Ship propulsion shaft systems are subjected to ice load excitation when ships are navigating in polar ice regions. Compared to conventional hydrodynamic effects, the ice load imposes higher requirements on the shaft system’s ability to withstand torsional stresses. To improve the power of the ship propulsion system when sailing in ice areas and reduce the power loss of the shaft system, while considering the vibration performance. In this paper, a multi-objective optimal design of the shaft system is carried out using the Non-dominated Sorted Whale Optimization Algorithm (NSWOA) to reduce stresses on both the motor shaft and the intermediate shaft. The coupled system model of motor-shaft system-propeller structural components is established, and the system dynamics response model is obtained by solving using the Newmark-β method. Based on the response model, a multi-objective whale optimization algorithm is used to optimize the power and vibration performance of the shaft system simultaneously. The optimized results show that the shaft system transfer efficiency is improved by 0.27%, and the stress at the shaft end is reduced by 11.8% and 12.3% respectively.

The vibration issues in various mechanical equipment and architectural structures have gradually developed into two directions: vibration control and vibration utilization. Developing better engineering structures and system models is a crucial step in realizing vibration control and utilization. A novel magnet-array quasi-zero stiffness energy-harvesting vibration isolator (MQZS EVI) is proposed; it mainly consists of three parallel negative stiffness mechanisms (NSMs), three series-connected electromagnetic shunt damping, and three parallel spring positive stiffness mechanisms. Firstly, the magnetic force analytical model of the electromagnetic NSM is established using the filament method and the finite element method. Structural parameter optimization analysis is then conducted for the NSM. Secondly, the dynamic equations of the MQZS EVI system are formulated. The vibration isolation performance and energy-harvesting characteristics of the MQZS EVI system are evaluated using the harmonic balance method and the pseudo-arc length continuation method. Finally, a prototype is manufactured and tested. The experimental results demonstrate that the MQZS EVI system can effectively isolate ultra-low-frequency vibrations while simultaneously capturing energy from low-frequency vibrations.

Low-frequency line spectrum is a crucial characteristic signal for detecting, tracking, and identifying targets in modern underwater acoustic warfare. The quasi-zero stiffness vibration isolator (QZS VI) possesses both high static stiffness and low dynamic stiffness, which can effectively suppress low-frequency vibrations. A novel quasi-zero stiffness vibration isolator with load adjustment (QZS VI-LA) is proposed. Firstly, a magnetic force analytical model of the ring magnet negative stiffness mechanism (NSM) is established using the filament method. A quasi-zero stiffness matching analysis of the QZS VI-LA system is conducted, and a non-ideal load adjustment mechanism (NLAM) is designed. Secondly, the dynamic equations of the QZS VI-LA system with the flexible foundation are formulated. The dynamic characteristics of the system are analyzed using the harmonic balance method and the pseudo-arc length method. Finally, a prototype of the QZS VI-LA is constructed, and experimental results demonstrate that the QZS VI-LA system has excellent low-frequency vibration isolation performance and load adjustment capability.

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.

To address the heat transfer degradation caused by fouling and dust accumulation on the stator windings of marine diesel generators, this study proposes a health condition assessment method based on the convective heat transfer coefficient. A numerical analysis model was developed using the Ansys Fluent platform to systematically investigate the effects of ambient temperature, load power, and fouling layer thickness on the stator winding temperature and convective heat transfer coefficient. The results demonstrate that the convective heat transfer coefficient is highly sensitive to variations in fouling layer thickness. On this basis, a health assessment model centered on the convective heat transfer coefficient was established and validated using experimental data from diesel generator tests. The results show that the proposed model accurately captures the performance degradation process and enables quantitative classification of operating states, including healthy, sub-healthy, degraded, and abnormal conditions. This research provides a feasible theoretical foundation and technical approach for the intelligent monitoring and condition evaluation of marine diesel generators, offering significant engineering value for enhancing the efficiency and reliability of marine power systems.

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.

