Lignum vitae had been used as seawater lubricated bearings for ships in the past. But nowadays, they are almost replaced by rubber bearings whose qualities are stable. This is because the rubber bearings have various excellent features such as self-alignment and vibration absorption, etc., and have shown good results. However, rubber bearings are elastically deformed by the shaft’s weight, and are inapplicable to large vessels. To solve this problem, PTFE bearings were developed. Friction coefficients of these bearings are greatly lower than those of rubber bearings due to the self-lubricity of the sliding material which lead to a greatly reduced fuel consumption. Moreover, application of these bearings in large vessels has shown good results; their abrasion resistance greatly exceeding that of rubber bearings.
The Super Eco-Ship Project was conducted by the National Maritime Research Institute of Japan (NMRI) as a national project from April, 2001, under the Ministry of Land, Infrastructure and Transport. It aims at achieving the ship with environment friendliness and economical benefit. The Super Eco-Ship has high propulsion efficiency by contra-rotating propeller (CRP) effect. The high propulsive efficiency due to the combination with the optimum hull design and podded propulsion system enables the reduction of CO2 compared with the conventional ship. In addition, the podded propulsion system enables drastically superior manoeuvrability and flexible control system in ship operation as well as high propulsive efficiency. NMRI developed, cooperated with ship owner Ube Shipping & Logistics, LTD., the modified buttock flow hull form equipped with one podded propulsion system close behind the conventional propulsion system for Cement Tanker “KOZAN MARU”. This paper introduced history on Research & Development of The Super Eco-Ship Project and described the Hybrid type’s Electric Podded Propulsion Cement Tanker.
Oil-lubricated sterntube system is generally used for merchant ships while water-lubricated sterntube system is generally used for passenger ships. Recently, the water-lubricated sterntube system is attracting keen interest from the viewpoint of oil-pollution prevention. Conventional seal used in water-lubricated sterntube system has a drawback in that the sealing ring cannot be easily replaced with a spare. This is a problem in large ships for which on-schedule voyage is strongly required. This paper introduces a new water-lubricated sterntube seal in which the sealing ring can be switched to a spare ring with just a simple valve operation.
At the narrow space in the dry dock, it is extremely difficult to measure the three-dimensional (3-D) surface profiling of the ship. Therefore, the authors considered to draw on our knowledge and experience for the 3-D laser beam scanning equipment. Because the 3-D laser beam scanner is a three-dimensional noncontact surface profiling equipment, this is much help to the effective work for the measurement of 3-D shape on the ship with an ease never before possible. Furthermore, the latest in 3-D laser beam scanners are becoming increasingly cheaper and more powerful. In this case, we had to use the 3-D laser beam scanner at the narrow space in the dry dock. Therefore, we adopted the way which is the measurement of 3-D surface profiling of the ship at the ground points on the parallel line to the keel line. This is an effective work procedure to get the information of the 3-D surface profiling of the ship.
Since 1996, the authors have systematically studied the ignition temperatures of diesel fuel oil, fuel oil A (MDF), fuel oil C (MFO), internal-combustion engine oil and turbine oil. The experimental apparatus consists of a gas burner and an exhaust gas pipe wound with asbestos. Sample oil was dropped on the surface of the heated exhaust gas pipe, and it was examined whether the sample oil ignited or not. The lowest temperature of the insulator surface at which the oil ignited was recorded as the ignition temperature. It was found that the ignition temperature was influenced by the drop amount and the surface conditions. Since asbestos could no longer be used, a new experimental apparatus without asbestos insulators was made. The results obtained from both apparatus were compared, and the validity of the new experimental apparatus was verified.
An early warning system for sensing suspicious ships approaching nuclear power plants and other important facilities located at the coast is necessary. Thus, the authors developed a buoy equipped with a marine surveillance system. In this paper, the results of actual sea trials of the prototype buoys for a two-month period from July to August in 2008 and 2009 are presented. The underwater sound recorded with hydrophones mounted on the buoy was analyzed, and the method used to detect underwater sound of ships approaching the buoys was evaluated. Next, the underwater sound from the experiment boat rotating around the buoys was observed and analyzed in order to build an algorithm for predicting the geometric direction and position of the boat’s underwater sound source. Results show that this technique can be one of the methods for real-time underwater sound monitoring. The authors expect that this surveillance buoy system will be useful in predicting the presence of dubious ships or poaching boats by sensing underwater sound.
