Design method of an intelligent active stern energy-saving and drag-reducing device

Abstract

The present invention provides a design method for an intelligent active stern energy-saving and drag-reducing device. The method specifically comprises: S1: designing the shape of the stern drag-reducing device and determining the parameters of the drag-reducing device; S2: geometrically modeling the ship's resistance by varying the downtilt angle a; S3: performing array calculations: setting an objective function f=min{R(a)} and calculating the minimum stern resistance under different speeds V and different drafts T; S4: establishing an optimal downtilt angle matrix, wherein the rows of the matrix represent the speed V and the columns represent the draft T; S5: performing model tests; S6: experimentally verifying and revising the optimal downtilt angle matrix; and S7: integrating the optimal downtilt angle matrix into the software and hardware control system of the stern drag-reducing device to adjust the downtilt angle a to achieve optimal drag reduction at different speeds and drafts. The present invention has a wide range of applications and exhibits good drag reduction effects for ships at different speeds and drafts, i.e., different cargo loads, in actual operation.

Description

Technical Field

[0001] The present invention relates to the technical field of ship energy conservation and drag reduction, and in particular to a design method for an intelligent active stern energy conservation and drag reduction device. Background Art

[0002] In the era of global advocacy of "energy conservation, emission reduction, environmental protection and low carbon", and under the urgent requirement of the ship and shipping industry to continuously reduce carbon emission intensity, how to reduce the resistance of ship navigation and improve the energy efficiency of ships is of great significance. At present, there are many drag reduction methods applied to ships, such as ship type optimization, installation of energy-saving appendages, rib drag reduction method, air curtain drag reduction method, bubble drag reduction method and polymer additive drag reduction method, etc. The technical difficulty varies. Some change the navigation state of the ship, and some add materials or appendage structures to the hull to ultimately achieve the effect of drag reduction and energy saving. Under the premise of not changing the hull line structure, the use of appropriate appendage structures to improve the flow field distribution of the ship, and thus improve the resistance performance of the ship at different speeds, is one of the hot spots in ship drag reduction research.

[0003] In the field of ship wave-cutting plate design optimization and application, existing technologies use CFD commercial software for numerical simulation analysis to explore the effects of different forms of wave-cutting plates on the ship's resistance performance under different scale parameters. During the numerical simulation process, the shape of the wave-cutting plate is optimized, and the relevant scale parameters of the optimal shape (including length, width, and angle) are optimized and analyzed to obtain the optimal wave-cutting plate with the highest drag reduction rate. Based on the resistance performance optimization of wave-piercing catamarans based on appendage drag reduction technology, the outer edge shape of the cutoff plate is optimized with the resistance at the design cruising speed and the maximum design speed as the target, and the external structure of the cutoff plate with the best drag reduction effect at a specific design speed is obtained. Based on the design method of wave-crushing plates for medium and high-speed ships with energy saving and drag reduction, the design parameters of the stern wave-crushing plate are studied, the significance analysis of the design parameters is carried out, the design space of the design parameters is selected, and the orthogonal design method is used to combine the two design parameters of the wave-crushing plate using an orthogonal table to perform multi-parameter combination, and the wave-crushing plate scheme is designed accordingly; the CFD simulation method is used to simulate the resistance of multiple wave-crushing plate schemes, summarize the drag reduction mechanism of the wave-crushing plate, summarize the change law of the drag reduction rate of the wave-crushing plate design parameter combination, and combine the engineering constraints to guide the direction of design parameter selection; ship model resistance test and self-propulsion test are carried out, and the best wave-crushing plate design scheme is optimized by comprehensively considering the drag reduction and energy saving effects.

[0004] In the application publication number CN 113919063A, "Design Method for Corrugated Plates for Medium- and High-Speed ​​Ships Based on Energy Saving and Drag Reduction," the design parameters of the stern corrugated plate are studied. Using an orthogonal design method, a multi-parameter combination of the two corrugated plate design parameters is created using an orthogonal table, and a corresponding corrugated plate design scheme is developed. Using CFD simulation methods, resistance simulation is performed on multiple corrugated plate schemes, ultimately resulting in an optimal fixed corrugated plate design scheme. The corrugated plate scheme proposed in this embodiment for energy saving and drag reduction has a length of 1.0% of the waterline length, a width equal to the intersection width of the design waterline and the stern plate, and a dihedral angle of 7 degrees.