The propulsion shaft system, as the core of the ship’s power system, has attracted widespread attention in terms of vibration. This paper is dedicated to the study of the dynamic response characteristics of the ship propulsion shafting system, with a particular focus on the impact of the shaft-driven generator supported by bearings on the dynamic torque of the shafting system. A classic lumped-parameter equivalent system model is adopted, and the time domain transient response simulation calculation is conducted based on the Newmark-β method. A comprehensive analysis is made of the vibration torque and vibration stress in the propulsion shaft system under different rotational speeds and working conditions, with or without the shaft-driven generator connected to the load. Dynamic vibration torque measurements are also taken on a 16100TEU ship for the propulsion shaft system to analyze the consistency between simulation results and experimental results. The results show that at the rated speed of the main engine at 80 rpm and adjacent speeds, the error between the simulation calculation results and the actual measured torque results at the pre- and post-motor measurement points is less than 10% and is much less than the continuous allowable torque of 4.01 × 106 N·m and the instantaneous torque. This installation state, including the propulsion shaft system with the shaft-driven generator supported by bearings, can safely navigate during normal operation. This provides theoretical and experimental support for the future installation of the propulsion shaft system with the shaft-driven generator supported by bearings. In addition, the actual ship experiment enhances the universality and reliability of the research.

Two-stage quasi-zero-stiffness vibration isolator(TQZS VI)can effectively suppress low-frequency vibrations and quickly attenuate high-frequency vibrations.An electromagnetic shunt damping(ESD)has also been proven to be a feasible way to harvest energy from vibrating structures.By integrating the TQZS VI and the ESD,a novel TQZS VI that realizes dual functions of vibration control and energy harvesting is proposed.Both layers of quasi-zero-stiffness are achieved by a vertical spring connected in parallel with two symmetrical transverse springs,and electromagnetic shunt damping as a viscous dissipative element between the upper and lower layers is provided by an ESD connected to an external resonant resistance-capacitance-inductance(RCI)series circuit.First,the mechanical and mathematical models of the two-stage quasi-zero-stiffness vibration isolator with electromagnetic shunt damping(ESD-TQZS VI)are established.Then,the amplitude-frequency response equation of the ESD-TQZS VI is solved using the harmonic balance method(HBM)and the arc length continuation method.Moreover,the force transmissibility and output power of the ESD-TQZS VI are defined,and the effects of system parameters on vibration isolation and energy harvesting are analyzed.It is found that a sizeable damping ratio is beneficial for attenuating resonance peaks while having a negligible effect on energy harvesting.Significant shunt resistance is not conducive to attenuating resonant peaks and can narrow the isolation frequency band of the system.Finally,the bifurcation and attractor coexistence characteristics of the ESD-TQZS VI system after parameter optimization are revealed.The results indicate that the ESD-TQZS VI can considerably attenuate resonance peaks of low-frequency vibration and achieve vibration energy harvesting at the same time.

In this paper, a three-dimensional numerical simulation platform for methanol cracked gas/diesel dual-fuel engine was constructed based on the three-dimensional simulation software of Computational Fluid Dynamics (CFD), and the effects of different pre-main injection intervals on the combustion and emission characteristics of methanol cracked gas/diesel dual-fuel engine were investigated in the large-load working condition. In the simulation, the pre-main injection interval was increased from 10°CA to 30°CA. The results show that the multiple inj ection strategy with pre-injection can effectively reduce the emissions of Soot, HC and CO with the increase of the pre-main injection interval, but a larger pre-main injection interval will affect the thermal efficiency, and the pressure rise may be too high and lead to the increase of NOx emission. When choosing the pre-main injection interval, 15°CA to 25°CA should be avoided as much as possible, since NOx emissions are relatively high in this region. Low emissions can be achieved by adopting an appropriate pre-main -after-inj ection strategy.

