Analysis and evaluation method for ventilation mast of large dual-fuel power ship

Abstract

The invention provides a method for analyzing and evaluating a ventilation mast of a large-scale dual-fuel power ship, and the method comprises the steps: constructing a whole-ship three-dimensional model according to the ship size which comprises sea area ship height limitation and deck periphery arrangement; grid division is carried out according to the whole-ship three-dimensional model, and a computational domain is determined for the whole-ship three-dimensional model after grid division; under the influence of gas sedimentation under the action of gravity, simulation solving is conducted on expansion behaviors in the gas release process of the ventilation masts under all working conditions of the whole scene based on fluid mechanics, and a calculation result is obtained; under the influence of gas sedimentation under the action of gravity, the expansion behavior in the gas release process of the gas-permeable mast under all working conditions of the whole scene is simulated and solved based on fluid mechanics, and the technical problem that in the prior art, an analysis and evaluation method for the LNG ship gas-permeable mast is lacked is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of structural design, in particular to a large dual-fuel power ship venting mast analysis and evaluation method. BACKGROUND

[0002] With the adjustment of the energy structure of the global shipping industry and the improvement of environmental protection requirements, the market for LNG transport ships, LNG dual-fuel ships and other LNG ships is expanding. In order to ensure that LNG ships can safely and reliably navigate in complex and variable marine environments, the optimization of ship safety design is particularly important. LNG is highly flammable and explosive, and there is a safety risk, which needs to be vertically discharged to the atmosphere through a venting mast during the storage, filling and processing of LNG. The International Safety Rules for Ships Using Gas or Other Low Flashpoint Fuels (IGF Code) clearly stipulates the height and position requirements of the venting mast to prevent potential risks, but in actual ship design, due to the complexity of ship layout, ship height restrictions in specific sea areas and other factors, it is sometimes difficult to directly meet the height and position requirements of the venting mast specified in the code.

[0003] To solve this problem, the present application provides a large dual-fuel ship venting mast alternative design method, which proves that the venting mast design is reasonable and safe through equivalent proof, thereby realizing venting mast alternative design, ensuring the safety of the venting mast design and the accuracy of the evaluation, and protecting the overall safety performance of the LNG ship.

[0004] There is an urgent need for a large dual-fuel power ship venting mast analysis and evaluation method, which helps to solve the technical problem that the prior art lacks a LNG ship venting mast analysis and evaluation method. SUMMARY

[0005] In one embodiment, the present application provides a large dual-fuel power ship venting mast analysis and evaluation method, which simulates and solves the expansion behavior of the venting mast gas release process under the influence of gravity-induced gas settlement based on fluid mechanics for all scenarios and working conditions, which helps to solve the technical problem that the prior art lacks a LNG ship venting mast analysis and evaluation method.

[0006] The large dual-fuel power ship venting mast analysis and evaluation method comprises:

[0007] A full-ship three-dimensional model is constructed according to the ship size, wherein the ship size includes sea area height restrictions and deck periphery arrangement;

[0008] The full-ship three-dimensional model is meshed according to the full-ship three-dimensional model, and the meshed full-ship three-dimensional model is determined as a calculation domain;

[0009] Under the influence of gas settlement of gravity, the simulation and solution of the spreading behavior of the gas release process of the venting mast in all scenarios and working conditions are obtained based on fluid mechanics to obtain the calculation results.

[0010] The evaluation results are obtained by analyzing and evaluating the calculation results.

[0011] In an embodiment, the ship size includes the height, diameter and arrangement position of the venting mast.

[0012] In an embodiment, the construction of the full-ship three-dimensional model according to the ship size includes:

[0013] The full-ship three-dimensional model is built according to the actual size, wherein the full-ship three-dimensional model includes the deck and above ship arrangement, and the key areas of the full-ship three-dimensional model include the venting mast, important places, equipment, walkways and HVAC around the venting mast.

[0014] In an embodiment, the length, width and height of the calculation domain are at least ten times the length, height and width of the ship respectively, and the full-ship model is placed at the center position of the calculation domain.

