An uncertainty of the relation between the energy supply and demand has been increased because of sudden changes of the petroleum price. The developments of the high efficiency and low emission technologies for marine diesel engines are more strengthened with the alternative energy because of the earth global warming and the air pollution. In connection with these, a lot of technology are being considered. In case of shipping, however, it seems that the interests tend to be concentrated on new technologies and new building ships. It should be necessary to have a deep interest about existing ships as ships are used for a long term more than 20 years.
The marine diesel engine is comparatively favorable for the CO2 which is the main cause of earth global warming, because it has the high thermal efficiency. The emissions reduction measures for NOx, SOx, and so on become major matter of concern as it is using low quality fuels. Although most of marine engines' performance may be kept generally with high level by the careful maintenance, their performances are deteriorated gradually and the operating conditions are also shifted as the long terms of operation. The operation of the engine optimized to operating conditions is very useful measure in a viewpoint of earth global warming and an economy too. So it is required that the deteriorated performance of the ship's engine should be evaluated quantitatively.
The deterioration of an engine performance is continued gradually. Many factors to be related to the deterioration of engine performance could be considered. For example decrease of the intake air mass due to drop in efficiency of turbocharger, change of combustion condition by getting worse to fuel injection system and increase of blow-by gas mass by wearing between cylinder liner and piston. They could occur independently or simultaneously.
In this study, the simulation program of marine two-stroke diesel engine was developed to predict the deteriorated performance according to the time elapsed for existing ship. The simulation result was shown good agreement compared with TOP-CODE which has been used by engine manufacturer MAN DIESEL. And the influences of some factors in relation to deterioration of engine performance were investigated.