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With the development of green tribology in the shipping industry, the application of water lubrication gradually replaces oil lubrication in stern bearings and thrust bearings. In terms of large-scale and high-speed ships, water-lubricated bearings with high performance are more strictly required. However, due to the lubricating medium, water-lubricated bearings have many problems such as friction, wear, vibration, noise, etc. This review focuses on the performance of marine water-lubricated bearings and their failure prevention mechanism. Furthermore, the research of marine water-lubricated bearings is reviewed by discussing its lubrication principle, test technology, friction and wear mechanism, and friction noise generation mechanism. The performance enhancement methods have been overviewed from structure optimization and material modification. Finally, the potential problems and the perspective of water-lubricated bearings are given in detail. [ABSTRACT FROM AUTHOR]

Printed circuit heat exchangers (PCHEs) are considered as the most promising heat exchangers for use of the supercritical carbon dioxide (S-CO2) Brayton cycle. As crucial components operating at high pressure and thermal load at the same time, PCHE structural integrity evaluations are essential. In this study, to assess the structural strength of PCHEs serving as recuperators and precoolers in the S-CO2 Brayton cycle as a waste heat recovery system for marine engines, the finite element method (FEM) is used and compared with a currently used method from ASME codes. The effects of temperature and pressure on the hot and cold sides are studied in terms of the temperature and pressure differences between the two sides and the main factors affecting its strength discussed. Then, detailed stress intensities of a PCHE under design conditions are investigated, and the results indicate that the highest stress appears at the middle of the semicircular arc of the channel, except for a concentration near the channel tip regions. Stresses of the PCHE are mainly caused by both pressure and temperature differences, with the minimum effect from temperature. The synthesis of the temperature and pressure fields exhibits a complicated action on the total stress under the design conditions. FEM was a more comprehensive means for structural assessment than the method from ASME codes. Further structural optimization of PCHE is conducted to ensure a maximum life span. This research work can provide theoretical guidance for structural integrity assessment of PCHE for the S-CO2 Brayton cycle. [ABSTRACT FROM AUTHOR]

The so-called "green ship" is being regarded as a potential solution to the problems that the shipping industry faces, such as energy conservation and environmental protection. Some new features, such as integrated renewable energy application, biomimetic materials, and antifriction and wear resistant coating have been accepted as the typical characteristics of a green ship, but the tribology problems involved in these domains have not been precisely redefined yet. Further, the related research work is generally focused on the technology or material itself, but not on the integration of the applicable object or green ship, marine environment, and tribological systematical analysis from the viewpoint of the energy efficiency design index (EEDI) and ship energy efficiency management plan (SEEMP) improvements. Aiming at the tribology problems of the green ship, this paper reviews the research status of this issue from three specific domains, which are the tribology problems of the renewable energy system, tribological research for hull resistance reduction, and energy efficiency enhancement. Some typical tribological problems in the sail‐auxiliary system are discussed, along with the solar photovoltaic system and hull drag reduction in traditional marine mechanical equipment. Correspondingly, four domains that should be further considered for the future development target of the green ship are prospected. [ABSTRACT FROM AUTHOR]

Gaskets are applied in PEMFCs (proton exchange membrane fuel cells) to keep reactant gases and liquid within their respective regions, which are of great significance for the both sealing and electrochemical performance of fuel cells during the long-term operation. In this study, the degradation of silicone rubbers, often selected as seals in PEMFCs, in Fenton’s reagents with different H2O2 concentrations was investigated. The changes in chemical properties, mechanical behavior and surface morphology of the samples were studied before and after exposure to the test environment over time. It is found that increasing H2O2 concentration will degrade the rubbers more severely. The experimental results elucidate the degradation mechanism of silicone rubbers in Fenton’s reagents and the influence of H2O2 in the degradation process. [ABSTRACT FROM AUTHOR]