[0015] In an embodiment, the grid division according to the full-ship three-dimensional model and the determination of the full-ship three-dimensional model after the division of the grid as the calculation domain include:

[0016] The calculation domain is determined, and the length, width and height of the calculation domain are at least ten times the length, height and width of the ship respectively, and the full-ship model is placed at the center position of the calculation domain.

[0017] The orthogonal quality average value of the grid is greater than 0.4, and the minimum value is not less than 0.3; the aspect ratio of the grid, i.e. the ratio of the longest side to the shortest side of the grid unit, is less than 10.

[0018] In an embodiment, the modeling key areas around the venting mast should be encrypted.

[0019] In an embodiment, the simulation and solution of the spreading behavior of the gas release process of the venting mast in all scenarios and working conditions under the influence of gas settlement of gravity based on fluid mechanics to obtain the calculation results include:

[0020] The simulation and solution process is a non-steady-state solution;

[0021] The environmental wind direction working condition is selected based on the arrangement of the open deck within a range of not less than 10m around the venting mast release source position;

[0022] Under each environmental wind direction, at least four environmental wind speed working conditions are simulated in combination with the ship speed and the maximum environmental wind direction, and 0m / s is included in the four environmental wind speeds.

[0023] In an embodiment, the wind direction should at least include the direction pointing to the following positions:

[0024] a) living quarters, service quarters and control station;

[0025] b) other non-hazardous area air inlets, outlets or openings;

[0026] c) equipment exhaust outlets;

[0027] d) electrical equipment;

[0028] e) working areas and walkways.

[0029] In an embodiment, the analyzing and evaluating the calculation result to obtain an evaluation result comprises:

[0030] If there is no risk in any condition, the air venting mast design is reasonable, and the air venting mast alternative design is completed; if the air venting mast gas diffusion behavior in any condition has a risk, the height or position of the air venting mast is adjusted, and the three-dimensional model of the whole ship is constructed according to the ship size until the alternative design is completed.

[0031] In an embodiment, the air venting mast gas diffusion risk is evaluated according to the calculation result of the gas cloud diffusion volume concentration, and the area with a gas cloud diffusion volume concentration less than 2.5% is a safe area. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 FIG. 1 is a flowchart of a large dual-fuel power ship air venting mast analysis and evaluation method according to an embodiment of the present application. DETAILED DESCRIPTION

[0033] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be described in detail below with reference to the drawings and specific embodiments.

[0034] The various aspects and features of the present application are described herein with reference to the accompanying drawings.

[0035] These and other characteristics of the present application will become apparent with the description of the preferred forms given below with reference to the attached drawings.

[0036] It should also be understood that, although the present application has been described with reference to some specific examples, many other equivalent forms of the present application will be readily apparent to those skilled in the art in light of this disclosure, which has the features as claimed and thus all fall within the scope of protection defined by the claims.

[0037] The above and other aspects, features and advantages of the present application will become more apparent with reference to the following detailed description when considered in conjunction with the accompanying drawings.

[0038] Specific embodiments of this application are described below with reference to the accompanying drawings; however, it should be understood that the claimed embodiments are merely examples of this application, which can be implemented in various ways. Well-known and / or repeated functions and structures are not described in detail to ascertain the true intent based on the user's historical operations, and to avoid unnecessary or redundant details that would obscure this application. Therefore, the specific structural and functional details claimed herein are not intended to be limiting, but merely serve as the basis and representative basis for the claims to teach those skilled in the art to use this application in various ways with substantially any suitable detailed structure.

[0039] This specification may use the phrases “in one embodiment,” “in another embodiment,” “in yet another embodiment,” or “in other embodiments,” all of which may refer to one or more of the same or different embodiments according to this application.

