A method and system for numerical prediction and control of vibration radiation noise of the shell of a multifunctional straw kneading machine

Abstract

The invention discloses a method and system for numerically predicting and controlling vibration radiation noise of a shell of a multifunctional straw kneading machine, including: calculating and analyzing the vibration excitation source of the shell of the multifunctional straw kneading machine; numerically simulating the vibration response of the shell of the multifunctional straw kneading machine based on the vibration excitation source of the shell of the multifunctional straw kneading machine; predicting the vibration radiation noise of the shell of the multifunctional straw kneading machine using ATV and MATV methods based on the numerical simulation results of the vibration response of the shell of the multifunctional straw kneading machine; and controlling the vibration radiation noise of the shell of the multifunctional straw kneading machine based on the prediction results of the vibration radiation noise of the shell of the multifunctional straw kneading machine. The invention can efficiently and accurately predict and control the vibration radiation noise of the shell of the multifunctional straw kneading machine in the design stage of the machine, providing a method reference for the development of crop straw processing machinery in the direction of low noise and high quality.

Description

Technical Field

[0001] The invention belongs to the field of noise testing, analysis and control of crop straw processing machinery, and specifically relates to a method and system for numerically predicting and controlling vibration radiation noise of a shell of a multifunctional straw kneading machine. Background Art

[0002] The crop straw processing machinery in my country mainly includes grass cutters, crushers, shredders and comprehensive straw processing machinery with multiple functions. The domestically developed multifunctional straw shredder is a roughage processing machinery that integrates shredding and crushing. It can convert straw that cannot be directly eaten by livestock into more digestible filamentous or granular feed through shredding or crushing, which significantly improves the utilization rate of straw and provides strong support for the development of animal husbandry.

[0003] The multifunctional straw shredder has a thin outer shell, a large surface area and low rigidity. It is very easy to be excited by the pulsating pressure generated by the multiple coupling flow fields of the airflow-straw material-mechanical structure in the machine and the dynamic force of the bearing generated by the hammer hinged on the pin during the rotation of the rotor shaft, and other excitation sources to produce vibration and radiate noise outward. The above reasons lead to problems such as shell vibration and high radiation noise when the multifunctional straw shredder is working, which not only affects the working performance and service life of the machine, but also affects the working environment and the physical and mental health of the operator, seriously restricting the development of this type of machinery in the direction of low noise and high quality.

[0004] At present, the main method for predicting vibration radiation noise of straw processing machinery is to regard the vibration response of the machine as the acoustic boundary condition and calculate the vibration radiation noise of the machine through the indirect boundary element method. When performing structural acoustic optimization design, this method needs to be recalculated according to the changes in the vibration structure and excitation conditions, which will cause the workload and time of the calculation to increase exponentially. In order to adapt to the calculation and analysis of vibration noise under different structures, working conditions and different excitations, the Acoustic Transfer Vector (ATV) and Modal Acoustic Transfer Vector (MATV) technologies came into being, making it possible to quickly calculate vibration noise and optimize structural acoustic vibration under multiple working conditions, and it has the characteristics of small calculation amount and high efficiency. At present, the application of ATV and MATV methods in the field of crop straw processing machinery has not been reported. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention proposes a method and system for numerically predicting and controlling the vibration radiation noise of the shell of a multifunctional straw shredder. The method combining ATV&MATV technology, plate acoustic contribution technology and noise test can quickly, accurately and efficiently predict and control the vibration radiation noise of the shell of the multifunctional straw shredder, thereby providing a new research idea for the low-radiation noise design of the multifunctional straw shredder, and at the same time providing a reference for the low-noise design of hammer mills and rotary mowing / cutting / chopping machines.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] A method for numerically predicting and controlling vibration radiation noise of a multifunctional straw kneading machine housing comprises the following steps:

[0008] Calculate and analyze the vibration excitation source of the shell of the multifunctional straw kneading machine;

[0009] Based on the vibration excitation source of the multifunctional straw shredding machine shell, the vibration response of the multifunctional straw shredding machine shell is numerically simulated.

[0010] Based on the numerical simulation results of the vibration response of the shell of the multifunctional straw shred machine, the vibration radiation noise of the shell of the multifunctional straw shred machine is predicted using the ATV and MATV methods.

[0011] Based on the prediction results of the vibration radiation noise of the shell of the multifunctional straw shredding machine, the vibration radiation noise of the shell of the multifunctional straw shredding machine is controlled.

[0012] Preferably, the method for calculating and analyzing the vibration excitation source of the housing of the multifunctional straw kneading machine includes:

[0013] Calculate and analyze the pulsating pressure of the coupled flow field on the inner wall of the shell of the multifunctional straw kneading machine;

[0014] Calculate and analyze the dynamic force of the hammer pin articulated rotor bearing of the multifunctional straw kneading machine;

[0015] Among them, the method for calculating and analyzing the coupled flow field pulsating pressure on the inner wall of the shell of the multifunctional straw kneading machine includes:

[0016] The CFD-DEM coupling method is used to numerically simulate the airflow-material-mechanical structure coupled flow field inside the multifunctional straw shred machine; a pressure monitoring point is set on the inner wall of the shell of the multifunctional straw shred machine, and a cycle of unsteady-state calculation is performed to obtain the pulsating pressure data of the monitoring point within the cycle, that is, the pulsating pressure data of the coupled flow field on the inner wall of the shell of the multifunctional straw shred machine;

[0017] Among them, the method for calculating and analyzing the dynamic force of the hammer pin articulated rotor bearing of the multifunctional straw kneading machine includes:

[0018] The three-dimensional model of the multifunctional straw shredder was imported into the dynamics module of the software LMS Virtual Lab to establish a virtual prototype model, and 25 dynamic coordinate systems of the 25 active components of the rotor system were established; a revolute pair was applied between the hammer and the pin shaft, a fixed pair was applied between the pin shaft and the hammer frame plate, a revolute pair was applied between the main shaft and the bearing seat, a fixed pair was applied between the bearing seat and the frame, and the casing was fixed on the frame ground; after the settings were completed, the bearing dynamic forces on both sides of the rotor main shaft were calculated and output in the Bushing Forces module of the LMS Virtual Lab software.

[0019] Preferably, the method of numerically simulating the airflow-material-mechanical structure coupled flow field inside the multifunctional straw shredding machine by using the CFD-DEM coupling method includes:

[0020] Calculate the airflow field through the CFD model until convergence;

[0021] Determine the position and volume fraction of the material particles according to the material particle motion equation, and calculate the airflow force on the material particles, and iterate the calculation until one CFD time step;

[0022] DEM recalculates the position and velocity of material particles according to the force conditions, and synchronizes the updated particle information to CFD until convergence again.

[0023] Preferably, based on the vibration excitation source of the shell of the multifunctional straw kneading machine, the method for numerically simulating the vibration response of the shell of the multifunctional straw kneading machine includes:

[0024] The finite element model of the shell of the multifunctional straw shredder is established, and after dividing the structural grid, the first six free modal frequencies and vibration shapes of the shell of the multifunctional straw shredder are solved;

[0025] On the basis of the free modal calculation results of the shell, the harmonic response analysis based on the modal superposition method was used to numerically simulate the vibration response of the shell of the multifunctional straw shredding machine. The modal analysis module and the harmonic response analysis module were connected in ANSYS Workbench to realize data sharing between the two modules.

