A closed cycle PTO dual cavity OWC wave energy device and numerical simulation method thereof

Abstract

The application discloses a closed circulation PTO double-cavity OWC wave energy device and a numerical simulation method thereof, and relates to the technical field of ocean clean energy development.The wave energy device comprises an OWC chamber, a high-pressure chamber and a low-pressure chamber, the high-pressure chamber and the low-pressure chamber are arranged side by side above the OWC chamber, the high-pressure chamber is communicated with the OWC chamber through an upward one-way valve, the low-pressure chamber is communicated with the OWC chamber through a downward one-way valve, the high-pressure chamber and the low-pressure chamber are communicated through a turbine, and the bottom of the OWC chamber comprises two sub-air chambers.The wave energy device has the advantages of the closed circulation PTO and the double-air-chamber structure, can effectively reduce the fluctuation of the aerodynamic power passing through the turbine, and can improve the overall energy acquisition efficiency.

Description

Technical Field

[0001] This invention relates to the field of marine clean energy development technology, and in particular to a closed-loop PTO dual-cavity OWC wave energy device and its numerical simulation method. Background Technology

[0002] A traditional oscillating water column (OWC) device consists of an air chamber with an open bottom connected to seawater and an air turbine system connected to the atmosphere at the top. Its working principle lies in the reciprocating oscillation of the water column within the air chamber under the influence of waves. The rise and fall of the water column, similar to piston motion, drives the periodic expulsion and intake of air within the air chamber, thus forming a high-speed reciprocating airflow that powers the air turbine to generate electricity. To handle the reciprocating airflow, traditional OWC devices typically employ self-rectifying bidirectional turbines. However, these turbines are less efficient than unidirectional turbines, and because the airflow direction always reverses, the aerodynamic power output of the air turbine fluctuates significantly, limiting the device's energy conversion efficiency and operational stability.

[0003] Existing open-circuit turbine (OWC) units mostly employ traditional open-circuit PTOs, where the upper part of the air chamber is directly connected to the external atmosphere via an air turbine. Under wave excitation, the water column inside the air chamber oscillates back and forth, acting like a piston to drive air periodically out and in, thus forming a reciprocating airflow that propels the air turbine to rotate. Due to the continuous reversal of the airflow direction, traditional OWC units are typically equipped with self-rectifying bidirectional turbines. However, this structure has two limitations: first, the aerodynamic efficiency of self-rectifying bidirectional turbines is lower than that of unidirectional turbines; second, the reciprocating airflow causes periodic fluctuations in aerodynamic power, limiting the energy conversion efficiency and output power stability of the unit.

[0004] To address the aforementioned issues, a closed-loop PTO (Pneumatic Rotation Toll Collection) system was proposed. In this configuration, a high-pressure chamber and a low-pressure chamber are added above the conventional OWC (Overflow-Controlled Cycle) unit, each connected to the oscillating water column chamber via one-way valves. A closed pneumatic loop is formed by a one-way turbine mechanism. During the oscillation of the water column, a stable pressure difference is created between the high and low-pressure chambers, driving a continuous unidirectional airflow through the turbine, thus converting reciprocating flow to unidirectional flow. This mechanism effectively reduces aerodynamic power fluctuations and improves turbine operational stability. However, while the introduction of the one-way valve improves flow characteristics, it also introduces additional energy losses, resulting in a certain degree of reduction in the overall system output power.

[0005] The above content is only used to help understand the technical solution of the present invention and does not represent an admission that the above content is prior art. Summary of the Invention

[0006] To address the drawback that while introducing a one-way valve into a closed-loop PTO improves flow characteristics, it also introduces additional energy losses, leading to a certain degree of reduction in the overall system output power, this invention proposes a closed-loop PTO dual-chamber OWC wave energy device and its numerical simulation method. This invention combines the advantages of both closed-loop PTO and dual-chamber structure, effectively reducing aerodynamic power fluctuations through the turbine and improving overall energy harvesting efficiency.

[0007] The objective of this invention is achieved through the following technical solutions: A closed-loop PTO dual-chamber OWC wave energy device includes an OWC chamber, a high-pressure chamber, and a low-pressure chamber. The high-pressure chamber and the low-pressure chamber are arranged side by side above the OWC chamber. The high-pressure chamber is connected to the OWC chamber through an upward one-way valve, and the low-pressure chamber is connected to the OWC chamber through a downward one-way valve. The high-pressure chamber and the low-pressure chamber are connected by a turbine. The bottom of the OWC chamber includes two sub-chambers.