[0005] From the above, it can be seen that when the current stern drag reduction appendage is subjected to CFD numerical simulation, model test research, and geometric parameter design of the drag reduction device, the drag reduction device includes a wave-breaking plate, a flow-blocking plate, or a wave-breaking strip, etc., only an optimal design scheme with fixed length and angle parameters is obtained, which cannot well cope with the changes in speed and draft during actual navigation of the ship, resulting in a large difference between the model test and the actual navigation effect. Summary of the Invention

[0006] In view of the problem that the fixed stern energy-saving and drag-reduction device cannot achieve a good drag reduction effect at different speeds and drafts during actual navigation due to the changeable actual navigation environment of ships, the present invention provides a design method for an intelligent active stern energy-saving and drag-reduction device, which achieves optimal drag reduction at different speeds and drafts by intelligently adjusting the downtilt angle.

[0007] A design method for an intelligent active stern energy-saving and drag-reducing device.

[0008] S1: Design the shape of the stern drag reduction device and determine the parameters of the drag reduction device, including the downward inclination angle a and width parameter of the drag reduction device;

[0009] S2: By changing the down-tilt angle a, the ship resistance is modeled in three dimensions to obtain the pressure distribution on the hull surface at different down-tilt angles a of the drag reduction device;

[0010] S3: Perform array calculation: Set the objective function f = min{R(a)} and perform parameter optimization to calculate the minimum stern resistance under different speeds V and different drafts T; the resistance value is calculated when R(a) is a certain downward angle a;

[0011] S4: Based on the results of S3, an optimal downtilt angle matrix of the drag reduction device at different ship speeds V and different drafts T is established, where the rows of the matrix represent the ship speed V and the columns represent the draft T. The empirical formula for fitting the optimal downtilt angle matrix of the drag reduction device is:

[0012]

[0013] Where: speed is V, draft is T, downtilt angle is a, fitting coefficient a ij ;

[0014] S5: Conduct model test: The ship model is towed by a trailer and sails in the pool. The resistance meter measures the resistance of the ship model, and the computer records the forces acting on the ship model at various speeds in real time.

[0015] S6: Based on the results of S5, the optimal downtilt matrix of S4 is tested and verified and modified;

[0016] S7: Finally, the optimal downtilt angle matrix perfected in S6 is built into the software and hardware control system of the stern drag reduction device to adjust the downtilt angle a to achieve optimal drag reduction at different speeds and drafts.

[0017] The specific method of array calculation described in S3 is:

[0018] Establish the control equations, which include the continuity equation and momentum equation of the incompressible fluid:

[0019] Continuity equation:

[0020] Momentum conservation equation:

[0021]

[0022] (2) Written in tensor form:

[0023]

[0024] Where: u, v, w are the velocity components in the x, y, and z coordinate directions respectively, p is the pressure, ρ is the density of the fluid, ν is the kinematic viscosity coefficient of the fluid, and t is the time.

[0025] The method for adjusting the rotation of the downtilt angle a by the software and hardware control system in S7 is as follows: the optimal downtilt angle matrix is ​​written into the host computer of the system, the host computer receives the speed and draft signals of the ship, reads the optimal downtilt angle a in the optimal downtilt angle matrix, and sends an adjustment instruction to the drive device, the drive motor or hydraulic device of the drive device moves up and down, and the rotation of the downtilt angle a is adjusted by rotating the mechanical rod.

[0026] By adjusting the downward inclination angle of the stern drag reduction device, the flow field and pressure at the stern of the ship can be changed, thereby reducing the resistance of the ship's navigation.

[0027] Beneficial effects: The present invention provides a design method for an intelligent active stern energy-saving and drag reduction device. Specifically, the optimal downtilt angle matrix is ​​obtained through: shape design, geometric three-dimensional modeling and array calculation; and the optimal downtilt angle matrix is ​​corrected through model experiments and uploaded to the host computer. The ship adjusts the downtilt angle of the drag reduction device at different speeds and drafts in real time through the host computer, further changing the flow field and pressure at the stern of the ship, so that the ship can travel under minimum resistance. The present invention has a wide range of applications and has good drag reduction effects for ships at different speeds, different drafts, and different loading conditions in actual operations. The device has an intelligent adjustment angle and is easy to operate. The system realizes intelligent adjustment of the stern drag reduction device according to the optimal downtilt angle matrix of the drag reduction device at different speeds and different drafts. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 : Flowchart of the design method of an intelligent active stern energy-saving and drag-reduction device.

