Extension on overhaul inspection period of the main bearing of main diesel engine is highly desired by carrying out its condition monitoring. The effective condition monitoring method is required instead of the temperature method which rises out the warning alarm after bearings appeared in critical condition. It was found also for plane bearing that the contact between the shaft and bearing may occur locally even in the oil film lubrication state. Result from this study, the high frequency vibration measurement and wear particle detection in lubrication oil were suggested to be the effective condition monitoring methods.
The Advanced Support System for Ship Administration executes diagnosis and remote condition monitoring of shipboard main propulsion engine from the support center at shore base using IT Technology. It aims at efficient, active, and safe transportation of domestic ships. Presently, this kind of maintenance service that performs integrated support between ship and shore are realizing. In this paper, case studies on the implementation of engine remote monitoring and diagnosis systems are introduced.
Abnormality diagnosis of low speed rotating machinery by the vibration method is often hard to achieve, because effective values of vibration are extremely low. This paper presents diagnosis of low speed rotating machinery using steel dust meter with application examples and discusses of its advantages in comparison with the vibration method. We have developed the steel dust meter, which enables quick on-site diagnosis of abnormalities in bearings and gears rotating machinery. Here presented is its outline.
For some time now we have been seeing an increasing demand for redundant propulsion concepts. Major Classification Societies have answered the desire of ship owners andyards to have theirredundant propulsion concepts evaluated andreceive Class notation. When we talk about redundancy we have to compare risks of different options that compete for the same final result and for this result we have to decide what our goal is. Most of the time everything is fine but once in its lifetime ship can experience event for which its abilities are surpassed. Either propulsion is lost and the ship cannot control its behavior during the storm and the final results are lost lives or the ship is lostwith apolluted environment. Most ofthe ships are not equippedwith redundantpamllel propulsion system. The most common is that any redundancy is cost which burdens the operating company through the years and that this kind of approach is not to follow. Even the Safety costs are not really defined since the compensation for the lost lives is negotiable and it also depends on the law skills ofthe lawyers. Therefore only the Business costs canbe definedwith relative correctness.
The authors have been engaged in the verification and basic study of a technology for perfect cleanliness and semi-permanent use of lubricating oil (LO) without any waste oil. Nephrons of animals keep their blood clean. Therefore the technology is called Nephron system because it always keeps LO clean. Nephron system has been in practical use in many marine and cogeneration diesel engines as well as in some other fields for a long time. In the course of their study, the authors have found that also another technology for semi-permanent use of LO has been developed and in practical use. The two technologies differ in their principles of removing LO sludge. Nephron system removes sludge mechanically while another does it electrically. Also, it is reported that a lot of waste LO is generated every day in industrialized countries. On the other hand, there seems to be no basic principle reported, so far, for the permanently perfect cleanliness of LO. Therefore, the authors have studied a basic principle to perfectly remove LO sludge and keep it clean permanently. This paper reports the principle and proposes worldwide R&D and practical use of those technologies of no waste oil for saving natural resources and protecting our environment.
In order to investigate the effects of mixture Inhomogeneity and gas flow on combustion and emissions in a premixed-charge compression ignition engine, three-dimensional numerical analysis of the combustion process was carried out by using the authors' GTT-CHEM code, which was linked to the CHEMKIN-II code. Combustion processes of gas oil and air mixtures (overall equivalence ratio was set at 0.4) under various initial conditions of mixture inhomogeneity and gas flow (swirl or tumble flow) were computed in consideration of chemical kinetics. It has been found that the maximum rate of pressure rise decreases as the mixture inhomogeneity becomes higher. On the contrary, the concentrations of combustion products NO, CO and HC increase, and the combustion efficiency becomes lower with the increase of mixture inhomogeneity. As a result, it has been shown that there exist appropriate initial conditions of mixture inhomogeneity and gas flow for suppressing the maximum rate of pressure rise with relatively low emissions of NO, CO and HC at high combustion efficiency.
In the investigation of cause for marine diesel engines operational problems, it is a very important to have an objective judgment standard in order to determine whether the main cause was the fuel being used or not. Combustion characteristics (ignition delay, combustion period and maximum rate of heat release) of marine heavy fuel oil are affected by many factors, including density, carbon residue, asphaltene content, aromaticity, carbonlhydrogen (CH) ratio, and others. These topics were studied for each item and some conclusions were obtained.