This paper presents an electromagnetic propulsion system using high frequency AC (Alternating Current), and power supply suitable for this system. It is known that poisonous gases are generated by electrolysis when DC (Direct Current) flows through sea water. The electrodes are also corroded. The electrolyte is generated even if low frequency AC, such as commercial frequency, flows through sea water. Therefore, it has been proven that generation of electrolytes is suppressed when a high frequency AC is applied to this system. However, gases are generated by electrolysis when DC component is contained in high frequency AC. In this paper, the characteristics of various power supplies are evaluated. In particular, four kinds of inverter, namely full bridge high frequency inverter, SEPP (Single Ended Push Pull) high frequency inverter, series resonant load and parallel resonant load inverters were compared and evaluated. Finally, a power supply suitable for an electromagnetic propulsion system is proposed.
A towed underwater vehicle is thought of as an effective method to survey the bottom of the seabed at large depths. A movable wing attached to it is one of the most effective systems to stabilize motion, and maintain the vehicle’s course and posture. In this paper, the authors discuss how to design and control the wings to attain maximum performance. For practical design, environmental conditions such as seabed topography, ocean current, depth, etc. must be considered. Here, computer simulation was applied and the validity of the design was confirmed. Furthermore, the analysis leads to an estimation of the controllability of the vehicle’s motion and its control method.
The ignition delay of a suspended fuel droplet in high ambient temperature was experimentally investigated. The fuel oils used in the experiment were 9 light cycle oils and 10 marine diesel fuels. The effect of ambient temperature on ignition delay was observed. The result shows that there is a good relationship between ignition delay and evaporation time of the oils under higher ambient temperatures. The ignition delay increases with a decrease in the ambient temperature. For lower temperatures, the ignition delay increases step-wise. The ignition temperatures of the light cycle oils are higher than those of marine diesel fuels.
Selective catalytic reduction (SCR) is an effective technique to reduce nitrogen oxides (NOx) from diesel engine emissions. In this study, a simple reaction model for predicting DeNOx performance deactivation and NH3 slip on a vanadia-based commercial catalyst is developed to evaluate the effects of the gas component and temperature, and NH3/NO feed ratio. This model predicted that NOx conversion rate does not depend on the catalyst temperature when the feed ratio becomes small. The calculation results at 250 deg. indicated that high excess air ratios and low NO and SO2 concentrations suppress the DeNOx performance deactivation. It was also shown that keeping the NH3/NO feed ratio small is necessary to avoid NH3 slip.
The SCR (selective catalytic reduction) DeNOx catalyst is deactivated when the exhaust gas contains SOx and the gas temperature is low. In this study, a simple reaction model for predicting DeNOx performance regeneration of deactivated vanadium-based commercial catalyst is developed to evaluate the effects of gas temperature, components, and DeNOx reaction in regeneration treatment. This model predicted the following: (1) When DeNOx reaction is not performed in regeneration treatment, low temperature (250 deg.) gas can regenerate the catalyst, and regeneration time is irrelevant to gas flow rate, NO, and SO2. (2) When DeNOx reaction is performed in regeneration treatment, regeneration time is longer, and low temperature (less than 275 deg.) gas cannot regenerate catalyst perfectly. It is necessary to keep temperatures high (more than 300 deg.) to ensure regeneration.
Light Cycle Oil (LCO) is provided as a by-product of catalytic cracking. Although its volatility and kinematic viscosity is similar to that of diesel gas oil, LCO has lower ignitability. Moreover, it has large amounts of aromatics and contains sulfur as well. These compounds aggravate engine exhaust emissions. However, from the viewpoint of the effective use of fuel resources, the utilization of LCO as fuel for industrial use is desired. Therefore, LCO is mixed with Low Sulfur A Fuel Oil (LSA) which has properties close to gas oil. This paper describes the spray and combustion characteristics of LSA and LCO mixed fuel. In the spray experiments, the spray characteristics were measured by shadowgraph photography and Mie-scattered light photography. In the combustion experiments using a constant volume combustion vessel, the soot formation characteristics were investigated by direct photography. From these experimental results, it was found that the liquid phase penetration is the same regardless of the mixture ratio of LCO, and that the soot formation characteristics can be controlled by changing the mixture ratio of LCO.
In this research, palm oil was used in a medium speed marine diesel engine as an alternative fuel. The combustion characteristics and the exhaust emissions were investigated by test bench experiments. Results show that: palm oil is suitable for the marine diesel engine, and is effective for CO2 reduction. Compared with the engine fueled with marine diesel oil and gas oil, the engine fueled with palm oil exhausts slightly higher NOx emissions but lower smoke, CO and THC emissions at high engine loads. On the other hand, it exhausts lower NOx emissions but higher smoke, CO and THC emissions at low engine loads.