Stabilized fin type selection method

Abstract

A stable fin type selection method comprises the steps that a single-layer stable fin or a double-layer stable fin is selected, when the single-layer stable fin is selected, the weight Weight1 = 7850 * S1 * d1n of the stable fin is calculated according to the thickness d1n of a stable fin plate and the lateral area S1 of the stable fin, and final parameters S1 and Weight1 are output; when a double-layer stable fin is selected, the stress Rw2 of the stable fin is evaluated and calculated according to the stress of a sub-fin plate and a T profile combined structure, then Weight 2 and S2 are obtained, a construction process weight P is introduced, and finally Judge is obtained, when Judge is larger than or equal to 1, a single-layer stable fin scheme is selected, and when Judge is smaller than 1, a double-layer stable fin scheme is selected. The course stabilizing fin is selected by judging the structure and performance of the stabilizing fin and comparing course stabilizing fin specification requirements and a load analysis method, guarantee is provided for reasonable design of the structure, advantages and defects are compared, limiting conditions are eliminated, and finally course stabilizing fin selection for ship types of different tonnages is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of ship gas drag reduction, and particularly relates to a method for selecting a stabilizing fin type. Background Art

[0002] In order to achieve energy conservation, emission reduction and improve the shipping safety of ships, some ships are provided with a course stabilizing fin, commonly known as a deadwood, at the center of the hull below the propeller at the stern. By setting the stabilizing fin, the side projection area of the ship can be increased, and the center of the side projection area of the ship can be shifted towards the stern, thereby improving the navigation stability of the ship. Ships with poor navigation stability will consume more fuel and reduce the economy of the ship.

[0003] Since the course stabilizing fin is installed on the outer plate of the ship's hull and is long-term affected by the bottom pressure and the lateral force at the bottom of the ship, the shipowner is concerned about the safety and vibration problems of this structure. Therefore, its strength needs to be evaluated at the initial design stage. At the same time, since it is welded to the outer plate, if it is damaged and replaced, the welding will damage the paint and curvature of the outer plate.

[0004] There are currently two forms of stabilizing fins, a single-layer stabilizing fin and a double-layer stabilizing fin. The single-layer stabilizing fin is usually installed on ships with a displacement of less than 80,000 tons, and the double-layer stabilizing fin is usually installed on ships with a displacement of more than 300,000 tons. For ships with a displacement between 80,000 tons and 300,000 tons, there is no method and description for the selection of stabilizing fins. Summary of the Invention

[0005] To solve the above problems, the present invention provides a method for selecting a stabilizing fin type, aiming to achieve the purpose of correctly selecting the type of stabilizing fin. The technical solution adopted is as follows:

[0006] A method for selecting a stabilizing fin type. The method for selecting a stabilizing fin for a ship with a displacement of 80,000 tons to 300,000 tons is as follows:

[0007] S1: Select a single-layer stabilizing fin. A web is fixed on the outer surface of the ship's outer plate, and the single-layer stabilizing fin is fixed on the web. The rearmost end of the stabilizing fin does not exceed the position of the tail shaft outlet. If there is an energy-saving device in front of the propeller, the rearmost end of the stabilizing fin should be before the rearmost end of the energy-saving device. There is a spacing between the bottom of the stabilizing fin and the baseline, and the front end of the stabilizing fin is chamfered and connected to the web, with a chamfer radius R2.

[0008] Calculate the lateral area S1 of the stabilizing fin, the lateral force F1 of the stabilizing fin, the thickness d11 of the stabilizing fin plate, the allowable stress Rw of the single-layer stabilizing fin material, and calculate the stress Rw1 of the stabilizing fin. When Rw1 < Rw, it meets the requirements. When Rw1 ≥ Rw, it does not meet the requirements. Increase the thickness of the stabilizing fin plate by 2 mm each time, set the thickness as d12, and continue the stress evaluation until the requirements are met. At this time, determine the thickness d1n of the stabilizing fin plate. The thickness d1n is calculated through multiple iterations.

