Chattering of the needle in a fuel-injection valve, which takes place at low speed operation of a fuel-injection pump, often has an influence on the forming of the mixture in a Diesel engine. An equation for getting chattering-frequencies and a criterion of stability, which are based on the unsteady flow theory, are developed. They may give help to discussing constructive dimensions of a fuel-injection system with regard to chattering of the needle.

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The deformation behavior in static condition of sealing rings in Stern Tube Sealing that has an important effect on the sealing performance such as their durability and oil leakage was studied. Keeping an eye on the lip of sealing rings, its deformation, width of contact at the lip and its displacement were measured, and also they were theoretically analyzed by the finite element method.
As a result, the deformation behavior of sealing rings was made considerably clear under several conditions and it was confirmed to be possible to predict that with the theoretical calculation by the finite element method. Moreover it was also found that the sectional shape of the present sealing rings was very desirable.
Furthermore, an experiment for the evaluation on the shape of support rings that was designed to make the durability of sealing rings longer was carried out. And it was found that the support rings should be ready for the Stern Tube Sealing and“back-up type support rings”was the most effective in shape for all type of them.

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In this paper, the difficulty index in design of CPP is proposed as“ (PN²) ^2/5”. This index is derived from the principle of similarity and may serve as a common scale among designers of engine plant and hull and shipowners to judge the reliability of CPPs.
The upper limit of this index in the present situation can be introduced from the reference list of each CPP maker in the world and various model test results. As CPPs for high speed vessels are sensitive to wake distribution behind hull with regard to fluctuating load on blades and cavitation, it is noticeable that the allowable upper limit of these vessels is especially restricted.
Some method to push up this limit line is proposed, but in any case it is very important that the CPP dimensions are chosen to be kept good relation to hull dimensions.

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The program which simulates the crash astern ability of direct coupled two stroke diesel engine was developed especially on the point of engine performance. And for the various kinds of ships the simulations were carried out with good accuracy. As the results of the simulations, the importance of various parameters which have the influence on the crash astern was found. We have selected three parameters as below.
•Specified engine revolution when brake air is put into
•The air pressure of air reservoir
•The open and close timing of starting valve
The valve timing is regulated by the distributor cam and the valve is opened by the elevated air pressure. So, the timing on the point of crank angle is delayed more when the revolution is higher.
We must consider both starting from 0 revolution and starting and braking from some revolution such as crash astern. And for these the time delay should not be ignored.

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Recently, the problem of less-maintenansability of ship machinery plants is attracting attention in the ship building industry.
This problem is closely concerned with reliability, so the authors studied the application of the fluidics which is very reliable since there are no mechanical moving elements.
As the object of application, the authors selected the controller which was causing troubles such as the sticking of the nozzle flapper or the abnormality of mechanics due to vibration, and made a comparative study of the fluidic controller and usual type controller in regards to less-maintenansability and controllability.
The process of study follows.
(1) Analysis of controllability of the fluidic controller.
(2) Analysis of controllability of the usual type controller.
(3) Experiments with both types of controller concerning less-maintenansability on board.
The results of this study show that the fluidic controller presents no problems under an unfavorable condition such as a board ship, and has superior controllability in comparison with usual ones.

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