[0026] Preferably, the method for predicting the vibration radiation noise of the housing of the multifunctional straw kneading machine using the ATV and MATV methods includes:

[0027] The 2D surface of the multifunctional straw shredding machine shell is extracted and acoustic meshing is performed, and the fluid properties of air are given to construct an acoustic boundary element model; based on the acoustic boundary element model, an ISO model of the external sound field of the multifunctional straw shredding machine is constructed;

[0028] Based on the ISO model of the external sound field of the multifunctional straw shredder, the vibration response data of the shredder shell is converted into acoustic boundary element data, that is, the finite element structure grid data is mapped to the acoustic boundary element grid using the Maximum Distance interpolation algorithm;

[0029] The ATV method is used to calculate the acoustic transfer vector between the acoustic boundary element grid and the acoustic field point grid of the external sound field;

[0030] Based on the ATV calculation results, the vibration radiation noise sound pressure level of the external sound field of the multifunctional straw kneading machine is calculated by the modal acoustic transfer vector (MATV) method, thereby completing the numerical prediction of the vibration radiation noise of the shell of the multifunctional straw kneading machine.

[0031] Preferably, the method for controlling the vibration radiation noise of the housing of the multifunctional straw kneading machine comprises:

[0032] The shell of the multifunctional straw shredder is divided into sections, and the ATV method is used to analyze the acoustic contribution of the panels at the peak frequency points of the shell vibration radiation noise to determine the panels of the shell that need to be optimized.

[0033] For the panels that need to be optimized for the shell of the multifunctional straw shredder, the number and size of the reinforcing ribs are selected according to the size of the corresponding area;

[0034] Perform vibration response analysis on the improved housing and calculate the maximum vibration velocity;

[0035] Based on the maximum vibration velocity, the verified noise prediction model and numerical calculation method are used to calculate the vibration radiation noise of the shell of the multifunctional straw shredder after structural improvement.

[0036] The present invention also provides a numerical prediction and control system for vibration radiation noise of a multifunctional straw shredder housing, comprising: a calculation module, a simulation module, a prediction module and a control module;

[0037] The calculation module is used to calculate and analyze the vibration excitation source of the shell of the multifunctional straw kneading machine;

[0038] The simulation module is used to perform numerical simulation on the vibration response of the shell of the multifunctional straw shredding machine based on the vibration excitation source of the shell of the multifunctional straw shredding machine;

[0039] The prediction module is used to predict the vibration radiation noise of the shell of the multifunctional straw shredding machine by using the ATV and MATV methods based on the numerical simulation results of the vibration response of the shell of the multifunctional straw shredding machine;

[0040] The control module is used to control the vibration radiation noise of the shell of the multifunctional straw kneading machine based on the prediction result of the vibration radiation noise of the shell of the multifunctional straw kneading machine.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The present invention combines ATV&MATV technology, plate acoustic contribution technology and noise test to predict and control the vibration radiation noise of the shell of the multifunctional straw kneading machine, overcoming the disadvantage that the traditional calculation method needs to be recalculated as the vibration structure and excitation conditions change, which makes the calculation amount and time very huge, making it possible to quickly realize acoustic vibration optimization and numerically predict the vibration radiation noise of the shell of the straw kneading machine under multiple working conditions; in the design stage of the machine, the vibration radiation noise of the shell of the multifunctional straw kneading machine can be predicted and controlled efficiently and accurately. It provides a new research idea for the low-radiation noise design of crop straw processing machinery, and at the same time provides methods and technical references for the noise prediction and control of hammer mills and rotary mowing / cutting / chopping machines. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0044] Figure 1 Schematic diagram of the structure of a multifunctional straw shredder according to an embodiment of the present invention; wherein (a) is a multifunctional straw shredder; (b) a hammer-pin articulated rotor and its multi-body dynamics coordinates;

[0045] Figure 2 It is a schematic diagram of the CFD-DEM coupling calculation process of the coupled flow field in the multifunctional straw kneading machine according to an embodiment of the present invention;

[0046] Figure 3 It is a schematic diagram of the position of the pressure measuring points of the coupled flow field on the inner wall of the housing of the multifunctional straw kneading machine according to an embodiment of the present invention;

[0047] Figure 4 A schematic diagram of a virtual prototype model of a multifunctional straw shredder according to an embodiment of the present invention;

[0048] Figure 5 The deformation cloud maps of the first six modal frequencies of the shell of the multifunctional straw shredder according to the embodiment of the present invention are shown in FIG. 1 ; wherein (a) is the first-order 24.64 Hz deformation cloud map; (b) is the second-order 33.95 Hz deformation cloud map; (c) is the third-order 52.89 Hz deformation cloud map; (d) is the fourth-order 68.82 Hz deformation cloud map; (e) is the fifth-order 72.78 Hz deformation cloud map; and (f) is the sixth-order 94.73 Hz deformation cloud map;

[0049] Figure 6Schematic diagram of the comparison between the vibration noise sound pressure level test and the simulation of the multifunctional straw shredding machine housing according to the embodiment of the present invention; wherein (a) is a schematic diagram of the first measuring point 2; (b) is a schematic diagram of the second measuring point 4; (c) is a schematic diagram of the third measuring point 1; (d) is a schematic diagram of the fourth measuring point 3;

[0050] Figure 7 This is a schematic diagram of the outer shell of the improved multifunctional straw kneading machine according to an embodiment of the present invention;

[0051] Figure 8 A comparison diagram of the maximum vibration speed of the housing of the multifunctional straw kneading machine with the first six excitation frequencies before and after the improvement of the embodiment of the present invention;

[0052] Fig. 9 The present invention is a flowchart of a method for numerically predicting and controlling the vibration radiation noise of a multifunctional straw shredder shell according to an embodiment of the present invention.

[0053] Description of the drawings: 1. Feed chute; 2. Fixed knife; 3. Rotor; 4. Lower discharge port; 5. Frame; 6. Upper discharge port; 7. Screen; 8. Tooth plate; 3-1. Main shaft; 3-2. Throwing blade; 3-3. Hammer frame plate; 3-4. Sleeve; 3-5. Hammer; 3-6. Pin; 3-7. Guillotine. DETAILED DESCRIPTION

[0054] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0056] Embodiment 1

[0057] like Fig. 9 As shown, the present invention provides a method for numerically predicting and controlling the vibration radiation noise of the housing of a multifunctional straw kneading machine, comprising the following steps:

[0058] Calculate and analyze the vibration excitation source of the shell of the multifunctional straw kneading machine;

[0059] Based on the vibration excitation source of the multifunctional straw shredding machine shell, the vibration response of the multifunctional straw shredding machine shell is numerically simulated.

[0060] Based on the numerical simulation results of the vibration response of the shell of the multifunctional straw shred machine, the vibration radiation noise of the shell of the multifunctional straw shred machine is predicted using the ATV and MATV methods.

[0061] Based on the prediction results of the vibration radiation noise of the shell of the multifunctional straw shredding machine, the vibration radiation noise of the shell of the multifunctional straw shredding machine is controlled.

[0062] In this embodiment, the vibration excitation source of the shell of the multifunctional straw kneading machine is calculated and analyzed: the reasons for the vibration of the shell of the multifunctional straw kneading machine and the radiation of noise are mainly the following two aspects. First, when the multifunctional straw kneading machine is working, the internal airflow-straw material-mechanical structure (hammer and the inner wall tooth plate of the shell) coupling flow field generates pulsating pressure on the inner wall of the shell, that is, the pulsating pressure generated by the collision between the material and the material, the airflow, the hammer and the inner wall tooth plate of the shell causes the shell to vibrate; second, the hammer hinged on the pin shaft will generate bearing dynamic force in the process of rotating with the rotor shaft, which is transmitted to the shell through the bearing seat, causing the shell to vibrate and radiate noise outward.

