If the factors which defferentiate a theoretical cycle frome an actual cycle and the factors which constitute a theoretical thermal efficiency of the theoretical cycle are analyzed, the thermal efficiency of the actual cycle can be evaluated with these factors. As the change of the thermal efficiency is directly compared to the change of the factors, so it will be possible to get the measure how to and much improve the thermal efficiency.
In the present paper, a new idea named the polytropic cycle is introduced. The polytropic cycle is related to the actual cycle with two diagram factors, and the theoretical thermal efficiency is expressed with the cycle factors and the cycle indexes which constitute the polytropic cycle. The heat balance is also expressed based on the polytropic cycle. To estimate the theory, some systematical experiments have been conducted changing the injection timing, compression ratio and boost pressure using a single cylinder fore-cycle test engine and a test equipment.
As a result of applying the theory to the experiment, the factors which strongly concern the thermal efficiency have been analyzed, and some characteristic tendencis have been found in the change of the factors. In addition, the calculated break thermal efficiency and exhaust gas temperature agree well with the measured data, so this theory can be applied to the practical analysis and evaluation of the engine performance.

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The behavior of cavitation bubbles derived from the cylinder liner vibration was observed by a high speed camera system (IMACON 790), and the numerical analysis as for their behavior was compared with experimental date. The variable were the cylinder liner vibration velocity and the distance from cylinder liner to plate, and the relation between water pressure fluctuation and the bubble behavior was made clear. And also the calculation was tried in regard to the maximum impact pressure when the bubble was broken.

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Since oil crisis in 1973, oil price has increased and the running cost of vessels has become enormously high, which has resulted in a necessity of much more economical designs for diesel engines as well as a decrease in the optimum speed of vessels. Consequently, many vessels in service have become equipped with overpowered and less economical propulsion machinery, compared when they were first launced in service. Under such circumstances, a concept for modernizing 2-stroke engines in service has been developed. The conversion for modernization is carried out mainly by using standard components from the new L-MC engines with a smaller cylinder diameter. The modernization brings almost the same specific fuel oil consumption figures as the L-MC engines, corresponding to a reduction about 20%, by means of conversion from impulse to constant pressure tubocharging systems and increase in a stroke/bore ratio, thereby increase in maximum cylinder pressure.
The first conversion in the world has been carried out from Mitsui-B&W 10K90GF to 10K90 70MG for modernization. A reduction in specific fuel oil consumption about 30g/BHP/h {11g/MW/s} has been reached, and a good service result has been obtained after the conversion.

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The relationship of soot concentration, gas temparature and intermediate hydrocarbon (polynuclear aromatic) compounds produced in the pyrolytic combustion paths in an important to understand the pathway of soot formation. This experimental object become evident the presence of emission excited in oilspray flame by the blue laser light (λ=488nm, 1.8W) . The scattering characteirgation from polynuclear aromatic hydrocarbons are not dealing here with elastic scattering phenomena, but rather with a fluoreseent emission.
The results obtained are as follows.
The maximum peak wavelength is in the neighbourhood of 530 nm. The fluorescent emissve intensity increases rapidly with soot concentration along the flow near the nozzle tip where fuel-rich condition prevail and hydrocarbons are formed by being reacted from original fuel of A oil. The decay of fuloreseus emissive intensity and soot concentration becomes significant near the maximum temperature. The peak of the fluorescent emissive intensity in the radial profiles near the nozzle tip is located just inside the position of the temperature peak, which indicates that hydrocarbons are produced in the fuel rich region near the peak of the temperature. In this experimental result the fluorecent matter is able to estimate the aromatic hydrocarbon such as Pyrene.

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This training system for students or ship operators has two major components.
One is a data filing component of engine fault examples in a personal computer taken from many publishments and on-board experience.
The other is an exercise-analysis system, composed of a fault diagnosis chart and a solution chart. A fault example chosen from the filed data can be resolved step by step by using these charts.

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