An appropriate assessment of the dynamic behavior of marine propulsion shaft in ships is essential to enable optional delivery of power to the propeller and to minimize unnecessary vibration. Various vibrations coupling with each other can significantly influence the dynamical behavior of the shaft and threaten the reliability of ships. This paper presents a finite element analysis model with multiple constraint conditions to analyze the coupled transverse and longitudinal vibrations of a marine propulsion shaft. Based on this model, in addition to the coupled natural frequencies of each direction, the maximum acceleration are also determined. Furthermore, the simulation of an idling and loading vibration analysis is discussed and validated against experimental results, over a range of rotational speeds. The output of numerical simulation is found to agree with the corresponding results from experimental tests. Finally, an accurate and applicative FEA model for coupled transverse-longitudinal vibration of shaft has been obtained. [ABSTRACT FROM AUTHOR]

With the prosperity of global shipping industry, a variety of shipping-induced environmental problems and increasingly rigid emission restrictions have drawn more attention to an emerging marine fuel-liquefied natural gas (LNG), a clean and efficient energy that conforms to the essence of green shipping. Although with superiority using onboard, there are only fewer than 40 fully LNG-fueled ships in service worldwide by June 2013, and the quantity of LNG-fueled ships in operation is even much lower in China. Moreover, the majority of those in China are inland ships, which mainly navigate along the Yangtze River and canals. By using the SWOT (strengths, weaknesses, opportunities, and threats) analysis in combination with the analytic hierarchy process (AHP), this paper analyzes the development prospect of LNG-fueled ships in inland waterway transportation in China, aiming to fill the gaps of inadequate understanding of the new marine energy. This paper offers some insight on the prospects of the application of LNG in the Chinese shipping industry and simultaneously provides useful information to stakeholders and policy makers for decision-making on the development of LNG-fueled ships. [ABSTRACT FROM AUTHOR]

Wear particle analysis can be developed as an effective method for assessment of the running conditions of concaved cylinder liners. The aim of this study was to numerically characterize the topographical features of wear particles generated from different surface textured cylinder liners and to investigate their changes with alternations in both rotational speeds and surface textures. To achieve this goal, cylinder liners with three different surface textures were prepared and tested in four different speeds. In addition to an untreated surface, concave cylinder liner surfaces with two different diameters (1 and 2 mm) and two different depths (200 and 300 μm) were investigated. Wear particles were extracted from the lubrication oil; three-dimensional images of the wear debris were acquired using laser confocal microscopy; and their topographical features were analyzed quantitatively. This study has revealed that running-in conditions and stable state can be detected using wear debris analysis techniques at a micrometer scale. It has also been discovered that concave B cylinder liner with a depth-diameter ratio of 0.1 always generated wear particles different to those from the other two cylinder liners on each rotational speed. It is believed that the quantitative surface topography characterization results obtained in this study provide a practical base for developing a new, non-intrusive tool for monitoring the operation conditions of cylinder liner-piston rings in diesel engines. [ABSTRACT FROM AUTHOR]

The tribological properties of ZrO 2 ceramic and 1Cr18Ni9Ti stainless steel rubbing pairs were investigated using a special tribotester under different concentrations of hydrogen peroxide (H 2O 2) solution. The comparison analyses of the friction coefficients, worn volume rates, worn particles and surface roughness were conducted under the tested conditions. There were significant differences of the tribological properties of the rubbing pairs in the different concentrations H 2O 2 solution because of oxidation and corrosion. This research has revealed that the main wear mechanisms between the rubbing pairs are severe adhesive wear, abrasive wear and corrosive wear in the H 2O 2 solution with different concentrations. A model has been established to assess the most suitable concentration of the H 2O 2 solution for the tribological properties of the rubbing pairs. The result shows that 50% concentration of the H 2O 2 solution is the most suitable. The assessment result is consistent with the experimental result. It is believed that the knowledge gained in this study is useful for the optimization of the friction pairs in the extreme condition. [ABSTRACT FROM AUTHOR]