[0063] Among them, the calculation and analysis of the pulsating pressure of the coupled flow field on the inner wall of the shell of the multifunctional straw shredded machine: In order to calculate the coupled flow field pressure data on the inner wall of the shell of the multifunctional straw shredded machine, the CFD-DEM coupling method is required to perform numerical simulation on the airflow-material-mechanical structure coupled flow field inside the shredded machine. Among them, CFD is calculated based on the fluid grid unit, while DEM is calculated based on a single particle. Through mutual coupling, the simulation of the interaction process between airflow, material particles and mechanical structure is completed. The specific coupling calculation process is: the airflow flow field is calculated through the CFD model (1), (2) and the turbulence model until convergence; secondly, the position and volume fraction of the material particles are determined according to the material particle motion equations (3) and (4), and the airflow force on the particles is calculated, and the iterative calculation is performed until a CFD time step; then, DEM recalculates the position and velocity of the particles according to the force conditions, and synchronizes the updated particle information to CFD. This process is iterated until the entire system reaches a convergence state. Its coupling calculation process is as follows: Figure 2 shown.

[0064] Among them, the continuity equation of the air flow phase in the CFD model (1) air flow-material-mechanical structure coupled flow field is:

[0065]

[0066] The momentum conservation equation of CFD model (2) is:

[0067]

[0068] In the formula, α fis the porosity of the continuous phase, that is, the volume ratio of the gas in the control volume; ρ g is the gas phase density; is the gas phase velocity; P is the gas phase pressure; is the viscous stress tensor of the gas; V is the acceleration due to gravity; cel is the volume of the grid unit, mm 3 ; n is the number of straw material particles in the grid unit volume, pieces; is the force exerted by a single straw particle on the airflow, N.

[0069] Material particle motion equation (3) The linear motion of straw particles can be described as:

[0070]

[0071] In the formula, m i is the mass of the i-th straw particle, kg; is the velocity of the i-th straw particle, m / s; is the centrifugal force and Coriolis force generated by the rotating reference system of the hammer pin articulated rotor, N; is the force of air on straw particle i, N and formula (2) The relationship between action and reaction force. is the contact force on the i-th straw particle, including the contact / collision force between particles and between particles and mechanical structure, N.

[0072] Material particle motion equation (4) The rotational motion of straw particles can be described as:

[0073]

[0074] In the formula, I i is the moment of inertia of the ith material particle, kg·m 2 ; is the particle rotation angular velocity, rad / s; is the moment generated by the tangential force on particle i, N / m; is the torque generated by the rolling friction force on particle i, N / m.

[0075] On this basis, a three-dimensional model of a multifunctional straw kneading machine was established in the software Solidworks, and the model was imported into the software ANSYS SpaceClaim to create a fluid calculation domain and an interface. The fluid calculation domain in the multifunctional straw kneading machine includes a stationary domain and a rotating domain. After completing the creation of the fluid calculation domain model, the model was imported into the software ANSYS ICEM to divide the mesh. Point and line cleaning and topological repair were performed to ensure that the entire flow channel space formed a closed geometric area. The octree method was used for mesh division, and a tetrahedral hybrid mesh was used. After the mesh independence test, the size of the global mesh was determined to be 14mm. After the division was completed, the number of fluid meshes in the multifunctional straw kneading machine was 2,766,751. The comprehensive quality index (quality) was used to evaluate the quality of the mesh. The results showed that the quality index of all meshes exceeded 0.3, which met the basic requirements of flow field simulation for mesh quality.

[0076] Secondly, the computational fluid dynamics (CFD) method is used to numerically simulate the flow field in the multifunctional straw shredder. The flow field grid file is imported into the computational fluid dynamics software Fluent for steady-state calculation under no-load. The finite volume method is used to discretize the control equations, the standard k-ε model is used as the turbulence model, the SIMPLE algorithm is used for numerical calculation, and the first-order upwind format is used for the discrete format. The boundary conditions are set according to the actual working conditions. The inlet boundary conditions are set as the velocity inlet, and the outlet is set as the pressure outlet (standard atmospheric pressure); at the same time, an interface is established to distinguish the rotating area from the non-rotating area. The numerical simulation results of the steady-state flow field provide the initial conditions for the unsteady calculation. It is only necessary to change the solver type from steady to unsteady flow domain parameters based on the steady-state setting parameters, change the rotating area to the sliding mesh (Mesh Motion) type, change the solution algorithm to the PISO algorithm, and determine the solution time step of each time step based on the time required for the rotor to rotate one degree. The unsteady flow field in the straw shredder under no-load conditions can be numerically simulated.

[0077] Third, the CFD-DEM coupling method is used to calculate the airflow-material-mechanical structure coupling flow field inside the multifunctional straw kneading machine. After the unsteady flow field is set in FLUENT, the calculation of the straw material particles uses the discrete element DEM method to set the material movement in EDEM, and finally the unsteady airflow-material-mechanical structure coupling flow field numerical simulation is performed through the coupling setting. In the discrete element analysis software EDEM, the material properties are set including the straw material properties and the material properties of each component. The material is yellow corn straw, with a moisture content of 9.45% and a density of 130.1kg / m3; the hammer and guillotine are 65Mn steel, etc.; a virtual particle generation plant plane is added to generate straw materials, and the particle generation speed is generated according to the actual measured feed amount of 0.145kg / s. The initial speed of the particles entering the forage kneading machine is 5m / s, and the rotor speed is 2800r / min. The interaction between straw particles, between straw particles and airflow, and between straw particles and mechanical structure is calculated using the Hertz-Mindlin contact model. When performing bidirectional coupling of CFD-DEM, the coupling module is started to couple with the EDEM software. Fluent software and EDEM software do not have built-in coupling software. It is necessary to compile the coupling interface and change the environment variables, load the UDF in the Fluent software for coupling, and set the solution time step for solution.

[0078] In order to obtain the pulsating pressure data of the coupled flow field on the inner wall of the shell of the multifunctional straw shredding machine, pressure monitoring points are set on the inner wall of the shell. The monitoring points include points on the four surfaces of the feed trough, points on the inner wall of the crushing chamber, points on the four surfaces of the upper discharge port, and points on the four surfaces of the lower discharge port. After setting the monitoring points, a non-steady-state calculation is performed for one cycle to obtain the pulsating pressure data of the coupled flow field on the monitoring points set on the shell wall in the cycle.

[0079] Among them, the dynamic force calculation and analysis of the hammer pin articulated rotor bearing of the multifunctional straw shredding machine: The hammer pin articulated rotor system of the multifunctional straw shredding machine is mainly composed of a main shaft, three hammer frame plates fixed on the main shaft, four pins and two guillotines, which together form a movable component; the 24 hammer pieces articulated on the pins are 24 movable components; a total of 25 movable components (see Appendix Figure 1 ).

[0080] In order to calculate the dynamic forces of the bearings on both sides of the hammer pin articulated rotor main shaft, a three-dimensional model of the multifunctional straw shredder (see attached) was constructed. Figure 1 a) Import the dynamics module of LMS Virtual Lab software to build its virtual prototype model (see attached) Figure 4), 25 dynamic coordinate systems of 25 active components of the rotor system are established. The revolute joint item is selected in the Joints option of the dynamics module between the hammer and the pin to apply the revolute pair, the Bracket joint item is selected in the Joints option of the dynamics module between the pin and the hammer frame plate to apply the fixed pair, the revolute joint item is selected in the Joints option of the dynamics module between the main shaft and the bearing seat to apply the revolute pair, the Bracket joint item is selected in the Joints option of the dynamics module between the bearing seat and the frame to apply the fixed pair, and the casing is fixed on the frame ground, and the working speed of 2800r / min is applied to the rotor shaft. After setting the simulation conditions, the dynamic simulation of the rotor system of the multifunctional straw kneading machine is carried out, and the simulation duration is set to 5s and the step size is 0.0002s. After the calculation is completed, the dynamic force of the hammer pin articulated rotor bearing is output in the Bushing Forces module of the LMS Virtual Lab software.