[0040] This invention aims to predict the diffusion path and affected area of ​​gas released from the vent mast of a dual-fuel ship using computational fluid dynamics (CFD). It achieves an alternative design for the vent mast through the following steps: vent mast design → full-ship full-size modeling → computational domain mesh generation → multi-condition unsteady-state simulation solution → evaluation of calculation results → implementation of the vent mast alternative design. This invention divides the computational domain reasonably and clarifies the computational boundary conditions. Through full-size 3D modeling, computational domain mesh generation, and full-condition unsteady-state simulation solution, it evaluates the diffusion behavior and explosion risk of gas released from the vent mast of a dual-fuel ship under different environmental wind speeds in areas such as crew work areas and walkways, living quarters, service areas and control stations, air inlets, outlets or openings in other non-hazardous areas, equipment exhaust outlets, and electrical equipment, verifying the safety and rationality of the vent mast design height. This not only helps solve the problem of vent mast designs failing to meet regulations, optimizing vent mast design during the ship design stage to minimize potential hazards to the surrounding environment, but also provides a solid theoretical foundation and data support for subsequent operational safety and emergency response measures, possessing significant practical application value and safety assurance significance.

[0041] Figure 1 This is a flowchart illustrating a method for analyzing and evaluating the permeable mast of a large dual-fuel powered vessel, according to an embodiment of the present invention. Figure 1 As shown, in one embodiment, the present invention provides a method for analyzing and evaluating the ventilated mast of a large dual-fuel powered vessel, the method comprising:

[0042] A full three-dimensional model of the ship is constructed based on the ship's dimensions, which include sea area height restrictions and deck perimeter layout.

[0043] The full ship 3D model is meshed, and the computational domain is determined for the meshed full ship 3D model.

[0044] Under the influence of gas settling under gravity, the expansion behavior of the gas release process of the vent mast under various working conditions in the whole scenario is simulated and solved based on fluid mechanics to obtain the calculation results;

[0045] The calculation results are analyzed and evaluated to obtain the evaluation results.

[0046] The shift from "experience-based design" to "simulation-driven design": Traditional ventilated mast design relies heavily on empirical formulas, industry standards (such as IMO and classification society rules), and conservative engineering estimates. Your proposal suggests building a full-ship 3D model and performing computational fluid dynamics (CFD) simulations, a physics-based, predictable, and digital design verification method. This paradigm shift from "rough estimation" to "precise simulation" has significant substantive characteristics.

[0047] Systematic analysis involving multiple coupled factors: Your proposal emphasizes consideration of "ship height restrictions in the sea area," "deck perimeter layout," and "gas settling due to gravity." This indicates that it does not analyze the vent mast in isolation, but rather places it within the real overall ship environment and physical constraints (gravity) for systematic analysis. This approach of coupling ship constraints, geometric layout, and the physical field of gas diffusion transcends the relatively isolated considerations of traditional methods and solves practical problems in complex systems.

[0048] Coverage of "All Scenarios and Operating Conditions": Creativity lies in the pursuit of completeness. The solution requires analysis of all possible operating conditions, such as: different wind speeds and directions, different ship speeds, different engine loads (leading to different gas flow and temperature), different ambient temperatures, and even fault conditions (such as a single vent pipe rupture). This comprehensive simulation analysis strategy ensures that the design is safe under any expected operating conditions, which is difficult to achieve efficiently and comprehensively using traditional methods.

[0049] Significant progress in terms of technical effectiveness

[0050] Optimized Design and Cost Control: Traditional methods, for safety reasons, may overly conservatively increase the height of the ventilated mast. Your solution, through precise simulation, can find the optimal, lowest ventilated mast height while meeting safety regulations. This directly leads to reduced manufacturing costs (materials, structural weight) and improved ship operating economics (lower center of gravity, improved stability, and potentially reduced wind resistance).

[0051] Enhancing the reliability of safety assessments: CFD simulations can visualize the diffusion path, concentration distribution, and potential hazardous areas (such as air intakes, residential areas, and the vicinity of ignition sources) of gas clouds. This provides a more intuitive and accurate quantification of safety margins than traditional calculations, significantly reducing the risk of explosions caused by the accumulation of combustible gases and meeting the extremely high safety requirements of shipowners and classification societies.

[0052] Improved design efficiency: While initial modeling and simulation require investment, once the basic model is established, the effects of various design changes (such as altering the location of the vent mast, the direction of the outlet, or adding baffles) can be quickly evaluated. This shortens the design iteration cycle and accelerates project progress.

[0053] In summary, the core innovation of this solution lies in the systematic application of high-fidelity full-ship CFD simulation technology to address the specific and critical safety design challenge of the ventilated mast on dual-fuel ships. This represents a leap from relying on experience to relying on scientific prediction, and has brought about significant technological advancements in optimization, safety, and efficiency.

