Many previous investigators have been engaged in estimating the cooling cycle of welded joint, which significantly affects the strength of welded joint. However, most of those researches have dealt with arc welding of‘bead on plate’ to examine essential thermal behaviors of welded joint. In actual arc welding practice, various types of groove configurations are adopted in accordance with plate thickness. V-shaped groove is widely used among them for plates with relatively large plate thickness. In this study, a welded joint with a single V-groove is treated, and a numerical approach to analyze its cooling cycle is proposed using three-dimensional finite difference method (FDM) in the quasi-transient temperature field. The accuracy of the numerical approach proposed here is demonstrated by comparing cooling cycles obtained by FDM with those measured from shield metal arc welding.
Components of high boiling point and asphartene in fuel are decomposed into cracked gas and carbonaceous residuum by heating. The purpose of the present is to make clear how far the quantity of products generated by thermal cracking of the fuel influences ignition delay and the making of soot. As a first step of this examination, this report investigated if the quantity of the thermal cracking components and of the carbone residue could. be estimated by thermogravimetry using a thermobalance, in regard to heating of the fuel. Samples are 4 kinds of marine diesel fuels, their distillates above 350°C and 4 kinds of marine fuel oils. Aluminagel column chromatography and IP 143/90 classified each of 12 samples in total into 4 types of hydrocarbons: saturate (Sa), aromatics (Ar), resin (Re) and asphartene (Asp) . These hydrocarbons were heated up to 500°C on the condition that the temperature continued to rise 20°C/min in the thermobalance. Gas chromatography analyzed vapor and gas which were generated from the heated components. As a result of investigating data, Ar, Re and Asp, except Sa, showed the same phenomenon: the three components above 400°C reduced their weight quickly and increased rapidly the volume of cracked gas, remained the carbonaceous residuum. These properties could be gotten from an analysis of the TG-curve obtained by thermobalance. And the weight of carbonaceous residuum at 500°C on the TG-curve were proportional to the value of conradson carbon residue test. These facts clarified that the thermobalance was very useful in estimating the quantity of the thermal cracking components and of the carbone residue which the heated fuel have.
It is said that the horse power of recent marine propulsion diesel engine corresponding to their ship's sizes has been reduced comparing with former ones. In transient operational condition, such engines with reduced power tend to work to the utmost of their power due to relatively enlarged inertia force of ships. Such being the case, it might be necessary for reconsideration of nowaday practice of design of propulsion system in view of strength. To meet this possible demands, the measuring have been made concerning to the torque acting on actual ship's propulsion shaftings. Through the measurement unexpected increases of the maximum torque from the normal value were observed during ship's crash astern operation, the increase rates of which spread out up to 1.6. In this paper, we will report the measuring results with additional breif study on the behaviour of propulsion diesel in transient condition.
In this paper, test results used water-emulsified fuel are reported. We used a high-speed diesel engine with 250mm-cylinder bore, 250mm-piston stroke. Tests were carried out varying the water-content of emulsion (0-110%) with MDO (Marine Diesel Oil) and MFO (Marine Fuel Oil), in order to confirm engine performance, fuel injection characteristics, exhaust gas characteristics and thermal load characteristics. The followings have been found. (1) At about 30% water-content, fuel consumption with MDO was improved, but fuel consumption with MFO was not improved. (2) The engine performance with MFO deteriorates rapidly once the water-content exceed 90%. (3) In the characteristics of fuel injection, there is a large difference between MDO and MFO. (4) In MFO, NOx emission is more than MDO, but the reduction rates of NOx emission achieved by water addition are the same for both fuel oil. (5) Cylinder liner temperatures are the same level for MDO and MFO burning.
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