A piezoelectric energy harvesting method for ship base based on structural acoustic intensity method

Abstract

This invention discloses a piezoelectric energy harvesting method for ship pedestals based on structural acoustic intensity, belonging to the interdisciplinary field of structural strength and energy harvesting. This invention solves the problem of low harvesting efficiency in traditional vibration energy harvesting methods. First, a high-precision simulation environment is constructed through finite element modeling and setting of operating parameters. Then, an excitation frequency consistent with actual operating conditions is applied at the engine location to obtain the structural dynamic response. Next, the structural strength vector at each point inside the structure is calculated based on displacement field data to obtain the structural strength vector field. Finally, piezoelectric elements are placed at the location with the highest structural strength. This method can directly harvest energy along the main energy transmission path, significantly improving energy harvesting efficiency and enabling more efficient capture of vibration energy. This method can be applied to piezoelectric energy harvesting for ship pedestals.

Description

Technical Field

[0001] This invention belongs to the technical field of structural dynamics, structural strength and energy harvesting, and specifically relates to a piezoelectric energy harvesting method for ship bases based on structural acoustic intensity method. Background Technology

[0002] The ship's base is a critical load-bearing structure for the ship's propulsion system. Its main function is to provide a stable mounting foundation for large equipment such as engines and to withstand the static loads and dynamic excitations generated by the equipment's operation. Because ship engines generate continuous and intense vibrations during operation, this vibrational energy is transmitted to the hull through the base structure, leading not only to structural fatigue and noise problems but also to energy waste. Therefore, the ship's base is both a vibration propagation path and a potential site for vibrational energy harvesting.

[0003] Traditional vibration energy harvesting methods typically involve attaching piezoelectric elements to the locations of maximum structural displacement. The underlying principle is that these locations usually possess high strain energy, thus generating a high voltage output. While this method relies on simple displacement or strain measurements and is relatively easy to operate, it has significant limitations: the location of maximum displacement is not always the region with the highest energy flux density, potentially leading to low energy harvesting efficiency. This is especially true in complex structures where the transmission path and distribution of vibration energy are not solely determined by displacement amplitude. Summary of the Invention

[0004] The purpose of this invention is to solve the problem of low acquisition efficiency of traditional vibration energy acquisition methods, and to propose a piezoelectric energy acquisition method for ship base based on structural acoustic intensity method.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0006] A method for harvesting piezoelectric energy from a ship's base based on structural acoustic intensity method, the method specifically includes the following steps:

[0007] Step 1: Construct a finite element model of the ship's base structure and set the damping parameters and boundary constraints of the finite element model;

[0008] Step 2: Apply excitation load to the ship engine mounting location in the finite element model of the ship base structure to calculate the displacement of each node on the mounting panel of the finite element model.

[0009] Step 3: Calculate the structural strength of each node location based on the displacement of each node on the surface of the mounting panel;

[0010] Step 4: Determine the location of the piezoelectric elements based on the structural strength distribution on the mounting panel, and then use the arranged piezoelectric elements to collect energy.

[0011] Furthermore, the specific process of step one is as follows:

[0012] Step 1: Create a finite element model of the ship's base structure in the CAD model, and then import the created finite element model into ANSYS software.

[0013] Steps 1 and 2: Divide each region of the finite element model of the ship's base structure into tetrahedrals;

[0014] Step 13: Set the damping parameters of the finite element model of the ship's base structure and apply boundary constraints at the connection between the base and the hull.

[0015] Step 14: Perform modal analysis on the finite element model of the ship's base structure to obtain the natural frequencies, and determine whether the difference between the natural frequencies obtained from the modal analysis and the actual natural frequencies is less than a threshold.

[0016] If the difference between the natural frequency obtained from modal analysis and the actual natural frequency is less than the threshold, then the final damping parameters and boundary constraints of the finite element model of the ship's base structure are obtained.

[0017] Otherwise, return to step one or three and readjust the damping parameters and boundary constraints.

[0018] Furthermore, the constitutive material of the finite element model of the ship base structure is a uniform linear elastic material, and the property parameters of the elastic material are defined.

