Optimization design method of LNG cargo containment system installation platform

Abstract

The invention relates to the technical field of liquefied natural gas ship construction, and discloses an optimization design method of an LNG cargo containment system installation platform, which comprises the following steps: inputting basic parameters: obtaining accurate three-dimensional model data of a target ship liquid cargo tank; defining a design constraint; preliminary scheme generation: preliminarily generating an overall arrangement scheme of the installation platform; carrying out multi-working-condition load simulation and finite element division; support leg layout and support leg force optimization: identifying support leg points with over-limit pressure or over-low pressure, and outputting an optimized support leg positioning coordinate matrix; optimizing the rigidity and inherent frequency of the platform; carrying out simulation verification on the overall rigidity, the low-order inherent frequency, the installability and the maintainability of the analysis platform: carrying out installation process simulation, and carrying out maintenance process simulation; and outputting a final design scheme, generating a whole set of design files, and realizing deep collaboration of platform design, a ship body, a construction process and specification requirements based on a systematic design process of parameterized input, multi-objective optimization and dynamic response simulation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of liquefied natural gas ship construction, in particular to an optimization design method of a LNG cargo containment system installation platform. BACKGROUND

[0002] In the construction process of an LNG transport ship, the installation of the liquid cargo tank containment system is a core link, and a large-scale, multi-level special installation platform needs to be erected in the tank. The platform needs to meet many harsh requirements such as large span, large cantilever, variable support, and adaptation to the complex geometry of the tank.

[0003] In the prior art, it is not disclosed how to customize a set of optimal installation platform from scratch for a specific LNG ship with unique characteristics. The traditional design method relies more on experience and lacks a systematic, quantifiable, and simulation-verified optimization design process. It is difficult to accurately predict the mechanical performance of the platform under different working conditions, the interaction with the ship body, and whether it fully meets all the detailed requirements of the GTT specification in the design stage, which may lead to repeated design, material waste, or potential lack of safety redundancy.

[0004] In document CN 116227021 A, a transport ship liquid cargo tank construction platform design method, computer storage medium and equipment are disclosed. Through simulation technology, the structure model is constructed as a three-dimensional model of the construction platform, and then the three-dimensional model of the construction platform is simulated and calculated as a whole. Unqualified structure model is found out, and the parameters of the unqualified structure model are adjusted and then simulated and calculated again until the simulation calculation result of the whole construction platform three-dimensional model meets the requirements. This method can also be optimized, but it does not involve the mechanical performance under different working conditions and the interaction with the ship body.

[0005] Therefore, a new technical solution is needed to solve the above technical problems. SUMMARY

[0006] To solve the above problems, the present application discloses an optimization design method of a LNG cargo containment system installation platform, which is a systematic design process based on parameterized input, multi-objective optimization and dynamic response simulation, realizing the deep cooperation of platform design with the ship body, construction technology and specification requirements.

[0007] The technical scheme of the present application is as follows: an optimization design method of a LNG cargo containment system installation platform, comprising the following steps: Step 1: input basic parameters: obtain the accurate three-dimensional model data of the target ship liquid cargo tank, and obtain the containment system technical parameters at the same time; Step 2: define design constraints; Step 3, Preliminary plan generation: Based on the inputs from Steps 1 and 2, a preliminary overall layout plan for the installation platform is generated; Step 4, Multi-load Simulation and Finite Element Analysis: Define multiple load conditions and perform finite element analysis on the preliminary scheme; Step 5, outrigger layout and outrigger force optimization: Analyze the outrigger reaction force distribution obtained in Step 4, identify outrigger points with excessive or insufficient pressure, and use "outrigger pressure uniformity" and "avoiding excessive pressure" as optimization objectives. Use an iterative algorithm to automatically adjust the outrigger layout on the bottom plane and output the optimized outrigger positioning coordinate matrix. Step 6, Platform stiffness and natural frequency optimization: Based on the optimized model in Step 5, analyze the overall stiffness and low-order natural frequencies of the platform. With the goal of avoiding resonance with the operating frequency of the construction equipment, adjust the cross-sectional parameters or arrangement of the main components of the frame system. By adopting the above technical solutions, the platform's dynamic characteristics are optimized; Step 7, Installability and Maintainability Simulation Verification: Perform installation process simulation and maintenance process simulation; Step 8, Output the final design scheme: Generate a complete set of design documents including the optimized support leg layout drawing, structural construction drawing, bill of materials, load report and FEA verification report.

