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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society of Marine Engineering
Journal Basic Information
Journal DOI :
Korean Society of Marine Engineers
Editor in Chief :
Volume & Issues
Volume 32, Issue 8 - Nov 2008
Volume 32, Issue 7 - Nov 2008
Volume 32, Issue 6 - Sep 2008
Volume 32, Issue 5 - Jul 2008
Volume 32, Issue 4 - May 2008
Volume 32, Issue 3 - May 2008
Volume 32, Issue 2 - Mar 2008
Volume 32, Issue 1 - Jan 2008
Selecting the target year
The Vibration Characteristic of Optimizing Snubber of Reciprocating Type Hydrogen Compressor for Pressure Loss Reduction
Kim, W.C. ; Kim, H.J. ; Jeong, J.H. ; Jang, Y.S. ; Choi, B.K. ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1116~1122
DOI : 10.5916/jkosme.2008.32.8.1116
The reciprocating type hydrogen compressor has a pulsation due to the reciprocative characteristics which results in noise and vibration. Snubber is installed for the relaxation of pulsation, but it causes reduction of compressor efficiency because of pressure loss. Five types of snubber were modeled for the numerical investigation of the effect of the relative position of inlet and outlet and buffer angle on the pulsation amplitude and pressure loss. MSC/NASTRAN is used as a numerical tool to identify the vibration characteristic of each type. Frequency responses in forced vibration mode are compared for various cases and buffer angles.
Generation Characteristic of WEC for Buoy
Oh, Jin-Seok ; Kwak, Jun-Ho ; Bae, Soo-Young ; Jung, Sung-Young ; Lee, Ji-Young ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1123~1128
DOI : 10.5916/jkosme.2008.32.8.1123
Marine facilities like buoy, lighthouse are operated with stand alone power supply system. This power system can consist of a stand-alone type power system such as PV(Photovoltaic) system, wave system or hybrid system which is not cooperated with a commercial power system. Generally, PV power system for marine facilities can not supply a sufficient power to buoy, because it is so influenced from weather condition. For solving this problem the hybrid power system with PV and wave is studied on a various area, that is why a hybrid power system is requires to overcome these problems. This paper will describe a generation characteristic of WEC(Wave Energy Converter) for buoy, and an AFS(Anti-Fouling System) influence on WEC.
Assessment of Turbulence Models for Engine Intake and Compression Flow Analysis
Park, Kweon-Ha ; Kim, Jae-Gon ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1129~1140
DOI : 10.5916/jkosme.2008.32.8.1129
Many turbulence models have been developed in order to analyze the flow characteristics in an engine cylinder. Watkins introduced k-
turbulence model for in-cylinder flow, and Reynolds modified turbulence dissipation rate by applying rapid transformation theory, Wu suggested k-
turbulence model in which length scale and time scale are separated to introduce turbulence time scale, and Orszag proposed k-
RNG model. This study applied the models to in-cylinder flow induced by intake valve and piston moving. All models showed similar flow fields during early stage of intake stroke. At the end of compression stroke,
RNG predicted well second and third vortex, especially
RNG produced new forth vortex near central axis at the lower part of cylinder which was not predicted by the other models.
A Study on the Theory Analysis and Engine Test Performance by a High Expansion Diesel Engine into Intake-Exhaust Consideration
Jang, Tae-Ik ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1141~1148
DOI : 10.5916/jkosme.2008.32.8.1141
One of the methods to increase the efficiency of an engine is to expand pressures obtained from combustions equal to the pressure of atmosphere as much as possible and then convert thermal energy into mechanical energy also as much as possible. In this research, the Diesel cycle was thermodynamically interpreted to evaluate the possibility of high efficiency by converting Diesel engines to the Atkinson cycle, and general cycle features were analyzed after comparing these two cycles. In the case of fuel air the Diesel-Atkinson cycle considering intake and exhaust similar to real cycles, the value of thermal efficiency and average effective pressure increased, though their values were smaller than those of standard air amount cycle, when expansion compression ratio increased. When normal Diesel engines of which compression stroke and expansion stroke are all the same, was converted to the Atkinson cycle by changing the time of intake value close, combustion pressure reduced due to reduced expansion compression ratio and intake air amount due to decreased effective cycle volume.