A marine diesel engine, where the cylinder liner-piston ring (CLPR) pair is one of the most important rubbing pairs, is the heart of a marine system. Studying the lubrication characteristics of the CLPR will provide a guide for rational design of the CLPR to reduce wear and prolong its service life. The surface texture features have a significant impact on the lubricating performance of the CLPR. In this study, the tribological system of the CLPR was investigated. Different surface textures (such as different sizes of surface concaves and grooves, etc.) were designed and produced on the cylinder liners using surface treatment. A series of experimental tests were then carried out in a specially designed diesel engine tester to investigate the tribological characteristics of the treated CLPR pairs. The comparison analyses of the worn surface texture features, element content of the lubrication oil, and abrasive particle characteristics were conducted under different wear surface texture features and cylinder liner speeds. The analysis results showed that there were significant differences in the tribological and lubrication properties of the rubbing pairs in different wear surface texture features. The wear performance of the CLPR pair with a regular concave texture was superior to that of the concave and groove, and regular groove textures. In addition, the regular concave with a depth-diameter ratio of 0.1 was the most effective surface texture to improve the lubrication and wear properties of the CLPR pairs. It is believed that the knowledge obtained in this study provides the real practical basis for tribological design and manufacturing of CLPR pair in marine diesel engines. [ABSTRACT FROM AUTHOR]

The Hardware-in-the-loop (HIL) simulation is both effective and necessary for Intelligent Vehicle-Highway Systems (IVHS). This paper introduces the prototype HIL simulation system, the Wuhan University of Technology Simulator (WUTS), which is a novel, mechatronic, and scaled testbed to conduct researches on cooperative vehicles in IVHS. An overview of this system, including system architecture, development process, and individual hardware implementation, is presented. A simplified vehicle model is proposed and applied into the WUTS using similarity principle based on the system modeling on the real vehicle and hardware. Two cooperative vehicles cases of following and lane-changing maneuvers were studied and emulated in the WUTS. Experimental results demonstrate that WUTS and developed vehicle models are effective and accurate for IVHS studies. [ABSTRACT FROM AUTHOR]

The normal operation of marine diesel engines ensures the scheduled completion and efficiency of a trip. Any failures may result in significant economic losses and severe accidents. It is therefore crucial to monitor the engine conditions in a reliable and timely manner in order to prevent the malfunctions of the plants. This work describes and evaluates the development and application of an intelligent diagnostic technique based on the integration of the empirical mode decomposition (EMD), kernel independent component analysis (KICA), Wigner bispectrum and support vector machine (SVM). It is an extension of the previous work on the fault detection for a diesel engine using the instantaneous angular speed (IAS). In this study, in order to solve the underdetermined blind source separation (BSS) problem the combination of EMD and KICA is firstly presented to estimate IAS signals from a single-channel IAS sensor. The KICA is also applied to select distinguished features extracted by Wigner bispectrum. The SVM is then employed for the multi-class recognition of the marine diesel engine faults in an intelligent way. Numerical simulations using a 6-cylinder engine model and real IAS data measured on the ship named 'Hangjun 20' are used to evaluate the proposed method. Both the numerical and experimental diagnostic results have shown high efficiency of the proposed diagnostic method. Distinct fault features of the IAS signals have been extracted by the EMD-KICA and Wigner bispectrum, and the fault detection rate of the SVM is beyond 94.0%. Thus, the proposed method is feasible and available for the fault diagnosis of marine diesel engines. [ABSTRACT FROM AUTHOR]