[0019] Furthermore, the specific process of step two is as follows:

[0020] Step 2: Under the final damping parameters and boundary constraints determined in Step 1, perform modal analysis on the finite element model of the ship's base structure to obtain the resonant frequency;

[0021] Step 22: Determine the excitation frequency based on the resonant frequency, and apply the excitation load at the ship engine installation location according to the determined excitation frequency;

[0022] Steps 2 and 3: Perform harmonic response analysis on the finite element model of the ship's base structure to obtain the vibration displacement of each node of the tetrahedron;

[0023] Step 24: Grid the surface of the mounting panel. Based on the vibration displacement of all nodes on the surface of the mounting panel obtained in Step 23, perform curve fitting to obtain the vibration displacement of each grid node on the surface of the mounting panel.

[0024] Furthermore, the excitation frequency is not equal to the resonance frequency, and the excitation frequency is within the actual operating frequency range of the ship engine.

[0025] Furthermore, the specific process of step three is as follows:

[0026] Position coordinates are The structural strength of the nodes is:

[0027]

[0028] in, The position coordinates are The node at Structural strength in the direction, The position coordinates are The node at Structural strength in the direction, The position coordinates are The structural strength of the nodes.

[0029] Furthermore, the position coordinates are The node at direction and The structural strengths in the directions are as follows:

[0030]

[0031] in, The position coordinates are The vibration displacement of the node, express conjugate, means taking an imaginary number, Poisson's ratio, For bending stiffness, Indicates the excitation frequency.

[0032] Furthermore, the bending stiffness for:

[0033]

[0034] in, For the thickness of the mounting panel, It is Young's modulus.

[0035] Furthermore, the specific process of step four is as follows:

[0036] Step 4: 1. Determine the node with the largest structural strength amplitude on the upper surface of the mounting panel, and install the first piezoelectric sheet at the node with the largest structural strength amplitude, so that the center of the first piezoelectric sheet coincides with the node with the largest structural strength amplitude;

[0037] A second piezoelectric element is simultaneously installed on the lower surface of the mounting panel, ensuring that the positions of the second piezoelectric element and the first piezoelectric element are strictly aligned.

[0038] Step 4.2: Energy is harvested using the piezoelectric sheets attached to the upper and lower surfaces of the mounting panel.

[0039] The beneficial effects of this invention are:

[0040] This invention first constructs a high-precision simulation environment through finite element modeling and setting of operating parameters. Then, an excitation frequency matching the actual operating conditions is applied, and the dynamic response of the structure is obtained by excitation at the engine location. Subsequently, based on displacement field data, the structural strength vector at each point inside the structure is calculated, resulting in a structural strength vector field. The structural strength vector comprehensively reflects the phase relationship between internal forces and velocities, and its magnitude directly characterizes the rate and direction of energy transfer within the structure. Finally, piezoelectric elements are placed at the location of maximum structural strength. This invention overcomes the limitations of traditional energy harvesting devices that are only deployed based on displacement amplitude. By using the structural acoustic intensity method to accurately locate the vibration energy accumulation area, it can directly collect energy along the "main channel" of energy transmission, significantly improving energy harvesting efficiency and enabling more efficient capture of vibration energy.

[0041] The method of this invention provides a reliable approach for the scientific utilization of ship vibration energy, and at the same time establishes a quantitative basis and engineering paradigm for the deployment of energy harvesting devices in complex structures. Attached Figure Description

[0042] Figure 1 This is a flowchart of a piezoelectric energy harvesting method for ship bases based on structural acoustic intensity method according to the present invention;

[0043] Figure 2 This is a schematic diagram of the ship's base structure;

[0044] Figure 3 A schematic diagram showing the displacement amplitude of each node on the surface of the mounting panel;

[0045] In this context, the planar coordinates represent the position of the node, and the third dimension represents the displacement of the node.

[0046] Figure 4 A three-dimensional schematic diagram of the structural strength amplitude of each node on the mounting panel;

[0047] Among them, the planar coordinates represent the position of the node, and the third dimension represents the structural strength amplitude;

[0048] Figure 5 This is a schematic diagram of a structure in which a piezoelectric sheet is attached to the upper surface at the point of maximum structural strength.

[0049] Figure 6 A schematic diagram of the connection structure between the ship's base and the piezoelectric element;

[0050] Figure 7 This is a schematic diagram of a structure where a piezoelectric element is attached at the point of maximum displacement.