A Study on the Transmitted Torque of Self Clamping Friction Clutch
Wang, Jee-Seok ; Kim, Jong-Do ; Yoon, Hee-Jong ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1149~1156
DOI : 10.5916/jkosme.2008.32.8.1149
The principle of self clamping friction clutch is presented in this paper and the transmitted torque capacity is also calculated. In order to enlarge the friction force, a part of rotating force of driving side is converted to normal force of friction materials by clamping arm. The increased normal force of friction materials assures the large friction force and the transmitted torque capacity of clutch becomes large. The self clamping friction clutch is adopted in the tube type air pressure clutch and the condition of stability is investigated. It is proven that the inclined angle of clamping arm and the friction factor of friction materials are the essential elements in stability and torque capacity of self clamping friction clutch. The transmitted torque capacity of self clamping friction clutch is compared with air pressure clutch. The normal force of friction lining is magnified by 1/(1-k) and the transmitted torque capacity is also magnified with same proportion comparing with air pressure clutch. The larger the friction factor of friction lining, the larger the magnification factor. The longer the clamping arm, the smaller the magnification factor. It must be also noted that the value of k=
is the criterion of stability. If the value of k=
is greater than or equal to 1, the self clamping friction clutch is unstable and it can not be used as clutch.
Study on the Electric Energy Saving System in Marine Cooling System
Kim, Yun-Hyung ; Bae, Soo-Young ; Jung, Sung-Young ; Oh, Jin-Seok ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1157~1163
DOI : 10.5916/jkosme.2008.32.8.1157
Fuel represents a significant portion of the operating costs of voyages of the vessel. Under this situation, dramatic increase in fuel price caused a problem that earnings of ship becomes decreased seriously. Pumps in a cooling system of the vessel are often operated inefficiently. The reasons will vary from process to process and application to application. Inefficiency of pumps is one of the reason for making the cost of operating the vessel increased. This paper suggests energy-effective cooling system that controls sea water pumps with inverters to reduce energy consumption in vessel by conducting simulation with LabVIEW. Results shows that electric energy consumption of pumps are significantly deceased. If this energy-effective cooling system is applied to other systems which need cooling, it could be useful in reducing electric energy wastage.
A Study on Performance Enhancement of AHU with a Pressure Type Fan
Jang, H.S. ; Kim, E.P. ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1164~1169
DOI : 10.5916/jkosme.2008.32.8.1164
The miniaturization of the Air Handling Unit (AHU) has become an actual need because of the restriction of the using space on the vessel. In modern AHU’s construction, in which the fan section is at the end part of the ship, it’s very difficult to select a suitable capacity of evaporators, because the fan motor emits heat. Thus, the AHU structure has been changed as the fan section has been set before the cooling coil to get temperature values similar to the designed amount. Also, the air guider is installed in order to maintain equal air distribution after it passed the fan section. So, it is possible for air to equally pass the cooling coil. It is investigated three different geometries to find the best performance. Also, It is compared with the numerical and experimental results. The study found the case 3 gives the best results. The results of this study show the possible application of the new design.
A Measurement and Evaluation of Indoor Thermal Conditions in Spring of a Coastal Passenger Ship - 590-Passenger Ro-Pax Type
Hwang, Kwang-Il ; Shin, Dong-Keol ; Kim, Eun-Su ; Do, Yo-Han ; Choi, Yun-Seok ; Cho, Jung-Yul ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1170~1177
DOI : 10.5916/jkosme.2008.32.8.1170
The purpose of this study is to measure and analyze the indoor thermal conditions in the spring of a korean coastal passenger ship which is 590-passenger Ro-Pax type built at 1997. Especially this study has focussed on the relations between the diffuser open ratio, which can be controlled by 12 steps, and the comfort. Followings are the results of this study. (1) The supply air volume to cabins are maximum 4.3 and 2 times more than design quantity when the diffusers in cabins are open 100% and 50%, respectively. (2) Regardless of diffuser open ratio, the supply air maintains constantly high temperature and below 10% of relative humidity through the experimental days. (3) All the cabins are not satisfied with the ASHRAE comfort criterion at the condition of 100% and 50% of diffuser open ratio, because of high temperature and low relative humidity. (4) At a low diffuser open ratio, number of cabins which satisfy the ASHRAE comfort criterion are increased. (5) Humidifying and dehumidifying, and hvac control system of each cabin must be reviewed and studied at the view of passengers to service more comfort environments.
