 150 | 200 | 250 | 300 |
| Sound pressure level/dB without sound insulation device | 27.0 | 67.7 | 59.4 | 61.0 | 61.1 | 63.6 |
| Sound pressure level/dB with sound insulation device | 35.0 | 49.4 | 30.1 | 47.8 | 40.9 | 51.5 |
As can be seen from the above table, the sound pressure level at 100Hz with/without the sound-proof housing is significantly higher than the sound pressure level at other frequencies. The sound pressure levels of the 100Hz noise at the measuring points when the sound shield is added and not added are 67.7dB and 49.4dB respectively, so that the sound shield can obviously reduce the noise level around the dry type air reactor coil.
The simulation results of the reactor temperature field with or without the acoustic insulator are shown in fig. 5-1 and 5-2.
Analysis shows that after the rain hat and the sound-proof cover are added, the highest temperature rise of the coil enclosed inside the reactor is different. The difference is mainly caused by the different effects of the rain cap on the air flow rate, resulting in higher air flow rate on the outside than on the inside, with a significant increase in internal coil temperature.
In the step 2, the structural optimization parameters of the sound insulation device of the air reactor are the height x1 of the rain hat, the radius x2 of the rain hat, the distance x3 between the outermost packaging coil and the outer side of the sound insulation device, the distance x4 between the rain hat and the sound insulation cover, and the distance x5 between the top end of the sound insulation cover and the top end of the coil. In order to meet the actual insulation requirement of the reactor, the following ranges should be selected for each parameter: x1 ranges from 0.1m to 0.3m, x2 ranges from 0.4m to 0.7m, x3 ranges from 0.1m to 0.4m, x4 ranges from 0.1m to 0.3m, and x5 ranges from 0.1m to 0.3m.
In step 3, 50 groups of optimized variables of the acoustic insulation device structure of the air reactor are sampled by a Latin square test design method, so that simulation results of sound fields and temperature fields under different structural parameters of the acoustic insulation device can be obtained, and the simulation results are shown in Table 3.
TABLE 3 simulation results of sound field and temperature field for different acoustic insulator structural parameters
As can be seen, the highest and lowest sound pressure levels of the reactor were 62.64dB and 35.7 dB, respectively, and the highest and lowest temperatures were 103.26 ℃ and 64.39 ℃, respectively. Therefore, the structural parameters of the sound insulation device have significant influence on the noise and the temperature of the reactor.
In step4, the neural network model is an approximation model covering the input layer, the intermediate layer and the output layer, which has the advantage of predicting unknown data points from known data points. A neural network model is constructed according to the data of Table 3, the fitting precision of the neural network model to the sound pressure level and the highest temperature of the measuring points is 0.93 and 0.92 respectively, and the response relation between the optimization parameters and the optimization targets is reflected.
And optimizing the reactor sound insulation device by adopting a multi-island genetic algorithm (MIGA). Compared with the traditional genetic algorithm, the MIGA algorithm divides the whole population into a plurality of populations, increases the overall crossover and mutation probability through operations such as migration and the like, and has better global solving capability and calculation efficiency. The weighting method is adopted to carry out normalization processing in the multi-objective optimization of the multi-island genetic algorithm, the importance degree of two indexes of noise and temperature is that the obtained weighting coefficients calculated according to the analytic hierarchy process are respectively 0.33 and 0.67, and the scale factors are 1. Wherein, the population number is set to be 50, the island number is set to be 4, the genetic algebra is set to be 5, and the iteration number is set to be 1000. The overall optimization flow chart is shown in fig. 6.
Based on the above method, the best acoustic insulator structure parameters are obtained as shown in table 4.
Table 4 structural parameter optimization values for sound insulation device
| Optimizing variables | X1 | X2 | X3 | X4 | X5 |
| Optimized value/m | 0.24 | 0.68 | 0.35 | 0.25 | 0.30 |
Simulation results of the reactor sound field and the temperature field under the optimal parameters are shown in figures 7-1 and 7-2. The sound pressure level and the highest temperature of the measuring point of the reactor are respectively 41.8dB and 66.8 ℃, compared with the noise and the highest temperature of the reactor before optimization, the sound pressure level and the highest temperature of the measuring point of the reactor are respectively reduced by 7.6dB and 6.5 ℃, and the simulation result verifies the correctness of the optimization method.
The above embodiments are only preferred embodiments of the present invention, and should not be construed as limiting the present invention, and the scope of the present invention should be defined by the claims, including the equivalents of the technical features in the claims. I.e., equivalent replacement modifications within the scope of this invention are also within the scope of the invention.
