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A comprehensive structural analysis simulation model is used for describing the thermal condition of a four-stroke, air-cooled, DI diesel engine under steady and transient operation. Two- and three- dimensional finite element analyses are implemented for the representation of the complex geometry metal components (piston, liner, cylinder head), in a way that the temperature and heat flux variations are calculated during any transient event. A detailed thermodynamic simulation model of engine operation is utilized for the determination of boundary conditions on the combustion chamber sides of each component. During an engine transient, processing of experimental cylinder pressure diagrams on a cycle to cycle basis resulted in the estimation of heat resease rate and boundary conditions (gas temperature, heat transfer coefficient) variation from the initial to the final engine thermodynamic state. Consequently, the power and specific fuel consumption curves can be accurately determined.

In the present work a multi-zone combustion model, initially developed for naturally aspirated, high-speed, direct injection diesel engines, is used for studying the performance and emission characteristics of large scale, slow-speed marine diesel engines. Up to now pollutant emissions was not considered a problem in the field of marine engines, since no specific legislation existed. However, the International Maritime Organization (IMO) is forwarding a legislation that will be applicable in the next years concerning soot and nitric oxide (NO) emissions. This legislation will make it impossible for vessels to enter the native waters into countries where this legislation applies. Due to this fact, engine manufacturers are making serious efforts to design new engine builds with reduced soot and nitric oxide emissions using new designs and exhaust gas aftertreatment systems.