A Study on Improvement of Material Characteristics by Control of Ion Implantation
Yang, Young-Joon ; Lee, Chi-Woo ; Fujita, Kazuhisa ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1178~1184
DOI : 10.5916/jkosme.2008.32.8.1178
In this study, techniques of ion implantation were used in order to improve the characteristics of metal materials such as the oxidation and wear resistant. In particular it is necessary to develope their oxidation and wear resistant that could be used in severe environmental conditions. There are mainly two elementary technologies including ion implantation and/or thin film coating. Ion implantation method was performed for surface modification. As a result, it was found that some ion implantations methods such as Nb, high-temperature Nb ion implantation and Nb+C combined implantation are somewhat effective for improving the oxidation resistance of TiAl alloy. Furthermore, the fluorine PBII treatment is more effective for improving the oxidation resistance of the TiAl alloy with three-dimensional shapes. The implantation of boron ion into thin film of TiN was also effective for improving the properties of materials like high temperature wear resistance. TiCrN film was applied to the actual seal ring for steam turbines, and it was observed that its sliding property showed a successfully good performance.
A Study on the MED-TVC Operating Performance Characteristics of using the Thermo-Compressor
Choi, Du-Youl ; Jin, Chang-Fu ; Song, Young-Ho ; Choi, Soon-Ho ; Chung, Han-Shik ; Kim, Pil-Hwan ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1185~1191
DOI : 10.5916/jkosme.2008.32.8.1185
The core design technology for the multi-effect desalination plant using the thermo compressor (MED-TVC) was investigated by the performance test of multi effect desalination plant in this paper. The final G.O.R (gain of output ratio) of MED-TVC type desalination plant is strongly affected by the performance of thermo-vapor compressor. The present experiments for the desalinating capacity and G.O.R were obtained for the range of the motive steam pressure, 266.0, 250.0, 230.0 and 200.0 kPa. And as a practical problem, to investigate the influence of the sea water temperature to the G.O.R, the inlet steam temperature of the suction water vapor was changed in the range of
K in the present experiment. Through the experiments, the maximum value of G.O.R was 8.5 at the condition of the motive steam pressure, 136.0 kPa and the minimum value of G.O.R was 8.1 at the condition of the motive steam pressure, 266.0 kPa. And it was confirmed that the range of desalination capacity was
ton/day in the normal operation condition.
A Study on the Safe Maneuvering Technology Based on the Thermal Calculation of Membrane Type LNG Carrier
Jin, Chang-Fu ; Kim, Kyung-Kuen ; Oh, Cheol ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1192~1200
DOI : 10.5916/jkosme.2008.32.8.1192
This paper is concerned with the thermal design of the
class membrane type LNGC. To predict the temperature distribution, BOG and BOR, 3-dimensional numerical calculation was carried-out for the quarter of No.3 LNG tank. These sequence analyses were performed under the standard conditions of IMO ship design condition, USCG ship design condition and the Korean flag LNGC's route condition according to the 6-voyage modes. As the results, temperature behavior, heat flux, total penetrating heat, BOG and BOR were obtained, and those were compared with the maneuvering results considering the real temperature variation of air and sea water temperature at noon time. For securing the safety of LNGC during the ballast voyage, optimum control patterns of pressure and temperature in LNG tank is suggested in this paper.
Numerical Analysis on the Working Fluid Flow of Suction-passage for Reciprocating Compressor
Lee, Gyeong-Hwan ; Rahman, Mohammad Shiddiqur ; Shim, Kyu-Jin ; Jeong, Hyo-Min ; Chung, Han-Shik ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1201~1207
DOI : 10.5916/jkosme.2008.32.8.1201
Numerical analysis information will be very useful to improve fluid system. General information about an internal gas flow is presented by numerical analysis approach. Relating with hydrogen compressing system, which have an important role in hydrogen energy utilization, this should be a useful tool to observe the flow quickly and clearly. Flow characteristic analysis, including pressure and turbulence kinetic energy distribution of hydrogen gas coming to the cylinder of a reciprocating compressor are presented in this paper. Suction-passage model is designed based on real model of hydrogen compressor. Pressure boundary conditions are applied considering the real condition of operating system. The result shows pressure and turbulence kinetic energy are not distributed uniformly along the passage of the Hydrogen system. Path line or particles tracks help to demonstrate flow characteristics inside the passage. The existence of vortices and flow direction can be precisely predicted. Based on this result, the design improvement, such as reducing the varying flow parameters and flow reorientation should be done. Consequently, development of the better hydrogen compressing system will be achieved.