[0051] Figure 8 A comparison of voltage amplitudes collected when the piezoelectric element is attached at the point of maximum displacement versus at the point of maximum structural strength;

[0052] In the figure, V represents the voltage measured in the frequency domain. Detailed Implementation

[0053] Specific implementation method one: Combining Figure 1 This embodiment describes a method for harvesting piezoelectric energy from a ship's base based on structural acoustic intensity. The method specifically includes the following steps:

[0054] Step 1: Construct a finite element model of the ship's base structure and set the damping parameters and boundary constraints of the finite element model;

[0055] Step 1: Create a finite element model of the ship's base structure in the CAD model, and then import the created finite element model into ANSYS software. By importing the finite element model into ANSYS software, the geometry of the finite element model can be cleaned and simplified, small features can be removed, and modeling efficiency can be improved.

[0056] The constitutive material of the finite element model of the ship's base structure is selected as a uniform linear elastic material, and the property parameters of the elastic material are defined.

[0057] Step 1 and Step 2: Divide each region of the finite element model of the ship's base structure into tetrahedrals according to the structural characteristics and analysis requirements. During the division process, it is necessary to balance the accuracy of key regions with the optimization of overall computational resources.

[0058] Step 13: Based on structural characteristics and materials engineering experience, set the damping parameters of the finite element model of the ship's base structure and apply boundary constraints at the connection between the base and the hull.

[0059] Step 14: Perform modal analysis on the finite element model of the ship's base structure to obtain the natural frequencies, and determine whether the difference between the natural frequencies obtained from the modal analysis and the actual natural frequencies is less than a threshold.

[0060] If the difference between the natural frequency obtained from modal analysis and the actual natural frequency is less than the threshold, then the final damping parameters and boundary constraints of the finite element model of the ship's base structure are obtained.

[0061] Otherwise, return to step one or three and readjust the damping parameters and boundary constraints.

[0062] Step one of this invention involves iteratively correcting and optimizing the damping parameters and boundary conditions in the finite element model. This ensures that the finite element model accurately reflects the actual dynamic characteristics of the ship's base, providing a highly reliable foundation for subsequent structural strength calculations and avoiding misjudgments of energy harvesting locations due to model distortion. The finite element model of the ship's base structure obtained in step one is as follows: Figure 2 As shown, 1 is a support frame, 2 is a mounting panel, 3 is a square base, and 4 is a support foot. The mounting panel 2 is fixed to the square base 3 by the support frame 1, and the square base 3 is provided with a support foot 4 at the bottom.

[0063] Step 2: Apply excitation load to the ship engine mounting location in the finite element model of the ship base structure to calculate the displacement of each node on the mounting panel of the finite element model.

[0064] Step 2: Under the final damping parameters and boundary constraints determined in Step 1, perform modal analysis on the finite element model of the ship's base structure to obtain the resonant frequency;

[0065] Step 22: Determine the excitation frequency based on the resonant frequency, and apply the excitation load at the ship engine installation location according to the determined excitation frequency;

[0066] The excitation frequency is not equal to the resonance frequency, and the excitation frequency is within the actual operating frequency range of the ship engine.

[0067] Steps 2 and 3: Perform harmonic response analysis on the finite element model of the ship's base structure to obtain the vibration displacement of each node of the tetrahedron;

[0068] Step 24: Grid the surface of the mounting panel. Based on the vibration displacement of all nodes on the surface of the mounting panel obtained in Step 23, perform curve fitting (it should be noted that although the node vibration displacement obtained in Step 23 includes not only the nodes on the surface of the mounting panel, only the nodes on the surface of the mounting panel are needed here) to obtain the vibration displacement of each grid node on the surface of the mounting panel.

[0069] Step two of this invention first identifies the resonant frequency by performing modal analysis on the finite element model of the ship's base. Then, it selects the excitation frequency within the actual operating frequency range of the engine while avoiding resonance. Next, it calculates the steady-state response of the structure under this simple harmonic excitation through harmonic response analysis. Finally, it re-meshes the surface of the mounting panel and obtains the result through curve fitting. Figure 3 The vibration displacements of each node shown provide reliable data support for subsequent calculations.

