The impact of ship vibrations on the external output performance of Proton Exchange Membrane Fuel Cells (PEMFCs) remains ambiguous, and the use of PEMFCs on ships is more challenging than on land. To establish a theoretical foundation for controlling PEMFCs in a maritime setting and facilitating their integration into marine power systems, this study develops a three-dimensional single-flow channel PEMFC model under ship vibration using computational fluid dynamics. Spectra correlating PEMFC performance characteristics with vibrational parameters are quantitatively established through the least squares method, reflecting PEMFC outputs under varying ship vibration intensities. Results indicate that weak vibrations lead to continuous PEMFC output with decreasing performance at higher frequencies, while strong vibrations result in PEMFC output truncation with exponentially decreasing truncation times at elevated frequencies. The error between simulation and prediction spectra is below 3% and 5% for weak and strong vibrations, respectively. This paper enhances the comprehension of vibration-induced effects on PEMFC performance and elucidates the operational characteristics of PEMFC under vibrational conditions, delivering actionable insights for the design and operation of PEMFC systems in maritime applications.

With the continuous advancement of intelligent, integrated, and sophisticated modern marine equipment, bearing fault diagnosis faces increasingly severe technical challenges. Compared with traditional industrial environments, marine propulsion systems are characterized by multi-bearing coupled vibrations and complex operating conditions. To address these characteristics, this paper proposes a fault diagnosis method that combines a least squares support vector machine (LSSVM) with multi-domain feature extraction based on an improved hippopotamus optimization algorithm (LCM-HO). This method directly extracts time, spectral, and time-frequency domain features from the raw signal, effectively avoiding complex preprocessing and enhancing its potential for field engineering applications. Experimental verification using the Paderborn bearing dataset and a self-built marine bearing test bench demonstrates that the LCM-HO-LSSVM method achieves diagnostic accuracy rates of 99.11% and 98.00%, respectively, demonstrating significant performance improvements. This research provides a reliable, efficient, and robust technical solution for bearing fault diagnosis in complex marine environments.

By re-liquefying the evaporated gas in the BOG reliquefaction process, operational expenses are minimized, simultaneously advancing environmental sustainability and improving resource usage. Most current reliquefaction processes untilize a single precooling cycle, with limited research on multi-stage precooling configurations. This paper proposes a dual precooling cycle that utilizes propane and BOG itself as precooling agents, and reliquefies BOG using a nitrogen inverse Brayton cycle. The design focuses minimizing specific energy consumption (SEC) through simulation and optimization. Optimization results indicate that the BOG reliquefaction process achieves an SEC of 1.017 kWh/kgLNG and an exergy efficiency of 27.29% respectively. More than 20% improvement in SEC compared to other single precooling processes. Cost analyses show that the dual precooled BOG liquefaction process is economically sound. Ultimately, through an analysis of the system based on BOG components and temperature variations, the system was able to operate stably.

The strong coupling between the ship’s sway and yaw motion increases the complexity of identifying hydrodynamic derivatives in mathematical models and reduces accuracy. To solve this problem, this paper proposes an identification method Alpha Evolution Multi-output Support Vector Regression (AE-MSVR) based on MSVR combined with AE. This method approaches the yaw and sway motion equations as a multi-input and multi-output (MIMO) problem, utilizing MSVR for modeling and optimizing hyperparameters with AE. It reduces parameter drift by restructuring the regression model’s input–output. Identification data is obtained via zigzag test simulation. The AE-MSVR method successfully identifies linear and nonlinear hydrodynamic derivatives in the 3 degree of freedom (DOF) Abkowitz model. Using clean simulation data, the results show promising agreement with experimental values from planar motion mechanism (PMM) tests and achieve improved accuracy compared with the standard SVR identification method. To assess robustness, simulated noise is introduced at different levels; maneuvering characteristics are evaluated using turning circle tests. Results demonstrate that AE-MSVR achieves promising accuracy in identifying ship hydrodynamic derivatives and shows encouraging robustness against noise. The method provides potential support for ship motion prediction and maneuverability forecasting.