[0008] Preferably, the technical parameters of the enclosure system in step 1 include the total thickness of the insulation layer and the thickness of the secondary shielding layer, and the model data includes the hull length, width, height, side process door dimensions and elevation, pump tower / liquid dome area geometry, and bottom plate slope data.

[0009] Preferably, the design constraints in step 2 include, but are not limited to, the design load values ​​of each platform, the loads of the working area, the expansion area, and the storage area; the maximum allowable ground pressure of the outriggers, of which ≤200kPa under normal working conditions and ≤350kPa under raised-leg conditions; the minimum clearance requirements between the platform and the bulkhead, especially the dihedral and trihedral areas; and the mandatory configuration requirements for stairs, elevators, and material openings. Preferably, the layout scheme in step 3 includes determining the initial grid layout of the outriggers, the number of platform layers and the elevation of each layer, and the preliminary positioning of the core support frame. Preferably, step 4 defines various load conditions, including static construction loads, dynamic equipment loads, and inertial loads simulating the floating state of a ship; finite element analysis is performed on the preliminary scheme, including calculating the stress distribution, deformation, and outrigger reaction force of the entire platform structure under various load conditions.

[0010] Preferably, when simulating the ship's floating condition in step 4, the inertial load directions considered include heel, trim, and sway.

[0011] Preferably, the optimization objective in step 6 is to control the platform's first-order natural frequency to be more than 1.3 times the device's main excitation frequency.

[0012] Preferably, in step 7, the installation process simulation platform module is used to verify the rationality of the module's size division by simulating the transportation and hoisting path through the process gate; the maintenance process simulation simulates the retraction and unfolding process of the platform's extendable parts to verify its interference with the enclosure system's installation process.

[0013] Preferably, a feedback loop is set in steps 7 to 3 to feed back the interference problem found in step S7 to step S3, modify the preliminary solution, and repeat the subsequent process until all constraints are satisfied.

[0014] The advantages of this invention are: 1. The optimization method of this invention meets many stringent requirements such as large span, large cantilever, variable support, and adaptation to complex ship cabin geometry, accurately predicts the mechanical performance of the platform under different working conditions and its interaction with the ship hull, and meets all the detailed requirements of GTT and other specifications.

[0015] 2. This invention integrates multi-dimensional constraints and objective function optimization design methods to reduce design iterations, material waste, and safety deficiencies, thereby enabling efficient, economical, and safe completion of customized design for LNG cargo containment system installation platforms.

[0016] 3. This invention is based on a systematic design process of parametric input, multi-objective optimization and dynamic response simulation, which realizes deep collaboration between platform design and ship body, construction technology and specification requirements. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the overall process of the optimized design method of this invention.

[0018] Figure 2 This is a schematic diagram of the support leg layout optimization process in step S5.

[0019] Figure 3 This is a stress cloud diagram of a platform under a certain working condition in finite element analysis (FEA).

[0020] Figure 4 This is a schematic diagram for verifying the module hoisting path in the installability simulation.

