In recent years, the depth of submarine oil wells and gas wells has increased quickly. The depth of an oil production well reached 1500-2000 meters in practical use, and will be 3000 meters in the next stage. Moreover, geophysical scientists plan to use the science drilling ship“Chikyu”to drill the earth from a seafloor of 4000-meter depth to the Mohorovicic discontinuity. This paper describes deep-sea drilling technology. Although a new method, dual gradient drilling, is proposed, I think that the riser drilling system will still be used in the future. Present techniques of riser drilling are therefore summarized briefly, and problems in deep-sea operation are pointed out. Lastly, I describe the new technology in which development is needed in order to adapt the present riser drilling system to deep-sea operation.
Most domestic high-speed ferries are powered by high-speed diesel engines with speeds above 1000 rpm. It is said that operator claims for engine failures of high-speed vessels remain high in comparison to conventional vessels. We considered that various engine failures were associated with the maneuvering patterns of high-speed ferries, such as short passages, fast turnarounds, etc. Our questionnaire survey of failures in high-speed diesel engines during the past five years covered the ship operating conditions, including ship speed during cruising, navigation distance, running hours, and number of round-trip crossings per year. We divided the engine into five basic failure areas for ease of analysis. The most frequent engine failures were crankshaft failure, main bearing failure, camshaft failure, and cylinder liner wear and cracks. The number of failures per year was associated with total navigation distance per year and engine load in cruising conditions.
Large-bore, low-speed diesel engines have traditionally been equipped with cylinder liners made of gray cast iron for its superior combination of strength and sliding performance. Recently, though, a dramatic improvement has been sought in this technology region to cope with demand for higher engine ratings, use of low quality fuel, reduction in lubricating oil consumption, and so on. To meet this demand, a spray-coated cylinder liner was developed and a full-scale onboard service test started in May 2000. The results, after more than 26, 000 operating hours, reveal that the wear rate of the spray-coating layer on the cylinder liner is quite low and the piston rings maintain an acceptable wear rate. In one case, initial wear of around 10/1000 mm was measured, then no more wear occurred afterward. The wear rate of the piston rings remained the same as that for piston rings combined with gray cast iron cylinder liners.
Semi-built-up and solid crankshafts, as a main part of diesel engines, have been subjected to increasingly severe service conditions to meet such engine requirements as higher output and more compact size. This has driven crankshaft manufacturers to improve the fatigue strength, quality, and reliability of crankshafts. This paper describes technical developments and recent trends, such as improved steel-making processes, new materials with higher strength, and new fillet hardening processes.
High strength cast steel, Throw Grade 5, has been developed for semi-built-up crankshafts to cover all current types of low speed diesel engines. Material test results with test pieces taken from a full-scale crankthrow are reported. Manufacturing approvals for this material have been taken from major classification societies. Prior to the application of this cast steel to an actual crankshaft, the crank pin fillet stresses at several points were measured in the workshop. The dynamic stress of each point, as analyzed with the finite element method, corresponds well with the measured data. Finally, application of this material to the crankshaft of an engine in a severe vibratory condition is introduced to show effective use of the material.
To obtain basic data for ballast water management, we examined the lethal effects of shock waves on a marine Vibrio. In the present experiment, shock waves were generated by hitting a projectile, which had been accelerated with a single-stage light gas gun, in an aluminum container having a cylindrical well where cell suspension was tightly maintained. We compared the shock wave effects to the isolate by use of two types of target containers with 5 and 25 mm well depths respectively. In the case of the shallow well, a lethal effect of shock compression was readily observed, but this did not occur for the deep well. Detailed pressure histories showed completely different peak patterns for the two well types. The propagation process of the shock wave was also analyzed theoretically and numerically. Results suggested that the lethal effects of shock waves are closely related to a narrow, rapid pressure change that occurs initially or a broad pressure change after the initial peak, rather than to the maximum pressure value.
A diesel fuel breakup model was developed in the framework of the three-dimensional fluid dynamics code KIVA-3V and validated with experimental data. This breakup model accounts for cavitation bubble collapse energy, turbulent kinetic energy, and aerodynamic forces on the liquid core. The primary breakup time is computed by a balance between surface tension of the liquid core and the breakup forces obtained as aerodynamic force and breakup force based on cavitation bubble collapse. The calculated diameter of the child droplet is based on the liquid core surface wavelength, which is caused by fluctuating turbulence velocities. At the time of primary breakup, a child droplet uses its turbulent energy to determine the ensuing trajectory. Hence, the proposed Cavitation Bubble Collapse Energy Breakup (CEB) model is capable of predicting the spray cone angle. Generation of child droplets as a result of primary breakup continues until all cavitation bubbles have totally collapsed. Subsequently, the Taylor Analogy Breakup (TAB) model is used for secondary droplet breakup. Model predictions of spray tip penetration, spray cone angle, and Sauter Mean Diameter (SMD) have been found in good agreement with experimental data for non-evaporating sprays under high injection pressure.