[0008] The present invention also adopts the following technical solution: A numerical simulation method for a closed-loop PTO dual-cavity OWC wave energy device, used in the wave energy device provided by this invention, includes the following steps: Step 1: Based on Sesam software, establish a wetted surface model of the wave energy device; import the model data into OrcaWave software for hydrodynamic analysis to obtain hydrodynamic parameters; Step 2: Based on the obtained hydrodynamic parameters, calculate the wave load using the first-order wave force transfer function; Step 3: Based on air thermodynamics, establish a numerical model of the wave energy device on the Matlab platform, including establishing an overall model based on dynamics theory, and establishing models of air quality and pressure changes in the OWC chamber, high-pressure chamber, and low-pressure chamber based on air thermodynamics theory; and solve the model.

[0009] Furthermore, in step 2, the wave load is calculated by combining the wave spectrum and using potential flow theory for modeling. Based on the principle of linear superposition, the irregular wave is decomposed into multiple regular wave units of different frequencies. The first-order wave force transfer function obtained by OrcaWave software is used to determine the amplitude and phase of the wave force on the wave energy device at each frequency. The wave forces of all regular wave units are linearly superimposed to obtain the wave excitation force.

[0010] Furthermore, in step 3, the overall model is established through the following steps: Step 3.1.1: Based on dynamic theory, the overall three-degree-of-freedom equations of motion for the system are constructed as follows: ; In the formula, The system's quality matrix, For heave displacement, For heave acceleration, For wave excitation force, For radiation force, For still water restoring power, The force generated by the PTO system, For viscous damping force, expressed as ,in The density of seawater, The viscous damping coefficient is... Let be the cross-sectional area of ​​the floating body and the water column. The velocity of the buoy and the water column.

[0011] Furthermore, in step 3.1.1, Represented as: ; In the formula, The pressure difference is the instantaneous pressure inside the chamber minus the standard atmospheric pressure under equilibrium conditions. When air pressure acts on the upper surface of the OWC chamber, Acting on the buoyant body, at this time The cross-sectional area of ​​the OWC chamber is... Take the positive sign; when air pressure acts on the surfaces of the two water columns, When it acts on the water column, at this time Let be the cross-sectional area of ​​the water column. Take the negative sign.

[0012] Furthermore, in step 3, models of the pressure change rates of the OWC chamber, high-pressure chamber, and low-pressure chamber are established through the following steps: Step 3.2.1: Construct the mass balance formulas for the air in the OWC chamber, high-pressure chamber, and low-pressure chamber, as follows: ; In the formula, The mass change rate of the gas in the chamber. For gas density, The volume of the chamber; Step 3.2.2: Construct the expressions for air pressure and density, as follows: ; ; In the formula, p is the air pressure at any time, and ρ is the air density at any time. Standard atmospheric pressure The density of air at standard atmospheric pressure. Specific heat ratio, For isobaric specific heat, Specific heat at constant volume; Step 3.2.3: Substitute the instantaneous air pressure and density in the OWC chamber, high-pressure chamber, and low-pressure chamber into the formula in Step 3.2.2 to obtain: ; In the formula, The instantaneous air pressure in the chamber. The instantaneous air density in the chamber; Step 3.2.4: Linearize the relationship between instantaneous air pressure and density in the OWC chamber, high-pressure chamber, and low-pressure chamber to obtain... Approximate expression: ; Differentiating it, we get: ; Step 3.2.5: Construct the volume formula for the OWC chamber, as follows: ; In the formula, Let be the volume of the OWC chamber in equilibrium. , The cross-sectional area of ​​the OWC chamber is... The height of the OWC chamber under equilibrium conditions. , These are the cross-sectional areas of the two water columns, respectively. , , , These represent the heave displacements of the floating body and the two water columns, respectively. Step 3.2.6: Differentiate the formula in Step 3.2.5 to obtain the volume change rate of the OWC chamber, as follows: ; In the formula, , , These are the sway velocities of the floating body and the two water columns, respectively. Step 3.2.7: Update the mass balance formula for the air in the chamber in Step 3.2.1 according to Steps 3.2.4 and 3.2.6, as follows: ; Step 3.2.8: Apply the formula from Step 3.2.7 to the OWC chamber, high-pressure chamber, and low-pressure chamber to obtain the linearized expressions for the mass flow rates of the three chambers, as follows: ; In the formula, The mass flow rate of air from the OWC chamber to the high-pressure chamber. The mass flow rate of air from the low-pressure chamber to the OWC chamber. The mass flow rate of air passing through the unidirectional turbine. The instantaneous air density of the OWC chamber. , , These represent the air densities of the OWC chamber, high-pressure chamber, and low-pressure chamber under equilibrium conditions. , , These represent the air pressures of the OWC chamber, high-pressure chamber, and low-pressure chamber under equilibrium conditions. , , These represent the pressure change rates of the OWC chamber, high-pressure chamber, and low-pressure chamber, respectively. , Let these be the volumes of the high-pressure chamber and the low-pressure chamber, respectively. ; Step 3.2.9: The mass flow rate of air through two one-way valves and one one-way turbine is modeled by the following formula: ; ; ; In the formula, , , These are the flow coefficients of the two one-way valves and the one-way turbine, respectively. , , These are the instantaneous air densities of the OWC chamber, high-pressure chamber, and low-pressure chamber, respectively. , , These are the instantaneous air pressures of the OWC chamber, high-pressure chamber, and low-pressure chamber, respectively. , , These are the surface areas of the two one-way valves and the one-way turbine, respectively. Step 3.2.10: Based on the formulas in Steps 3.2.8 and 3.2.9, the expressions for the pressure change rates of the OWC chamber, high-pressure chamber, and low-pressure chamber are obtained as follows: ; ; .

