Marine energy-saving duct fin with bionic trailing edge

Abstract

The invention relates to a marine energy-saving duct fin with a bionic trailing edge, comprising: an annular duct, the outer edge of which is fixed to the tail of a hull; the multiple fins are evenly distributed in the circumferential direction of the annular guide pipe, and the tail edge of each fin is provided with a bionic zigzag structure; the bionic zigzag structure is composed of tooth peaks and tooth valleys which are arranged periodically, and the height of each sawtooth and the distance between the tooth peaks are different and change randomly within the coverage range. The height difference between the adjacent tooth peaks and tooth valleys does not exceed 1 / 30 of the maximum chord length of the fin blades, and the distance between the adjacent tooth peaks or tooth valleys does not exceed 1 / 30 of the extension length of the fin blades. According to the marine energy-saving duct fin with the bionic trailing edge, the energy-saving effect can be effectively improved, and the vibration and noise reduction effect is enhanced.

Description

Technical Field

[0001] The present invention relates to a ship energy-saving device, specifically a marine energy-saving duct fin that optimizes the flow field through bionic trailing edges, and is applicable to improving the propeller propulsion efficiency and reducing vibration and noise. Background Art

[0002] At present, the market demand for marine energy-saving devices is relatively large. The common types of energy-saving devices in front of the propeller include pre-swirl guide wheels, compensating ducts, pre-swirl stators, double-arm shaft brackets, etc. The duct fin in front of the propeller is a combination of a pre-swirl guide wheel and multiple pre-swirl stators. The blades of the pre-swirl stators extend out of the guide wheel and have a certain pitch angle. The guide wheel rectifies the oncoming flow in front of the propeller, and the pre-swirl stator pre-swirls the water flow. The combination of these two can make the water flow more uniform and have a certain pre-swirl when reaching the propeller disk, improving the operating efficiency of the propeller.

[0003] Conventional duct fins or energy-saving ducts can reduce the energy lost due to the rotation of the propeller wake flow field and make the oncoming flow more uniform, but there are still some inherent problems to be improved. One is that the airfoil of the fin is relatively regular, and flow separation occurs after the fluid flows through the airfoil of the fin, generating eddies behind the fin and gradually spreading, which will cause energy consumption and reduce the rectifying ability of the duct fin, deteriorating the flow field in front of the propeller. On the other hand, the generation of vortices at the ship's tail is often accompanied by vortex impact vibration and noise, which will have an adverse impact on the comfort of personnel.

[0004] Patent document CN109987210A discloses the trailing edge serration structure of a pump-jet propeller, but it is for optimizing the stator wake, and the parameters are fixed; while the helical duct of CN113879498A focuses on flow field rectification and does not consider bionic noise reduction.

[0005] In view of the above deficiencies, the present invention proposes an energy-saving duct fin with a bionic trailing edge, which redesigned the trailing edge of the fin of the duct fin by referring to the trailing edge structure of a bird's wing. The trailing edge of a bird's wing is serrated, which can break up the eddies at the end of the airfoil and accelerate the dissipation of the eddies, maintaining the uniformity of the flow field around the airfoil, effectively reducing energy loss and noise. In the energy-saving duct fin, applying the serrated trailing edge to the trailing edge of the fin, on the one hand, can break up the eddies behind the fin and accelerate the dissipation of the eddies, effectively reducing energy loss and enhancing the energy-saving effect; on the other hand, the reduction of the eddy field intensity also reduces the risk of vibration and noise; finally, the dissipation of the eddies can maintain the uniformity of the flow field in front of the propeller, thereby further optimizing the working environment of the propeller and improving the propeller propulsion efficiency. Summary of the Invention

[0006] The present invention provides a marine energy-saving duct fin with a bionic trailing edge, which redesigned the fin of the energy-saving duct fin according to the trailing edge structure of a bird's wing, improving the energy-saving effect of the duct fin and reducing the eddy vibration and noise intensity.