Marine diesel engines, a critical component to provide power for entire ships, have been received and still need considerable attentions to ensure their safety operation. Vibration and wear debris analysis are currently the most popular techniques for diesel engine condition monitoring and fault diagnosis. However, they are usually used independently in practice, and limited work has been done to address the integration of data collected using the two techniques. To enhance early fault detections, a new fault diagnosis technique for the marine diesel engine has been proposed by the information fusion of the vibration and wear particle analyses in this paper. A new independent component analysis with reference algorithm (ICA-R) using the empirical mode decomposition based reference extraction scheme was adopted to identify the characteristic source signals of the engine vibration collected from multi-channel sensors. The advantage of this approach performed at a data fusion level is that the ICA-R can extract only the relevant source directly related to the engine fault features in one separation cycle via incorporating prior knowledge. The statistical values of the recovered source signals were then calculated. The above vibration features, along with the wear particle characteristics, were used as the feature vectors for the engine fault detection. Lastly, the improved simplified fuzzy ARTMAP (SFAM) was applied to integrate the distinctive features extracted from the two techniques at a decision level to detect faults in a supervised learning manner. Particularly, the immune particle swarm optimization was used to tune the vigilance parameter of the SFAM to improve the identification performance. The experimental tests were implemented on a diesel engine set-up to evaluate the effectiveness of the proposed diagnosis approach. The diagnosis results have shown that distinguished fault features can be extracted and the fault identification accuracy is satisfactory. Moreover, the fault detection rate of the integration approach has been enhanced by 16.0 % or better when compared with using the two techniques separately. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (HO) is a kind of ideal green propellant. It is crucial to study the wear behavior and failure modes of the metal materials under the strong oxidizing environment of HO. This study aims to investigate the wear of rubbing pairs of 2Cr13 stainless steel against 1045 metal in HO solutions, which has a great effect on wear, the decomposition and damage mechanism of materials. The comparison analysis of the friction coefficients, wear mass loss, worn surface topographies and current densities was conducted under different concentrations of HO solutions. There were significant differences in the tribological and electrochemistry properties of the rubbing pairs in different HO solutions. [ABSTRACT FROM AUTHOR]

marine propulsion system is a very complicated system composed of many mechanical components. As a result, the vibration signal of a gearbox in the system is strongly coupled with the vibration signatures of other components including a diesel engine and main shaft. It is therefore imperative to assess the coupling effect on diagnostic reliability in the process of gear fault diagnosis. For this reason, a fault detection and diagnosis method based on bispectrum analysis and artificial neural networks (ANNs) was proposed for the gearbox with consideration given to the impact of the other components in marine propulsion systems. To monitor the gear conditions, the bispectrum analysis was first employed to detect gear faults. The amplitude-frequency plots containing gear characteristic signals were then attained based on the bispectrum technique, which could be regarded as an index actualizing forepart gear faults diagnosis. Both the back propagation neural network (BPNN) and the radial-basis function neural network (RBFNN) were applied to identify the states of the gearbox. The numeric and experimental test results show the bispectral patterns of varying gear fault severities are different so that distinct fault features of the vibrant signal of a marine gearbox can be extracted effectively using the bispectrum, and the ANN classification method has achieved high detection accuracy. Hence, the proposed diagnostic techniques have the capability of diagnosing marine gear faults in the earlier phases, and thus have application importance. [ABSTRACT FROM AUTHOR]

To examine how the superior colliculus, the motor center of orientation and avoidance, could interact with postural reflexes, we investigated effects of unilateral and bilateral ablations on air-righting reflex movements in otherwise intact rats. Superior colliculus ablations variously modified righting movements: After falling from the supine position, the rats sometimes showed dorsiflexion instead of normal ventriflexion; the motor sequence of rotation from the fore- to the hindquarter was often modified to simultaneous rotation; lateral turn from supine to prone position was occasionally insufficient; body direction that was normally kept constant during falling was often changed; final posture sometimes deviated from the horizontal position. The first three abnormalities occurred almost twice in frequency as lesions increased from unilateral to bilateral ablation, and in unilaterally ablated rats, did so in righting contraversive to the lesions. Multiple influences of tectoreticular input to the air-righting reflex center are discussed. [ABSTRACT FROM AUTHOR]

Study on surface features of wear particles generated in wear process provides an insight into the progress of material failure of artificial joints. It is very important to quantify the surface features of wear particles in three dimensions. In this study, a new approach using atomic force microscopy was proposed to carry out 3D numerical surface characterization of wear debris generated from artificial joints. Atomic force microscopy combined with image processing techniques was used to acquire appropriate 3D images of wear debris. Computerized image analysis techniques were then used to quantify surface texture features of wear debris such as surface roughness parameters and surface texture index. The method developed from the present study was found to be feasible to quantity the surface characterization of nano- and micro-sized wear debris generated from artificial joints. [ABSTRACT FROM AUTHOR]