[0009] Among them, S1 can be directly obtained using the surface query function in CAD software. F1 can refer to patent: CN117799796A,

[0010] F1=c1*ρ*g*t s .

[0011] ρ is the density of seawater, and g is the acceleration due to gravity.

[0012] ts is the height from the centroid position of the wooden structure to the waterline of the structure.

[0013] c1 is the statistical coefficient, 0.2≤c1≤0.25.

[0014] When the ratio of the ship's depth D to its breadth B is D / B<0.5, c1=0.25.

[0015] When the ratio of the ship's depth D to its breadth B is D / B>0.5, c1=0.2.

[0016] According to the plate thickness d1n and the lateral area S1, the weight Weight1=7850*S1*d1n is calculated, and the final parameters S1 and Weight1 are output.

[0017] S2: Double-layer stabilizing fins are used. The double-layer stabilizing fins are made of two fins with the same structure butt-jointed symmetrically. Each fin is made of two sub-fins butt-jointed. The butt of the two sub-fins is at an obtuse angle and forms a fold line. The fold line forms an angle β with the baseline. The maximum spacing between the two sub-fins is dmax. The value of dmax is between 260mm and 340mm. Generally, the smaller value is taken. Multiple T-profiles are fixed between the two fins.

[0018] Calculate the lateral area S2 of the stabilizing fin, the lateral force F2 of the stabilizing fin, and the allowable stress Rw' of the double-layer stabilizing fin material. The allowable stress is a fixed value, usually 235Mpa for ordinary steel or 315Mpa for high-strength steel. Set the initial angle β, the initial thickness d21 of the sub-fin plate, and take half of the initial thickness d11 of the single-layer stabilizing fin. The angle β between the angle line and the baseline and the spacing between the T-profiles are mainly located by marking the inside and outside of the outer plate to determine whether the T-profile is aligned with the internal structure of the hull as much as possible.

[0019] Among them, S2 can be directly obtained using the surface query function in the CAD software. F2 can refer to patent: CN117799796A, F2 = c1*ρ*g*t s .

[0020] ρ is the density of seawater, and g is the acceleration due to gravity.

[0021] ts is the height from the centroid position of the wooden structure to the waterline of the structure.

[0022] c1 is a statistical coefficient, where 0.2 ≤ c1 ≤ 0.25.

[0023] When the ratio D / B of the ship's depth D to the beam B < 0.5, c1 = 0.25.

[0024] When the ratio D / B of the ship's depth D to the beam B > 0.5, c1 = 0.2.

[0025] Design the dimensions of the T-section panel and web. The initial dimension of the T-section panel is T21, and the web is taken as 100 - 200 mm. This is for welding use, and usually the smaller value is taken.

[0026] According to the lateral force F2 acting on the T-section panel to form a shear force, calculate its stress Rw3. When Rw3 < Rw’, proceed to the next step if the requirement is met. When Rw3 ≥ Rw’, if the requirement is not met, set the thickness of the T-section panel to T22 by increasing it by 2 mm each time, and continue the stress assessment until the requirement is met to determine the thickness T2n of the T-section panel and web.

[0027] For the stress assessment of the combined structure of the sub-fin plate and the T-section, calculate the stress Rw2 of the stabilizing fin. When Rw2 < Rw’, proceed to S29 if the requirement is met. When Rw2 ≥ Rw’, if the requirement is not met, set the fin plate to d22 by increasing it by 2 mm each time, and continue the stress assessment until the requirement is met to determine the fin plate thickness d2n.

[0028] Output the final parameters S2 and Weight2 through Weight2 = 7850*(2*S2*d2n+(ST1*dT1+ST2*dT2+……STn*dTn)+(SF1*dF1+SF2*dF2+……SFn*dFn)).

[0029] Among them, ST1, ST2……STn are the projected areas of the T-section panels.

[0030] dT1, dT2……dTn are the thicknesses of the T-section panels.

[0031] SF1, SF2……SFn are the projected areas of the T-section webs.

[0032] dF1, dF2……dFn are the thicknesses of the T-section webs.

