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.

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This paper describes the experimental study on ignition delay of the suspended single droplet of marine fuel oils in high ambient temperature under atmospheric pressure. Fuel oils used in the experiment were twelve marine fuel oils.
The results show that the ignitions of single droplet of marine fuel oils were classified into the two cases which were controlled by the initial droplet diameter and ambient air temperature. The droplet was ignited through the vapor of low boiling component in the first case, and through that of high boiling component in the second case. The mechanism of the ignition of single droplet in both cases was discussed.
Those results suggest that the ignition delay of diesel engine is estimated by that of the single droplets.

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For the final goal of developing the natural gas-fueled spark-ignition engines with high thermal efficiency and low pollutant emission, the effects of the fluid flow inside a combustion chamber on the combustion process of a homogeneous lean methane/air mixture were examined using a rapid compression combustor. The rapid compression combustor was designed to simulate the combustion process in a spark-ignition engine involving the rapid compression of a mixture and the heat release during the flame propagation. The main advantage of using this combustor is that experiments can be made under the idealized and well-controlled conditions. The time history of pressure in the combustion chamber was measured with a pressure transducer. The fluid flow in the combustion chamber was varied as follows; the mixture was injected into the combustion cylinder before the compression stroke, and the direction of the injection and the time interval between the end of mixture charge and the start of compression stroke were varied. The position of spark ignition was also varied. And the flame propagation was photographically observed. Moreover, the two-dimensional velocity distribution of the swirl flow was measured with particle image velocimetry. As expected, the combustion duration decreased with increases in the mean velocity and the turbulence intensity of the fluid flow. When the intense swirl flow existed in the combustion chamber, the combustion duration was minimized with spark ignition at the eccentric location.

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In order to improve the boiler efficiency, latent heat recovery from the flue gas is very important concept. Condensation heat transfer on horizontal spirally finned tubes was investigated experimentally by using an actual flue gas from a natural gas boiler. The experiments were conducted at different steam mass concentrations of the flue gas and a wide range of tube wall temperature. The mass concentration was controlled with a steam injection into the flue gas. Fin efficiency at the condensation region was significantly lower than that at the dry region. The empirical correlation developed for a single-phase fluid was extrapolated to the condensation heat transfer region. The fin efficiency was evaluated with an equivalent heat transfer coefficient used as a first approximation. The heat and mass transfer behaviors on the spirally finned tubes were well predicted with the analogy correlation based on the empirical correlation.

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Mitsui Engineering & Shipbuilding Co. Ltd. started the production of B&W licensed diesel engines, and has accumulated the produced power to 34 million BHP by the end of March 1999. In recent years we are mainly producing MC type engines which entered in 1983. Licenser MAN-B&W has made several times of rating up on MC engines so far. And this time, they have added new type of S-MC-C engines in their line up as one of the engine type for next generation. S-MC-C type is so attractive, as the weight and length are reduced by approximately 10% but the output is increased by approximately 10% from MC type, meeting the upcoming requests from the marine market. Mitsui produced 6S50MC-C for the prototype of all S-MC-C types in 1997, and 8S60MC-C for the prototype of S60MC-C types in 1998, and performed the prototype tests and type approval tests on their shop tests. They and following series of engines have entered in service, and been recording good service data. This report shows some features of main parts, measurement results, and service experiences for S-MC-C types, mainly focusing on S60MC-C.

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In general when water emulsified fuel is used in diesel engines, burning speed is enhanced and vibration/noise is increased. Experimental results showed that noise in the range of high frequency increases rapidly due to the vibration resonance of engine parts and stronger pressure oscillation with increasing of a water addition amount of emulsified fuel. Especially, stronger combustion noise was caused in the range of 1.2kHz due to engine structure vibration resonance for the engine. But noise in the range of lower frequency slightly rises. The experimental results shown also that NOx Emission can be reduced and combustion can be controlled, and good economy still be keep if the burning start is properly delayed. For the experimental engine, when injection timing was 6deg retarded from the original and 30% water emulsified fuel was used, NOx emission was reduced by 60% without bad fuel economy and noise increasing compared with normal injection timing and using pure fuel.

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For quicker response of engine, we developed jet assist system. High pressure air is generated by the screw compressor driven by marine-gear and flows into the MAN/B&W turbo charger with the jet assist system. We accomplished quicker response of engine by optimization of compressor capacity, the area of jet nozzle, the pressure of air and timing of jet assist.

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