Claims (5)
1. The reactor sound insulation device optimization method considering noise reduction and heat dissipation double optimization is characterized by comprising the following steps of:
Step 1, constructing a three-dimensional electromagnetic-structure-sound field and flow field-temperature field coupling simulation model of an air-core reactor, and obtaining simulation results of the sound field and the temperature field of the reactor under the condition of adding and not adding a sound insulation device;
Step 2, analyzing the distribution characteristics of the sound field and the temperature field of the reactor under the added and non-added sound insulation devices, and determining the structural optimization parameters of the sound insulation devices of the reactor;
step 3, adopting a Latin square test design and finite element simulation combined method to obtain simulation results of a reactor sound field and a temperature field under sound insulation devices with different structural parameters;
and 4, constructing an approximate model according to experimental data, and obtaining the optimal structural parameters of the sound insulation device by adopting a multi-island genetic optimization algorithm.
2. The optimization method of the reactor sound insulation device considering noise reduction and heat dissipation double optimization according to claim 1, wherein in the step 1, a three-dimensional electromagnetic-structure-sound field coupling simulation model of the air core reactor is built by using COMSOL simulation software according to structural parameters of the air core reactor, and the specific process is as follows:
Under the excitation of time-varying current, the air-core reactor is driven by the electromagnetic force under the combined action of the time-varying current and the magnetic field, so that the reactor encapsulation generates forced vibration, and noise is generated to the surrounding environment; based on a magnetic-solid coupling mode, calculating electromagnetic force vibration unfolding numerical values of the air-core reactor to obtain sound field distribution of the reactor;
The current of the air-core reactor mainly depends on the inductance matrix of the encapsulated coils, wherein the current distribution of each encapsulated coil of the reactor meets the impedance matrix, as shown in a formula (1);
（1）
In the method, in the process of the invention, For/>Equivalent resistance of layer winding,/>For/>Self-inductance of individual encapsulated coil windings,/>For/>Layer and/>Mutual inductance between individual encapsulated coils,/>Is angular frequency;
under normal working state of the reactor, the current flowing through the winding generates an alternating magnetic field around the coil, wherein the magnetic field calculation equation is as follows:
（2）
Wherein: Is angular frequency,/> For conductivity,/>Is magnetic sagittal,/>Is relative permeability,/>Is relative permeability,/>Is coil current density;
When the air-core reactor winding passes through the current, the current flowing through the winding can generate a magnetic field inside and outside the reactor, and the magnetic field acts on the current-carrying winding in turn to generate magnetic field force on the winding; when the passing current alternates with time, the magnitude and direction of the magnetic field also change, so that the magnetic field force borne by the winding wire changes, and the winding vibrates; for the coil of the air-core reactor, the magnetic field intensity and the magnetic induction intensity are unevenly distributed on the reactor winding, so that the magnetic field force born by each winding and each coil is different, but the stress of each point is always in direct proportion to the current of the point and the magnetic induction intensity at the point; the magnetic induction intensity is in direct proportion to the current generating the magnetic field, so that the magnetic field force acting on each coil winding for the current with single frequency can be expressed by the formula (3);
（3）
In formula (3) Representing the integrated coefficient, as determined by geometry and magnetic permeability, and current/>Is independent of the size and frequency of (a);
Setting current By expanding equation (3-3) using the half-angle equation, it can be obtained that the frequency is/>Magnetic field force/>, formed by single-frequency sinusoidal currentAs shown in formula (4);
（4）
Wherein the vibration component is represented by the following formula;
（5）
（6）
Wherein: -a current magnitude function; /(I) -Square of the amplitude of the current; /(I)Frequency of the vibrating magnetic field force,/>，/>Is the current frequency; from the above, it can be obtained: frequency/>Single current/>Generating a static magnetic field force (/ >) corresponding to the pre-application) And a main vibration frequency/>Amplitude/>；
The time-varying electromagnetic force exerted by the encapsulated coil windings is a major source of noise; coupling with the acoustic field by electromagnetic force, thereby obtaining acoustic field distribution around the encapsulated coil; in the simulation process, a solid mechanical module is selected, and a structural force field solving domain equation set is shown as a formula (7);
（7）
In the method, in the process of the invention, Is a quality matrix; /(I)Is a damping coefficient matrix; /(I)Is a rigidity matrix; /(I)Is a displacement vector;
Selecting a pressure acoustic module in sound field analysis, wherein the variable solved by the pressure sound field module is sound pressure ; Solving a domain sound pressure fluctuation equation:
（8）
In the method, in the process of the invention, Is sound velocity,/>For sound pressure, the relationship between sound pressure and velocity is described as follows:
（9）
The conversion of sound pressure to sound pressure level can be represented by the following formula:
（10）
In the method, in the process of the invention, Is air density/>Is sound pressure level,/>Is the pressure.