[0070] Step 3: Calculate the structural strength of each node location based on the displacement of each node on the surface of the mounting panel;

[0071] Wherein, the position coordinates are The structural strength of the nodes is:

[0072]

[0073] in, The position coordinates are The node at Structural strength in the direction, The position coordinates are The node at Structural strength in the direction, The position coordinates are The structural strength of the nodes;

[0074]

[0075] in, The position coordinates are The vibration displacement of the node, express conjugate, means taking an imaginary number, Poisson's ratio, For bending stiffness, Indicates the excitation frequency;

[0076]

[0077] in, Indicates Young's modulus. This indicates the thickness of the mounting panel.

[0078] In step three of this invention, the introduction of structural strength vector calculation allows for a complete characterization of the amplitude and direction of bending wave energy transfer within the mounting panel structure. This overcomes the shortcomings of traditional displacement methods that neglect phase information, providing a rigorous theoretical basis for accurately locating the main energy transmission path. After obtaining the structural strength components and vectors in the x and y directions at each node position on the mounting panel, the amplitude of the structural strength at each node position can be obtained, thus revealing the structural strength distribution on the surface of the ship base mounting panel. This provides a basis for piezoelectric element positioning, ensuring that the piezoelectric element placement position captures the maximum effective structural strength.

[0079] Step 4: Determine the location of the piezoelectric elements based on the structural strength distribution on the mounting panel, and then use the arranged piezoelectric elements to harvest energy;

[0080] Step 4: 1. Determine the node with the largest structural strength amplitude on the upper surface of the mounting panel. Install the first piezoelectric element at the node with the largest structural strength amplitude, ensuring that the center of the first piezoelectric element coincides with the node with the largest structural strength amplitude. Figure 5 As shown;

[0081] A second piezoelectric element is simultaneously installed on the lower surface of the mounting panel, so that the positions of the second piezoelectric element and the first piezoelectric element are strictly corresponding, that is, the second piezoelectric element and the first piezoelectric element are symmetrical with respect to the mounting panel.

[0082] Step 4.2: Energy is harvested using the piezoelectric sheets attached to the upper and lower surfaces of the mounting panel.

[0083] This invention generates three-dimensional images based on the structural strength amplitude of each node on the mounting panel, such as... Figure 4 As shown, the concentrated areas of structural strength are analyzed through three-dimensional image analysis. By combining double-sided synchronously bonded piezoelectric sheets, bidirectional capture of vibration energy is achieved, significantly improving energy recovery efficiency. Simultaneously, it provides an intuitive and reliable engineering implementation path for the deployment of energy harvesting devices in complex structures.

[0084] To compare the effectiveness of the method of this invention, the voltage output was verified in the excitation frequency domain, such as... Figure 6 As shown, the voltage between the first piezoelectric element 5 on the upper surface and the second piezoelectric element 6 on the lower surface can be obtained through an external circuit (including a capacitor C, an inductor L, and a resistor R) connected to the piezoelectric elements on the upper and lower surfaces; then, the frequency domain voltage can be obtained based on the measured voltage. Figure 7 As shown, the third piezoelectric element 7 is attached to the high-value distribution area of ​​the node displacement on the mounting panel. By attaching the same piezoelectric element to the area of ​​maximum displacement to collect the voltage in the area of ​​maximum displacement, interference caused by differences in piezoelectric material properties, shape, size, etc., can be eliminated from the output voltage. A comparison of the voltage amplitudes collected by attaching piezoelectric elements at the location of maximum displacement and the location of maximum structural strength is shown below. Figure 8 As shown in the figure, it can be seen that attaching the piezoelectric element at the location of maximum structural strength results in a larger voltage than attaching it at the location of maximum displacement, thus improving the efficiency of vibration energy acquisition.

[0085] In summary, this invention, by identifying the location of maximum structural strength and attaching piezoelectric elements at this location, allows for direct energy collection along the "main pathway" of energy transmission. Theoretically, this enables more efficient capture of vibration energy, significantly improving the efficiency of vibration energy acquisition. Furthermore, in-depth analysis of structural energy flow contributes to understanding vibration transmission mechanisms, providing valuable assistance for vibration reduction, noise control, and structural health monitoring in ships. This invention can also serve as a reference for vibration energy acquisition in other similar fields.