It is considered that the elucidation of the dynamic fracture mechanism under a complex load is of very high importance. In this study, fracture behavior by adding an impact load to a rectangular plate with a parallel double notch was discussed using the moving finite element method based on the Delaunay-automatic-triangulation. Since the notch interval is narrow, reflection, refraction, diffraction and interference of the stress wave were generated; this fracture phenomenon becomes the complex mixed mode condition. The various fracture mechanics parameters of this fracture phenomenon were calculated by the use of the numerical analysis. Then, the dynamic fracture path of this experiment was estimated by the propagation-direction criterion which in turn confirmed to agree very well with the experimental results. As a result, the validity of fracture simulation by this technique was shown.
This study aimed at finding out a suitable material for sliding bearings used in seawater. We carried out two types of wear experiments: oscillatory sliding type and ball-on-disc type; using phenolic resin, PTFE resin, polyamide (PA) resin and Pb-Cu sintered alloy sliding against SUS304. As a result, PA resin shows high wear resistance and low friction, whereas phenolic and PTFE resin indicates different tribocharacteristics depending on the type of wear experiment. Pb-Cu sintered alloy is an unsuitable material for bearings in seawater because of its high corrosive wear rate and high fiction.
Axial fatigue tests of SNCM630 forgings, which are often used for high-strength components in diesel engines, have been carried out with various stress ratios (R) for fatigue life N≤107 cycles. S-N curves obtained from the experimental results have shown fatigue limits of 500, 400, 300 and 190 MPa for R=-1, 0, 0.3 and 0.6, respectively. The results suggest that the fatigue strength of SNCM630 is highly improved from a similar material, SNCM439. Study on the effect of stress ratio using a fatigue limit diagram with failure probability shows that modified Goodman diagram is applicable for the determination of fatigue strength of this material. However, under a stress condition of high R where the maximum applied stress may exceed the proportional limit, as for in the design it is recommended that the applied stress will not exceed the proportional limit. SEM observations of the fracture surfaces have revealed that fatigue cracks initiated from subsurface inclusions which are identified as alumina particles of 35μm in diameter in only two specimens while crack initiated from surface flaws in other samples. Using the √area parameter model for internal defects, the fatigue limit for N>109is estimated as approximately 410 MPa in case of R=-1.
The drag reduction of cylinder having square dimpled surface was studied by measuring the drag force acting on the cylinder. Level of drag reduction was changed by an arrangement shape of the square dimples and Reynolds number. Drag of the cylinder was reduced about 28% with proper arrangement of square dimples. The flow field around the cylinder having dimples at the minimum drag was visualized by using post color ink in order to see the influence of the dimples. In this case, the separation points were shifted rearward and the wake region was smaller than that of the smooth surface cylinder.
A corrosion mitigation technique based on radiation induced surface activation (RISA) from the gamma ray irradiation on a metal surface is reported in this paper. This study aimed to develop a RISA method to prevent crevice corrosion in SUS304 stainless steel using low-intensity radioactive material. Experiment showed that an electrode potential of -100 mV vs. Ag/AgCl was produced and maintained on TiO2-coated SUS304 stainless steel specimens immersed in artificial seawater and in close contact with a small, sealed60Co source or activated by spontaneous neutron irradiation, with no corrosion observed for more than 7 days. On the contrary, the potential of the specimen without a radiation source decreased less than-280 mV vs. Ag/AgCl and crevice corrosion occurred beneath the O-ring within few days. The RISA effect of low-intensity radioactive material has the potential to prevent crevice corrosion of SUS304 stainless steel in actual seawater.
The International Maritime Organization (IMO) has been adopted the International Convention for the Control and Management of Ship's Ballast Water and Sediments (the Ballast Water Management Convention) in 2004. The atmospheric pressure non-equilibrium discharge is useful as one of the plasma generation methods that are the most suitable, when it adapts to energy and environmental study. By irradiating the plasma to the seawater surface, the possibilities of ballast processing were examined. As the effect, it was proven that pH value decreases. The following factors effect the pH value: 1) The reaction with the radical. 2) The bond dissociation by the collision with electrons or ions. It is considered from the results that there is a possibility of ballast processing by plasma irradiation. However, it is necessary to carry out further verification.
