To find a basic principle of residual fuel combustion, tests were conducted on heavy fuels of 34.4 cSt and 75.9 cSt at 50°C (200 and 500 sec RW No. 1 at 100°F) using small-sized, high speed diesel engines with a cylinder bore of 110 mm, a stroke of 125 mm and speeds of 2500 and 2600 rpm. Using a natural-aspirated engine, the effects of individual factors on engine performance were confirmed by changing the fuel injection mode, the cooling water temperature, the suction air flow quantity and the temperature respectively. Then using a turbocharged engine, the optimum combustion method was established by chiefly improving the fuel injection mode. Fuel combustion was evaluated by means of accurate indicator diagrams obtained by the CB-366 combustion analyzer. The reliability and durability of the engines were confirmed through thermal load analysis based on temperature measurements of the combustion chamber walls.

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Recently, the crankshaft vibration of reciprocating internal combustion engines is becoming a problem not only on torsional vibration but on bending vibration as speeding up, powering up and lightening of the engines.
On crankshaft vibration of reciprocating internal combustion engines, there are many studies on torsional vibration but less on bending or multi-mode vibration.
It is difficult to apply the conventional methods for such a complex vibration.
The complex vibration has been analyzed precisely by Prof. Iwamoto and Prof. Wakabayashi using the Transfer Matrix Method.
But as the accuracy of result obtained from this method has been largely depend on how accurately the stiffness of the crankshaft is estimated on its coarse modelling, it is necessary to correct the crankshaft model, and it has been corrected by measured value.
In this paper, the Finite Element Method is used to correct the crankshaft model.
The values of the stiffness calculated by the Finite Element Method and measured by unit tests have good coincidence.
As a result, the crankshaft model of the Transfer Matrix Method is corrected accurately and as shown in this paper, the accuracy of crankshaft natural frequency calculated is more than 90 percent to the measured one.

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Recently, some kinds of high-frequency inverters using reverse-conducting thyristors have been attractively used as the exciting sources for ultrasonic transducer systems.
Both of voltage and current-fed inverters have been widely used for these purpose. In general, there are some problems in starting and high di/dt for the current-fed type inverters, and also in high dv/dt for the voltage-fed type inverters. Furthermore the maximum frequency of these inverters are limited by turn-off time rating.
This paper describes some transient and steady-state characteristics of a center-tapped highfrequency inverter using ASCR, which is capable of operating at 100 KHz. First of all, the basic operation of the inverter is discussed and then the normalized numerical solution is elucidated. Effects of inductance ratio and capacitance ratio on the steady-state characteristics for the inverter are fully discussed on the basis of numerical analysis.
Secondly, load characteristics attributed to load variations on the steady-state operation are illustrated in relation to some normalized circuit constants and operating frequency.
In addition, the transient response of margin time of commutation for ASCR is studied in relation to the practical maximum operating frequency.

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Today the auxiliary diesel engines on the ship use the degraded fuel oil of 3500 sec or equivalent Redwood No. 1 at 100°F.
The authors have conducted a study on the reliability and the durability of small or mediumsized medium speed diesel engines burning the low grade fuel oils.
In order to evaluate the combustion tests of degraded fuels, the ignition lag and the combustion mode of those fuels are analyzed by the combustion pressure measured at the fire side of the combustion chamber.
The test engine is medium speed engine with 240 mm bore. The maximum power is 1125 PS at 720 rpm.
The test fuels are light cycle gas oil (LCGO) from catalystic cracking units, and residual low grade heavy fuel of 3500 sec or equivalent RW. No. 1 at 100°F from the vacuum distillation etc.
It is confirmed that the ignitability of LCGO and the combustion characteristics of residual low grade heavy fuel are inferior to those of marine diesel oil from the straight distillation.

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