Recently, the importance of underwater welding has been increasing as a number of waterfront projects are progressing. Underwater “wet type” welding is considered to be particularly useful for repairing offshore structures so built. It has essential drawbacks, however, that the weld portions are rapidly cooled due to high rates of heat dissipation into surrounding water, which decreases the strength of welded joints. In the previous paper, three dimensional Finite Difference Method has been applied to evaluate the cooling rates of underwater welding. In this report, the numerical method is improved to obtain better results to simulate the specific characteristics of cooling rates in underwater welding. The amount of heat transferred into surrounding water is evaluated by following calculation procedures proposed for corresponding heat transfer mechanism, such as free convection, nucleate boiling, etc., with surface temperatures of plates measured by thermocouples. The validity of numerical method presented here is ascertained by comparing experimental results.

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We have been developing a soot removing system for a diesel engine emission.
This system, used granular filter, is set in a exhaust gas manifold, and soot is collected and burned continuously during engine running.
In this paper, the removing conception, and diesel emission constituent, soot characteristic and results of granular characteristics test are reported.
Results of this research are summarized below.
(1) . The emission rate of soot for diesel engines is about 100mg/Nm³., and depends on used fuel properties.
(2) . Properties of soot vary with sulfur content of used fuel.
(3) . A calorific value and a ignition temperature point of soot become high with carbon content.
(4) . When mechanical and thermal strength, density and compact installation are considered, silica-alumina, for example a mullite ball is suitable as a granular.
(5) . This trapping rate of granular element is hight.
Soot is burned by heating air at 600°C, and the granular is renewed.

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We have been developing a dust removal plant which can trap and incinerate the dust from the disel engine by the granular type filter.
We conducted the dust removal characterictic test and operation characteristic test of the dust removal plant following the element test stated in the 1st report.
Results of this research are summarized below.
(1) More than 70% of the trap efficiency can be achieved even in the low pressure loss region of the granular section.
(2) The trapped dust can be incinerated by setting the temperature at 550°C for 10 minutes and at 600°C for 5 minutes.
(3) The dust removal plant can continuously remove 70% of the dust in any load condition and any type of the fuel for the test engine.
(4) The dust removal plant can remove dust operating with the other exhaust gas purification method.

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In order to protect crew against a large accerelation caused by sailing in the rough waves, high-speed patrol ships have been equipped with shock-absorbing seats (seat damper), now. Although the seat damper is popular among the crew, there are some reports of doubtful whether the seat damper is effective to reduce the shock or not.
The author investigated the shock-absorbing effect of the seat damper with a vibration testing machine and the accerelation measurement onboard ship.
The present investigations are as follows. The natural frequency of the seat damper is about 1.8 Hz when a person is seatted on it, and it is considered theoretically that the damper has no shock-absorbing effect unless the frequencies of the impact accerelation are higher than 4 Hz. Both the present results with the vibration testing machine and the data onboard ship endorses also the vibration isolation theory.
When the patrol ship runs in full speed, the main spectrum of the accerelation caused by the sea waves is about 0.3Hz, and no shock-absorbing effect of the seat damper is obserbed in these frequency region. However, in the higher frequencies up to several decade Hertz, considerable vibration reduction is recogniged by using the seat damper.

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The economizer is the most important component in the ultra small combined cycle (USCC) using gas and steam turbines to utilize the high energy in the exhaust gas from the gas turbine. The flow pattern of the exhaust gas through the finned tubes of evaporation and superheating strongly affected the thermal efficiency of the present compact economizer. When the inlet exhaust pipe was simply connected to the economizer, sufficient steam to operate the steam turbine could not be obtained. To investigate the low heat recovery rate and the flow pattern in the economizer, 1/5 scale model experiment by using a water was conducted. The observation showed non-uniform flow cased by the eddy in the inlet plenum. A flow nozzle was installed at the inlet plenum of the actual USCG economizer to suppress the non-uniform flow. After the installation of the flow nozzle, the heat recovery rate in the economizer was increased from 41.4% to 51.1%.

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