This paper shows coefficients of skin friction of high-viscosity oil flow in pipes. The pressure drop from entrance to exit of the pipe was measured, and the coefficient of skin friction was obtained. The coefficients of skin friction of high-viscosity oil flow in pipes are very large. To reduce the pressure drop, oil was injected into the water flow and then the coefficient of skin friction in pipe was investigated. Using the obtained coefficient of skin friction, the oil flow rate in a pipe is calculated. The oil flow rate that was obtained from oil injection into water was compared to the case of oil only flow and an annular water injection method (AWI) . Flowing viscous oil injection into water current is a simple method and the coefficient of skin friction in the pipe can thus be reduced.
Generally, for numerically analyzing gas jets, computational mesh spacing must be smaller than the diameter of an injector nozzle. However, in performing three-dimensional flow analysis in the combustion chamber of a gas fuel injection engine, it is not realistic due to very long calculation time to use a fine mesh with spacing comparable to the diameter of an injector nozzle. Then, the authors devised a gas parcel method expressing local gas velocity distribution within mesh spacing, and verified its validity as follows: Firstly, an air jet injected into air was numerically analyzed using this method with a mesh having ten times larger spacing than the diameter of an injector nozzle. Basic characteristics (maximum velocity, velocity distribution and half width) of the calculated results were compared with theoretical values. It was found that the calculated results nearly reproduce the tendencies of theoretical values. Secondly, this method was applied to the numerical analysis of a hydrogen gas jet injected into air. It was found that the penetration, concentration distribution and shape of the jet are qualitatively in agreement with experimental results. As a result, it was shown that the proposed gas parcel method is effective in improvement of the accuracy of practical gas jet analysis.
The lubricating performance of a segment-type seawater lubricated stem tube bearing is examined in this paper. The effect that the number of bearing segments and water supply grooves has on bearing load capacity is clarified. When there are few segments and the width is wide, the load capacity of stem tube bearing becomes greater. If a relative inclination exists between the propeller shaft and stem tube bearing, the pressure on the bearing stem edge will increase. In this paper, a quantitative evaluation of this pressure is also presented.
Light Cycle Oil (LCO) is distillate oil obtained from Fluid Catalytic Cracking (FCC) unit. The calorific value per volume (J/cm3) is higher, while the cetane index is lower than A-type fuel oil (JIS K2205) . It was found in this study that a single cylinder engine with a two-stage injection system of pilot and main charge of fuel realized stable operation for LCO with lower fuel consumption per volume and equivalent quality of exhaust gases as compared with A-type fuel oil. In pilot injection, there were two effects, combustion promotion by premixing and pressure increasing rate control by division injection. In main injection, the difference of ignition delay based on cetane index decreased with the fuel injection into combustion chamber warmed at 1000K or more by pilot combustion.
Radar is essential to safety navigation for ships. However, it is not perfect equipment and there exist marine accidents. The authors propose using stereo vision that automatically detects ships and/or other objects and measures their 3D locations in order to assist usual navigation equipment. This paper focuses on a novel method to detect ships from stereo images. The proposed method is composed of detection of edges from images, confirmation of corresponding points between left and right images, and final judgment of ships from 3D measurement results. An experiment, which used twelve pairs of stereo images obtained at Akashi Strait, was conducted. The result indicates good possibility of the proposed method, although there is room for improvement in order to ensure the detection.
Medium and large merchant vessels use oil-lubricated shafting and bearings in the sterntube. Oil leakage from the sterntube is a serious environmental issue and the biodegradable oil beings an interest measure for its solution. Biodegradable oil is environmentally friendly due to its characteristic of quick decomposition into carbon dioxide and water in the marine environment. Existing biodegradable oils, however, do not satisfy all the properties required for sterntube lubricants. The authors newly developed a soluble, biodegradable lubricant based on polyethylene glycol, and a sterntube seal material compatible with the lubricant. The lubricant and the seal material were practically applied to a vessel on January 2006. Until now, they are running normally and the vessel experiences no trouble. In this paper, the field test of the lubricant and seal material is presented. The results for the lubricant sample analysis and the lubricant consumption measurement, which were derived until January 2007, are described. In addition, the sterntube seal performance of the field test vessel is discussed as compared with seal bench test results.