[0081] In this embodiment, the vibration response of the housing of the multifunctional straw shredding machine is numerically simulated:

[0082] First, use the software Solidworks to create a three-dimensional model of the shell of the multifunctional straw shredder and save it in .stp format. Then import this model into the Model module of Workbench, and select carbon structural steel Q235 as the shell material from the material library. When meshing, the mesh type is set to tetrahedral mesh, and the mesh unit size is 14mm. After the division is completed, the number of mesh units is 65282, and the number of mesh nodes is 133288. In the Model module, the shell of the multifunctional straw shredder is calculated for free modal calculation without applying external loads. In order to meet the accuracy of the modal solution, the natural frequency and vibration mode of the first six modes of the shell are generally solved, that is, the calculation of the first six modes is selected in the modal analysis settings. The simulation results are shown in the attached figure. Figure 5 .

[0083] Secondly, based on the free modal calculation results of the shell, the harmonic response analysis based on the modal superposition method is used to numerically simulate the vibration response of the shell of the multifunctional straw shredder. The modal analysis module and the harmonic response analysis module are connected in ANSYS Workbench to realize data sharing between the two modules. Harmonic response analysis mainly applies external loads on the basis of modal analysis. The coupled flow field pulsating pressure on the inner wall of the shell and the bearing dynamic force on both sides of the hammer pin articulated rotor main shaft are used as excitation to apply loads to the shell of the multifunctional straw shredder. In order to ensure that the excitation can be effectively transmitted to the shell, nodes are first established at the center of the shell of the multifunctional straw shredder and the wall of the bearing seat on both sides, and then the coupled flow field pulsating pressure and bearing dynamic force are applied to the corresponding nodes, and the surface of the shell of the multifunctional straw shredder is selected as the vibration response calculation area. The vibration velocity is selected as the output result to provide acoustic boundary conditions for the subsequent prediction of vibration radiation noise of the shell of the multifunctional straw shredder.

[0084] In this embodiment, the vibration radiation noise prediction and experimental verification of the housing of the multifunctional straw shredding machine based on the ATV and MATV methods are as follows:

[0085] When predicting the vibration radiation noise of the shell of the multifunctional straw shredder based on the ATV and MATV methods, the acoustic transfer vector (ATV) is a correspondence established between the sound pressure at the field point and the vibration velocity of the structure surface. By introducing the modal parameters of the structural model into the sound transfer, the modal acoustic transfer vector (MATV) can be obtained. When the pressure on the surface of the shell of the multifunctional straw shredder is small, there is a certain linear relationship between the vibration velocity in the normal direction of the surface and the sound pressure at a certain point in the sound field, which can be expressed as

[0086] p(ω)={ATV(ω)} T {v n (ω)} (5)

[0087] Where p(ω) is the sound pressure at a point in the sound field, {ATV(ω)} is the sound transfer vector, and v n is the vibration velocity in the normal direction of the structure surface, and ω is the angular frequency.

[0088] The displacement response of the shavings kneading machine housing in the frequency domain can be obtained by linear superposition of the modal vibration vectors.

[0089]

[0090] By projecting the displacement response {x(ω)} of the shell structure to the normal direction of the structure surface and taking the derivative, the vibration velocity in the normal direction of the shell structure can be obtained.

[0091]

[0092] In the formula, It represents the component of the j-th mode shape in the normal direction of the structure surface.

[0093] Combining equation (5) and equation (7), we can get:

[0094]

[0095] In the formula, {MATV(ω)} is the modal acoustic transfer vector, that is, the sound pressure value at a certain point in the sound field based on the unit modal response at a specific frequency. Its expression is:

[0096]

[0097] On this basis, the acoustic boundary element model of the shell of the multifunctional straw shredder is established by importing the three-dimensional model of the shell of the multifunctional straw shredder in the LMS Virtual Lab software, and extracting its surface mesh through the acoustic boundary element module to establish the shell acoustic boundary element model. Since the acoustic boundary element theory stipulates that the maximum unit size should not exceed one-sixth of the wavelength, the upper limit of the calculation frequency is 1200Hz, and the speed of sound propagation in the air is 340m / s, the size of the acoustic boundary element grid unit of the shell of the multifunctional straw shredder is determined. After the acoustic grid is given the fluid properties of the air, the establishment of the acoustic boundary element model of the shell of the shredder is completed, and a total of 13448 grid units and 6450 nodes are divided. On this basis, the external sound field model of the shell of the multifunctional straw shredder is established, and the ISO sound field model in the LMS virtual.lab software is selected. There are 38 acoustic field points, and no reflection surface is set to simulate the ground reflection. The acoustic boundary element model of the shell of the multifunctional straw shredder is located at the center of the external sound field model and the A-weighted measurement method is used to simulate the subjective feeling of the human ear to the sound.

[0098] Secondly, the modal acoustic transfer vector (MATV) method is used to calculate the vibration radiation noise of the shell of the multifunctional kneading machine. The vibration response data of the shell needs to be converted into acoustic boundary element data. Therefore, the Maximum Distance interpolation algorithm is used to map the structural vibration data information to the acoustic boundary element mesh, and establish the coupling relationship between the finite element structural mesh and the acoustic mesh. The algorithm uses the target node as the reference point. Through this mapping method, several finite element mesh nodes with the closest distance can be obtained, so that the vibration data of the finite element node can be effectively mapped to the boundary element mesh.

[0099] Thirdly, in the LMS Virtual Lab software, the acoustic boundary element model of the shell of the multifunctional straw shredding machine is set as the acoustic mesh attribute and the fluid material and properties are defined. The ATV Analysis Cases module is inserted, and the analysis frequency is set to 5-1200 Hz with a step size of 5 Hz in the ATV AnalysisSolution. The acoustic transfer vector ATV between the acoustic boundary element mesh and the 38 acoustic field point meshes in the external sound field is calculated. Based on the calculation results and data mapping of the acoustic transfer vector ATV of the acoustic field point mesh of the external sound field, the Modal ATV Response Analysis module is inserted, and the modal acoustic transfer vector (MATV) method is used to calculate the sound pressure level of the vibration radiation noise of the external sound field of the multifunctional straw shredding machine, thereby completing the numerical prediction of the vibration radiation noise of the shell of the multifunctional straw shredding machine.

[0100] Finally, the vibration radiation noise prediction results were compared with the test results to verify the accuracy of the numerical prediction model and method for the shell vibration radiation noise. The sound pressure method was used to measure the shell vibration radiation noise under load conditions of the multifunctional straw shredder. Figure 6 As shown, Figure 6 The A-weighted total sound pressure level is obtained by superimposing the effective peak values ​​of the measured and simulated sound pressure levels using formula (10), as shown in Appendix 1.

[0101]

[0102] Table 1

[0103]

[0104] By the attached Figure 6 As shown in Table 1, the variation law and trend of the sound pressure level spectrum curve of the multifunctional straw shredder shell vibration radiation noise test and simulation are basically consistent, and the frequencies of high sound pressure levels are the same, which verifies the accuracy of the prediction model and method of shell vibration radiation noise. The total sound pressure level test values ​​of each load measurement point are greater than the simulation values, with a maximum difference of 3.71dB(A), which is relatively small. This is because the process of hammers crushing materials is not considered in the simulation. In fact, mechanical noise and unbalanced rotation of the rotor will also be generated in this process, which increases the noise.