A Study on the Resistance Performance of 39feet-class Leisure Boat with Propulsion Type of In-Board and In.Out-Board Engine
Park, Chung-Hwan ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1208~1214
DOI : 10.5916/jkosme.2008.32.8.1208
The propulsion type of a small boats mainly were divided that the In-board and In out-board position located engine. The boats of the In-board and In out-board engine individually were propelled by propeller and stern drive. In this paper, 39feet-class leisure boats with propulsion type of In-board and In.out-board engine were performed to compare the effect of resistance performance using model test. As a result, leisure boat with In out-board engine is ascertained the optimum boat affects the speed and fuel efficiency.
Study on the Shape of Free Surface Waves by the Scheme of Volume Fraction
Kwag, Seung-Hyun ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1215~1220
DOI : 10.5916/jkosme.2008.32.8.1215
To obtain the shape of the free surface more accurately, computations are carried out by a finite volume method using unstructured meshes and an interface capturing method. Free-surface flow, which is very important in the fields of ship and marine engineering, is numerically simulated for flows of both water and air. Control volumes are used with an arbitrary number of faces and allows a local mesh refinement. The integration is of second order, with a midpoint rule integration and linear interpolation. The method is fully implicit and uses quadratic interpolation. The solution method of pressure-correction type solves sequentially equations of momentum, continuity, conservation, and two-equations turbulence model. Comparison are quantitatively made between the computation and experiment in order to confirm the solution method.
Analysis of Fluid-Structure Interaction for Development of Korean Inflatable Rubber Dams for Small Hydropower
Hwang, Tae-Gyu ; Kim, Jin-Gu ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1221~1230
DOI : 10.5916/jkosme.2008.32.8.1221
Inflatable rubber dams are used for controlling flood, impounding water for recreations, preventing beach erosions, diverting water for irrigations, and generating hydropower. They are long, flexible, inflated with air, cylindrical structures on a rigid horizontal foundation such as concrete. The dam is modeled as an elastic shell inflated with air. The mechanical behaviors of the inflated dam model were investigated by using the finite element method. The analysis process such as One Way Coupling Fluid-Structure Interaction consists of two steps. First, the influences of the fluid side were investigated, viz, the shape changes of the inflated rubber dam due to the fluid motions was captured when the height of the dam was 30cm with air pressure 0.01MPa, at which the pressure distributions over the surface of the dam were calculated. And next, the structural deformations were calculated using the pressure distributions. The initial inlet velocity for flow field was set to 0.1m/s. The structural deformation behaviors were investigated. The final research goal is to develop a Korean Inflatable Rubber Dam to be used for generating small hydropower.
The Flow Characteristics with Variation of Nozzle-to-nozzle Angles on Unventilated Dual Jests
Kim, Dong-Keon ; Kim, Moon-Kyoung ; Yoon, Soon-Hyun ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1231~1239
DOI : 10.5916/jkosme.2008.32.8.1231
The characteristics of flow on unventilated dual jets was experimentally investigated. The two nozzles each with an aspect ratio of 20 were separated by 6 nozzle widths. Reynolds number based on nozzle width was set to 5,000 by nozzle exit velocity. All measurements were made over a range of nozzle-to-nozzle angles from
. The particle image velocimetry and pressure transducer were employed to measure turbulent velocity components and mean static pressure, respectively. It was shown that a recirculation zone with sub-atmospheric static pressure was bounded by the inner shear layers of the individual jets and the nozzles plated. As nozzle-to-nozzle inclined angles were decreased, it was found that the spanwise turbulent intensity is greater than the streamwise turbulent intensity in the merging region. In the combined region, the velocity of dual jets agree well with that of single jet, but the turbulence intensity of dual jets not agree with that of single jet.