[0013] Furthermore, in step 3.2.9, , , The surface areas of the two one-way valves and the one-way turbine are respectively calculated using the following formula: ; In the formula, Let be the damping coefficients of the two one-way valves. This is the damping coefficient of a unidirectional turbine.

[0014] Furthermore, a model of the instantaneous aerodynamic power of the unidirectional turbine is established through the following steps: Step 3.2.11: Construct the expression for the instantaneous aerodynamic power of the unidirectional turbine, as follows: ; Step 3.2.12: Update the expression for the instantaneous aerodynamic power of the unidirectional turbine in Step 3.2.11 according to the formula for the mass flow rate of the unidirectional turbine in Step 3.2.9, as follows: .

[0015] Compared with the prior art, the beneficial effects of this invention are as follows: 1. To improve energy harvesting efficiency, this invention introduces a dual-chamber structure into the closed-loop PTO OWC device, dividing the oscillating water column chamber into two sub-chambers by adding a baffle in the middle. By adjusting the phase difference of the two water columns, the energy harvesting bandwidth and energy harvesting efficiency of the device can be improved. Therefore, the device of this invention combines the advantages of closed-loop PTO and dual-chamber structure, effectively reducing aerodynamic power fluctuations through the turbine while improving overall energy harvesting efficiency.

[0016] 2. The numerical simulation method for wave energy devices of the present invention is based on dynamic theory, potential flow theory, and air thermodynamics theory. For the device provided by the present invention, an integrated coupled analysis model and dynamic analysis model including a dual-cavity phase coupling mechanism and a nonlinear PTO model are constructed to accurately characterize the dynamic characteristics of the aerodynamic process, the multi-cavity coupling mechanism, and nonlinear flow losses, thereby achieving high-precision prediction of the system's energy conversion efficiency and power stability. Through numerical simulation, the coupling mechanism between the floating body, water column, and PTO system is revealed. The dynamic response of the closed-loop PTO dual-cavity OWC device under different sea conditions can be calculated, revealing the impact of key parameters on the device's performance. The device's performance in terms of aerodynamic power and wave characteristics is demonstrated, verifying its feasibility and superiority. This provides key theoretical support for the structural optimization, energy harvesting efficiency, and stability design of OWC devices, contributing to the efficient development of wave energy resources. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a closed-loop PTO dual-cavity OWC wave energy device. Figure 2A flowchart of a numerical simulation method for a closed-loop PTO dual-cavity OWC wave energy device; Figure 3 A schematic diagram of the main dimensions of a closed-loop PTO dual-cavity OWC wave energy device platform. Figure 4 The wave force experienced by the floating body and the water column; Figure 5 This represents the displacement of the water column relative to the floating body. Figure 6 For changes in air quality in the OWC chamber, high-pressure chamber, and low-pressure chamber; Figure 7 This refers to the pressure changes within the OWC chamber, high-pressure chamber, and low-pressure chamber. Figure 8 The aerodynamic power of open OWC, closed single-chamber OWC, and closed double-chamber OWC; Figure 9 The average aerodynamic power of open OWC, closed single-chamber OWC, and closed double-chamber OWC; Figure 10 For open OWC, closed single-cavity OWC, and closed double-cavity OWC, the aerodynamic power fluctuation is considered. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0019] Example 1: A closed-loop PTO dual-cavity OWC wave energy device, such as Figure 1 As shown, it includes: an OWC chamber, a high-pressure chamber, and a low-pressure chamber. The high-pressure chamber and the low-pressure chamber are arranged side by side above the OWC chamber. The high-pressure chamber is connected to the OWC chamber through an upward one-way valve, and the low-pressure chamber is connected to the OWC chamber through a downward one-way valve. The high-pressure chamber and the low-pressure chamber are connected by a turbine. The bottom of the OWC chamber includes two sub-chambers.