[0105] In this embodiment, the vibration radiation noise of the multifunctional straw shredding machine housing is controlled as follows:

[0106] First, the shell boundary element model is divided into panels according to the shell structure of the multifunctional straw shredding machine, and a total of 13 panels are divided, including the left part of the feed trough 1, the upper part of the feed trough 2, the right part of the feed trough 3, the lower part of the feed trough 4, the annular surface of the crushing chamber 5, the front part of the crushing chamber 6, the rear part of the crushing chamber 7, the right part of the upper discharge port 8, the lower part of the upper discharge port 9, the left part of the lower discharge port 10, the right part of the lower discharge port 11, the upper part of the lower discharge port 12 and the lower part of the lower discharge port 13. Taking the acoustic field point with the largest vibration radiation noise as an example, the acoustic contribution of each structural panel of the shell to the radiation noise of this field point is calculated. From the main peak frequency obtained by the previous analysis, the panel acoustic contribution of each panel at this frequency is extracted respectively, and multiplied by the normalization coefficient to obtain the panel acoustic contribution. The analysis shows that panels No. 4, 6, 8 and 11 have a greater contribution to the acoustics of the outer shell. Therefore, when optimizing the outer shell of the multifunctional straw shredding machine, panels No. 4, 6, 8 and 11 can be considered as the key panels for vibration and noise reduction.

[0107] Secondly, based on the contribution analysis results of the shell panels, the optimized panels are determined to be the lower part of the feed trough (panel No. 4), the rear part of the crushing chamber (panel No. 6), the front part of the upper discharge port (panel No. 8) and the lower part of the lower discharge port (panel No. 11). Taking into account the difficulty and cost of structural improvement, reinforcing ribs are added to the four plate parts of the shell (i.e. welding 20×20×3 angle steels) to increase its stiffness and reduce vibration, thereby reducing the radiation noise of the shell. Since the areas that need to be reinforced for panels No. 4, 6, 8, and 11 are different, the principle of determining the number of reinforcements based on the reinforced area is adopted for improvement. The improved structure is as follows Figure 7 shown.

[0108] Finally, the vibration response analysis of the reinforced shell was carried out, and the maximum vibration speed of the shell before and after improvement under the first six excitation frequencies was selected for comparison, such as Figure 8 As shown in the figure, the purpose of reducing the vibration of the shell is achieved after the structural improvement. The total sound pressure level of the vibration radiation noise band of the representative measuring point 2 on the first side of the belt drive, measuring point 4 on the second side of the lower discharge port, and measuring point 3 on the fourth side of the upper discharge port after the structural improvement is recalculated by using the verified noise prediction model and numerical calculation method, and compared with the corresponding total sound pressure level before the improvement, as shown in Table 2. It can be seen from Table 2 that after the structural improvement, the total sound pressure level of the noise of measuring point 2 on the first side of the belt drive, measuring point 4 on the second side of the lower discharge port, and measuring point 3 on the fourth side of the upper discharge port are all lower than the 90dB(A) requirement specified in the national standard, while the total sound pressure level of the noise of measuring point 1 on the third side of the feed trough is still higher than 90dB(A), mainly because the measuring point is facing the feed port. The noise here is the coupling noise of the shell vibration noise and the aerodynamic noise. Therefore, changing the shell structure alone has limited effect on it, and it is necessary to further optimize its aerodynamic noise to reduce the coupling noise.

[0109] Table 2

[0110]

[0111] Embodiment 2

[0112] The present invention also provides a numerical prediction and control system for vibration radiation noise of a multifunctional straw shredder housing, comprising: a calculation module, a simulation module, a prediction module and a control module;

[0113] The calculation module is used to calculate and analyze the vibration excitation source of the shell of the multifunctional straw kneading machine;

[0114] The simulation module is used to numerically simulate the vibration response of the shell of the multifunctional straw shredding machine based on the vibration excitation source of the shell of the multifunctional straw shredding machine;

[0115] The prediction module is used to predict the vibration radiation noise of the shell of the multifunctional straw shredding machine using the ATV and MATV methods based on the numerical simulation results of the vibration response of the shell of the multifunctional straw shredding machine;

[0116] The control module is used to control the vibration radiation noise of the shell of the multifunctional straw kneading machine based on the prediction result of the vibration radiation noise of the shell of the multifunctional straw kneading machine.

[0117] In this embodiment, the process of calculating and analyzing the vibration excitation source of the housing of the multifunctional straw kneading machine includes:

[0118] Calculate and analyze the pulsating pressure of the coupled flow field on the inner wall of the shell of the multifunctional straw kneading machine;

[0119] Calculate and analyze the dynamic force of the hammer pin articulated rotor bearing of the multifunctional straw kneading machine;

[0120] The process of calculating and analyzing the pulsating pressure of the coupled flow field on the inner wall of the shell of the multifunctional straw kneading machine includes:

[0121] The CFD-DEM coupling method is used to numerically simulate the airflow-material-mechanical structure coupled flow field inside the multifunctional straw shred machine; a pressure monitoring point is set on the inner wall of the shell of the multifunctional straw shred machine, and a cycle of unsteady-state calculation is performed to obtain the pulsating pressure data of the monitoring point within the cycle, that is, the pulsating pressure data of the coupled flow field on the inner wall of the shell of the multifunctional straw shred machine;

[0122] The process of calculating and analyzing the dynamic force of the hammer pin articulated rotor bearing of the multifunctional straw kneading machine includes:

[0123] The three-dimensional model of the multifunctional straw shredder was imported into the dynamics module of the software LMS Virtual Lab to establish a virtual prototype model, and 25 dynamic coordinate systems of the 25 active components of the rotor system were established; a revolute pair was applied between the hammer and the pin shaft, a fixed pair was applied between the pin shaft and the hammer frame plate, a revolute pair was applied between the main shaft and the bearing seat, a fixed pair was applied between the bearing seat and the frame, and the casing was fixed on the frame ground; after the settings were completed, the bearing dynamic forces on both sides of the rotor main shaft were calculated and output in the Bushing Forces module of the LMS Virtual Lab software.

[0124] In this embodiment, the process of numerically simulating the airflow-material-mechanical structure coupling flow field inside the multifunctional straw shredding machine by using the CFD-DEM coupling method includes:

[0125] Calculate the airflow field through the CFD model until convergence;

[0126] Determine the position and volume fraction of the material particles according to the material particle motion equation, and calculate the airflow force on the material particles, and iterate the calculation until one CFD time step;

[0127] DEM recalculates the position and velocity of material particles according to the force conditions, and synchronizes the updated particle information to CFD until convergence again.

[0128] In this embodiment, based on the vibration excitation source of the multifunctional straw shred machine housing, the process of numerically simulating the vibration response of the multifunctional straw shred machine housing includes:

[0129] The finite element model of the shell of the multifunctional straw shredder is established, and after dividing the structural grid, the first six free modal frequencies and vibration shapes of the shell of the multifunctional straw shredder are solved;

[0130] On the basis of the free modal calculation results of the shell, the harmonic response analysis based on the modal superposition method was used to numerically simulate the vibration response of the shell of the multifunctional straw shredding machine. The modal analysis module and the harmonic response analysis module were connected in ANSYS Workbench to realize data sharing between the two modules.

[0131] In this embodiment, the process of predicting the vibration radiation noise of the housing of the multifunctional straw kneading machine using the ATV and MATV methods includes:

[0132] The 2D surface of the multifunctional straw shredding machine shell is extracted and acoustic meshing is performed, and the fluid properties of air are given to construct an acoustic boundary element model; based on the acoustic boundary element model, an ISO model of the external sound field of the multifunctional straw shredding machine is constructed;

[0133] Based on the ISO model of the external sound field of the multifunctional straw shredder, the vibration response data of the shredder shell is converted into acoustic boundary element data, that is, the finite element structure grid data is mapped to the acoustic boundary element grid using the Maximum Distance interpolation algorithm;

[0134] The ATV method is used to calculate the acoustic transfer vector between the acoustic boundary element grid and the acoustic field point grid of the external sound field;

[0135] Based on the ATV calculation results, the vibration radiation noise sound pressure level of the external sound field of the multifunctional straw kneading machine is calculated by the modal acoustic transfer vector (MATV) method, thereby completing the numerical prediction of the vibration radiation noise of the shell of the multifunctional straw kneading machine.