In research concerning the impact resistance characteristics of ship power transmission shaft systems incorporating a high-elasticity coupling, a significant challenge lies in ascertaining the displacement compensation metrics for the high-elasticity coupling. This study constructs a finite element model of the ship power transmission shaft system with an entity equivalent model of the high-elasticity coupling. Utilizing the Dynamic Design Analysis Method (DDAM) and the time-history method, the dynamic responses of the high-elasticity coupling, the propulsion shaft system, and its critical cross-sections under explosive impact loads are analyzed. The findings indicate that the maximum impact displacement of the propulsion shafting system, as calculated by DDAM, is 22.47 mm in the vertical direction at the driven end of the high-elasticity coupling. In contrast, the maximum impact displacement determined by the time-history method is 15.23 mm in the same direction. The study corroborates the precision of the high-elasticity coupling equivalent model establishment methodology and confirms that the entity equivalent model of the power transmission shaft system with a high-elasticity coupling is capable of fulfilling the criteria for a swift evaluation of impact resistance characteristics. This provides theoretical backing for the forecasting of impact resistance performance in ship propulsion shaft systems.

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A combination of Fourier cosines series and polynomials (4 terms, 4th order) in Rayleigh–Ritz method is proposed to solve the vibration problem of a generally restrained beam. The characteristics of auxiliary polynomials, which actually are determined by homogeneous boundary conditions of the beam under consideration, can directly change the convergence properties and numerical instabilities of vibration results significantly. Fast convergence and reliability of the proposed polynomials are illustrated with numerical examples in comparisons with available results.

The objective of the paper is to propose the empirical formulas of the entrained water effect based on numerical method to estimate the virtual mass and the virtual moment of inertia for tandem propellers. The fluid-solid interaction of combined propellers in the flow field has been taken into consideration in the calculation. The axial added mass and the added moment of inertia of the entrained water are calculated for a single propeller using the finite element method and the existing empirical formulas to verify the feasibility and accuracy of numerical method. Consequently, the numerical calculation of tandem propellers is conducted to obtain the novel empirical formulas of entrained water properties, which are available to evaluate the influence of the blade diameter, the expanded area ratio and the pitch/diameter ratio. The corresponding correction coefficients in the empirical formulas considering the entrained water effect of tandem propellers are given. The empirical formulas are beneficial to relevant practical engineering calculation of entrained water properties for combined propellers.

在含高弹性联轴器的舰船推进轴系抗冲击设计中,针对高弹性联轴器位移补偿指标难以确定的问题,开展了高弹性联轴器当量模型与推进轴系抗冲击模型的研究;提出了当量模型的建立方法,将高弹性联轴器2种模型与推进轴系组合建立成推进轴系4种模型,分别对4种模型进行抗冲击计算,确定实体等效模型是最佳模型,并对其进行抗冲击性能分析.研究表明,高弹性联轴器当量模型建立方法和实体等效模型能快速、高效地预估含高弹性联轴器的推进轴系的抗冲击性能,设计方法可为高弹性联轴器的选型设计提供指导.

In recent times, there has been a significant focus on electromagnetic resonant shunt damping (ERSD) and quasi-zero-stiffness vibration isolators (QZS VI) as prominent solutions for vibration mitigation or energy harvesting. In this paper, an innovative retrofittable model is proposed for dual-functional energy harvesting and low-frequency vibration attenuation by combining the ERSD and two-stage quasi-zero-stiffness vibration isolator (TQZS VI). The viscous dissipative element between the TQZS VI upper and lower layers is implemented using an electromagnetic shunt transducer that is connected in parallel with a resonant RLC (resistor–inductor–capacitor) circuit. Firstly, the mathematical model of the electromagnetic resonant shunt series quasi-zero-stiffness isolator (ERS-TQZS VI) is developed. Then, the magnitude-frequency response equations of the ERS-TQZS VI system are approximately solved using the harmonic balance method (HBM) in combination with the pseudo-arc-length method (PLM). The analytical approach is validated using numerical simulations. Moreover, the force transmissibility and output power of the ERS-TQZS VI are defined, and detailed parametric analysis for energy harvesting and low-frequency vibration attenuation is performed to assess the critical design parameters that result in optimal performance of the ERS-TQZS VI. The results demonstrate that the ERS-TQZS VI exhibits a significant reduction in resonance peaks of low-frequency vibration while simultaneously enabling effective vibration energy harvesting.