[0086] The above examples of the present invention are merely illustrative of the computational model and process of the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is impossible to exhaustively list all possible implementations here. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for harvesting piezoelectric energy from a ship's base based on structural acoustic intensity method, characterized in that, The method specifically includes the following steps: Step 1: Construct a finite element model of the ship's base structure and set the damping parameters and boundary constraints of the finite element model; Step 2: Apply excitation load to the ship engine mounting location in the finite element model of the ship base structure to calculate the displacement of each node on the mounting panel of the finite element model. Step 3: Calculate the structural strength of each node location based on the displacement of each node on the surface of the mounting panel; The specific process of step three is as follows: Position coordinates are The structural strength of the nodes is: in, The position coordinates are The node at Structural strength in the direction, The position coordinates are The node at Structural strength in the direction, The position coordinates are The structural strength of the nodes; The position coordinates are The node at direction and The structural strengths in the directions are as follows: in, The position coordinates are The vibration displacement of the node, express conjugate, means taking an imaginary number, Poisson's ratio, For bending stiffness, Indicates the excitation frequency; Step 4: Determine the location of the piezoelectric elements based on the structural strength distribution on the mounting panel, and then use the arranged piezoelectric elements to harvest energy; The specific process of step four is as follows: Step 4:

1. Determine the node with the largest structural strength amplitude on the upper surface of the mounting panel, and install the first piezoelectric sheet at the node with the largest structural strength amplitude, so that the center of the first piezoelectric sheet coincides with the node with the largest structural strength amplitude; A second piezoelectric element is simultaneously installed on the lower surface of the mounting panel, ensuring that the positions of the second piezoelectric element and the first piezoelectric element are strictly aligned. Step 4.2: Energy is harvested using the piezoelectric sheets attached to the upper and lower surfaces of the mounting panel.

2. The method for harvesting piezoelectric energy from a ship's base based on structural acoustic intensity method according to claim 1, characterized in that, The specific process of step one is as follows: Step 1: Create a finite element model of the ship's base structure in the CAD model, and then import the created finite element model into ANSYS software. Steps 1 and 2: Divide each region of the finite element model of the ship's base structure into tetrahedrals; Step 13: Set the damping parameters of the finite element model of the ship's base structure and apply boundary constraints at the connection between the base and the hull. Step 14: Perform modal analysis on the finite element model of the ship's base structure to obtain the natural frequencies, and determine whether the difference between the natural frequencies obtained from the modal analysis and the actual natural frequencies is less than a threshold. If the difference between the natural frequency obtained from modal analysis and the actual natural frequency is less than the threshold, then the final damping parameters and boundary constraints of the finite element model of the ship's base structure are obtained. Otherwise, return to step one or three and readjust the damping parameters and boundary constraints.

3. The method for harvesting piezoelectric energy from a ship's base based on structural acoustic intensity method according to claim 2, characterized in that, The constitutive material of the finite element model of the ship's base structure is a uniform linear elastic material, and the property parameters of the elastic material are defined.

4. The method for harvesting piezoelectric energy from a ship's base based on structural acoustic intensity method according to claim 3, characterized in that, The specific process of step two is as follows: Step 2: Under the final damping parameters and boundary constraints determined in Step 1, perform modal analysis on the finite element model of the ship's base structure to obtain the resonant frequency; Step 22: Determine the excitation frequency based on the resonant frequency, and apply the excitation load at the ship engine installation location according to the determined excitation frequency; Steps 2 and 3: Perform harmonic response analysis on the finite element model of the ship's base structure to obtain the vibration displacement of each node of the tetrahedron; Step 24: Grid the surface of the mounting panel. Based on the vibration displacement of all nodes on the surface of the mounting panel obtained in Step 23, perform curve fitting to obtain the vibration displacement of each grid node on the surface of the mounting panel.

5. The method for harvesting piezoelectric energy from a ship's base based on structural acoustic intensity method according to claim 4, characterized in that, The excitation frequency is not equal to the resonance frequency, and the excitation frequency is within the actual operating frequency range of the ship engine.

6. The method for harvesting piezoelectric energy from a ship's base based on structural acoustic intensity method according to claim 5, characterized in that, The bending stiffness for: in, For the thickness of the mounting panel, It is Young's modulus.

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