Evaluation of Corrosion Characteristics on Welding Zone of Leakage SeawaterPipe Welded by Underwater Welding Electrode
Moon, Kyung-Man ; Lee, Sung-Yul ; Kim, Yun-Hae ; Lee, Myung-Hyoon ; Kim, Jin-Gyeong ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1240~1247
DOI : 10.5916/jkosme.2008.32.8.1240
Leakage trouble on the sea water pipeline in engine room is often resulted from a localized corrosion due to severe corrosive environment caused by both high speed and high pressure of sea water flowing through the inner pipe. In addition, when the ship is in stand-by or emergency condition, underwater welding to control the leakage of sea water from a hole of its pipe is very important in an industrial safety point of view. In this study possibility of underwater welding to control leakage of sea water and corrosion property of its welding zone were investigated with the electrochemical methods by parameters of welding methods and welding electrodes when underwater welding is achieved with a such case that sea water is being leaked out with a height at 50mm from a hole of
of test pipe. Corrosion resistance of weld metal zone is better than the base metal and its hardness is higher than that of the base metal. However corrosion potential of weld metal zone showed a negative value than that of the base metal, therefore weld metal zone is preferentially corroded rather than the base metal by performance of galvanic cell due to difference of corrosion potential between weld metal zone and base metal. Eventually it is suggested that leakage of sea water is successfully controlled by underwater welding,
A Study on Characteristics of the Transmission Line Employing Periodically Perforated Ground Metal on GaAs MMIC and Its Application to Highly Miniaturized On-chip Impedance Transformer Employing Coplanar Waveguide
Yun, Young ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1248~1256
DOI : 10.5916/jkosme.2008.32.8.1248
In this paper, basic characteristics of transmission line employing PPGM (periodically perforated ground metal) were investigated using theoretical and experimental analysis.According to the results, unlike the conventional PBG (photonic band gap) structures, the characteristic impedance of the transmission line employing PPGM structure showed a real value, which exhibited a very small dependency on frequency. The transmission line employing PPGM structure showed a loss (per quarter wave length) higher by
than the conventional microstrip line. According to the investigation of the dependency of RF characteristic on ground condition, the RF characteristic of the transmission line employing PPGM structure was hardly affected by the ground condition in the frequency lower than Ku band, but fairly affected in the frequency higher than Ku band, which indicated that coplanar waveguide employing PPGM structure was optimal for RF characteristic and reduction of size. Considering above results, impedance transformer was developed using coplanar waveguide with PPGM structure for the first time, and good RF characteristics were observed from the impedance transformer. In case that
impedance transformer with a center frequency of 9 GHz was fabricated for a impedance transformation from 20 to10
, the line width and length were 20 and
, respectively, and its size was only 0.64 % of the impedance transformer fabricated with conventional microstrip lines. Above results indicate that the transmission line employing PPGM is a promising candidate for a development of matching and passive elements on MMIC.
Remote Measurement of a Distant Temperature and Current using Fiber Bragg Grating Sensors and Erbium-doped Fiber Ring Laser
Sohn, Kyung-Rak ; Shim, June-Hwan ; Yang, Gyu-Sik ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1257~1262
DOI : 10.5916/jkosme.2008.32.8.1257
A long-distance remote sensing of temperature and current based on a fiber Bragg grating (FBG) is proposed and demonstrated. The thermal expanding effect of the epoxy and the Er-doped fiber ring laser (EFRL) are applied to the sensor system to enhance the temperature and current sensitivity. An EFRL with a 5 km-single-mode fiber and a FBG shows a high extinction ratio of more than 60 dB and a low power fluctuation of less than 1 dB. The metal wires are used to supply the current to the sensors. When the NOA65 puts on the FBG as a thermal expanding material, the temperature and current sensitivity of the lasing wavelength shift are about
and 3pm/mA, respectively. The proposed sensing scheme is useful for measurement of current or temperature at a distant object of more than several km.
LNA Design Uses Active and Passive Biasing Circuit to Achieve Simultaneous Low Input VSWR and Low Noise
Jeon, Joong-Sung ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1263~1268
DOI : 10.5916/jkosme.2008.32.8.1263
In this paper, the low noise power amplifier for GaAs FET ATF-10136 is designed and fabricated with active bias circuit and self bias circuit. To supply most suitable voltage and current, active bias circuit is designed. Active biasing offers the advantage that variations in the pinch-off voltage(
) and saturated drain current(
) will not necessitate a change in either the source or drain resistor value for a given bias condition. The active bias network automatically sets a gate-source voltage(
) for the desired drain voltage and drain current. Using resistive decoupling circuits, a signal at low frequency is dissipated by a resistor. This design method increases the stability of the LNA, suitable for input stage matching and gate source bias. The LNA is fabricated on FR-4 substrate with active and self bias circuit, and integrated in aluminum housing. As a results, the characteristics of the active and self bias circuit LNA implemented more than 13 dB and 14 dB in gain, lower than 1 dB and 1.1 dB in noise figure, 1.7 and 1.8 input VSWR at normalized frequency
EZR: Expansive Search Zone Routing Protocol for Ship Ad Hoc Networks
Son, Joo-Young ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1269~1277
DOI : 10.5916/jkosme.2008.32.8.1269
Ships at sea cannot exchange data among them easily so far. Basically voice-oriented communication systems are the main methods, some of them utilize the HF radio systems at lower bit rates, and for higher bit rates, the Inmarsat or VSAT are adopted. None of them are used widely because of lower qualities and higher costs. There exist many technical and economical limits to have the Internet service just like on land such as the WWW service. In order to achieve the improved transmission rates of the maritime communication networks at farther sea, MANET(Mobile Ad Hoc Network) is one of the most practical models. In this paper, a new routing protocol named EZR (Expansive Search Zone Routing Protocol) is proposed, which is based on SANET (Ship Ad Hoc Network) model that has some different features from MANET and VANET (Vehicular Ad Hoc Network). The search zone for the shortest path is firstly found by EZR. If no path is searched in the zone, the zone is expanded according to the rule of EZR. The zone-expanding and path-searching procedures are repeated until the path is found out. The performance of EZR is evaluated and compared with LAR protocol which is one of the most typical routing protocols based on geographical information. The simulated results show that EZR is much better than LAR at sea environments in terms of routing success rate, route optimality, and a single index of performance combined the previous two metrics.
