Transient concentration of a single-shot gas jet was measured by using laser interf erometry. A He-Ne laser beam was divided by a beam splitter into test and reference beams, and interference fringes were produced by making the beams intersect after the test beam has passed through the test medium. Hydrogen gas jet was injected into the atmosphere passing through the test beam. When the density of the mixed gas of hydrogen and air changes, the optical path length of the test beam changes with a corresponding change of the refractive index, and then the interference fringes move. Two photo-transistors located in π/2 phase difference were used to detect the movement of the interference fringes by translating the luminousity into voltages.
The change in the refractive index mesured in this study indicates the change in total optical length of the laser beam. The jet is assumed to be axisymmetric. By means of the onion peeling method, the concentration distribution of the gas jet in each section was determined.
Tht penetration distance of the jet agrees with the configurations of the jet observed from schlieren photographs. The laser interf erometry is extremely useful for the measurement in the transient concentration of unsteady gas jet because this method has a high response and no intrusion into the jet. The concentration distribution from this method shows a similar result to that obtained by using a hot-wire as concentration measurement.

View full abstract

The former experiments have revealed that the ventilation mode can be classified into the partial ventilation characterized by the unstable air cavity and the full ventilation characterized by the very stable sheet cavity formed over the whole blade, and as for the vibratory shaft force, revealed that (i) the shaft forces are induced only by the partial ventilation region, (ii) the shaft force becomes very large in a certain range of experimental conditions. In the former experiments, however, the dynamic interaction between the free surface and the ventilation phenomenon could not be observed in detail. So the following experiments were carried out by the use of the newly improved measuring apparatus. It has been made clear that (i) the main frequency component of the shaft force due to the ventilation is equal to the shaft revolution rate, (ii) the strong interaction between the free surface and the ventilation occurs in a certain range of the partial ventilation region, and induces the very violent shaft forces.

View full abstract

Studies have been conducting on the suppressing effects of soluble fuel additives on soot emission from standard laboaratory spray flame and diesel engine combustion. In these studies, soot reduction was systematically examined by adjusting the amount of two kinds of additives. The one, composed of chain compound, is to increase cetane number and the other one, containing Ba, is to reduce the smoke in exhaust gases.
Flame temperature and soot concentration of the inside of steady spray flame were measured when using fuels mixed with each additive. These fuels with the additives were also used in a diesel engine to measure the exhaust smoke for comparison and investigation.
The results may be summarized as follows;
(1) On the effect of using the additive composed of chain compound, the maximum temperature point and soot formation zone in the steady spray flame are shifted to the upstream. The soot concentration is increased, however, the reaction of the soot decomosition becomes active, resulting in decrease the soot emission.
In the deisel engine, although ignition delay time is shortened and the diffusion combustion is promoted, which makes the soot emission increase.
(2) On the additive contained Ba, the soot exhausted from both of the spray flame and the diesel engine is decreased due to the decrease in soot formation and aggregation.

View full abstract

Many kinds of sea livings accrete to the propeller surface of ships at anchor. As a result, main engine gets into the torque-rich condition and the rotational frequency of propeller decreases. These cause the drop of propulsion efficiency.
To prevent the accretion of sea livings, propeller-coating has recently been examined by using anti-fouling and self-polishing type paint which contains copper compounds and organic tin compounds. This type of paint is much used now for the bottom plates of ships or fishing nets for ocean cultivation etc.
It becomes, however, one of the severe social problems since our sea environments is polluted by the toxic components or heavy metal of the paint dissolving out into the sea.
Then, the experiments wrer made applying propeller-coating to our training ship “YUGE-MARU” by using a nontoxic paint which is made of special silicon resin and which is fit for special uses at land.
The results of one year's experiment show that the surface of propeller is kept clean and the film of painting is attached firmly to the surface.
By these effects of this coating, the corrosion protection of ship has been improved and the amount of fuel consumption of main engine has been reduced 6%.

View full abstract

The purpose of this study is to investigate the performances of the electronic units installed out-board the pressure hull of the deep submergence research vehicle and the other deep sea equipments.
This paper presents the results of the measurement of the electric characteristics of various devices, i. e., a resistor, a condenser, an operational amplifier, a diode, a thyristor, and many electronic circuits.
Each devices were coated by an insurating rubber and tested with the finger-pin-closer type high hydrauric vessel at max. 450 kgf/cm².
As a results, the resistance of the metal film resistor was 1% low, the capacitance of the electrolytic capacitor was nearly constant, and the gain of the operational amplifier increased slightly.
Also, the out-put characteristics of the diode and the gate control of thyristor were normal.
In this paper, the applicable posibilities of the electronic devices under the high hydrauric pressure are indicated on many trials.

View full abstract