Nobukazu Shimada

Analysis of Submerged Water Jets by Visualization Method: Flow Pattern and Self-Induced Vibration of Jet

This paper is concerned with an experimental investigation on plane submerged water jets discharged into quiescent water in an open channel. Flows are visualized by using hydrogen bubbles, solid particles and dye. The results show that the jets attaching to the water surface by the Coanda effect are classified into six types according to their behavior after issuing from the nozzle, and that the self-induced vibration of the jet, which is one of six flow patterns, occurs under the condition of the reduced Froude numberFr*≒0.7∼1.0. An additional analysis of the photographs reveals that the self-induced vibration of the jet is caused by attachment of the jet to the water surface and the ensuing bifurcation of the jet at an attachment point, and that the frequency of vibration is independent of the water level.

Self-Ignition Temperature of Lubricating Oil Dropped into the Surface of Heat Insulator

The lubricating oil is important material for a marine diesel engine. But it is inflammable liquid same as fuel oil, so it has prospect of being ignited and burning when it leaks and spatters on the high temperature surface of the heat insulator of the exhaust pipe and so on. This is the cause of ships fire disasters. We examined the ignition characteristics of the gas oil, marine diesel oil and heavy fuel oil, and reported the ignition temperature of these inflammable liquids.In this study, we aim to confirm self ignition temperature of the lubricating oil at the atmospheric pressure. As a result, we found that the boundary temperature region of the lubricating oil, which is the area between ignition and non-ignition temperature line of it, is included within that of heavy fuel oil.

Self-Ignition of Fuel Oil dropped on Surface of Heat Insulator of the Exhaust Pipe

In the engine room area. the leakage or the spray of inflammable oil from the pipe lines gives the cause of a fire. Oil will self-ignite by contact with the high temperature surface of the heat insulator.In regard to the self-ignition temperature, there are many data, obtained from the experiment under the closed, highly pressurized circumstances, but there are few data under the opened circumstances at atmospheric pressure.A purpose of this research is to confine the self-ignition temperature within narrow limits for marine diesel gas oil, contain various kinds of hydrocarbon, in the case of dropping oil on high temperature surface. As a result of an experiment, it is confirmed that gas oil ignite certainly at temperature above 398°C, not below 337°C, on dropping volume 0.04cm3-0.3cm3.