[0136] In this embodiment, the process of controlling the vibration radiation noise of the housing of the multifunctional straw kneading machine includes:

[0137] The shell of the multifunctional straw shredder is divided into sections, and the ATV method is used to analyze the acoustic contribution of the panels at the peak frequency points of the shell vibration radiation noise to determine the panels of the shell that need to be optimized.

[0138] For the panels that need to be optimized for the shell of the multifunctional straw shredder, the number and size of the reinforcing ribs are selected according to the size of the corresponding area;

[0139] Perform vibration response analysis on the improved housing and calculate the maximum vibration velocity;

[0140] Based on the maximum vibration velocity, the verified noise prediction model and numerical calculation method are used to calculate the vibration radiation noise of the shell of the multifunctional straw shredder after structural improvement.

[0141] Embodiment 3

[0142] As attached Figure 1 As shown, the multifunctional straw kneading machine is mainly composed of a feed trough 1, a fixed knife 2, a rotor 3, a lower discharge port 4, a frame 5, an upper discharge port 6, a screen 7 (or a tooth plate 8) (as shown in FIG. Figure 1 As shown), the rotor system mainly consists of a main shaft 3-1, a hammer frame plate 3-2, a throwing blade 3-3, a sleeve 3-4, a guillotine 3-5, a pin shaft 3-6 and a hammer piece 3-7 ( Figure 1 b), the guillotine, hammer frame plate, pin shaft and throwing blade are fixedly connected to the main shaft, the hammer pieces are hinged on the pin shaft, and the hammer pieces are separated by sleeves with equal spacing.

[0143] The present invention takes the 9ZR-2.2 multifunctional straw kneading machine as the research object. The supporting power is 3.0kW, the kneading machine shell is 1250mm long, 580mm wide, and 950mm high, the radius of the kneading chamber is 220mm, the length of the kneading chamber is 247mm, the rotation radius of the rotor is 181mm, the rotor speed is 2800r / min, the feed amount is 0.236kg / s, and the processed straw is corn stalks harvested in Hohhot and Linger County in 2022. Due to space limitations, the present invention mainly takes the kneading working condition as an example, and the inner wall of the kneading chamber is added with a tooth plate, and the lower discharge port is closed.

[0144] In this embodiment, the analysis and calculation of the vibration excitation source of the multifunctional straw shredding machine housing include:

[0145] Calculation and analysis of the coupled flow field pressure on the inner wall of the multifunctional forage shredder shell: The CFD-DEM coupling method is used to numerically simulate the airflow-material-mechanical structure coupled flow field inside the multifunctional straw shredder to obtain the pulsating pressure data of the coupled flow field on the inner wall of the multifunctional straw shredder shell. The airflow flow field is calculated using the computational fluid dynamics CFD method, the straw material particles are calculated using the discrete element DEM method, and the airflow, straw material and mechanical structure coupled flow field is calculated using the CFD-DEM coupling method.

[0146] First, a solid model of the multifunctional straw kneading machine was established in the software Solidworks, and the model was imported into the software ANSYS SpaceClaim to create a fluid calculation domain and an interface. The fluid calculation domain in the multifunctional straw kneading machine includes a stationary domain and a rotating domain. After completing the creation of the fluid calculation domain model, the model was imported into the software ANSYSICEM to divide the mesh. Point and line cleaning and topological repair were performed to ensure that the entire flow channel space formed a closed geometric area. The octree method was used for meshing, and a tetrahedral hybrid mesh was used. After the mesh independence test, the size of the global mesh was determined to be 14mm. After the division was completed, the number of fluid meshes in the multifunctional straw kneading machine was 2,766,751. The comprehensive quality index (quality) was used to evaluate the quality of the mesh. The results showed that the quality index of all meshes exceeded 0.3, which met the basic requirements of flow field simulation for mesh quality.

[0147] Secondly, the computational fluid dynamics (CFD) method is used to numerically simulate the flow field in the multifunctional straw shredder. The flow field grid file is imported into the computational fluid dynamics software Fluent for steady-state calculation under no-load. The finite volume method is used to discretize the control equations, the standard k-ε model is used as the turbulence model, the SIMPLE algorithm is used for numerical calculation, and the first-order upwind format is used for the discrete format. The boundary conditions are set according to the actual working conditions. The inlet boundary conditions are set as the velocity inlet, and the outlet is set as the pressure outlet (standard atmospheric pressure); at the same time, an interface is established to distinguish the rotating area from the non-rotating area. The numerical simulation results of the steady-state flow field provide the initial conditions for the unsteady calculation. It is only necessary to change the solver type from steady to unsteady flow domain parameters based on the steady-state setting parameters, change the rotating area to the sliding mesh (Mesh Motion) type, change the solution algorithm to the PISO algorithm, and determine the solution time step of each time step based on the time required for the rotor to rotate one degree. The unsteady flow field in the straw shredder under no-load conditions can be numerically simulated.

[0148] Third, the CFD-DEM coupling method is used to calculate the airflow-material-mechanical structure coupling flow field inside the multifunctional straw kneading machine. After the unsteady flow field is set in FLUENT, the calculation of the straw material particles uses the discrete element DEM method to set the material movement in EDEM, and finally the unsteady airflow-material-mechanical structure coupling flow field numerical simulation is performed through the coupling setting. In the discrete element analysis software EDEM, the material properties are set including the straw material properties and the material properties of each component. The material is yellow corn straw, with a moisture content of 9.45% and a density of 130.1kg / m3; the hammer and guillotine are 65Mn steel, etc.; a virtual particle generation plant plane is added to generate straw materials, and the particle generation speed is generated according to the actual measured feed amount of 0.145kg / s. The initial speed of the particles entering the forage kneading machine is 5m / s, and the rotor speed is 2800r / min. The interaction between straw particles, between straw particles and airflow, and between straw particles and mechanical structure is calculated using the Hertz-Mindlin contact model. When performing bidirectional coupling of CFD-DEM, the coupling module is started to couple with the EDEM software. Fluent software and EDEM software do not have built-in coupling software. It is necessary to compile the coupling interface and change the environment variables, load the UDF in the Fluent software for coupling, and set the solution time step for solution.

[0149] In order to obtain the pulsating pressure data of airflow and material on the inner wall of the shell of the multifunctional straw shredder, 16 pressure monitoring points are set on the inner wall of the shell. Figure 3As shown. The monitoring points include points 1, 2, 3 and 4 on the four sides of the feed trough, points 5 and 7 on the two side surfaces of the crushing chamber, points 6 and 8 on the arc plate of the crushing chamber, points 9, 10, 11 and 12 on the four sides of the upper discharge port, and points 13, 14, 15 and 16 on the four sides of the lower discharge port. The solid points are visible side points, and the hollow points with numbers in brackets are invisible side points. After setting the monitoring points, perform a cycle of non-steady-state calculation to obtain the pulsating pressure data of the monitoring points in the cycle.

[0150] Multi-body dynamics simulation of the multi-functional straw shredder: In order to calculate the dynamic forces of the bearings on both sides of the main shaft of the hammer-pin articulated rotor, appropriate simplification was first performed in the process of modeling the multi-functional straw shredder. The three-dimensional model was converted into the stp format and imported into the LMS Virtual Lab dynamics module to establish its virtual prototype model. The coordinate system of the 25 active components of the rotor system was established according to the multi-body dynamics model of the hammer-pin articulated rotor. A revolute pair was applied between the hammer and the pin shaft, a fixed pair was applied between the pin shaft and the hammer frame plate, a revolute pair was applied between the main shaft and the bearing seat, a fixed pair was applied between the bearing seat and the frame, and the casing was fixed on the ground. After the settings were completed, the dynamic forces of the bearings on both sides of the rotor main shaft were calculated and output in the Bushing Forces module of the LMS Virtual Lab.