Gas diffusion layer (GDL) is an essential component of proton exchange membrane fuel cells, serving the functions of gas-water transport, thermal-electrical conduction and mechanical support. The various microstructural characteristics of the GDL have coupled and complex impact on transport properties, which is not comprehensively considered in previous studies. This study combines stochastically reconstruction techniques, pore-scale modeling and orthogonal design method to evaluate the coupling effect of multiple microstructural characteristics on transport properties, and determine the impact degree of each microstructural characteristics, including fiber diameter, porosity, GDL thickness, fiber orientation coefficient, binder and PTFE content. Finally, new mathematical models are developed and validated to predict and optimize the anisotropic transport properties accurately and rapidly by considering the coupling effect of multiple microstructural characteristics. The results showed that porosity has higher impact degree on gas diffusion and heat conduction than other microstructural characteristics. The combinations of microstructural parameters are optimized to achieve higher performance, with thermal conductivity and gas diffusivity increased by ≥139% and 62%, respectively. The prediction mathematical models are validated with the error ranging from 1% to 8%, which can predict transport properties and optimize the GDL microstructure accurately and rapidly.

In a marine salt spray environment, sodium chloride poisoning will significantly deterio-rate the performance of the hydrogen fuel cells; for example, proton exchange membrane fuel cells (PEMFCs). Currently, the degradation mechanisms of the PEMFC caused by the sodium chloride poisoning are often evaluated by the pollution of the F ions; however, the pollution of the sodium chloride in the membrane electrodes is seldomly inspected. In this avail, this work experimentally explores the influence of the sodium chloride pollution on the PEMFC performance in the marine salt spray environment by analyzing the concen-tration diffusion characteristics of the sodium chloride in the PEMFC membrane electrodes. Firstly, a set of experiments were carried out to determine the distribution of the sodium chloride components in the membrane electrodes, where five different salt spray envi-ronments (i.e., 100 mg/L, 200 mg/L, 300 mg/L, 400 mg/L, and 500 mg/L of the salt compo-nent, respectively) were used/employed to analyze the concentration diffusion characteristics of the sodium chloride. Then, the obtained samples were microscopically characterized and elementally analyzed by the field emission scanning electron micro-scopy (FESEM) and the energy spectrometry. Subsequently, a least squares-based model was proposed to predict the diffusion rate of the contaminating ions in the membrane electrodes. Lastly, the pollution of the sodium chloride was evaluated/assessed to reveal the performance degradation of the PEMFCs. The experimental results demonstrated that (1) the sodium chloride fraction existed as crystals or ions in the membrane electrodes in the marine salt spray environment; (2) the sodium chloride poisoning was founded in the proton exchange membrane in the form of sodium ions; (3) and the sodium-to-chloride ratio was proportional to the contamination time and the salt spray in the proton exchange membrane. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

In the maritime setting, Proton Exchange Membrane Fuel Cells (PEMFCs) are subjected to salt spray, posing a risk of contaminating internal components and leading to irreversible degradation in the performance of the PEMFCs. Thus, it is crucial to assess the impact of sodium chloride contamination on PEMFC operation. To address challenges related to prolonged cycle times, high costs, and intricate sample preparation in sodium chloride contamination experiments for PEMFCs, this Article replicates the marine atmospheric conditions using a standard salt spray experimental chamber. The liquid nitrogen fracture method is employed for cost-effective and efficient preparation of experimental samples. The meteorological environment with varying salt content in the salt spray is achieved through precise control of sodium chloride concentration. The Article systematically presents the salt spray experimental method for the membrane electrode assembly (MEA) of PEMFCs. A dedicated salt spray experimental rig was constructed to validate this method for the MEA of PEMFCs. The results indicate that the salt spray experimental method for the MEA of PEMFCs can effectively explore internal component contamination and is well-suited for analyzing the physicochemical effects of NaCl on MEA components, along with their microscopic characterization under salt spray conditions.

受复杂多变的海况和航行环境的影响,船用液化天然气((Liquefied Natural Gas,LNG)燃料罐在船舶航行过程中承受着交变应力的作用,面临着疲劳损伤风险.为分析船用LNG燃料罐的疲劳损伤情况和使用寿命,以某18 m3船用LNG燃料罐为研究对象,采用有限元分析方法找到其最大应力热点,根据装置的长期分布载荷谱、材料的疲劳曲线和疲劳累积损伤准则计算得到LNG燃料罐的疲劳损伤数据并对其进行量化分析.研究结果显示,该LNG燃料罐的疲劳性能满足中国船级社(China Classification Society,CCS)规范的设计要求,采用的燃料罐疲劳损伤量化分析方法是可行的,可供船用LNG燃料罐的工程设计参考.