[0020] In this embodiment of the wave energy device, to reduce aerodynamic power fluctuations, a closed-loop PTO design is introduced. Based on the traditional OWC structure, a high-pressure chamber and a low-pressure chamber are added above the OWC chamber. Both are connected to the OWC chamber via one-way valves and form a closed aerodynamic loop through a one-way turbine. Its working principle is as follows: when the water column rises, the air pressure inside the OWC chamber increases, and air flows into the high-pressure chamber through the one-way valve; when the water column falls, the air pressure inside the OWC chamber decreases, and air in the low-pressure chamber flows into the OWC chamber through the one-way valve.

[0021] The oscillation of the water column no longer generates reciprocating airflow. Instead, the rising water column forces air into the high-pressure chamber, and the falling water column draws air out of the low-pressure chamber. This creates a relatively stable pressure difference between the high-pressure and low-pressure chambers, allowing the airflow to pass through a unidirectional turbine and continuously perform work in one direction. Due to the action of the one-way valve, the gas can only flow along a fixed path, forming a closed loop. The stable and unidirectional airflow through the air turbine effectively reduces aerodynamic power fluctuations passing through the turbine.

[0022] The wave energy device in this embodiment incorporates two one-way valves, which results in additional energy loss and an unavoidable reduction in output power. To improve energy harvesting efficiency, this embodiment introduces a dual-chamber structure, dividing the oscillating water column chamber into two sub-chambers by adding a partition in the middle. By adjusting the phase difference between the two water columns, the energy harvesting bandwidth and energy harvesting efficiency of the device can be improved.

[0023] In summary, the wave energy device of this embodiment combines the advantages of a closed-loop PTO and a dual-chamber OWC device with a dual-chamber structure, effectively reducing the aerodynamic power fluctuations through the turbine and improving the overall energy harvesting efficiency.

[0024] Example 2: A numerical simulation method for a closed-loop PTO dual-cavity OWC wave energy device, such as Figure 2 As shown, it includes the following steps: Step 1: Based on Sesam software, establish a wetted surface model of the wave energy device; import the model data into OrcaWave software for hydrodynamic analysis to obtain hydrodynamic parameters.

[0025] In this embodiment, as Figure 3 (The upper gray part in the figure is the floating body, and the lower sphere is the counterweight) and as shown in Table 1, a wet surface model of the wave energy device in Example 1 is established based on Sesam software (the wet surface model refers to the part of the device that is submerged in water when it is in equilibrium, and is used for hydrodynamic calculations).

[0026] Table 1. Principal Scale Parameters

[0027] Step 2: Based on the obtained hydrodynamic parameters, the wave load is calculated using the first-order wave force transfer function.

[0028] Actual ocean waves are irregular waves, and their incident wave period, wave height, and phase angle are not fixed. In numerical simulations, irregular waves are considered to be composed of an infinite number of regular waves with different periods, wave heights, and initial phases superimposed. Therefore, in this embodiment, in step 2, the wave load calculation is performed by combining the wave spectrum and using potential flow theory for modeling; based on the principle of linear superposition, the irregular wave is decomposed into multiple regular wave units of different frequencies, and the first-order wave force transfer function obtained by OrcaWave software is used to determine the amplitude and phase of the wave force experienced by the wave energy device at each frequency. By linearly superimposing the wave forces of all regular wave units, the wave excitation force can be obtained. The wave forces experienced by the floating body and water column are obtained as follows: Figure 4 As shown (wave forces acting on the buoy and the water column).

[0029] Step 3: Based on air thermodynamics, establish a numerical model of the wave energy device on the Matlab platform, including establishing an overall model based on dynamics theory, and establishing models of air quality and pressure changes in the OWC chamber, high-pressure chamber, and low-pressure chamber based on air thermodynamics theory; and solve the model.

[0030] In this embodiment, step 3 involves establishing the overall model through the following steps: Step 3.1.1: Based on dynamic theory, the overall three-degree-of-freedom equations of motion for the system are constructed as follows: ; In the formula, The system's quality matrix, For heave displacement, For heave acceleration, For wave excitation force, For the radiative force, the convolution integral term is approximated by the state-space equation. For still water restoring power, The force generated by the PTO system, For viscous damping force, expressed as ,in The density of seawater, Let be the viscous damping coefficient, taken as 1.2. Let be the cross-sectional area of ​​the floating body and the water column. The velocity of the buoy and the water column.

