Gas burning diesel engines with using LNG as fuel have been developed for the purpose of applying to prime movers of LNG carriers and electric generators. For developing these engines, the investigations of the methods of ensuring for ignition of fuel are important, because natural gas is harder to ignite than conventional liquid fuel. This study has been carried out as a fundamental study of ignition of fuel jets in gas burning diesel engines.
Methane was injected in a closed vessel filled with the hot burnt gas, in which remained oxygen concentration was about 21vol%, and then the ignition delay, ignition temperature, and heat release rate for initial combustion duration were investigated. Moreover, the ignition delays measured in the closed vessel were compared with that in a gas burning diesel engine. The results are as follows:
(1) The data of ignition delays of transient methane jets measured in the closed vessel can be applied to gas burning diesel engines.
(2) In order to shorten the ignition delays to the allowable level for gas burning diesel engines, it is necessary to raise the temperature of gas in their combustion chamber above 1100K.
(3) The heat release rates for initial combustion duration of transient methane jets increase in proportion to their ignition delays.

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In the recent years, some damages of propeller blades due to fatigue were experienced on the liner ships, which make a demand to develop the strength evaluation method of the propeller blade considering the alternative stress, instead of the traditional methods bosed on the mean stress.
There are a few methods to calculate the alternative stress on the propeller blade. However, these methods are inconvenient to discuss comparatively the strengthes of many propellers, because they are based on the flow around the propeller which can only be calculated numerically using rather large computer.
In this paper, a formula for calculating blade stress using few parameters is led from Schoenherr's thrust equation, and the results are compared with the ones of a computer calculation based on the lifting surface theory and with the measured stresses on several actual ship propellers.
Further, a practical design formula to calculate the blade thickness is presented, considering the sea states or the condition under which ship is operated, and the allowable stress of propeller materials provided from the latest fatigue test results.

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An investigation of the wear diagnosis of marine diesel engines is carried out to confirm the applicability of ferrography.
In this report, as the first step, oil samples taken periodically from engines in service are analyzed by means of both quantitave and analytical ferrography.
Results are summerized as follows:
(1) The initial wear condition of the sliding machinery parts is distinguished from the normal wear condition by the observation of the wear particles concentration (WPC) and/or the wear severity index (Is) .
(2) The quantity of wear particles in the cylinder/system oil increses where crank-pin bearengs failed.
(3) The values of the wear particles concentration (WPC) and the wear severity index (Is) for the cylinder oil increase extremely where the abnormal wear of piston rings occured.
These results suggest that the ferrography for lubricating oil is effective in the monitoning the condition of the diesel engines.

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The measurement of wear of piston rings and cylinder liners is one of the most important points to maintain a marine diesel engine. The wear conditions of engine parts have been usually examined by periodical overhaul. In this study, 252-Cf neurton activation analysis is applied to the estimation of wear without overhaul. The extent of wear of engine parts can be estimated from the contents of metal particles, which are produced by wear, in the circulating fluid such as lubricating oil or exhaust gas of the engine. In this study, wear of piston rings and cylinder liners are presumed by manganese contents in the cylinder oil drain of an actual marine diesel engine.
The results of the analyzed manganese contents in the cylinder oil drain under variable running conditions show the good relation between the manganese contents and measured wear volume during overhaul periods.

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The discharge into the sea of tank washings of the chemical tanker shall be prohibited except when the regular conditions are satisfied. It is decided by THE INTERNATIONAL CONVENTION FOR THE PREVENTION OF POLLUTION FROM SHIPS, 1973 AS MODIFIED BY THE PROTOCOL OF 1978 RELATING THERETO (MAR-POL 73/78) and the concerned domestic law. Concerning hazard liquid substances, the effluent from the tank washing operation shall be dischanged to a reception facility at least until the concentration of the substance in the discharge has fallen to the residual concentration specified for the substance.
Therefore it is necesary for the estimation of the amount of the needed water that the relation between the residual concentration and the amount of the used water is grasped. It is investigated using a model tank and the amount of the water for tank washing is estimated by the results.

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