[0033] S3: Introduce the construction process weight P. According to the double-layer stabilizing fin structure, P is taken as a coefficient not greater than 1, where 0.8 < P < 0.95.

[0034]

[0035] When Judgement≥1, the single-layer stable fin solution is selected; when Judgement<1, the double-layer stable fin solution is selected.

[0036] In the above-mentioned method for selecting a stabilizing fin, further, in step S1, a distance of 50 mm between the bottom of the stabilizing fin and the baseline is provided.

[0037] In the above-mentioned method for selecting a stabilizing fin, further, in step S1, when a single-layer stabilizing fin is selected, the web area is larger than the installation and fixing area of ​​the stabilizing fin and the ship.

[0038] In the above-mentioned method for selecting a stabilizing fin, further, in step S2, the parameters of the T-shaped panel and the web must satisfy the lateral load stress.

[0039] In the above-mentioned method for selecting a stabilizing fin, further, in step S2, lightening holes may be provided on the web of the T-shaped material with a length exceeding 2 meters.

[0040] The present invention selects the heading stabilizing fin by judging the structure and performance of the stabilizing fin, comparing the requirements of the heading stabilizing fin specification and the load analysis method, and provides a guarantee for the reasonable design of the structure. The single-layer and double-layer heading stabilizing fin process installation methods are judged, the advantages and disadvantages are compared, and the restrictive conditions are eliminated, and finally the heading stabilizing fin selection for ships of different tonnages is realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a side view of a single-layer stabilizing fin and a detailed view of the connection structure;

[0042] Figure 2 It is a top view of a single-layer stabilizing fin and a detailed view of the connection structure;

[0043] Figure 3 It is a side view of the double-layer stabilizing fin and a detailed view of the connection structure;

[0044] Figure 4 This is a top view of the double-layer stabilizing fin and a detailed view of the connection structure;

[0045] Figure 5 Example diagram;

[0046] Figure 6 It is a flow chart;

[0047] Among them, 1-single-layer heading stabilizing fin, 2-welded web, 3-double-layer stabilizing fin T-profile, 4-hull outer plate, 5-round steel, 6-dull board A, 7-dull board B, 8-sub-fin plate, 9-lightening hole. DETAILED DESCRIPTION

[0048] The present invention will be further described in conjunction with the accompanying drawings.

[0049] The single-layer heading stabilizing fin is simple in design, and its primary goal is to obtain the largest possible side projection area without affecting propeller propulsion. If the ship is equipped with a propeller-front energy-saving device, consideration should also be given to not affecting the effect of the energy-saving device.

[0050] The single-layer stabilizing fin solution is selected. Due to the single-layer structure, the welding connection between the stabilizing fin and the hull is subject to a large torsional stress from the lateral load. In order to protect the hull outer plate, a web is welded on the outside of the hull, and the single-layer stabilizing fin is welded on the web. Figure 2 shown.

[0051] The external dimensions of a single-layer heading stabilizing fin are determined according to the shape of the tail frame. The rear end of the stabilizing fin shall not exceed the tail shaft outlet position. If a propeller-front energy-saving device is configured, the rear end of the stabilizing fin shall be before the rear end of the energy-saving device (e.g. Figure 1 To avoid touching the bottom, the bottom of the stabilizing fin is separated from the baseline by a certain distance Zl, which is generally 50mm for ships under construction.

[0052] The maximum distance M between the overhang and the web is used to calculate the torsional stress of the lateral load on the stabilizing fin and affects the design of the plate thickness.

[0053] For the calculation of M, please refer to patent: CN117799796A.

[0054] The effective fillet weld area of ​​the brace end connection is not less than A weld :

[0055] A weld =f*(235 / R eH_weld ) 0.75 *F weld

[0056] in:

[0057] F=M / (0.5*L3) / 2,

[0058] M is the bending moment from the wood to the outer plate, M = P*S*L4

[0059] L4 is the vertical distance from the core of the wood to the outer plate;

[0060] L3 is the pad width;

[0061] P=max{P1, P2}, which is the maximum value of the above-mentioned calculated load.