3. The method for optimizing the reactor sound insulation device by considering noise reduction and heat dissipation double optimization according to claim 1, wherein in the step 1, a flow field-temperature field three-dimensional simulation model of the air core reactor is built by using COMSOL simulation software according to structural parameters of the air core reactor, and specifically comprises the following steps:
(1) Heat source
The loss of the reactor envelope coil consists of resistance loss and eddy current loss;
The resistance loss of the reactor envelope can be calculated by formula (11):
（11）
Wherein, For/>Number encapsulated Joule thermal Power,/>、/>、/>、/>Respectively is/>Envelope current, turns, diameter and conductor cross-sectional area,/>Is the conductivity of a metal conductor;
the eddy current loss can be calculated from equation (12);
（12）
In the method, in the process of the invention, For angular velocity,/>For the envelope radial width,/>Is the axial height of single turn,/>For the axial component of the magnetic induction,Is a radial component of magnetic induction;
According to the current of the reactor coil and the distribution condition of the surrounding magnetic field, the total loss of different encapsulated coils can be obtained, and the total loss can be calculated by a formula (13); in a simulation model, taking the obtained total loss of each encapsulated coil as a heat source of each coil;
（13）
(2) Control equation
When the air core reactor works, heat can be transferred to the surrounding environment through three modes of heat conduction, heat convection and heat radiation;
Heat conduction: in the solid region of the reactor, heat is transferred from the hot region to the cold region mainly by heat conduction, and the heat conduction control equation is shown in formula (14);
(14)
Wherein t is temperature, phi is heat generated by unit volume of the encapsulated coil, lambda is the heat conductivity coefficient of the encapsulating material, and x, y and z are lengths along the directions of all coordinate axes respectively;
Thermal convection: in the fluid region of the reactor and the surface of the encapsulated coil, heat convection is the main heat exchange mode; using continuity, momentum and energy equations to describe this process, as shown in equation (15);
(15)
Wherein ux, uy and uz are components of fluid velocity in x, y and z directions respectively, fx, fy and Fz are components of volume force in x, y and z directions respectively, p is pressure of fluid, ρ is density of fluid, v is kinematic viscosity of fluid, and cp is constant pressure specific heat capacity of fluid;
heat radiation: for the innermost and outermost surfaces of the encapsulated coil, heat radiation is a primary heat sink; wherein the heat radiation control equation can be represented by formula (16);
（16）
wherein: ψ is the heat flux, ε is the object surface emissivity, S is the radiating area, δ is the Boltzmann constant, T is the coil temperature, and Tair is the ambient temperature.
4. The method for optimizing the reactor sound insulation device in consideration of noise reduction and heat dissipation double optimization according to claim 3, wherein in the step 1, boundary conditions and mesh subdivision settings are further included:
(1) Boundary conditions
Boundary conditions of the sound field model are set as follows: the sound field adopts four modules of magnetic field, circuit, solid mechanics, pressure acoustics and frequency domain; the electromagnetic force applied by the encapsulated coil is used as a body load condition of the structural field; the star-shaped frame has the reinforcing effect on the encapsulated coil, so that the upper and lower boundaries of the star-shaped frame are set to be fixed and restrained, namely the vibration displacement is zero; considering that engineering is actually an open boundary, setting an external boundary of a calculation domain as a plane wave radiation condition for absorbing sound waves on the boundary;
the boundary conditions of the temperature field model are set as follows: the model uses laminar flow and fluid heat transfer modules; the surfaces of the encapsulation coil and the sound insulation cover are static wall surfaces, and no sliding occurs; the bottom surface of the calculation area is an inlet of outside air, the other surfaces are outlets, and the initial speed and static pressure are all zero; the surface emissivity of the innermost and outermost surfaces of the encapsulated coil was 0.9 in view of heat radiation; the initial temperature and the ambient temperature of the reactor are set to be 20 ℃;
(2) Mesh subdivision
The density of the grid directly influences the simulation calculation precision of the temperature field, and in order to ensure the calculation precision, a free split method is used for grid subdivision of the model in consideration of the calculation speed; a fine mesh is used in the area of the encapsulated coil and a coarsened mesh is used in the other air area.
5. The method for optimizing the reactor soundproof device taking into consideration noise reduction and heat dissipation double optimization according to claim 1, wherein in the step 2, the structural optimization parameter of the air reactor soundproof device is a rain hat height x1, a rain hat radius x2, a distance x3 between the outermost package coil and the outside of the soundproof device, a distance x4 between the rain hat and the soundproof cover, and a distance x5 between the top end of the soundproof cover and the top end of the coil; in order to meet the actual insulation requirement of the reactor, the following ranges should be selected for each parameter: x1 ranges from 0.1m to 0.3m, x2 ranges from 0.4m to 0.7m, x3 ranges from 0.1m to 0.4m, x4 ranges from 0.1m to 0.3m, and x5 ranges from 0.1m to 0.3m.
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