为了进一步优化海事事故知识表示,有效地解决我国海事事故记录格式与内容不统一、内容不完整、用词用语不规范等问题,本文提出了一种基于本体理论的海事事故知识表示本体模型.首先,结合海事领域知识,分析并概括出海事事故知识主要成分;然后,分析了海事事故知识构成的基础元组,初步提出了海事事故知识表示八元组模型,进而得到了用于构建本体模型的8个核心概念:船舶信息、事故类型、事故原因、事故经过、事故后果、事故时间、事故地点和应急投入;最后,分析并确定了概念层、属性层、关系层、实体层4个层次,进而提出并构建了海事事故知识表示本体模型.基于Protégé工具,展示了本体模型的应用,对1个海事事故的知识进行本体化的表示.研究表明:构建的海事事故知识表示本体模型能够从格式、内容等方面将海事事故知识进行规范化表示并记录,进而便于知识共享和知识重用.

Increasing the transfer(HT) coefficient used in thermal industries is very important. Various methods are used to improve the efficiency of thermal heat HT so that maximum HT takes place in a smaller space. Ethylene glycol (EG) is generally used as an agent for convective HT. EG obtains energy from a hot source and discharges it to the required location. At present, the most consumption of EG is to produce engine cooling fluid. In the upcoming research, the TB of EG fluid in two-dimensional microchannels(MCs) has been investigated using molecular dynamics (MD) simulations, and the effect of variables such as MC dimensions and MC wall temperature(Temp) on the TB of the simulated fluid has been investigated. The results revealed that by increasing the Temp difference of the MC wall from 10 to 50 K, the maximum temperature (Max-Temp) and velocity (Max-Vel) of the target sample increased to 640.94 K and 0.024 Å/ps. It can be concluded that the increase in the cross-sectional area and the wall Temp difference leads to an increase in the HT rate in the MC.

针对老龄液氨储罐Q245R钢内表面筒体和封头两处存在的不规则腐蚀现象,采用二值化图像处理技术提取腐蚀形貌图像的特征参数,实现储罐腐蚀区域面积定量化分析.通过扫描电镜观测Q245R钢不同取样部位下样品腐蚀形貌并结合能谱仪检测其腐蚀成分,进行微观表征.结果表明:腐蚀率、腐蚀等级、腐蚀区域扁平量3个特征参量反映的储罐腐蚀规律与微观形貌图表征分析的腐蚀行为特征相一致,即氨罐封头部位相对筒体部位整体腐蚀严重,且主要部位集中在下部液相区域,最大腐蚀率达62.75％;腐蚀形貌是以氧化物为主的不规则图像,其扁平量服从正态概率密度分布.

For the sake of study the applicability of PEMFC on ships, a three-dimensional single channel fuel cell model was established. The vibration load was loaded on the model through dynamic grid technology and user-defined function (UDF) method. The output voltage and reactive gas distribution of PEMFC loaded in different vibration directions were compared and analyzed. The results show that ship vibration will affect the transmission of components in the battery, resulting in incomplete electrochemical reaction and degradation of PEMFC performance. The influence of vertical vibration is greater than that of longitudinal vibration and lateral vibration.

In view of the problems of clean electricity consumption of berthing ships and rapid response of power supply of some ports,small islands,and offshore platforms,the development status of large Liquefied Natural Gas(LNG)generating ships and their main systems are expounded,the relevant design experience of LNG ships at home and abroad is cited,and the hull,LNG piping system,and power-propulsion complex system of 20 MW LNG generating ship are designed with the modular design method,which can provide the optional solutions to the main difficulties in the design of the ship.

In view of the existing shortcomings such as complex solution of ship navigation safety degree at sea and difficult weight determination of reference factors, etc., the problems such as data sources and model construction methods that influence the accuracy of evaluation model are studied, a ship important index screening method and a design scheme of database construction and retrieval are proposed based on the relational database. A ship collision risk solution model based on the fuzzy mathematics method, Analytic Hierarchy Process（AHP）, and expert evaluation method is constructed, and the ship navigation safety evaluation mathematical model and constructed database are verified according to the real ship Automatic Identification System（AIS） data. The results show that the ship navigation safety evaluation database based on the AIS data is of better reliability and usability. The calculation results of ship navigation safety evaluation model are reliable and accord with the expert experience and the requirements of The International Regulations for Preventing Collisions at Sea 1972, which can provide technical and theoretical support for the evaluation of ship navigation safety at sea.