[0031] In this embodiment, the oscillating water column is modeled using a piston model, treating it as a rigid body. A dual-chamber structure is adopted, where a baffle is added to the middle of the single-chamber cylindrical water column, dividing it into two identical semi-cylindrical water columns. The float significantly lowers the center of gravity through ballast, generating a large restoring torque. Since the OWC device mainly generates electricity through heave motion, only the heave motion of the device needs to be considered for simplicity. Based on dynamic theory, the above-mentioned three-degree-of-freedom motion equation model is constructed.

[0032] In this embodiment, the PTO system is modeled based on air thermodynamics. It is the force generated by the air pressure inside the chamber acting on the inner surface of the device, expressed as: ; In the formula, The pressure difference is the instantaneous pressure inside the chamber minus the standard atmospheric pressure under equilibrium conditions. When air pressure acts on the upper surface of the OWC chamber, Acting on the buoyant body, at this time The cross-sectional area of ​​the OWC chamber is... Take the positive sign; when air pressure acts on the surfaces of the two water columns, When it acts on the water column, at this time Let be the cross-sectional area of ​​the water column. Take the negative sign.

[0033] In this embodiment, in step 3, the pressure change rates of the OWC chamber, high-pressure chamber, and low-pressure chamber, as well as the instantaneous aerodynamic power model of the unidirectional turbine, are established through the following steps: Step 3.2.1: Construct the mass balance formula for the air inside the chamber, as follows: ; In the formula, The mass flow rate is the rate of change of the gas in the chamber. For gas density, Let be the volume of the chamber.

[0034] In this embodiment, the chambers refer to the OWC chamber, the high-pressure chamber, and the low-pressure chamber.

[0035] Step 3.2.2: Construct the expressions for air pressure and density, as follows: ; ; In the formula, p is the air pressure at any time, and ρ is the air density at any time. Standard atmospheric pressure This refers to the air density at standard atmospheric pressure. Specific heat ratio, For isobaric specific heat, This is the specific heat at constant volume.

[0036] Step 3.2.3: Substitute the instantaneous air pressure and density in the chamber into the formula of Step 3.2.2 to obtain: ; In the formula, The instantaneous air pressure in the chamber. The instantaneous air density in the chamber.

[0037] Step 3.2.4: Linearize the relationship between instantaneous air pressure and density in the chamber to obtain... Approximate expression: ; Differentiating it, we get: .

[0038] Due to the pressure change in the air chamber It is much smaller than the standard atmospheric pressure. Therefore, the approximate processing in step 3.2.4 can be performed.

[0039] Step 3.2.5: Construct the volume formula for the OWC chamber, as follows: ; In the formula, Let be the volume of the OWC chamber in equilibrium. , The cross-sectional area of ​​the OWC chamber is... The height of the OWC chamber under equilibrium conditions. , These are the cross-sectional areas of the two water columns, respectively. , , , These represent the heave displacements of the buoy and the two water columns, respectively.

[0040] Step 3.2.6: Differentiate the formula in Step 3.2.5 to obtain the volume change rate of the OWC chamber, as follows: ; In the formula, , , These represent the heave speeds of the buoy and the two water columns, respectively.

[0041] Step 3.2.7: Update the mass balance formula for the air in the chamber in Step 3.2.1 according to Steps 3.2.4 and 3.2.6, as follows: .

[0042] In this embodiment, the formula obtained by differentiation in step 3.2.4 and the formula obtained in step 3.2.6 are substituted into the formula obtained in step 3.2.1 to update the mass balance formula of the air in the cavity.

[0043] Step 3.2.8: Apply the formula from Step 3.2.7 to the OWC chamber, high-pressure chamber, and low-pressure chamber to obtain the linearized expressions for the mass flow rates of the three chambers, as follows: ; In the formula, The mass flow rate of air from the OWC chamber to the high-pressure chamber. The mass flow rate of air from the low-pressure chamber to the OWC chamber. The mass flow rate of air passing through the unidirectional turbine. The instantaneous air density of the OWC chamber. , , These represent the air densities of the OWC chamber, high-pressure chamber, and low-pressure chamber under equilibrium conditions. , , These represent the air pressures of the OWC chamber, high-pressure chamber, and low-pressure chamber under equilibrium conditions. , , These represent the pressure change rates of the OWC chamber, high-pressure chamber, and low-pressure chamber, respectively. , Let these be the volumes of the high-pressure chamber and the low-pressure chamber, respectively. .

[0044] Step 3.2.9: The mass flow rate of air through two one-way valves and one one-way turbine is modeled by the following formula: ; ; ; In the formula, , , Let be the flow coefficients of the two one-way valves and the one-way turbine, respectively. , , , , These are the instantaneous air densities of the OWC chamber, high-pressure chamber, and low-pressure chamber, respectively. , , These are the instantaneous air pressures of the OWC chamber, high-pressure chamber, and low-pressure chamber, respectively. , , These represent the surface areas of two one-way valves and a one-way turbine, respectively.