[0007] To achieve the above object, the technical solution of the present invention is: an energy-saving duct fin for a ship with a bionic trailing edge, comprising:

[0008] An annular duct, the outer edge of which is fixed to the stern of the hull;

[0009] A plurality of fin blades, evenly distributed circumferentially along the annular duct, and a bionic serrated structure is provided at the trailing edge of each fin blade;

[0010] The bionic serrated structure is composed of periodically arranged tooth crests and tooth valleys, and the height of each serration and the distance from the tooth crest are different, randomly varying within the coverage range.

[0011] Furthermore, the height difference between adjacent tooth crests and tooth valleys does not exceed 1 / 30 of the maximum chord length of the fin blade, and the spacing between adjacent tooth crests or tooth valleys does not exceed 1 / 30 of the span length of the fin blade.

[0012] Furthermore, the parameters of the serration shape are randomly distributed within the allowable range, covering at least 80% of the span length of the trailing edge of the fin blade.

[0013] Furthermore, each serration of the bionic serrated structure is triangular or trapezoidal, the tooth height ranges from 0.5 to 5 mm, and the tooth width ranges from 2 to 15 mm.

[0014] Furthermore, the number of fin blades is 4 - 8, the angle of attack of the fin blade is 5° - 25°, and the ratio of the span length of the fin blade to the radius of the duct is 0.3 - 0.7.

[0015] Furthermore, the angle of attack of the duct is 3° - 15°, and the thickness of the duct is 1 / 20 - 1 / 10 of the radius of the duct.

[0016] Furthermore, the bionic serrated structure is integrally formed on the trailing edge of the fin blade by laser cutting or 3D printing.

[0017] A marine propulsion system, comprising a propeller and the energy-saving duct fin according to any one of claims 1 - 8, wherein the duct fin is located upstream of the propeller, at a distance of 0.5 - 1.5 times the diameter of the propeller from the propeller disk.

[0018] Furthermore, the serrated structure at the trailing edge of the fin blade of the duct fin reduces the turbulence intensity of the flow field on the propeller disk by 10% - 25% and improves the propulsion efficiency by 3% - 8%.

[0019] A method for reducing vibration and noise of a ship, the energy-saving duct fin reduces the wake vortex noise of the ship by 2 - 5 dB and reduces the vibration amplitude by 15% - 30%.

[0020] The beneficial effects of the present invention are:

[0021] The energy-saving duct fin with a bionic trailing edge adopting the above technical solution has the main structure remaining unchanged before and after the change of the fin blade form, without affecting the original fin blade strength. Before the structure change, the eddy current intensity at the trailing edge of the fin blade is large, which will cause energy dissipation and a certain degree of impact vibration noise. After the structure change, the eddy current intensity at this position decreases, and it is divided into several small eddies, accelerating the dissipation of the eddies and reducing the generated vibration noise.

[0022] The principle that the marine energy-saving duct fin with a bionic trailing edge can effectively improve the energy-saving effect and enhance the vibration and noise reduction effect is as follows: Before the sawtooth structure is cut, the fin blade is regular, and the eddy current intensity at the trailing edge is large, which will cause energy dissipation and a certain degree of impact vibration noise; after the sawtooth structure is cut, the eddy current at this position is divided into several small eddies, accelerating the dissipation of the eddies, reducing the eddy current intensity, further maintaining the energy, and reducing the generated vibration noise; after the eddy current is dispersed, the fluid flows through the propeller disk surface more evenly, which is beneficial to improving the working environment of the propeller and enhancing the propulsion efficiency. Brief Description of the Drawings

[0023] Figure 1 It is a schematic diagram of the marine energy-saving duct fin with a bionic trailing edge of the present invention;

[0024] Figure 2 It is a schematic diagram of a single fin blade with a serrated trailing edge;

[0025] Figure 3 It is an enlarged view of the serrated trailing edge of the fin blade. Detailed Embodiments

[0026] The following uses specific examples to illustrate the embodiments, but it is not a limiting condition of the present invention.