[0151] In this embodiment, the vibration response calculation and analysis of the shell of the multifunctional straw shredding machine is as follows:

[0152] First, use the software Solidworks to create a model of the multifunctional straw shredder shell and save it in .stp format. Then import this model into the Model module of Workbench, and select carbon structural steel Q235 as the shell material from the material library. When meshing, the mesh type is set to tetrahedral mesh, and the mesh unit size is 14mm. After the division is completed, the number of mesh units is 65282, and the number of mesh nodes is 133288. In the Model module, the shell free modal calculation is performed on the shell of the multifunctional straw shredder without applying external loads. In order to meet the solution accuracy of the mode, the natural frequency and vibration mode of the first six modes of the shell are generally solved, that is, the calculation of the first six modes is selected in the modal analysis settings. The simulation results are as follows. Figure 5 .

[0153] Secondly, based on the free modal calculation results of the shell, the harmonic response analysis based on the modal superposition method is used to numerically simulate the vibration response of the shell of the multifunctional straw shredder. The modal analysis module and the harmonic response analysis module are connected in ANSYS Workbench to realize data sharing between the two modules. Harmonic response analysis mainly applies external loads on the basis of modal analysis. The coupled flow field pulsating pressure on the inner wall of the shell and the bearing dynamic force on both sides of the hammer pin articulated rotor main shaft are used as excitation to apply loads to the shell of the multifunctional straw shredder. In order to ensure that the excitation can be effectively transmitted to the shell, nodes are first established at the center of the shell of the multifunctional straw shredder and the wall of the bearing seat on both sides, and then the coupled flow field pulsating pressure and bearing dynamic force are applied to the corresponding nodes, and the surface of the shell of the multifunctional straw shredder is selected as the vibration response calculation area. The vibration velocity is selected as the output result to provide acoustic boundary conditions for the subsequent prediction of vibration radiation noise of the shell of the multifunctional straw shredder.

[0154] In this embodiment, the numerical prediction of the vibration radiation noise of the multifunctional straw shredding machine shell based on ATV and MATV is as follows:

[0155] First, to establish the acoustic boundary element model of the shell of the multifunctional straw shredder, it is necessary to import the three-dimensional model of the shell of the multifunctional straw shredder in the LMS Virtual Lab software, and extract its surface mesh through the acoustic boundary element module to establish the shell acoustic boundary element model. Since the acoustic boundary element theory stipulates that the maximum unit size should not exceed one-sixth of the wavelength, the upper limit of the calculation frequency is 1200Hz, and the speed of sound propagation in the air is 340m / s, the size of the acoustic boundary element grid unit of the shell of the multifunctional straw shredder is determined. After the acoustic grid is given the fluid properties of the air, the establishment of the acoustic boundary element model of the shell of the shredder is completed, and a total of 13448 grid units and 6450 nodes are divided. On this basis, the external sound field model of the shell of the multifunctional straw shredder is established, and the ISO sound field model in the LMS virtual.lab software is selected. There are 38 acoustic field points, and no reflection surface is set to simulate the ground reflection. The acoustic boundary element model of the shell of the multifunctional straw shredder is located at the center of the external sound field model and the A-weighted measurement method is used to simulate the subjective feeling of the human ear to the sound.

[0156] Secondly, the modal acoustic transfer vector (MATV) method is used to calculate the vibration radiation noise of the shell of the multifunctional kneading machine. The vibration response data of the shell needs to be converted into acoustic boundary element data. Therefore, the Maximum Distance interpolation algorithm is used to map the structural vibration data information to the acoustic boundary element mesh, and establish the coupling relationship between the finite element structural mesh and the acoustic mesh. The algorithm uses the target node as the reference point. Through this mapping method, several finite element mesh nodes with the closest distance can be obtained, so that the vibration data of the finite element node can be effectively mapped to the boundary element mesh.

[0157] Third, the acoustic transfer vector ATV between the acoustic boundary element grid and the 38 acoustic field point grids of the external sound field is calculated in the LMS Virtual Lab software; the vibration radiation noise sound pressure level of the multifunctional silk kneading machine's external sound field is calculated by the modal acoustic transfer vector (MATV) method based on the acoustic transfer vector ATV calculation results of the acoustic field point grid of the external sound field. The analysis frequency is set to 5~1200Hz with a step size of 5Hz.

[0158] Finally, the numerical prediction results of the shell vibration radiation noise were compared with the test results of the shell vibration noise of the multifunctional straw shredder to verify the accuracy of the numerical prediction model and method of the shell vibration radiation noise. The shell vibration radiation noise of the multifunctional straw shredder under load conditions was measured using the sound pressure method. The comparison results of the shell vibration radiation noise test and numerical prediction are shown in the figure. Figure 6 As shown, Figure 6 The A-weighted total sound pressure level is obtained by superimposing the effective peak values ​​of the measured and simulated sound pressure levels using formula (1), as shown in Appendix 1.

[0159]

[0160] Table 1

[0161]

[0162] By the attached Figure 6 As shown in Table 1, the variation law and trend of the sound pressure level spectrum curve of the multifunctional straw shredder shell vibration radiation noise test and simulation are basically consistent, and the frequencies of high sound pressure levels are the same, which verifies the accuracy of the prediction model and method of shell vibration radiation noise. The total sound pressure level test values ​​of each load measurement point are greater than the simulation values, with a maximum difference of 3.71dB(A), which is relatively small. This is because the process of hammers crushing materials is not considered in the simulation. In fact, mechanical noise and unbalanced rotation of the rotor will also be generated in this process, which increases the noise.

[0163] In this embodiment, the vibration radiation noise of the multifunctional straw shredding machine housing is controlled as follows:

[0164] First, the shell boundary element model is divided into panels according to the shell structure of the multifunctional straw shredding machine, and a total of 13 panels are divided, including the left part of the feed trough 1, the upper part of the feed trough 2, the right part of the feed trough 3, the lower part of the feed trough 4, the annular surface of the crushing chamber 5, the front part of the crushing chamber 6, the rear part of the crushing chamber 7, the right part of the upper discharge port 8, the lower part of the upper discharge port 9, the left part of the lower discharge port 10, the right part of the lower discharge port 11, the upper part of the lower discharge port 12 and the lower part of the lower discharge port 13. Taking the acoustic field point with the largest vibration radiation noise as an example, the acoustic contribution of each structural panel of the shell to the radiation noise of this field point is calculated. From the main peak frequency obtained by the previous analysis, the panel acoustic contribution of each panel at this frequency is extracted respectively, and multiplied by the normalization coefficient to obtain the panel acoustic contribution. The analysis shows that panels No. 4, 6, 8 and 11 have a greater contribution to the acoustics of the outer shell. Therefore, when optimizing the outer shell of the multifunctional straw shredding machine, panels No. 4, 6, 8 and 11 can be considered as the key panels for vibration and noise reduction.

[0165] Secondly, based on the contribution analysis results of the shell panels, the optimized panels are determined to be the lower part of the feed trough (panel No. 4), the rear part of the crushing chamber (panel No. 6), the front part of the upper discharge port (panel No. 8) and the lower part of the lower discharge port (panel No. 11). Taking into account the difficulty and cost of structural improvement, reinforcing ribs are added to the four plate parts of the shell (i.e. welding 20×20×3 angle steels) to increase its stiffness and reduce vibration, thereby reducing the radiation noise of the shell. Since the areas of panels No. 4, 6, 8, and 11 that require reinforcement are different, the principle of determining the number of reinforcements based on the reinforcement area is adopted for improvement. The improved structure is as follows Figure 7 shown.