[0045] For a closed-loop PTO, there are two one-way valves and one one-way turbine. The one-way valves are not always open; they only open when the pressure difference exceeds a given positive threshold. Otherwise, no airflow occurs. Assuming the valves are ideal, the pressure threshold for valve opening is 0, meaning the valves can only be fully open or fully closed. The one-way turbine is also modeled as a valve. Based on this, step 3.2.8 is performed.

[0046] For a closed-loop PTO, the pressures corresponding to the OWC chamber, high-pressure chamber, and low-pressure chamber are respectively... , and .when At this time, the one-way valve opens, and air flows from the OWC chamber to the high-pressure chamber. At that time, air flows from the high-pressure chamber to the low-pressure chamber through a unidirectional turbine. At that time, another one-way valve opens, and air flows from the low-pressure chamber back to the OWC chamber.

[0047] In this embodiment, in step 3.2.9, , , The surface areas of the two one-way valves and the one-way turbine are respectively calculated using the following formula: ; In the formula, Let be the damping coefficients of the two one-way valves. This is the damping coefficient of a unidirectional turbine.

[0048] Step 3.2.10: Based on the formulas in Steps 3.2.8 and 3.2.9, the expressions for the pressure change rates of the OWC chamber, high-pressure chamber, and low-pressure chamber are obtained as follows: ; ; .

[0049] Step 3.2.11: Construct the expression for the instantaneous aerodynamic power of the unidirectional turbine, as follows: .

[0050] Step 3.2.12: Update the expression for the instantaneous aerodynamic power of the unidirectional turbine in Step 3.2.11 according to the formula for the mass flow rate of the unidirectional turbine in Step 3.2.9, as follows: .

[0051] In this embodiment, the formula for the mass flow rate of the unidirectional turbine in step 3.2.9 is substituted into the formula in step 3.2.11 to obtain an updated expression for the instantaneous aerodynamic power of the unidirectional turbine.

[0052] Combining step 3, the modeling of the closed-loop PTO dual-cavity OWC wave energy device is completed, as follows: .

[0053] In this embodiment, in step 3, the oscillating water column, as well as the pressure change rates of the OWC chamber, high-pressure chamber, and low-pressure chamber, are solved using a fourth-order Runge-Kutta method, and the instantaneous aerodynamic power of the unidirectional turbine is solved by incorporating the pressure at each moment.

[0054] Verification of Examples To verify the effectiveness of the device in Example 1 and the method in Example 2, an irregular wave with a wave period of 8s, a wave height of 1.5m, a spectral peak factor of 3.3, and an incident angle of 0° was used as the external load input, and the calculation time was 1200s for verification.

[0055] like Figure 5 As shown, the displacement of the water column relative to the floating body is illustrated. It can be seen that there is a phase difference in the motion of the two water columns. The dual-chamber design improves energy capture efficiency through this phase difference, demonstrating the rationality of the numerical simulation.

[0056] like Figure 6 , 7 As shown, the changes in air quality and pressure in the OWC chamber, high-pressure chamber, and low-pressure chamber are illustrated. It can be seen that the air quality and pressure in the high-pressure chamber are always higher than those in the low-pressure chamber, and there is always a pressure difference between the high-pressure chamber and the low-pressure chamber, which makes the air flow steadily and unidirectionally through the turbine.

[0057] like Figure 8 The diagram shows a comparison of the aerodynamic power of open-type OWC, closed-type single-chamber OWC, and closed-type dual-chamber OWC devices (in this embodiment). It can be seen that the aerodynamic power of the open-type OWC always drops to zero due to the frequent changes in airflow direction, which is the reason for its high volatility. The airflow of the closed-type OWC is stable and unidirectional, and its aerodynamic power curve is smoother, with much less volatility compared to the open-type OWC. The curves of the closed-type single-chamber OWC and closed-type dual-chamber OWC show that the closed-type dual-chamber OWC has higher aerodynamic power.

[0058] like Figure 9 , 10The diagram shows a comparison of the average aerodynamic power and fluctuation of open-type OWC, closed-type single-chamber OWC, and closed-type dual-chamber OWC devices (in this embodiment) during a wave period of 6-10 seconds. It can be seen that the average aerodynamic power of the closed-type single-chamber OWC is slightly lower than that of the open-type OWC due to energy losses from the two valves, but its aerodynamic power fluctuation is much smaller. The average aerodynamic power of the closed-type dual-chamber OWC is higher than that of the closed-type single-chamber OWC, and its aerodynamic power fluctuation is even smaller, indicating that the closed-type dual-chamber OWC improves energy capture efficiency while maintaining lower fluctuation.