[0029] Figure 2 : Geometric three-dimensional model of the drag reduction device when the downward tilt angle is 0°.

[0030] Figure 3 : Geometric three-dimensional model of the drag reduction device when the downward inclination angle is 90°.

[0031] Figure 4 : Array calculation simulation diagram.

[0032] Figure 5(a)-Figure 5(b) : Schematic diagram of the driving device adjusting the downward tilt angle a.

[0033] Figure 6 : Schematic diagram of the drive unit installation position. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0035] like Figure 1 As shown in FIG, a design method for an intelligent active stern energy-saving and drag-reducing device is provided.

[0036] S1: Design the shape of the stern drag reduction device and determine the parameters of the drag reduction device, including the downward inclination angle a and width parameter of the drag reduction device;

[0037] S2: By changing the down-tilt angle a, the ship resistance is modeled in three dimensions to obtain the pressure distribution on the hull surface at different down-tilt angles a of the drag reduction device;

[0038] S3: Perform array calculation: Set the objective function f = min{R(a)} and perform parameter optimization to calculate the minimum stern resistance under different speeds V and different drafts T; the resistance value is calculated when R(a) is a certain downward angle a;

[0039] S4: Based on the results of S3, an optimal downtilt angle matrix of the drag reduction device at different ship speeds V and different drafts T is established, where the rows of the matrix represent the ship speed V and the columns represent the draft T, and an empirical formula that is convenient for calculation is then fitted;

[0040]

[0041] Where: speed is V, draft is T, downtilt angle is a, fitting coefficient a ij ;

[0042] S5: Conduct model test: The ship model is towed by a trailer and sails in the pool. The resistance meter measures the resistance of the ship model, and the computer records the forces acting on the ship model at various speeds in real time.

[0043] S6: Based on the results of S5, the optimal downtilt matrix of S4 is tested and verified and modified;

[0044] S7: Finally, the optimal downtilt angle matrix perfected in S6 is built into the software and hardware control system of the stern drag reduction device to adjust the downtilt angle a to achieve optimal drag reduction at different speeds and drafts.

[0045] The specific method of array calculation described in S3 is:

[0046] Establish the control equations, which include the continuity equation and momentum equation of the incompressible fluid:

[0047] Continuity equation:

[0048] Momentum conservation equation:

[0049]

[0050] (2) Written in tensor form:

[0051]

[0052] Where: u, v, w are the velocity components in the x, y, and z coordinate directions respectively, p is the pressure, ρ is the density of the fluid, ν is the kinematic viscosity coefficient of the fluid, and t is the time.

[0053] The method for adjusting the rotation of the downtilt angle a by the software and hardware control system in S7 is as follows: the optimal downtilt angle matrix is ​​written into the host computer of the system, the host computer receives the speed and draft signals of the ship, reads the optimal downtilt angle a in the optimal downtilt angle matrix, and sends an adjustment instruction to the drive device, the drive motor or hydraulic device of the drive device moves up and down, and the rotation of the downtilt angle a is adjusted by rotating the mechanical rod.

[0054] By adjusting the downward inclination angle of the stern drag reduction device, the flow field and pressure at the stern of the ship can be changed, thereby reducing the resistance of the ship's navigation.

[0055] The parametric optimization method is specifically as follows: numerical calculation means and tools, such as Fluent, ShipFlow, STAR CCM+ and CAESES software tools, are used to perform parametric optimization of the stern drag reduction devices such as wave suppressors and interceptor plates by inputting parameters such as ship size, draft, speed and drag reduction device parameters and to establish a geometric three-dimensional model (such as Figure 2 、 Figure 3 shown).

[0056] The principle of the drag reduction device established by the above method is: under certain draft and speed, i.e. water flow speed, adjusting the dip angle can change the pressure distribution on the hull surface, such as Figure 2 and Figure 3 As shown in the figure (blue indicates high pressure value and yellow indicates low pressure value), the stern increases with the increase of the down-tilt angle, and the resistance of the appendage itself increases appropriately. By calculating, the optimal down-tilt angle when the total resistance is the smallest can be obtained, which can appropriately reduce the total resistance of the ship.

