High pressure and short period injection systems have been recently applied to cope with the increasing demands to improve the thermal efficiency and to use heavy fuel oil on medium-speed diesel engines. In such injection systems, however, secondary injection or cavitation in the system tends to occur. Under these conditions, constant pressure delivery valves which have two ball type check valves and a return orifice have been increasingly used in the medium-speed DI diesel engines to work out them.
In this delivery valve system, however, the secondary injection and the risk of cavitation have to be avoided only by the pressure regulating function of the return ball valve and the return orifice. As it was thought that the return orifice is an important factor for avoiding the above problems, it should be optimized in the design.
The authors have experimented the influence of the return orifice diameter on the injection characteristics by using an injection test rig. As a result, the optimum return orifice could be obtained in the range of our present study. Furthermore, the improvement of engine performance was confirmed by using the optimized constant pressure delivery valve.
This paper describes the results of injection characteristics and engine performance at changing the return orifice diameter.

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A 4 cycle diesel engine, whose rated power is 25ps {18.4kW}, is used in this experimental study. Valve clearance of the exhaust valve and injection pressure of fuel valve are selected as an abnormal portion, and its standard values are 0.4mm (clearance) and 190kg/cm² {18.6MPa} (pressure) .
A series of experiments are carried out for various valve clearance ranging from 0.1 to 1.45mm (valve clearance experiment) and injection pressure ranging from 100 to 305kg/cm² (injection pressure experiment) . The spectral analysis of sound from funnel outlet is made by an FFT analyzer. Using the analyzed data, multivariate analysis is made to infer the degree of the clearance and the pressure, thus ten categories (clearance or pressure) are obtained and which category a given sample belongs to is determined by the Mahalanobis' generalized distance.
As a result in the valve clearance experiment, 91.2 percent of cases are judged correct to sample cases (sample size is 400) .
In the injection pressure experiment, 95.0 percent of cases are judged correct to sample cases (sample size is 400) when the revolution is 800rpm and the load is 2/4, in case of the transformed data obtained by converting measured data at various loads into 4/4 load data by use of regression equation, 97.6 percent of cases are judged correct to sample cases (sample size is 500) .

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Pursuant to the relevant provisions and regulations of Marine Pollution Prevention Law, revised in 1973, the specified ships and coastal institutions for holding oil, had been obliged to stockpile the definite amount of competent boom, oil dispersant and sorbent.
Since then such articles have been called “The legal oil spill treating materials” and gelling agent was included to them by the revision of Transportation Ministry Ordinance in 1983. Soon after the Mizushima Accident, these materials were often examined or investigated on their properties and performances. The interest in them, however, has been gradually decreased during these 10 years.
This paper describes the past circumstance and the present situation of materials for treating oil spill and introduces other agents which are desirable to be legally approved.

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This report describes the experimental study of acoustical characteristics of gas jet noise through the straight nozzles, whosc diameters are 0.28mm to 1.00mm.
Jet force and noise level are measured under the range of pressure from 1 to 60 atg at nozzle inlet.
The obtained results are as follows;
1. Overall sound pressure level and A-weighted sound pressure level rise simply with increase of the pressure ratio.
2. Values of the A-weighted sound pressure level can be expressed well as a function of d²·Δp√T_o, where d is nozzle diameter, Δp is pressure difference between nozzle inlet gas and atmosphere, and T_o is nozzle inlet gas temperature.
3. Maximum value of the directivity of the gas jet noises is obtained at 30° to the jet flow axis. Noise levels at the discrete frequencies of 1.25, 2.5, 4.0, and 16 kHz, are lowered at 55° to the jet flow axis.
4. The gas jet noises are lowered slightly at the ratio of length to diameter 4: 1.

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The temperature rise characteristics of the induction motor can be calculated, if the copper loss, the iron loss and thermal model constants are given. The thermal model constants of the wound rotor type induction motor are calculated for the various value of rotor resistance. The thermal unit capacities of coils (H_c) and iron cores (H_f) are made to hold constant. The temperature rise and the time constant for the intermittent operation of the induction motor are calculated within the error of 3°C and 8 minutes. The influence of the value of source voltage and rotor resistance for the induction motor were analyzed, and the value calculated by using thermal model constants were similar to the measured value.

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The product name of the bolts newly developed is PILLAR NS REAMER BOLTS. They represent resins coated reamer bolts and nuts used as the torque-transmission coupling bolts for ships' propulsion shafting systems.
The bolts are featured by the ease of their pressure fitting and extraction, also their freedom from seizure though they are provided with 0.01 to 0.05 mm of interference against reamer holes.
The PILLAR NS REAMER BOLTS can ensure electrical discontinuity between the matching shafts by inserting an insulating sheet in a space between the flange surface and contact face of bolt head. The intermediate shafts of a ship electrically insulated by this method can effectively prevent spark erosion which is otherwise generated between the crankshaft journal and main bearing of the main engine due to potential induced between ship's propulsion shafting and hull.

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