Autonomous surface ships have become increasingly interesting for commercial maritime sectors. Before deep learning (DL) was proposed, surface ship autonomy was mostly model-based. The development of artificial intelligence (AI) has prompted new challenges in the maritime industry. A detailed literature study and examination of DL applications in autonomous surface ships are still missing. Thus, this article reviews the current progress and applications of DL in the field of ship autonomy. The history of different DL methods and their application in autonomous surface ships is briefly outlined. Then, the previously published works studying DL methods in ship autonomy have been categorized into four groups, i.e., control systems, ship navigation, monitoring system, and transportation and logistics. The state-of-the-art of this review paper majorly lies in presenting the existing limitations and innovations of different applications. Subsequently, the current issues and challenges for DL application in autonomous surface ships are discussed. In addition, we have proposed a comparative study of traditional and DL algorithms in ship autonomy and also provided the future research scope as well.

建立冰载荷作用下船舶推进轴系疲劳分析计算模型,提出基于全转速轴段冰载荷最大峰值扭矩确定、S-N曲线设计及线性损伤系统的求解方法,给出冰区船舶轴系疲劳分析流程及评估准则.基于C#与Matlab联合编程,开发冰区船舶推进轴系疲劳分析软件.与国外主流软件计算报告的对比结果验证了本文软件的正确性.

The study focuses on the fault signals of rolling bearings, which are characterized by nonlinearity, periodic impact, and low signal-to-noise ratio. The advantages of entropy calculation in analyzing time series data were combined with the high calculation accuracy of Multiscale Fuzzy Entropy (MFE) and the strong noise resistance of Multiscale Permutation Entropy (MPE), a multivariate coarse-grained form was introduced, and the coarse-grained process was improved. The Composite Multivariate Multiscale Permutation Fuzzy Entropy (CMvMPFE) method was proposed to solve the problems of low accuracy, large entropy perturbation, and information loss in the calculation process of fault feature parameters. This method extracts the fault characteristics of rolling bearings more comprehensively and accurately. The CMvMPFE method was used to calculate the entropy value of the rolling bearing experimental fault data, and Support Vector Machine (SVM) was used for fault diagnosis analysis. By comparing with MPFE, the Composite Multiscale Permutation Fuzzy Entropy (CMPFE) and the Multivariate Multiscale Permutation Fuzzy Entropy (MvMPFE) methods, the results of the calculations show that the CMvMPFE method can extract rolling bearing fault characteristics more comprehensively and accurately, and it also has good robustness.

船舶在极地海域航行时,将面对恶劣的冰载荷工况,冰-桨的相互作用致使船舶推进系统产生转速降,系统同时产生较大的扭矩波动,动力推进系统的安全受到威胁.论文以某重型破冰船电力推进系统为研究对象,建立电力推进系统转速-时间仿真模型和扭振时域动态响应计算数学模型,重点研究了冰载荷激励力矩作用时电力推进系统在不同调速控制策略下的电机转速降及轴系扭矩动态响应,通过全转速分析得到不同调速控制策略下电机转速降和轴段最恶劣冰载荷扭矩幅值随初始转速的分布规律,并对推进系统在各冰载荷工况及各冰厚条件下的螺旋桨破冰性能作出了预测,结果可为冰区电力推进装置的设计及性能分析提供参考.

以单支点可倾瓦推力轴承为研究对象,基于流体动压润滑原理,建立推力轴承油膜的几何模型,采用计算流体力学的方法分析轴系非倾斜和轴系倾斜2种状态下推力轴承油膜的静动特性.通过Fluent仿真计算得到油膜表面的压强分布以及油膜提供给推力环的承载力,将计算结果处理后得到了转速-刚度表和转速-阻尼表.结果表明:轴系倾斜对油膜所产生的承载力的影响较小,但会导致不同瓦块所受的载荷大小不一,造成不同瓦块之间的性能差异;推力轴转速的变化对油膜刚度系数的影响较大,对油膜阻尼系数的影响较小;在转速不变的情况下,轴系倾斜时油膜所产生的刚度系数和阻尼系数大于非倾斜时的刚度系数和阻尼系数.