[0027] As Figures 1 to 3 shown, a marine energy-saving duct fin with a bionic trailing edge of the present invention includes an energy-saving duct 1, several fin blades 2, and a serrated trailing edge 3 of the fin blade. The outer edge of the energy-saving duct 1 is fixed to the tail 4 of the hull, and a plurality of fin blades 2 are evenly distributed along the circumference of the energy-saving duct 1. The trailing edge of each fin blade is a serrated trailing edge 3 of the fin blade. Among them, the serrated trailing edge 3 of the fin blade includes a tooth peak 3-1 and a tooth valley 3-2.

[0028] After the design of the conventional duct fin is completed, without changing the shape of the duct fin, that is, fixing parameters such as the duct radius of the duct fin, the duct angle of attack, the fin blade distribution angle, the number of fin blades, the fin blade extension length, and the fin blade angle of attack, a serrated structure is cut at the trailing edge of all fin blades, so that the trailing edge of the fin blade has a bionic feature. According to the numerical calculation results under different serrated trailing edge shape parameters, the present invention draws the conclusion of the serration parameter design: the height of each serration and the distance from the tooth peak do not have to be exactly the same and can vary randomly within a certain range; the height difference between an adjacent tooth peak and a tooth valley does not exceed 1 / 30 of the maximum chord length of the fin blade; the distance between two adjacent tooth peaks does not exceed 1 / 30 of the fin blade span; similarly, the distance between two adjacent tooth valleys does not exceed 1 / 30 of the fin blade span; the serration shapes are randomly arranged within the specified parameter range and should cover as much as possible of the entire fin blade span.

[0029] The implementation process of the present invention: First, after determining parameters such as the duct radius of the duct fin, the duct angle of attack, the duct thickness, the fin blade distribution angle, the number of fin blades, the fin blade extension length, the fin blade angle of attack, and the fin blade thickness, a bionic serrated structure is cut at the trailing edge of the fin blade. The serrated structure features are expressed by the tooth peak and tooth valley parameters, showing that: all fin blades need to be provided with a serrated structure at the trailing edge, the height of each serration and the distance from the tooth peak do not have to be exactly the same and can vary randomly within a certain range; the height difference between an adjacent tooth peak and a tooth valley does not exceed 1 / 30 of the maximum chord length of the fin blade; the distance between two adjacent tooth peaks does not exceed 1 / 30 of the fin blade span; similarly, the distance between two adjacent tooth valleys does not exceed 1 / 30 of the fin blade span; the serration shapes are randomly arranged within the specified parameter range and should cover as much as possible of the entire fin blade span.

[0030] The principle by which the device can effectively improve the energy-saving effect and enhance the vibration reduction and noise reduction effect is as follows: Before the serrated structure is cut, the fin blades are regular, and the eddy current intensity at the trailing edge is large, which will cause energy dissipation and a certain degree of impact vibration noise; after the serrated structure is cut, the eddy current at this position is divided into several small eddies, accelerating the dissipation of the eddies, reducing the eddy current intensity, further maintaining the energy, and reducing the generated vibration noise; after the eddy current is broken up, the fluid flows through the propeller disk surface more evenly, which is beneficial to improving the working environment of the propeller and enhancing the propulsion efficiency.

[0031] Example 1:

[0032] The duct radius R = 1.2 m, the angle of attack is 8°, there are 4 fin blades, and the span is 0.5R; the serration height h at the trailing edge of the fin blade = 2 mm (1 / 30 of the maximum chord length of 60 mm), and the tooth pitch d = 4 mm (1 / 150 of the span of 600 mm); Test results: The propeller efficiency is increased by 6.2%, and the hull vibration is reduced by 22%.

[0033] Example 2:

[0034] Integrally formed fins and serrations are made by 3D printing of titanium alloy, and the serration parameters are randomly generated:

[0035] Tooth height h = 1.5 - 3 mm (meeting h ≤ 60 / 30 = 2 mm); tooth pitch d = 3 - 6 mm (meeting d ≤ 600 / 30 = 20 mm); test results: fatigue life is increased by 15%, and the high-frequency components in the noise spectrum are reduced.