[0062] R eH_weld It is the yield limit of the welding material on the wood;

[0063] S is the dead wood area;

[0064] f is the coefficient. When the support material is under pressure, f=0.05; when the support material is under tension, f=0.14.

[0065] Since the wood is subjected to lateral force, when calculating the effective weld area, only the situation where the weld on one side is tensile is calculated, that is, only the effective weld area required for the weld on one side to be tensile is calculated.

[0066] Check the effective welding area of ​​the weld.

[0067] A=H1*X;

[0068] Among them, H1 is the welding throat, H2 is the length of the weld angle.

[0069] X is the length of the weld along the length of the ship.

[0070] When A>A weld When A≤A weld When the weld area is larger than A weld Then end the process.

[0071] Here are the specification calculation requirements, which treat the stabilizing fin as a beam in order to calculate the welding area.

[0072] The chamfer radius R1 is to reduce the maximum distance between the overhanging edge of the stabilizing fin and the web. A chamfer is set at the overhanging edge to slightly reduce the side projection area of ​​the stabilizing fin, so as to optimize the plate thickness design and improve the aesthetics of the stabilizing fin.

[0073] Chamfer radius R2, considering the actual construction, the front end of the stabilizing fin cannot be made into a sharp angle shape and welded with the web, it can be cut into a right angle or a small chamfer. Considering the impact on the incoming flow and the smoothness of the structure, it is recommended to take a small chamfer.

[0074] Stabilizing fin plate thickness dn: Determined according to the lateral load, the stabilizing fin is modeled as a cantilever beam, and the welding position with the hull is the fixed end. The plate thickness is designed so that the stress borne by the fixed end does not exceed the allowable stress.

[0075] The double-layer stabilizing fin solution is selected, and the stabilizing fin shape is designed according to the shape of the tail frame. The double-layer heading stabilizing fin is a conical structure formed by splicing four symmetrical wooden boards, and the side projection is a right angle. Each side is welded and spliced ​​by two wooden boards with an obtuse angle, and a fold line is formed at the splicing point. The fold lines on both sides reach the maximum thickness of the stabilizing fin at the outer plate of the hull. The hanging ends of the wooden boards on the left and right sides are connected by round steel welding to reduce the precision requirements of welding alignment; the wooden boards on both sides of the double-layer stabilizing fin are V-shaped with the hull. This structural form can provide more effective support, increase the stabilizing fin's ability to withstand lateral loads and torsional stress, and improve the stability of the product. At the same time, it can save the setting of the belly plate and weld the stabilizing fin directly to the outer plate of the hull.

[0076] Multiple T-profiles are arranged at equal intervals inside the stabilizing fin. The direction of the T-profiles is parallel to the angle line. The wing plates are welded to the rigid boards on both sides to effectively transfer the lateral load and improve the supporting strength of the component.

[0077] The design principle of the external dimensions is the same as that of the single-layer stabilizing fin. It is designed according to the hull stern frame line without affecting the effect of the energy-saving device.

[0078] Since the supporting strength of the double-layer structure is better than that of the single-layer structure, the influence of the maximum distance M between the hanging edge and the hull outer plate on the thickness of the dull board is greatly reduced and is not the main influencing parameter of the dull board thickness. Therefore, the chamfer radius R1, that is, the chamfer farthest from the hull, can be appropriately reduced to more effectively utilize the tail space to increase the side projection area of ​​the stabilizing fin.

[0079] The angle β between the kink line and the baseline and the spacing between T-profiles are mainly considered to be aligned with the internal structure of the hull as much as possible. The final plate thickness d2n of the stabilizing fin takes into account the internal welding space requirements of the double-layer structure and the support for lateral loads. The thickness of the double-layer stabilizing fin is minimized to reduce the impact on hydrodynamics.