[0021] The accompanying diagrams should be in color. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0023] An optimized design method for an LNG cargo containment system installation platform includes the following steps: Step 1, Input basic parameters: Obtain accurate 3D model data of the target ship's liquid cargo tank, including tank length, width, height, side process door dimensions and elevation, pump tower / liquid dome area geometry, and bottom plate slope data; at the same time, obtain the technical parameters of the containment system, including the total thickness of the insulation layer and the thickness of the secondary shielding layer; Step 2: Define Design Constraints: Define design constraints according to the GTT specification document OPNB-CDC-000001 "Technical Requirements for Installation Platforms", including but not limited to: design load values ​​for each platform level, distinguishing between work area, expansion area, and storage area loads; maximum allowable ground pressure of outriggers (≤200kPa under normal working conditions, ≤350kPa under outrigger-raised conditions); minimum clearance requirements between the platform and bulkheads (especially dihedral and trihedral areas); mandatory configuration requirements for stairs, elevators, and material access points; Step 3, Preliminary Scheme Generation: Based on the inputs from Steps 1 and 2, a preliminary overall layout scheme for the installation platform is generated, including determining the initial grid layout of the outriggers, the number of platform layers and the elevation of each layer, and the preliminary positioning of the core support frame. Step 4, Load Simulation and Finite Element Analysis (FEA): Define various load conditions, including static construction loads, dynamic equipment loads (such as elevator operation), and inertial loads simulating the floating state of a ship; perform finite element analysis on the preliminary scheme to calculate the stress distribution, deformation, and outrigger reaction forces of the entire platform structure under various load conditions. When simulating the load conditions under the floating state of a ship, the inertial load directions considered include heel, trim, and sway. Step 5, outrigger layout and outrigger force optimization: Analyze the outrigger reaction force distribution obtained in Step 4, identify outrigger points with excessive or insufficient pressure, and use "outrigger pressure uniformity" and "avoiding excessive pressure" as optimization objectives. Use an iterative algorithm to automatically adjust the outrigger layout on the bottom plane and output the optimized outrigger positioning coordinate matrix. Step 6, Platform Stiffness and Natural Frequency Optimization: Based on the optimized model in Step S5, analyze the overall stiffness and low-order natural frequencies of the platform; with the goal of avoiding resonance with the operating frequency of construction equipment (such as elevators and resin machines), optimize the platform's dynamic characteristics by adjusting the cross-sectional parameters or arrangement of the main components of the frame system (such as columns and main beams). The optimization goal is to control the platform's first-order natural frequency to be more than 1.3 times the main excitation frequency of the equipment. Step 7, Simulation verification of installability and maintainability: Simulate the installation process, simulating the transportation and hoisting path of the platform module through the process door to verify the rationality of the module size division; simulate the maintenance process, simulating the retraction and unfolding process of the platform's retractable parts to verify its interference with the installation process of the enclosure system. Step 8, Output the final design scheme: Generate a complete set of design documents including the optimized support leg layout drawing, structural construction drawing, bill of materials, load report and FEA verification report.

[0024] The following are embodiments of the above scheme: like Figure 1 As shown, taking the installation platform design of an LNG ship (4 cargo tanks) as an example, the present invention will be further described in detail with reference to the accompanying drawings.

[0025] Step 1: Obtain accurate CAD models of cargo holds 1 and 2, 3 and 4 of the LNG ship, and extract key dimensions (such as L=32105mm, H=30405mm for hold 1; process door height H=9790mm, etc.).

[0026] Step 2: According to GTT specifications, set the load on the technical platform (process gate layer) to 250 kg / m², the top layer load to 100 kg / m², and other layers to 200 kg / m². Set the outrigger pressure constraint to 200 kPa for standard and 350 kPa for raised outrigger.

[0027] Step 3: Generate the initial design scheme. Initially set the outrigger grid as a uniform grid along the hull's transverse and longitudinal directions. The platform is divided into 9 layers (L0 to L8), and the elevation is determined according to the hull shape.

[0028] Step 4: Import the initial model into finite element software (such as ANSYS), and define the load cases, such as... Figure 3 As shown: Working condition 1: Static load + full-coverage construction load; Working condition 2: Static load + elevator dynamic load (considering a dynamic load factor of 1.5). Working condition 3: Simulating the load on a ship with a 5° heel; Analysis revealed that under the initial design, the pressure on the side outriggers reached 380 kPa in operating condition 3, exceeding the specification limit. Step 5: Activate the outrigger layout optimization algorithm. With the goal of reducing outrigger pressure exceeding limits, the algorithm automatically refines the outrigger mesh in the side area and adjusts the spacing of the outriggers in the mid-section. After multiple iterations, the pressure at all outrigger points stabilized below 350 kPa under all operating conditions, achieving good matching with the insulation plate layout. The optimization process is as follows: Figure 2 As shown; Step 6: Modal analysis shows that the first-order vertical frequency of the platform is 2.1Hz. The main excitation frequency of the elevator operation is expected to be below 1.5Hz, with a frequency ratio greater than 1.3, which meets the frequency avoidance requirements. Therefore, no stiffness adjustment is needed. Step 7: As Figure 4As shown, during the installation simulation, it was found that a certain frame module in the initial division had dimensional interference or excessive hoisting stress. The problem was reported, and the module division dimensions were adjusted in the S3 stage and re-analyzed until all modules could be successfully hoisted and installed. Step 8: Output the final complete set of design drawings and reports, and deliver them for manufacturing and installation.

