Wear resisting steel (WRS), improved scuffing characteristics was newly developed in order to apply to the frictional parts for machinary. The two rollers tests were carried out using the newly developed WRS, steels with Ni-P electroless plating, and with electrolyzed and sulfurizing treatment. Then the scuffing characteristics of these materials were discussed.The anti-scuffing characteristics of WRS were very good and the frictional coefficient was as small as about (1/3) of SUJ2, a reference material. From the test results using WRS specimen of two kinds of hardness, the anti-scuffing characteristics of specimen of which the hardness was low was higher. The anti-scuffing characteristics of steel with Ni-P electroless plating were good. The part of Ni-P electroless plating layer remained during the test period but the other part of plating layer disappeared. On the other hand, the electrolyzed and sulfurizing layer which is effective for running-in, disappeared in a short time, and became that of base material.As the result of observation of surface and cross section of specimen, the white layer on the scuffing surface was found from 30 to 50μm thickness. It seemed that the layer is a martensite including supersaturatedly solidified carbon which is a part of cementite at the sub-surface dissolved by thermal and mechanical energies.
In recent years, the demand for the reduction of noise emitted into the environment has strongly increased in order to prevent noise pollution. As the major contributor of emitted noise into the environment is exhaust noise in ships, it is necessary to reduce exhaust noise as much as possible. Conventionally, passive silencer techniques are used, but larger silencers are now needed in order to achieve larger noise reduction. However, because of the limitation of space, it was actually difficult to reduce the exhaust noise on a ship. In order to reduce the exhaust noise as well as minimizing the occupied space, the active noise cancellation technique was applied to the exhaust noise silencer for diesel engines. To reduce the exhaust noise efficiently, at first, the acoustic behavior in an exhaust pipe was calculated by the boundary element method. At first, by optimizing the length of pipes and the positions of microphones and speakers, the active exhaust noise cancellation system (AENC) was applied to the main engine for marine use. Also, by applying acoustic resonance aggressively, the AENC, with only one speaker system, was developed for auxiliary engines. Finally, by assembling a passive silencer for high frequency noise, the active exhaust noise silencer was developed.
Recently, the regulation to the air pollution is required from a viewpoint of environmental issue. The exhaust gas from the diesel engine is one of the factor that the air pollution is caused. Authors have taken note of PM (Particulate Matter) in exhaust gas and have proposed the combustion system of PM by means of high frequency induction heating. In this paper, as experimental results, it is proved that PM is reduced by PM reduction system utilizing high frequency induction heating. Furthermore, a novel high frequency inverter as the power supply for high frequency induction heating is proposed. And the circuit characteristics are clarified. As a result, although the circuit parameters are changed according to temperature in order to heat a metallic filter to high temperature, this inverter has realized stable operation.
In cross head type marine diesel engines, cylinder oil is supplied at regular intervals and constant quantity from oil-feed holes to lubricate the running surface of piston rings and cylinder liner. Accordingly it is important to determine position of oil-feed holes, timing of oil-feed, running surface profile of piston rings and cylinder liner and so on to make cylinder oil spread wider and form thicker oil film. In this study, the authors examined how the factors influence the extension of cylinder oil using the tester which simulated cross head type marine diesel engines for the purpose of utilizing small quantities of cylinder oil effectively. We found that wave-cut surface of cylinder liner has better spreadability of cylinder oil than honed surface and wave-cut surface with oil grooves has the effect of circumferential spreadability especially.
In recent years, we must make an effort to develop an advanced technique for recycling of waste plastics in order to utilize scrapped plastics as fuel source for diesel engines. It is necessary for us to cope with the increasing calorific value and the growing needs of environment protection. At Kobe University of Mercantile Marine and Nippo Sangyo K.K, we experiment on the dynamic and exhaust gas characteristics from the standpoint of usage for marine diesel engines.The experimental fuel oil was obtained by mixing of diesel oil, WPD and water. Although the experiment is difficult, we experiment on NOx reduction by addition of water.There is great hope of the future development in this experiment about the application of WPD.
The marine diesel engine using water emulsified fuel was operated in a diesel engine plant for the electric generator on Training Ship “Nippon Maru”.This practical operation was carried out 2, 063 hours of total running.However several problems such as the lack of response performance to rapid increase of electricload and difficulty in disposal of leaked emulsified fuel from fuel injection system, occured in this operation.Further more the influence of emulsified fuel to the constituent parts of diesel engine was investigated when it was overhauled and the followings were found:1) On the case of using emulsified fuel, the opening pressure of injection valve lowered always in comparison with using marine diesel fuel.2) Slight abnormal wear was observed at the fuel injection nozzle and pump plunger.3) Glassy white deposit and wrinkled traces which were caused by the water contained in emulsified fuel were found on the piston herd.
From the viewpoint of global environment protection, regulations for prevention of air pollution from ships have been discussed in the International Maritime Organization (IMO) and the regulations about NOx and SOx are expected to enter into force January 1st of 2000.And global warming is recently such a serious problem that it is necessary to reduce greenhouse gas emissions. CO2 and N2O in exhaust gas contribute to global warming.In addition to the above, IMO will revise the regulations every five years. Then emission will be expected to be applied to other air pollutants including N2O in the near future.Under these circumstances, we studied effect of fuel property or SCR system on harmful exhaust emissions such as N2O by using a 4-stroke diesel engine.The following are found:(1) N2O concentration from Marine Fuel Oil is approximately 10 times as high value as that from Marine Diesel Fuel.(2) N2O concentration from a diesel engine is influenced more strongly by sulphur content in fuel than by nitrogen content in fuel.(3) In using same fuel for a diesel engine, N2O concentration is influenced by NOx concentration. N2O concentration increases with an increase in NOx concentration.(4) In addition to NOx reduction, reduction of N2O and HC is possible by using this SCR system.
Techniques for low NOx combustion without degrading the specific fuel consumption were developed for the medium speed diesel engine. First concept for low NOx is the reduction of high temperature combustion zone. Owing to this concept, the high-temperature combustion flame zone is reduced by the injection direction near to the piston surface. Second concept for low NOx is the reduction of the flame temperature owing to the quick mixing of the high-temperature combustion zone and the low-temperature air portion. It is necessary to obtain the air motion which has the quick mixing of combustion zone and air portion. The air motion adopted in this study was the intake swirl induced by the intake valve with shroud. The medium speed engine with a bore of 280mm was used in the application of the new techniques for reducing NOx emission. The engine based on the low NOx techniques has the decrease in NOx emissions by 40 % and almost the same specific fuel consumption compared with the base engine.
Developing techniques to evaluate fuel stability and combustibility is essential to ensure the quality of marine fuel oil.Experimental research was performed to determine the combustion performance of marine fuel using the thermogravimetry-differential thermal Analysis (TG-DTA) and the fuel droplet combustion method and the fuel ignition Analyzer (FIA-100) .The results made it possible to distinguish between normal fuel and fuels which caused combustion problems.Compatibility of fuel oils follows solubility theory. The solubility of asphaltene can be predicted by the Scatchard-Hildebrand equation. This paper describes how to apply the solubility theory to evaluate fuel stability of marine fuel oil.
This paper describes the application of a engine total electronic control system for marine engines. This system makes it possible to control engine performance according to the operation conditions. First, concept and structure of such a system are discussed as a feasibility study. Second, results of tests to confirm the functions of electronic controlled fuel injection and exhaust valve systems are introduced.
* Translated from Journal of MESJ Vol. 34, No. 4 (Manuscript received Oct. 28, 1998) ** Kawasaki Heavy Industries, Ltd. (Chuou-ku, Kobe City)
