It is Known that the brake power of Stirling Engine is decreased by leak of working gas from contact-surface between the inner-wall of cylinder and the ring. To recover part of the leaked working gas out of cylinder, a special piston ring was designed and manufuctured for trial.
Comparing this ring with the conventional one on Stirling Engine operating under the atomosphere pressure, it is confirmed that the brake power is remarkably increased by using the new ring, which is most appropriate for Stirling Engine.

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To reduce the quantity of remaining noxious liquid substances in piping arrangement after the unloading, the effectiveness of gas blowing which is commonly applied to the chemical tankers is examined analytically. Two different test arrangements are considered for the means to maintain back pressure at the end of horizontal pipe. Back pressure is maintained by 10m. long vertical riser pipe (10mP) or constant pressure valve (CPV) . Model for predicting the quantity of remaining water and pressure in horizontal pipe during the process of air blowing for the test arrangement of CPV is developed, based on physical mechanism presented in previous paper for the test arrangement of 10mP. Results predicted by the present analysis are both compared with experimental data for 4-inch and 6-inch diameter horizontal pipe lines and with the predicted results for the test arrangement of 10mP. Good coincidence with experimental data is obtained and two predictions are in satisfactory coincidence. This suggests that constant pressure valve has an equivalent function to the 10m. long vertical riser pipe.

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The electronic digital governor can control revolution of main engine of ship more accurately compared with the conventional mechanical governor. However, it is difficult to set control parameters to an appropriate value for each engine.
To solve this problem, the computer software which simulates the dynamic behavior of engine was developed. Applying nonlinear programming techniques to this simulation program, the computer program which calculates the appropriate control parameters optimizing a performance of engine was developed.
Using this system, the dynamic behavior of any engine under optimal value of control parameters can be automatically determined before operation that results in the reduction of setting time.
The applicability of this system has been verified through actual operation.

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In the recent years, it has been supposed a difficult circumstance to maintain good properties of the marine diesel oil since the increasing of a demand for middle distillates of petroleum products. Especially on a small sized high speed diesel engine used in a fishing boat, these will be serious problems caused by low cetane index fuel blended with cracked gas oil.
The performance of starting mobility and the combustion analysis of diesel engine related with cetane index, from 30 to 61, of fuel were examined in details by the experimental study in the case of small high speed engines for coastal fishing boats. As a result, the performance of starting up of the engine was remarkably influenced by cetane index of fuel. The period for starting was long in low cetane index fuel (particularly less than 45) . And also the fluctuate of engine speed was larger with decrease in cetane index just after starting up. Interestingly, the smoke density of exhaust gas was dwindled with decrease in cetane index of fuel. It was interpreted in terms of a tendency of reduction for the period of combustion of the low cetane index fuel.
The following conclusion was obtained from this study: cetane index of the marine diesel oil is required to keep above 45 for the small high speed diesel engine.

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