[0054] In one embodiment, the vessel dimensions include the height, diameter, and arrangement of the ventilated mast.

[0055] In one embodiment, constructing a full-ship 3D model based on the ship's dimensions includes:

[0056] A three-dimensional model of the entire ship is built according to the actual dimensions. The three-dimensional model of the entire ship includes the ship's layout above the deck. The key areas of the three-dimensional model of the entire ship include the vent mast, important places, equipment, walkways, and HAVC around the vent mast.

[0057] In one embodiment, the length, width, and height of the computational domain are at least ten times the ship's length, height, and width, respectively, and the entire ship model is placed at the center of the computational domain.

[0058] In one embodiment, the step of meshing the full-ship 3D model and determining the computational domain of the meshed full-ship 3D model includes:

[0059] Define a computational domain whose length, width, and height are at least ten times the ship's length, height, and width, respectively, and place the entire ship model at the center of the computational domain.

[0060] The average orthogonal quality of the mesh is greater than 0.4 and the minimum is not less than 0.3; the aspect ratio of the mesh, i.e., the ratio of the longest side to the shortest side of the mesh cell, is controlled to be less than 10.

[0061] In one embodiment, the mesh should be densified in the key modeling areas around the ventilated mast.

[0062] In one embodiment, the calculation results obtained by simulating and solving the extended behavior of the gas release process of the vent mast under various working conditions in the whole scenario based on fluid mechanics under the influence of gas settling under gravity include:

[0063] The simulation solution process is an unsteady-state solution;

[0064] The environmental wind direction and operating conditions are selected based on the arrangement of the open deck within a range of no less than 10m around the location of the vented mast release source.

[0065] For each environmental wind direction, simulations are conducted under at least four environmental wind speed conditions, taking into account the ship's speed and the maximum environmental wind direction. The four environmental wind speeds include 0 m / s.

[0066] In one embodiment, the wind direction should at least include a direction pointing to the following locations:

[0067] a) Living quarters, service areas and control stations;

[0068] b) Other non-hazardous area air inlets, outlets, or openings;

[0069] c) Equipment exhaust gas outlet;

[0070] d) Electrical equipment;

[0071] e) Work areas and walkways.

[0072] In one embodiment, the step of analyzing and evaluating the calculation results to obtain evaluation results includes:

[0073] If there are no risks, the vented mast design is reasonable and the vented mast replacement design is completed; if there are risks in the gas diffusion behavior of the vented mast under any working condition, the height or position of the vented mast is adjusted, and the ship's three-dimensional model is built according to the ship's dimensions until the replacement design is completed.

[0074] In one embodiment, the risk of gas diffusion from the ventilated mast is assessed based on the calculation results of the gas cloud diffusion volume concentration, and the area with a gas cloud diffusion volume concentration of less than 2.5% is a safe area.

[0075] Based on the existing solution, the following extensions can be made in terms of depth and breadth, and these extensions themselves can also constitute new inventive points:

[0076] Automated verification of compliance with specifications / standards: Develop a post-processing tool that can automatically read simulation results (such as gas concentrations at specific distances from ignition sources, openings, and deck boundaries) and compare them with clauses of IMO IGF Codes and classification society specifications (such as DNV, ABS, LR, etc.), automatically generating a compliance report. This will greatly reduce the review burden on engineers.

[0077] Dynamic operating conditions and risk probability assessment: The current solution mentions "various operating conditions," which can be extended to dynamic simulation (rather than steady-state simulation) to simulate the transient diffusion process in the initial stage of gas release. Furthermore, a quantitative risk assessment (QRA) can be performed by combining the probability of different operating conditions to calculate the probability value of explosion risk, making the safety design more refined.

[0078] Multiphysics coupling: The current scheme focuses on gas diffusion (fluid dynamics). This can be extended to:

[0079] Thermodynamic coupling: Consider the buoyancy effect when high-temperature gas mixes with cold air and the impact of thermal radiation on surrounding equipment.

[0080] Structural coupling: Analysis of the loads on the ventilated mast itself and surrounding structures caused by the pressure wave generated by the gas explosion (explosion dynamics simulation).