[0059] In summary, the numerical simulation method of this embodiment, based on dynamics theory, potential flow theory, and aerodynamics theory, constructs an integrated coupled analysis model (including a dual-cavity phase coupling mechanism and a nonlinear PTO model) for the wave energy device of Embodiment 1. This model accurately characterizes the dynamic characteristics of the aerodynamic process, the multi-cavity coupling mechanism, and nonlinear flow losses, thereby achieving high-precision prediction of the system's energy conversion efficiency and power stability. The numerical simulation reveals the coupling mechanism between the floating body, water column, and PTO system, enabling the calculation of the dynamic response of the closed-loop PTO dual-cavity OWC device under different sea conditions. It reveals the impact of key parameters on the device's performance, demonstrates the device's performance in terms of aerodynamic power and wave characteristics, verifies the device's feasibility and superiority, and provides crucial theoretical support for the structural optimization, energy harvesting efficiency, and stability design of OWC devices, thus contributing to the efficient development of wave energy resources.

[0060] The numerical simulation method in this embodiment simulates the hydrodynamics of the floating body and two water columns based on potential flow theory and calculates the corresponding hydrodynamic parameters (step 1). It then performs overall modeling based on dynamics theory (step 3.1.1) and simulates the air mass changes (step 3.2.8) and air pressure changes (step 3.2.10) in the oscillating water column chamber, high-pressure chamber, and low-pressure chamber based on air thermodynamics theory (steps 3.2.1~3.2.2). By solving the multibody coupled motion equations, the dynamic response of the device under wave action is efficiently and accurately simulated. Figure 5 The aerodynamic power and its fluctuations of the device were then calculated.

[0061] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A closed-loop PTO dual-cavity OWC wave energy device, characterized in that, include: The OWC chamber consists of a high-pressure chamber and a low-pressure chamber. The high-pressure chamber and the low-pressure chamber are arranged side by side above the OWC chamber. The high-pressure chamber is connected to the OWC chamber through an upward one-way valve, and the low-pressure chamber is connected to the OWC chamber through a downward one-way valve. The high-pressure chamber and the low-pressure chamber are connected by a turbine. The bottom of the OWC chamber includes two sub-chambers.

2. A numerical simulation method for a closed-loop PTO dual-cavity OWC wave energy device, characterized in that, The wave energy device according to claim 1 comprises the following steps: Step 1: Based on Sesam software, establish a wetted surface model of the wave energy device; import the model data into OrcaWave software for hydrodynamic analysis to obtain hydrodynamic parameters; Step 2: Based on the obtained hydrodynamic parameters, calculate the wave load using the first-order wave force transfer function; Step 3: Based on air thermodynamics, establish a numerical model of the wave energy device on the Matlab platform, including establishing an overall model based on dynamics theory, and establishing models of air quality and pressure changes in the OWC chamber, high-pressure chamber, and low-pressure chamber based on air thermodynamics theory; and solve the model.

3. The numerical simulation method for a closed-loop PTO dual-cavity OWC wave energy device according to claim 2, characterized in that, In step 2, the wave load is calculated by combining the wave spectrum and using potential flow theory for modeling. Based on the principle of linear superposition, the irregular wave is decomposed into multiple regular wave units of different frequencies. The first-order wave force transfer function obtained by OrcaWave software is used to determine the amplitude and phase of the wave force on the wave energy device at each frequency. The wave forces of all regular wave units are linearly superimposed to obtain the wave excitation force.

4. The numerical simulation method for a closed-loop PTO dual-cavity OWC wave energy device according to claim 2, characterized in that, In step 3, the overall model is established through the following steps: Step 3.1.1: Based on dynamic theory, the overall three-degree-of-freedom equations of motion for the system are constructed as follows: ； In the formula, The system's quality matrix, For heave displacement, For heave acceleration, For wave excitation force, For radiation force, For still water restoring force, The force generated by the PTO system, For viscous damping force, it is expressed as ,in The density of seawater, The viscous damping coefficient is... Let be the cross-sectional area of ​​the buoy and the water column. The velocity of the buoy and the water column.

5. The numerical simulation method for a closed-loop PTO dual-cavity OWC wave energy device according to claim 4, characterized in that, In step 3.1.1, Represented as: ； In the formula, The pressure difference is the instantaneous pressure inside the chamber minus the standard atmospheric pressure under equilibrium conditions. When air pressure acts on the upper surface of the OWC chamber, Acting on the buoyant body, at this time The cross-sectional area of ​​the OWC chamber is... Take the positive sign; when air pressure acts on the surfaces of the two water columns, When it acts on the water column, at this time Let be the cross-sectional area of ​​the water column. Take the negative sign.