[0057] According to the optimal down-tilt angle matrix of the drag reduction device at different speeds V and different drafts T, an empirical formula for calculating the down-tilt angle a is fitted:

[0058]

[0059] The fitting coefficient a in the empirical formula ij As shown in Table 1.

[0060] Table 1 Coefficients aij in empirical formulas

[0061] aij j＝1 j＝2 j＝3 i＝1 9.209E-01 1.657E-02 -2.633E-04 i＝2 -1.392E+00 -5.748E-02 5.603E-03 i＝3 1.530E+00 2.687E-01 1.140E-02

[0062] For example, under the conditions of V1 speed and T1 draft, the resistance value calculated for a 5-degree heel angle is 222kN, and the resistance values ​​calculated for other heel angles are all greater than this value. In this case, a 5-degree heel angle is considered to be the optimal heel angle for V1 speed and T1 draft.

[0063] The effectiveness of the drag reduction device was tested through a model experiment.

[0064] Example 1: As shown in Table 2, the drag reduction situation of a ship with a draft of T = 1.65m and V = 18kn is shown by the application of a drag reduction device.

[0065] Table 2 Drag reduction effect examples

[0066] Working conditions Hydrostatic resistance / kN difference / % original 194.10 - Using this device 172.72 -11.02％

[0067] The above embodiments are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications based on the above descriptions are possible. It is not possible to enumerate all embodiments here. Any obvious variations or modifications arising from the technical solutions of the present invention remain within the scope of the present invention.

Claims

1. A design method for an intelligent active stern energy-saving and drag-reducing device, characterized in that: S1: Design the shape of the stern drag reduction device and determine the parameters of the drag reduction device, including the downward inclination angle a and width parameter of the drag reduction device; S2: By changing the down-tilt angle a, the ship resistance is modeled in three dimensions to obtain the pressure distribution on the hull surface at different down-tilt angles a of the drag reduction device; S3: Perform array calculation: Set the objective function f = min{R(a)} and perform parameter optimization to calculate the minimum stern resistance under different speeds V and different drafts T; the resistance value is calculated when R(a) is a certain downward angle a; S4: Based on the results of S3, an optimal downtilt angle matrix of the drag reduction device at different ship speeds V and different drafts T is established, where the rows of the matrix represent the ship speed V and the columns represent the draft T. The empirical formula for fitting the optimal downtilt angle matrix of the drag reduction device is: Where: speed is V, draft is T, downtilt angle is a, fitting coefficient a ij ; S5: Conduct model test: The ship model is towed by a trailer and sails in the pool. The resistance meter measures the resistance of the ship model, and the computer records the forces acting on the ship model at various speeds in real time. S6: Based on the results of S5, the optimal downtilt matrix of S4 is tested and verified and modified; S7: Finally, the optimal downtilt angle matrix perfected in S6 is built into the software and hardware control system of the stern drag reduction device to adjust the downtilt angle a to achieve optimal drag reduction at different speeds and drafts.

2. The design method of an intelligent active stern energy-saving and drag-reducing device according to claim 1 is characterized in that: The specific method of array calculation described in S3 is: Establish the control equations, which include the continuity equation and momentum equation of the incompressible fluid: Continuity equation: Momentum conservation equation: (2) Written in tensor form: Where: u, v, w are the velocity components in the x, y, and z coordinate directions respectively, p is the pressure, ρ is the density of the fluid, ν is the kinematic viscosity coefficient of the fluid, and t is the time.

3. The design method of an intelligent active stern energy-saving and drag-reducing device according to claim 1 is characterized in that: The method for adjusting the rotation of the downtilt angle a by the software and hardware control system in S7 is as follows: the optimal downtilt angle matrix is ​​written into the host computer of the system, the host computer receives the speed and draft signals of the ship, reads the optimal downtilt angle a in the optimal downtilt angle matrix, and sends an adjustment instruction to the drive device, the drive motor or hydraulic device of the drive device moves up and down, and the rotation of the downtilt angle a is adjusted by rotating the mechanical rod.

4. The design method of an intelligent active stern energy-saving and drag-reducing device according to claim 1 is characterized in that: By adjusting the downward inclination angle of the stern drag reduction device, the flow field and pressure at the stern of the ship can be changed, thereby reducing the resistance of the ship's navigation.

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