The authors have been studied on an optical measurement named the “transmissive light extinction method” to investigate the soot density and its behavior in a diesel combustion chamber. In the previous reports, the theoretical principle of the method was discussed and its applicability was examined in a few calibration tests. The method was applied to the actual measurement of soot density in an experimental engine which was modified to provide a facility to visualize the inside of the combustion chamber. The experiment was successful in obtaining the progress of the particle density of soot and proved that the method was rather easy to apply and reliable.
However, since the method is principally a local measurement, ie. a measurement on line in sight, it has a limitation in explaining the behavior of soot throughout the entire combustion process.
Then this time, the authors set about highspeed photographing of transmitted light all through the combustion chamber. In this, soot was recognized as shadow. An optical arrangement was made to remove the disturbance of the flame light on the shadowgraph. It also enabled simultaneous photographing of the direct image of the combustion flame on the same film. Besides, an image processing system was developed and used for analysis of the photographed results.
As a result, soot behavior was successfully observed as a total picture comparing it with that of fuel spray and combustion flame. In this way, the result of the local measurement by the transmissive light extinction method was explained fairly well.

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Prediction of soot formation and decomposition together with flow-pattern and chemical reactions in turbulent diffusion sooting flame have become very important in recent years. The rate of chemical reactions are determined by the eddy-break-up model (k-ε model) . In the present model on soot, it has been assumed that soot is formed from the total hydrocarbon in two stages, where the first stage represents formation of radical nuclei, and the second stage represents soot particle formation from these nuclei (this model has been well studied and improved the method suggested by Tesner et al.), soot decomposition is determined by the model of Magnussen et al.
The predicted results of the profiles of gas species and soot concentrations are in close agreement with the experimental data.

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The empirical formulae, being able to estimate engine damping ratio and torsional vibration amplitude, are derived from the experimental results both for high-speed and for low-speed diesel engines mentioned in the previous paper, in which the torsional angular displacements were measured at the free-end of the crankshafts. The relationship between the main dimension of the diesel engines and the damping ratio is individually investigated by adopting the empirical formulae, and the obtained results are as follows:
1) Which loss is dominant in engine damping friction or hysteresis can be judged from the value given by the equation (5) in this paper: that is Q (n, D) ≡ (n^1.6/R) √ D/I_F kgf^-1/2 s^-1. Where, D: cylinder bore, n : number of equivalent masses except for a flywheel-mass in an engine system, R =I_F/I_E: mass ratio, I_F : inertia moment of flywheel, I_E : sum of effective inertia moments of an engine system except for flywheel.
2) Damping ratio due to friction loss is in proportion to Q (n, D), so it is related to the main dimension of an engine. As the value of the proportional constant varies from 0.21×10^-2 to 0.75×10^-2kgf^1/2s, it becomes difficult to decide the value definitely.
3) Damping ratio due to hysteresis loss has nothing to do with the main dimension of an engine, and is in proportion to θ^0.3₁₀ (where, θ₁₀ : angular displacement in the free-end of crankshaft) . The values of θ₁₀ in critical engine speed are those of the order of 10^-3, so the values of engine damping due to hysteresis loss are those of the order of 10^-3.
From the above-mentioned results, it has become easy to judge which loss is dominant in engine damping, friction or hysteresis, when the main dimension of an engine is given.

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The history of each branch of technology is postulated to have its particular intrinsic laws of development. It is now generally agreed that technology in general is presently undergoing a fundamental change toward a new era in which artificial means do jobs in place of the human brain. Natural inferences are that ship automation should be strengthened further. The history of ship propulsion is relatively independent from the history of propulsive prime-movers; the end of the era of rotating propellers is not yet in sight. However, the recent trend of building many types of voluminous-cargo vessels such as the container ship is understandable as an example of the general pattern in technological developments, e.g. the cargo carrying function is largely separated from the buoyant hull and is transferred to the deck, resulting in energy saving. The proper domain of the ship among various means of transportation is the low-speed, highly energy-efficient domain. The history of the internal combustion engine is briefly reviewed and the soundness of the basic construction of the diesel engine is confirmed. The fundamental factor in the internal combustion engine is postulated as “scavenging followed by compression”. It is then inferred that the introduction of turbocharging is the functional differentiation and re-integration in the internal-combustion engine's fundamental factor. It is concluded that the study of the history of technology from the viewpoint of the intrinsic laws of development is necessary for the formation of correct overviews and right strategies.

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In case sealing rings and shaft liners are injured on the oil lubricated stern tube seal, the liners cannot be replaced without withdrawing the tail shaft, while sealing rings can be. There are strong demands to make it possible to replace both the sealing rings and liners without withdrawing the tail shaft, especially, for vessels equipped with controllable pitch propeller. To meet with these demands, the split seal which consists of split liners and split housings has been developed.
The mechanism of the oil oozing out of the joint of split liner on the running test has been studied and the manufacturing technique of split liner to prevent the oil oozing has been developed. The most important problem of split seal has been found to be the displacement at the joint of split liner which affects the oil leakage and wear of sealing rings. These problems were thoroughly investigated through the tests and the allowable displacement at the joint has been determined.

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