[0036] Example 3:

[0037] The duct is installed at the stern of a VLCC oil tanker, at a distance of 1.2 times the diameter from the propeller; the serrated trailing edge reduces the turbulent kinetic energy on the propeller disk surface by 18%, and the fuel consumption of the actual ship is reduced by 4.5%.

[0038] The core innovation points of the present invention:

[0039] (1) A random serration structure imitating the wings of birds is introduced at the trailing edge of the fin, and the parameters are dynamically adjustable;

[0040] (2) The serration size is designed in relation to the fin span and chord length to ensure the vortex breakdown effect;

[0041] (3) Random distribution avoids periodic resonance, taking into account both the processing feasibility and the flow field adaptability.

[0042] The technical effects of the present invention are as follows:

[0043] (1) The propeller efficiency is increased by more than 5%;

[0044] (2) The ship stern noise is reduced by 3 dB - 6 dB;

[0045] (3) The structural strength of the duct remains unchanged, and the manufacturing cost increases by < 10%.

[0046] The above are only the preferred embodiments of the present invention, and do not limit the implementation manners and protection scope of the present invention. For those skilled in the art, it should be realized that all equivalent replacements and obvious changes made by using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. An energy-saving duct fin with a bionic trailing edge for a ship, characterized in that: include: an annular duct, the outer edge of which is fixed to the stern of the hull; A plurality of fin blades are evenly distributed along the circumference of the annular duct, and the trailing edge of each fin blade is provided with a bionic sawtooth structure; The bionic sawtooth structure is composed of periodically arranged tooth peaks and tooth valleys, and the height and tooth peak distance of each sawtooth are different and vary randomly within the coverage range.

2. The energy-saving duct fin with bionic trailing edge for ship according to claim 1, characterized in that: The height difference between adjacent tooth peaks and tooth valleys shall not exceed 1 / 30 of the maximum chord length of the fin blade, and the spacing between adjacent tooth peaks or tooth valleys shall not exceed 1 / 30 of the fin blade extension length.

3. The energy-saving duct fin with bionic trailing edge for ship according to claim 1, characterized in that: The parameters of the sawtooth shape are randomly distributed within the allowed range, covering at least 80% of the extension of the trailing edge of the fin lobe.

4. The energy-saving duct fin with bionic trailing edge for ship according to claim 1, characterized in that: Each sawtooth of the bionic sawtooth structure is triangular or trapezoidal, with a tooth height ranging from 0.5 to 5 mm and a tooth width ranging from 2 to 15 mm.

5. The energy-saving duct fin with bionic trailing edge for ship according to claim 1, characterized in that: The number of fin blades is 4-8, the attack angle of the fin blades is 5°-25°, and the ratio of the fin blade length to the duct radius is 0.3-0.

7.

6. The energy-saving duct fin with bionic trailing edge for ship according to claim 1, characterized in that: The attack angle of the catheter is 3°-15°, and the thickness of the catheter is 1 / 20-1 / 10 of the catheter radius.

7. The energy-saving duct fin with bionic trailing edge for ship according to claim 1, characterized in that: The bionic serrated structure is integrated into the trailing edge of the fin by laser cutting or 3D printing.

8. A marine propulsion system, characterized in that: The invention comprises a propeller and the energy-saving duct fin according to any one of claims 1 to 7, wherein the duct fin is located upstream of the propeller and is 0.5 to 1.5 times the propeller diameter away from the propeller disk.

9. The propulsion system according to claim 8, characterized in that The serrated structure of the trailing edge of the fin blade of the duct fin reduces the turbulence intensity of the propeller disk flow field by 10%-25% and improves the propulsion efficiency by 3%-8%.

10. A method for reducing vibration and noise of a ship, characterized in that: By using the energy-saving duct fin described in any one of claims 1 to 7, the stern vortex noise can be reduced by 2 to 5 dB and the vibration amplitude can be reduced by 15% to 30%.

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