• Journal of Advanced Marine Engineering and Technology
• /
• v.35 no.6
• /
• pp.835-841
• /
• 2011

Wave power generation systems operated in the ocean, has been developed as large power and grid power connection systems in general. However, small wave power generation systems offer operational efficiency for the lighted (navigation aids) buoy. They simply adopts a full-wave rectification for charging battery (direct connection method). In this paper, a wave power controller based on a booster converter is developed by considering a characteristic of the wells turbine. Both direct connection and booster converter power controller is designed and tested to compare the characteristics. Experiments demonstrate that the output of the proposed controller has improved the characteristic of output power, when generator output voltage is low.

• Journal of Advanced Marine Engineering and Technology
• /
• v.37 no.7
• /
• pp.677-684
• /
• 2013

A lot study of convection heat transfer on internal flow has been extensively conducted in the past decades using of high specific surface area, increasing heat transfer coefficient, swirling flow and improving the transport properties. This study concerned with the application of a tangential slot swirl generator for improving heat transfer in a horizontal circular copper tube. The Al particles(about $100{\sim}130{\mu}m$) was employed for this experimental work. 3D PIV(particle image velocimetry) technique has employed to measure velocity profiles of Al particles with and without swirl flow. The copper tube is heated uniformly by winding of a heating coil for heat transfer work, having a resistance of 9 ohm per meter. Experiments are performed in the Reynolds number range of 6,800~12,100 with swirl and without swirl using Al particles. Experimental data for comparison of Nusselt number is presented that of with swirl and without swirl along the test tube for the Reynolds numbers. The Nusselt number is improved with increasing of Reynolds numbers or swirl intensities along the test tube. The Nusselt number with swirl flow is about 60.0% to 119.0% higher than that obtained by the Dittus-Boelter equation.

• Journal of the Korean Society for Precision Engineering
• /
• v.28 no.7
• /
• pp.805-813
• /
• 2011

The dynamic stress of the diesel engine block is analyzed by using flexible-body dynamic analysis. Multiple loadings including the pressure load due to gas combustion, thermal load, and dynamic load are considered. Thermal load is assumed constant, however, pressure load and dynamic load are treated as time dependent. The present work is focused on the dynamic stress analysis, especially on finding critical points of the engine block. The analysis model includes four parts - engine block, generator, bed, and mounts. On the other hand, crank shaft, pistons, and main bearings are excluded from the model. However, their dynamic effects are applied by dynamic forces, obtained in the separate analysis. Dynamic stress is found by using flexible body dynamic analysis, and compared to the measured data.

• Smart Structures and Systems
• /
• v.8 no.1
• /
• pp.39-52
• /
• 2011

We are developing a biomimetic robot based on the Sea Lamprey. The robot consists of a cylindrical electronics bay propelled by an undulatory body axis. Shape memory alloy (SMA) actuators generate propagating flexion waves in five undulatory segments of a polyurethane strip. The behavior of the robot is controlled by an electronic nervous system (ENS) composed of networks of discrete-time map-based neurons and synapses that execute on a digital signal processing chip. Motor neuron action potentials gate power transistors that apply current to the SMA actuators. The ENS consists of a set of segmental central pattern generators (CPGs), modulated by layered command and coordinating neuron networks, that integrate input from exteroceptive sensors including a compass, accelerometers, inclinometers and a short baseline sonar array (SBA). The CPGs instantiate the 3-element hemi-segmental network model established from physiological studies. Anterior and posterior propagating pathways between CPGs mediate intersegmental coordination to generate flexion waves for forward and backward swimming. The command network mediates layered exteroceptive reflexes for homing, primary orientation, and impediment compensation. The SBA allows homing on a sonar beacon by indicating deviations in azimuth and inclination. Inclinometers actuate a bending segment between the hull and undulator to allow climb and dive. Accelerometers can distinguish collisions from impediment to allow compensatory reflexes. Modulatory commands mediate speed control and turning. A SBA communications interface is being developed to allow supervised reactive autonomy.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.18 no.4
• /
• pp.282-290
• /
• 2015

In this study, a latching control technology, proposed by Sheng et al.(2015), was applied in order to maximize the extraction efficiency of WEC (Wave Energy Converter), which is the heaving buoy coupled with linear electric generator. The latching control is the phase-control technique for improving the wave energy conversion with appropriate latching duration of keeping the buoy fixed. From the time-domain analysis in regular waves, the latching control technology can significantly improve the heave velocity and extracted power, even though the resonance condition is not satisfied. By using the latching control technology, the draft of buoy as well as the required PTO damping force can be significantly reduced along with increased extracted power, which is a big advantage in manufacturing the WEC.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.1 no.2
• /
• pp.18-26
• /
• 1998