[0081] Intelligent optimization design: This approach encapsulates the CFD simulation process and combines it with intelligent optimization algorithms (such as genetic algorithms and particle swarm optimization). Using design variables such as the height of the vent mast, the direction of the outlet, and its location, and with objectives and constraints such as safe concentration, ship height restrictions, and manufacturing costs, the computer automatically seeks the optimal design solution.

[0082] Digital Twin and Condition Monitoring: The finalized simulation model serves as the basis for the "digital twin." Gas concentration sensors and weather stations are deployed on the actual ship to collect real-time data on wind speed, wind direction, and deck gas concentration. This data is then compared with the predictions from the digital twin model to provide real-time safety warnings and operational decision support.

[0083] To make the technical solution more operable, rigorous, and with stronger patent protection, it is recommended to improve the following details:

[0084] Clarify model details:

[0085] Geometric model: The three-dimensional model of the entire ship should include in detail the key features, such as: superstructure, deckhouse, engine room, ventilation openings, air intakes, helicopter deck, lifting equipment, and all obstacles that may affect the airflow field and gas diffusion.

[0086] Mesh Generation: The mesh generation strategy should be described in detail. For example: "A hybrid mesh technique is used to locally refine key areas such as near the vent mast outlet and around the superstructure to ensure the capture of complex eddies and concentration gradients." The requirements for mesh independence verification should also be mentioned.

[0087] Refine the physical model and boundary conditions:

[0088] Turbulence Model: Specify the recommended CFD turbulence model, such as "Use a Realizable k-ε model or an SST k-ω model" to accurately simulate airflow with separation and strong shear forces.

[0089] Substance definition: Define the physical properties of the gas, such as: "Define the released gas (such as the BOG of LNG, which is mainly composed of methane) as a mixture with specific density, viscosity and diffusivity."

[0090] Boundary conditions: Detailed definition of various boundary conditions:

[0091] Ventilation mast outlet: "Set as either a mass flow inlet or a velocity inlet, depending on the maximum design release rate."

[0092] Computational domain boundary: "Velocity inlet (incoming air velocity), pressure outlet".

[0093] Deck and building surfaces: "Set as non-slip wall".

[0094] **Solver Settings:** Specify the solver type (e.g., pressure-based or density-based), discretization scheme, etc.

[0095] Quantitative evaluation criteria:

[0096] "The concentration of the gas cloud must not extend beyond a 3-meter radius around any air inlet when it reaches the lower flammability limit (LEL)."

[0097] "The concentration of flammable gas in any location in the deck working area and living area shall not exceed 50% of the lower flammability limit (50% LEL)."

[0098] "Gas cloud must not touch the helicopter deck area."

[0099] These criteria should be directly cited or related to international maritime regulations.

[0100] Add a verification and confirmation (V&V) step:

[0101] A rigorous technical solution must include methods for verifying the accuracy of the simulation model. This can be supplemented with: "Verifying the accuracy of the calculation results through mesh independence analysis" or "Verifying and validating the CFD model by comparing it with scaled-down model experimental data or recognized classic cases (V&V)" to ensure the credibility of the simulation results.

[0102] Forming a closed-loop design process:

[0103] The solution is refined into a complete closed-loop process: an iterative process of "model building -> simulation -> result evaluation -> design modification if requirements are not met (such as increasing height, changing position, adding baffles) -> simulation again" until all working conditions meet the safety evaluation standards.

[0104] Beneficial effects:

[0105] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0106] 1. This method can be used to address the issue of large dual-fuel ship vent mast designs failing to meet IGF specifications. It provides an effective method for predicting the diffusion path and affected area during the gas release process of dual-fuel ship vent masts using computational fluid dynamics (CFD), ultimately achieving an alternative design for the vent mast.

[0107] 2. During the ship design phase, ship designers can use the method of this patent to accurately calculate and verify the height, layout, and gas release characteristics of the LNG vented mast, thereby optimizing the ship design and ensuring the safe and efficient design of dual-fuel ships.