6. The numerical simulation method for a closed-loop PTO dual-cavity OWC wave energy device according to claim 2, characterized in that, In step 3, the pressure change rate models for the OWC chamber, high-pressure chamber, and low-pressure chamber are established through the following steps: Step 3.2.1: Construct the mass balance formulas for the air in the OWC chamber, high-pressure chamber, and low-pressure chamber, as follows: ； In the formula, The mass change rate of the gas in the chamber. For gas density, The volume of the chamber; Step 3.2.2: Construct the expressions for air pressure and density, as follows: ； ； In the formula, p is the air pressure at any time, and ρ is the air density at any time. Standard atmospheric pressure The density of air at standard atmospheric pressure. Specific heat ratio, For isobaric specific heat, Specific heat at constant volume; Step 3.2.3: Substitute the instantaneous air pressure and density in the OWC chamber, high-pressure chamber, and low-pressure chamber into the formula in Step 3.2.2 to obtain: ； In the formula, The instantaneous air pressure in the chamber. The instantaneous air density in the chamber; Step 3.2.4: Linearize the relationship between instantaneous air pressure and density in the OWC chamber, high-pressure chamber, and low-pressure chamber to obtain... Approximate expression: ； Differentiating it, we get: ； Step 3.2.5: Construct the volume formula for the OWC chamber, as follows: ； In the formula, Let be the volume of the OWC chamber in equilibrium. , The cross-sectional area of ​​the OWC chamber is... The height of the OWC chamber under equilibrium conditions. , These are the cross-sectional areas of the two water columns, respectively. , , , These are the heave displacements of the floating body and the two water columns, respectively. Step 3.2.6: Differentiate the formula in Step 3.2.5 to obtain the volume change rate of the OWC chamber, as follows: ； In the formula, , , These are the sway velocities of the floating body and the two water columns, respectively. Step 3.2.7: Update the mass balance formula for the air in the chamber in Step 3.2.1 according to Steps 3.2.4 and 3.2.6, as follows: ； Step 3.2.8: Apply the formula from Step 3.2.7 to the OWC chamber, high-pressure chamber, and low-pressure chamber to obtain the linearized expressions for the mass flow rates of the three chambers, as follows: ； In the formula, The mass flow rate of air from the OWC chamber to the high-pressure chamber. The mass flow rate of air from the low-pressure chamber to the OWC chamber. The mass flow rate of air passing through the unidirectional turbine. The instantaneous air density of the OWC chamber. , , These represent the air densities of the OWC chamber, high-pressure chamber, and low-pressure chamber under equilibrium conditions. , , These represent the air pressures of the OWC chamber, high-pressure chamber, and low-pressure chamber under equilibrium conditions. , , These represent the pressure change rates of the OWC chamber, high-pressure chamber, and low-pressure chamber, respectively. , Let these be the volumes of the high-pressure chamber and the low-pressure chamber, respectively. ; Step 3.2.9: The mass flow rate of air through two one-way valves and one one-way turbine is modeled by the following formula: ； ； ； In the formula, , , These are the flow coefficients of the two one-way valves and the one-way turbine, respectively. , , These are the instantaneous air densities of the OWC chamber, high-pressure chamber, and low-pressure chamber, respectively. , , These are the instantaneous air pressures of the OWC chamber, high-pressure chamber, and low-pressure chamber, respectively. , , These are the surface areas of the two one-way valves and the one-way turbine, respectively. Step 3.2.10: Based on the formulas in Steps 3.2.8 and 3.2.9, the expressions for the pressure change rates of the OWC chamber, high-pressure chamber, and low-pressure chamber are obtained as follows: ； ； 。 7. The numerical simulation method for a closed-loop PTO dual-cavity OWC wave energy device according to claim 6, characterized in that, In step 3.2.9, , , The surface areas of the two one-way valves and the one-way turbine are respectively calculated using the following formula: ； In the formula, Let be the damping coefficients of the two one-way valves. This is the damping coefficient of a unidirectional turbine.

8. The numerical simulation method for a closed-loop PTO dual-cavity OWC wave energy device according to claim 7, characterized in that, The instantaneous aerodynamic power model of a unidirectional turbine is established through the following steps: Step 3.2.11: Construct the expression for the instantaneous aerodynamic power of the unidirectional turbine, as follows: ； Step 3.2.12: Update the expression for the instantaneous aerodynamic power of the unidirectional turbine in Step 3.2.11 according to the formula for the mass flow rate of the unidirectional turbine in Step 3.2.9, as follows: 。

Images