[0166] Finally, the vibration response analysis of the reinforced shell was carried out, and the maximum vibration speed of the shell before and after improvement under the first six excitation frequencies was selected for comparison, such as Figure 8 As shown in the figure, the purpose of reducing the vibration of the shell is achieved after the structural improvement. The total sound pressure level of the vibration radiation noise band of the representative measuring point 2 on the first side of the belt drive, measuring point 4 on the second side of the lower discharge port, measuring point 1 on the third side of the surface and measuring point 3 on the fourth side of the surface after the structural improvement of the kneading machine shell is recalculated by using the verified noise prediction model and numerical calculation method, and compared with the corresponding total sound pressure level before the improvement, as shown in Table 2. It can be seen from Table 2 that after the structural improvement, the total sound pressure level of the noise of measuring point 2 on the first side of the belt drive, measuring point 4 on the second side of the lower discharge port, and measuring point 3 on the fourth side of the upper discharge port are all lower than the 90dB(A) requirement specified in the national standard, while the total sound pressure level of the noise of measuring point 1 on the third side of the feed trough is still higher than 90dB(A), mainly because the measuring point is facing the feed port. The noise here is the coupling noise of the shell vibration noise and the aerodynamic noise. Therefore, changing the shell structure alone has limited effect on it, and it is necessary to further optimize its aerodynamic noise to reduce the coupling noise.

[0167] Table 2

[0168]

[0169] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A numerical prediction and control method for vibration radiation noise of a multifunctional straw kneading machine housing, characterized in that: The following steps are involved: Calculate and analyze the vibration excitation source of the shell of the multifunctional straw kneading machine; Based on the vibration excitation source of the multifunctional straw shredding machine shell, the vibration response of the multifunctional straw shredding machine shell is numerically simulated. Based on the numerical simulation results of the vibration response of the shell of the multifunctional straw shred machine, the vibration radiation noise of the shell of the multifunctional straw shred machine is predicted using the ATV and MATV methods. Based on the prediction results of the vibration radiation noise of the shell of the multifunctional straw shred machine, the vibration radiation noise of the shell of the multifunctional straw shred machine is controlled; The method of predicting the vibration radiation noise of the shell of the multifunctional straw shredder using the ATV and MATV methods includes: The 2D surface of the multifunctional straw shredding machine shell is extracted and acoustic meshing is performed, and the fluid properties of air are given to construct an acoustic boundary element model; based on the acoustic boundary element model, an ISO model of the external sound field of the multifunctional straw shredding machine is constructed; Based on the ISO model of the external sound field of the multifunctional straw shredder, the vibration response data of the shredder shell is converted into acoustic boundary element data, that is, the finite element structure grid data is mapped to the acoustic boundary element grid using the Maximum Distance interpolation algorithm; The ATV method is used to calculate the acoustic transfer vector between the acoustic boundary element grid and the acoustic field point grid of the external sound field; Based on the ATV calculation results, the vibration radiation noise sound pressure level of the external sound field of the multifunctional straw kneading machine is calculated by the modal acoustic transfer vector (MATV) method, thereby completing the numerical prediction of the vibration radiation noise of the shell of the multifunctional straw kneading machine.

2. The method for numerical prediction and control of vibration radiation noise of the shell of the multifunctional straw kneading machine according to claim 1 is characterized in that: The method for calculating and analyzing the vibration excitation source of the shell of the multifunctional straw kneading machine includes: Calculate and analyze the pulsating pressure of the coupled flow field on the inner wall of the shell of the multifunctional straw kneading machine; Calculate and analyze the dynamic force of the hammer pin articulated rotor bearing of the multifunctional straw kneading machine; Among them, the method for calculating and analyzing the coupled flow field pulsating pressure on the inner wall of the shell of the multifunctional straw kneading machine includes: The CFD-DEM coupling method is used to numerically simulate the airflow-material-mechanical structure coupled flow field inside the multifunctional straw shred machine; a pressure monitoring point is set on the inner wall of the shell of the multifunctional straw shred machine, and a cycle of unsteady-state calculation is performed to obtain the pulsating pressure data of the monitoring point within the cycle, that is, the pulsating pressure data of the coupled flow field on the inner wall of the shell of the multifunctional straw shred machine; Among them, the method for calculating and analyzing the dynamic force of the hammer pin articulated rotor bearing of the multifunctional straw kneading machine includes: The 3D model of the multifunctional straw shredder was imported into the dynamics module of the LMS Virtual Lab software to establish a virtual prototype model, and 25 dynamic coordinate systems of the 25 active components of the rotor system were established; a revolute pair was applied between the hammer and the pin shaft, a fixed pair was applied between the pin shaft and the hammer frame plate, a revolute pair was applied between the main shaft and the bearing seat, a fixed pair was applied between the bearing seat and the frame, and the casing was fixed on the frame ground; after the settings were completed, the bearing dynamic forces on both sides of the rotor main shaft were calculated and output in the BushingForces module of the LMS Virtual Lab software.

3. The method for numerical prediction and control of vibration radiation noise of the shell of the multifunctional straw kneading machine according to claim 2 is characterized in that: The method of numerically simulating the airflow-material-mechanical structure coupled flow field inside the multifunctional straw shredder using the CFD-DEM coupling method includes: Calculate the airflow field through the CFD model until convergence; Determine the position and volume fraction of the material particles according to the material particle motion equation, and calculate the airflow force on the material particles, and iterate the calculation until one CFD time step; DEM recalculates the position and velocity of material particles according to the force conditions, and synchronizes the updated particle information to CFD until convergence again.

4. The method for numerical prediction and control of vibration radiation noise of the housing of the multifunctional straw kneading machine according to claim 1 is characterized in that: Based on the vibration excitation source of the multifunctional straw shredder shell, the method for numerically simulating the vibration response of the multifunctional straw shredder shell includes: The finite element model of the shell of the multifunctional straw shredder is established, and after dividing the structural grid, the first six free modal frequencies and vibration shapes of the shell of the multifunctional straw shredder are solved; On the basis of the free modal calculation results of the shell, the harmonic response analysis based on the modal superposition method was used to numerically simulate the vibration response of the shell of the multifunctional straw shredding machine. The modal analysis module and the harmonic response analysis module were connected in ANSYS Workbench to realize data sharing between the two modules.

5. The method for numerical prediction and control of vibration radiation noise of the shell of the multifunctional straw kneading machine according to claim 1 is characterized in that: The method for controlling the vibration radiation noise of the shell of the multifunctional straw kneading machine includes: The shell of the multifunctional straw shredder is divided into sections, and the ATV method is used to analyze the acoustic contribution of the panels at the peak frequency points of the shell vibration radiation noise to determine the panels of the shell that need to be optimized. For the panels that need to be optimized for the shell of the multifunctional straw shredder, the number and size of the reinforcing ribs are selected according to the size of the corresponding area; Perform vibration response analysis on the improved housing and calculate the maximum vibration velocity; Based on the maximum vibration velocity, the verified noise prediction model and numerical calculation method are used to calculate the vibration radiation noise of the shell of the multifunctional straw shredder after structural improvement.

6. A numerical prediction and control system for vibration radiation noise of a multifunctional straw kneading machine housing, the system being used to implement the method described in any one of claims 1 to 5, characterized in that: include: Calculation module, simulation module, prediction module and control module; The calculation module is used to calculate and analyze the vibration excitation source of the shell of the multifunctional straw kneading machine; The simulation module is used to perform numerical simulation on the vibration response of the shell of the multifunctional straw shredding machine based on the vibration excitation source of the shell of the multifunctional straw shredding machine; The prediction module is used to predict the vibration radiation noise of the shell of the multifunctional straw shredding machine by using the ATV and MATV methods based on the numerical simulation results of the vibration response of the shell of the multifunctional straw shredding machine; The control module is used to control the vibration radiation noise of the shell of the multifunctional straw kneading machine based on the prediction result of the vibration radiation noise of the shell of the multifunctional straw kneading machine.

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