The major interest of this paper is how the spilled oil over the sea is dispersed into water column especially under the shear and turbulence such as breaking wave. Two hydraulic experiments were conducted to investigate the oil stick break-up characteristics into small and large droplets under the variation of velocity shear and breaking waves. From the experiments in the shear generator and the wave flume, small droplets which have diameters of tens to hundreds of micrometers were uniformly distributed throughout the whole control volume as time goes by. In addition, it can be seen that the weathered spilled oil has a different break-up mechanism from fresh spilled oil.

• Journal of Advanced Marine Engineering and Technology
• /
• v.36 no.7
• /
• pp.935-941
• /
• 2012

This paper describes a study of conventional electrical rig and simulated application of Flywheel Energy Storage system on the power system of the offshore plants with dynamic positioning system with the following aims: improve fuel consumption on engines, prevent blackout and mitigate voltage sags due to pulsed load and fault. Fuel consumption has been analyzed for the generators of the typical drilling rigs compared with the power plant with Flywheel Storage Unit which has an important aid in avoiding power interruption during DP (Dynamic Positioning) operation. The FES (Fly wheel Energy storage System) releases energy very quickly and efficiently to ensure continuity of the power supply to essential consumers such as auxiliary machinery and thrusters upon main power failure. It will run until the standby diesel generator can start and supply the electric power to the facilities to keep the vessel in correct position under DP operation. The proposed backup method to utilize the quick and large energy storage Flywheel system can be optimized in any power system design on offshore plant.

• Journal of Advanced Marine Engineering and Technology
• /
• v.36 no.7
• /
• pp.869-875
• /
• 2012

In the past decades, extensive studies on convection heat transfer on internal flow have been conducted by using high specific surface area, by increasing heat transfer coefficient and swirl flow, and by improving the transport properties. In this study, we applied a tangential slot swirl generator to improve heat transfer in a horizontal circular copper tube. The Al-Mg particles (approximately $100{\mu}m$ to $130{\mu}m$) were employed for this experimental work. The copper tube was heated uniformly by winding a heating coil with a resistance of 9 ohm per meter for heat transfer. Using Al-Mg particles, experiments were performed in the Reynolds number range of 5,000 to 13,130, with and without swirl. Experimental data transfers or comparisons between Nusselt numbers with and without swirl along the test tube and Reynolds numbers are presented. The Nusselt number is improved by increasing Reynolds numbers or swirl intensities along the test tube.

• Journal of Advanced Marine Engineering and Technology
• /
• v.32 no.1
• /
• pp.169-174
• /
• 2008

Floating devices, such as a cavity resonance device take advantage of both the water motion and the wave induced motions of the floating body itself. The wave energy converter is known commercially as the WAGB(Wave Activated Generator Buoy) and is used in some commercially available buoys to power navigation aids such as lights and horns. This wave energy converter consists of a circular floatation body which contains a vertical center pipe that has free communication with the sea. A theoretical analysis of this power generated by a pneumatic type wave energy converter is performed and the results obtained from the analysis are used for a real wave energy converter for buoy. This paper presents the analysis results and the design method for the WEC(Wave Energy Converter), and the associate results are application to the commercially available WEC for buoy. Maximum performance of WEC occurs at resonance with driving waves. The analysis of WEC is performed with LabVIEW program, and the design method of WEC for buoy is suggested in this paper.

• Proceedings of the Korean Society of Marine Engineers Conference
• /
• 2006.06a
• /
• pp.261-262
• /
• 2006

The effect of tube diameter on heat transfer characteristics of absorber in absorption chiller/heater using LiBr solution as a working fluid has been investigated by experimental study to develop a high performance and compact absorber. A system Includes a tube absorber, a generator, solution distribution system and cooling water system was set up. The diameter of the heat exchanger tube inside absorber was changed from 15.88mm to 12.7mm and 9.52mm. The experimental results show that the heat transfer coefficient, Nusselt number and heat flux increase as solution flow rate and cooling water flow rate increase. The heat transfer performance increases as tube diameter decreases. Among three different tube diameters, the smallest tube diameter 9.52mm has highest heat transfer performance. A comparison of the heat transfer coefficient obtained by the present study with those of previous experimental results showed good overall agreement.