[0029] Those skilled in the art should understand that the embodiments of the present invention described above and shown in the accompanying drawings are merely examples and do not limit the present invention; the objectives of the present invention have been fully and effectively achieved. The functions and structural principles of the present invention have been demonstrated and explained in the embodiments, and any modifications or variations of the embodiments of the present invention may be made without departing from the stated principles.

Claims

1. An optimized design method for an LNG cargo containment system installation platform, characterized in that, Includes the following steps: Step 1, Input basic parameters: Obtain accurate 3D model data of the target ship's liquid cargo tank, and at the same time obtain the technical parameters of the containment system; Step 2: Define design constraints; Step 3, Preliminary plan generation: Based on the inputs from Steps 1 and 2, a preliminary overall layout plan for the installation platform is generated; Step 4, Multi-load Simulation and Finite Element Analysis: Define multiple load conditions and perform finite element analysis on the preliminary scheme; Step 5, outrigger layout and outrigger force optimization: Analyze the outrigger reaction force distribution obtained in Step 4, identify outrigger points with excessive or insufficient pressure, and use "outrigger pressure uniformity" and "avoiding excessive pressure" as optimization objectives. Use an iterative algorithm to automatically adjust the outrigger layout on the bottom plane and output the optimized outrigger positioning coordinate matrix. By adopting the above technical solutions, the layout of the support leg grid and the insulation plate can be matched as much as possible, so as to achieve the ideal support state of "one plate for one leg" or "one plate for multiple legs". Step 6, Platform stiffness and natural frequency optimization: Based on the optimized model in Step 5, analyze the overall stiffness and low-order natural frequencies of the platform. With the goal of avoiding resonance with the operating frequency of the construction equipment, adjust the cross-sectional parameters or arrangement of the main components of the frame system. Step 7, Installability and Maintainability Simulation Verification: Perform installation process simulation and maintenance process simulation; Step 8, Output the final design scheme: Generate a complete set of design documents including the optimized support leg layout drawing, structural construction drawing, bill of materials, load report and FEA verification report.

2. The optimized design method for an LNG cargo containment system installation platform according to claim 1, characterized in that: The technical parameters of the enclosure system in step 1 include the total thickness of the insulation layer and the thickness of the secondary shielding layer. The model data includes the length, width, height of the hull, dimensions and elevation of the side process doors, geometric dimensions of the pump tower / liquid dome area, and bottom plate slope data.

3. The optimized design method for an LNG cargo containment system installation platform according to claim 1, characterized in that: The design constraints in step 2 include, but are not limited to, the design load values ​​of each platform, the loads of the working area, the expansion area, and the storage area; the maximum allowable ground pressure of the outriggers, of which ≤200kPa is required under normal working conditions and ≤350kPa is required under raised outrigger conditions; the minimum clearance requirements between the platform and the bulkhead, especially the dihedral and trihedral areas; and the mandatory configuration requirements for stairs, elevators, and material access points.

4. The optimized design method for an LNG cargo containment system installation platform according to claim 1, characterized in that: The layout scheme in step 3 includes determining the initial grid layout of the outriggers, the number of platform layers and the elevation of each layer, and the preliminary positioning of the core support frame.

5. The optimized design method for an LNG cargo containment system installation platform according to claim 1, characterized in that: Step 4 defines various load conditions, including static construction loads, dynamic equipment loads, and inertial loads simulating the floating state of a ship; finite element analysis is performed on the preliminary scheme, including calculating the stress distribution, deformation, and outrigger reaction forces of the entire platform structure under various load conditions.

6. The optimized design method for an LNG cargo containment system installation platform according to claim 4, characterized in that: When simulating the ship's floating condition in step 4, the inertial load directions considered include heel, trim, and sway.

7. The optimized design method for an LNG cargo containment system installation platform according to claim 1, characterized in that: The optimization objective in step 6 is to control the platform's first-order natural frequency to be more than 1.3 times the device's main excitation frequency.

8. The optimized design method for an LNG cargo containment system installation platform according to claim 1, characterized in that: In step 7, the installation process simulation platform module verifies the rationality of the module's size division by simulating the transportation and hoisting path through the process door; the maintenance process simulation simulates the retraction and unfolding process of the platform's retractable parts to verify its interference with the enclosure system's installation process.

9. The optimized design method for an LNG cargo containment system installation platform according to claim 1, characterized in that: In steps 7 to 3, a feedback loop is set up to feed back the interference problem found in step S7 to step S3, modify the preliminary solution, and repeat the subsequent process until all constraints are satisfied.

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