[0080] Evaluation of T-profile layout, T-profile panel and web parameters to meet lateral load requirements; T-profile length (Si) and bottom web height (k). Due to space limitations, the T-profile cannot be extended to the round steel. The bottom web height (k) is the minimum height to meet narrow space operations; the T-profile length (Si) depends on parameter k.

[0081] Lightening hole design: For T-shaped materials with a length of more than 2 meters, lightening holes can be set on the web to reduce the weight of the structure. At the same time, when the stabilizing fins shrink inwards under water pressure, the internal pressure can be balanced to avoid stress concentration. The size of the lightening hole is only based on process evaluation and does not affect the design of the double-layer stabilizing fin scheme; when the requirements are met, proceed to the next step.

[0082] The design of single-layer heading stabilizing fin is simple, and the maximum distance M from the overhang to the web is the main factor affecting the plate thickness design. Taking a certain ship as an example, the length and height of the single-layer stabilizing fin structure are 10.3m*4.2m. If the maximum distance M from the overhang to the web reaches 2.7m, the side projection area is about 14.0m2, and the thickness of the stabilizing fin structure that meets the load strength is 50mm. The length of the web at both ends exceeds the stabilizing fin by 100mm, the width is 80mm, and the thickness is 20mm. The weight of the stabilizing fin and the web is 5.5 tons and 0.15 tons respectively, S1 = 14.0m2, weight1 = 5.65 tons.

[0083] The double-layer stabilizing fin structure with a length and height of 10.3m*4.2m is adopted, the chamfer radius is 200mm, that is, the chamfer farthest from the hull, the maximum distance M between the hanging edge and the hull outer plate reaches 3.15m, and the side projection area is about 14.8m2. The thickness of the wooden board that meets the load strength is only 25mm, and the weight of the stabilizing fin (including the internal T-profile) is about 5.5 tons. The side area is increased by more than 5% compared with the single-layer stabilizing fin of the same weight, and the structural stability is better.

[0084] The main difficulty in the design of double-layer stabilizing fins is the determination of the maximum thickness (dmax), which determines the feasibility of T-profile welding and cutting. Taking the above-mentioned ship type as an example, as shown in the figure below: the length of the angle line is about 3.5 meters, the distance between the bottom of the T-profile and the round steel is 1000mm, and the minimum height of the web at the bottom of the T-profile that meets the cutting and welding process requirements is 150mm. The design of T-profiles with different schemes for dmax values ​​in the range of 260mm to 340mm is shown in the figure below. According to the comparison, the scheme with lower impact on hydrodynamics is the better feasible scheme under the premise of meeting the lateral stress strength requirements.

[0085] P is taken as 0.95, Judgement = (14 / 5.65) / (0.94*(14.8 / 5.5)) = 0.97 < 1, and the double-layer stable fin solution is selected.