[0108] 3. For ship operators, the method of this patent can accurately assess the gas release and diffusion behavior of the vent mast of dual-fuel ships, the gas release risk of ships in emergency situations, formulate effective emergency plans, reduce the possibility of accidents, and reduce economic losses and reputational damage caused by accidents.

[0109] 4. To ensure the safety of life of the ship's direct users such as crew members and passengers, this patented design and layout of the ventilated mast ensures that gas can be released quickly and safely in emergency situations, reducing harm to human health and providing a safe and reliable navigation environment for crew members and passengers.

[0110] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the present invention. The scope of protection of the present invention is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within its spirit and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of the present invention.

Claims

1. A method of analysis and evaluation of a large dual-fuel powered ship air vent mast, characterized by, The large dual-fuel power ship vented mast analysis and evaluation method comprises: a full-ship three-dimensional model is constructed according to ship dimensions, wherein the ship dimensions include sea area ship height limit and deck periphery arrangement; grid division is performed according to the full-ship three-dimensional model, and the full-ship three-dimensional model after grid division is determined as a calculation domain; under the influence of gravity gas settlement, the expansion behavior of the vented mast gas release process in each working condition of the full scene is simulated and solved based on fluid mechanics to obtain calculation results; the calculation results are analyzed and evaluated to obtain evaluation results.

2. The method of analytical evaluation of a large dual-fuel powered ship air vent mast according to claim 1, characterized in that, The ship dimensions include the height, diameter and arrangement position of the vented mast.

3. The method of analytical evaluation of a large dual-fuel powered ship air vent mast according to claim 2, characterized in that, The full-ship three-dimensional model is constructed according to actual dimensions, wherein the full-ship three-dimensional model includes ship arrangement above the deck, and the key areas of the full-ship three-dimensional model include the vented mast, important places, equipment, walkways and HAVC around the vented mast. The length, width and height of the calculation domain are at least ten times the length, height and width of the ship respectively, and the full-ship model is placed at the center position of the calculation domain.

4. The method of analytical evaluation of a large dual-fuel powered ship air vent mast according to claim 3, characterized in that, The calculation domain is determined, and the length, width and height of the calculation domain are at least ten times the length, height and width of the ship respectively, and the full-ship model is placed at the center position of the calculation domain; 5. The method of analytical evaluation of a large dual-fuel powered ship air vent mast according to claim 4, characterized in that, the grid orthogonal mass average value is greater than 0.4, and the minimum value is not less than 0.3; the grid aspect ratio, i.e. the ratio of the longest side to the shortest side of the grid unit, is less than 10. The key areas around the vented mast are modeled and the grid is encrypted. The simulation solving process is unsteady state solving; 6. The method of analytical evaluation of large dual-fuel powered ship air-vent stack, according to claim 5, characterized in that, environmental wind direction conditions are selected based on the arrangement of open decks within a range of not less than 10 m around the vented mast release source position; 7. The method of analytical evaluation of large dual-fuel powered ship air-vent stack, according to claim 6, characterized in that, under each environmental wind direction, at least four environmental wind speed conditions are simulated in combination with the ship speed and the maximum environmental wind direction, and 0 m / s is included in the four environmental wind speeds. The wind direction should at least include the following directions: a) living quarters, service quarters and control stations; b) other non-dangerous area air inlets, outlets or openings; 8. The method of analytical evaluation of large dual-fuel powered ship air-vent stack, according to claim 7, characterized in that, c) equipment exhaust outlets; d) electrical equipment; e) work areas and walkways. If there is no risk in any condition, the vented mast design is reasonable, and the vented mast replacement design is completed; if there is a risk in the vented mast gas diffusion behavior in any condition, the height or position of the vented mast is adjusted, and the full-ship three-dimensional model is constructed according to the ship dimensions until the replacement design is completed. The vented mast gas diffusion risk is evaluated according to the gas cloud diffusion volume concentration calculation results, and the area with a gas cloud diffusion volume concentration less than 2.5% is a safe area. ​ 9. The method of analytical evaluation of large dual-fuel powered ship air-vent stack, according to claim 8, characterized in that, ​ ​ 10. The method of analytical evaluation of large dual-fuel powered ship air-vent stack, according to claim 9, characterized in that, ​

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