The effects of ship vibrations on the mass transfer and performance of proton exchange membrane fuel cells (PEMFCs) have many vague aspects. Hence, the method of loading ship vibrations with the sliding mesh is first proposed in this paper. Furthermore, this method is adopted to form the solution of the simulation study of PEMFC performance under ship vibrations. In the framework of computational fluid dynamics, the ship vibration is loaded into the three-dimensional PEMFC model and successfully solved. Then, a series of special cases are performed to explore the gas distribution and output features of PEMFCs in ship environments with different vibrations. Finally, the results show that the ship vibrations have vectorial effects on the gas transfer in the PEMFC. Additionally, vibrations perpendicular to the channel evidently affect the gas transfer. Moreover, while the vibrations are parallel to the channel, they remain nearly normal. Relatively, a more significant influence on the output voltage of the PEMFC will occur under smaller frequencies and/or greater amplitudes of ship vibrations.

确定燃料电池的动态特性对于燃料电池的长期稳定运行有着重要意义.基于模态分析理论,使用有限元分析软件,以质子交换膜燃料电池单电池为研究对象,分析得到其前6阶固有频率和振型,并在模态分析的基础上对单电池进行谐响应分析,分析其X、Y、Z三个方向自由度的位移频谱特性.对比分析所得数据,得出单电池在振动环境中的危险频率点为1050和1830 Hz附近,该结果为单电池的设计与优化提供参考依据.

Gas diffusion layer (GDL) plays a key role in proton exchange membrane fuel cells, which provides multi-functions for gas transport, thermal-electrical conduction and mechanical support. Coupling manipulation of different microstructural characteristics could poten-tially improve transport properties of GDLs. This work proposes an approach to reconstruct heterogenous GDLs and conduct pore-scale modeling to evaluate the anisotropic transport properties. The models are reconstructed using X-ray computed tomography, stochasti-cally reconstruction methods and morphological processing techniques, which consider different fiber diameter, GDL thickness and local porosity distribution type. Combined ef-fects of microstructure characteristics on tortuosity, diffusivity, thermal-electrical con-ductivity and anisotropic ratios are investigated comprehensively. The results show that the diffusivity with fiber diameter of 7 mm is approximately 7% lower, and the conductivity is 8% higher than that of 9 mm. The anisotropic ratios of diffusivity, thermal conductivity and electrical conductivity range from 1.25 to 1.65, 5 to 20, and 20 to 55, respectively. Local porosity distribution of uniform-fluctuated type, fiber diameter of 7 mm and GDL thickness of 126 mm are suggested to balance diffusivity and thermal-electrical conductivity simul-taneously. The methods and results can guide microstructure design of other porous electrodes with higher performance.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

The fault diagnosis is always a key issue in the security field of marine propulsion system. There are obvious problems like the unsteady working of sensors, distortion of original data, and ambivalent feature information from marine shafting’s vibration or motion. It is therefore critical to develop a more effective method to identify the fault information so that the safety of marine propulsion system can be pre-estimated. Hence, a composite method which is based on the ensemble empirical mode decomposition (EEMD) and coupled with the autocorrelation method (AM), the fast Fourier transform (FFT), is mixed and applied to identify the fault information of marine shafting during its operating by hull vibration. The contrastive analysis of the three methods and fault feature study are then conducted to assess the effectiveness of the proposed method thoroughly and validated by the author previously. The research indicates that the composite method is available to fault diagnosis of marine shafting by hull vibration which coupled the shafting vibration with fault feature.

In view of the automatic welding production line of large-sized H-section steel structure, the H-section steel welding procedure is introduced, the basic welding production procedure of large-sized H-section steel structure is analyzed, the procedure flow of production line is designed, and the structure characteristics and technology characteristics of key equipment are discussed. The production line achieves the expected goal of efficient production during the operation, and can fully meet the technology requirements of relevant industry specifications.

Aiming at the problem that small unmanned surface vehicle (USV) are affected by wind waves, undercurrents and other factors affecting navigation safety, a navigation state perception system is designed. The system is equipped with high-precision six-axis attitude sensors, ship-borne smart terminals, GPRS wireless communication units and other equipment. Obtain the attitude information of the USV through the high-precision IMU six-axis attitude sensor, and provide data support for the remote operator's attitude control of the USV; calculate the heading angle through the shore-based terminal; build the ship-borne intelligent terminal through the GPRS wireless communication unit and the data transmission path of the shore-based terminal. The system satisfies the needs of USV sensing applications, and effectively realizes the detection of attitude and heading.