Claims

1. A method for selecting a stabilizing fin, characterized in that: The method for selecting stabilizing fins for ships with a displacement of 80,000 to 300,000 tons is as follows: S1: Select a single-layer stabilizing fin. A web is fixed on the outer surface of the ship's outer plate, and the single-layer stabilizing fin is fixed on the web. The rearmost end of the stabilizing fin does not exceed the position of the tail shaft outlet. If there is an energy-saving device in front of the propeller, the rearmost end of the stabilizing fin should be in front of the rearmost end of the energy-saving device. There is a spacing between the bottom of the stabilizing fin and the baseline. The front end of the stabilizing fin is chamfered and connected to the web, with a chamfer radius R2; Calculate the lateral area S1 of the stabilizing fin, the lateral force F1 of the stabilizing fin, the thickness d11 of the stabilizing fin plate, and the allowable stress Rw of the single-layer stabilizing fin material. Calculate the stress Rw1 of the stabilizing fin. When Rw1 < Rw, it meets the requirements. When Rw1 ≥ Rw, it does not meet the requirements. Increase the thickness of the stabilizing fin plate by 2 mm each time, set the plate thickness to d12, and continue the stress evaluation until the requirements are met. At this time, determine the stabilizing fin plate thickness d1n; According to the stabilizing fin plate thickness d1n and the lateral area S1 of the stabilizing fin, calculate the weight of the stabilizing fin Weight1 = 7850 * S1 * d1n, and output the final parameters S1, Weight1; S2: Select a double-layer stabilizing fin. The double-layer stabilizing fin is formed by symmetrically butting two fin plates with the same structure. Each fin plate is formed by butting two sub-fin plates. The butting part of the two sub-fin plates forms an obtuse angle and a fold line. The fold line forms an angle β with the baseline. The maximum distance dmax between the two sub-fin plates ranges from 260 mm to 340 mm, and generally the smaller value is taken. A plurality of T-sections are fixed between the two fin plates; Calculate the lateral area S2 of the stabilizing fin, the lateral force F2 of the stabilizing fin, and the allowable stress Rw' of the double-layer stabilizing fin material. Set the initial degree β of the angle and the initial thickness d21 of the sub-fin plate. Take half of the initial thickness d11 of the single-layer stabilizing fin plate. The angle β between the fold line and the baseline and the spacing between the T-sections are mainly positioned by scribing on the inside and outside of the outer plate, and judge that the T-sections are as aligned as possible with the internal structure of the hull; Design the dimensions of the T-section panel and web. The initial dimension of the T-section panel is T21, and the web is taken as 100 - 200 mm; According to the lateral force F2 acting on the T-section panel and web to form a shear force, calculate its stress Rw3. When Rw3 < Rw', it meets the requirements and proceed to the next step. When Rw3 ≥ Rw', it does not meet the requirements. Increase the thickness of the T-section panel and web by 2 mm each time and set it to T22, and continue the stress evaluation until the requirements are met. Determine the thickness T2n of the T-section panel and web; Stress evaluation of the combined structure of the sub-fin plate and T-section. Calculate the stress Rw2 of the stabilizing fin. When Rw2 < Rw', it meets the requirements. When Rw2 ≥ Rw', it does not meet the requirements. Increase the thickness of the fin plate by 2 mm each time and set it to d22, and continue the stress evaluation until the requirements are met. Determine the fin plate thickness d2n; Output the final parameters S2, Weight2 through Weight2 = 7850 * (2 * S2 * d2n + (ST1 * dT1 + ST2 * dT2 + …… STn * dTn) + (SF1 * dF1 + SF2 * dF2 + …… SFn * dFn)); Among them, ST1, ST2...STn are the projection areas of the T-shaped profile panels; dT1, dT2…dTn are the thickness of the T-profile panel; SF1, SF2…SFn are the projected areas of the web of the T-shaped profile; dF1, dF2…dFn are the web thicknesses of the T-shaped profile; S3: Introduce the construction process weight P, and take P as a coefficient not greater than 1 according to the double-layer stable fin structure, 0.8 <P<0.95; When Judgement≥1, the single-layer stable fin solution is selected; when Judgement<1, the double-layer stable fin solution is selected.

2. A method for selecting a stabilizing fin according to claim 1, characterized in that: In step S1, the bottom of the stabilizing fin is 50 mm away from the baseline.

3. A method for selecting a stabilizing fin according to claim 1, characterized in that: In step S1, when a single-layer stabilizing fin is selected, the web area is larger than the installation and fixing area of ​​the stabilizing fin and the ship.

4. A method for selecting a stabilizing fin according to claim 1, characterized in that: In step S2, the parameters of the T-type panel and the web must satisfy the lateral load.

5. A method for selecting a stabilizing fin according to claim 1, characterized in that: In step S2, for T-shaped materials with a length exceeding 2 meters, lightening holes may be provided on the web.

6. A method for selecting a stabilizing fin according to claim 1, characterized in that: In step S2, the T-profile layout is evaluated, and the parameters of the T-shaped panel and web are determined to meet the requirements of lateral load. The length Si of the T-profile and the bottom web height k are determined. Due to space limitations, the T-profile cannot be extended to the round steel. The bottom web height k is the minimum height required for operation in a narrow space. The length Si of the T-profile depends on the parameter k.

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