A Study on the Performance Analysis for Power Converters of Electric Propulsion Ship
Kim, Jong-Su ; Oh, Sae-Gin ; Kim, Sung-Hwan ; Kim, Hyun-Soo ; Kim, Deok-Ki ; Yoon, Kyoung-Kuk ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1278~1284
DOI : 10.5916/jkosme.2008.32.8.1278
Electric propulsion motors are operated from a variable frequency drive, which supplies power to motors at a frequency appropriate to the desired speed. The objective of this study was to evaluate power converters for shipboard applications and to recommend converters that meet lower harmonic distortion levels and torque ripples. Two systems were studied in detail : Cyclo-converters and PWM-converters. Cyclo-converters are the obvious choice where size, weight and efficiency are the most critical issues. However they have a disadvantage in power factor and they produce severe torque ripples in the motor which makes them unacceptable without special systems. PWM-converters produces better motor current waveform and eliminates common mode voltage issues at the motor, but suffers a multiple stages of power conversion and the isolating transformer. Results of this case study show that PWM-converters are more advanced and efficient drives for induction motor of electric propulsion ship.
Study on a Simulator for Generating Side Walking Path of the Biped Walking Robot
Choi, Hyeung-Sik ; Jeon, Chang-Hoon ; Kang, Jin-Il ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1285~1295
DOI : 10.5916/jkosme.2008.32.8.1285
A research on a simulator for a side walking path of a 16 degree-of-freedom (d.o.f) biped walking robot(BWR) which is composed of 4 d.o.f upper-part body and 12 d.o.f lower-part of the body is presented. For generation of stable side walking motion, the kinematics, dynamics and the zero moment of point(ZMP) of the BWR were analyzed analytically and included in the simulator. To operate the motion simulator for stable side walking of the BWR, a graphic user interface program was developed which needs inputs for the side distance between legs, base joint angle, walking type, and walking velocity. The simulator was developed to generate joint angle data of legs for side walking, and the data are transmitted to the BWR for stable side walking. In the simulator, a new path function for smooth walking motion was proposed and applied to the simulator and actual motion of a BWR. Also for actual side walking, an algorithm for estimating backlashes of the actuating joint motors was proposed and included in the simulator. To validate the performance of the proposed motion simulator, the simulator was operated and its side walking data of the simulator were generated for a period of side walking.
Dynamic Characteristic Analysis at Each Operating Condition for Electric Ship Propulsion System
Jeon, Won ; Wang, Yong-Peel ; Jung, Sang-Yong ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1296~1302
DOI : 10.5916/jkosme.2008.32.8.1296
This paper deals with modeling and dynamic characteristic analysis of a large-powered LNG electric ship propulsion system. Basically, we perform to verify the adequacy of system modeling on the sea going mode and LNG unloading mode based on load flow analysis. And then, we observe the dynamic characteristic of system to perform motor starting analysis and transient stability analysis. Particularly, this paper examine analysis results in comparison with the IEEE standard 141 and the class rule. Hence, this paper has evaluated stability of the electric ship propulsion system at static and dynamic conditions.
Configuration and Analysis of a Feed-forward Control System for Jacket Cooling Water Temperature of Marine Prime Diesel Engine
Choi, Soon-Man ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1303~1308
DOI : 10.5916/jkosme.2008.32.8.1303
Keeping cooling water temperature higher within the allowable range helps marine engines to run in more efficient condition especially when the engine load is low. Temperature control of jacket cooling water in outlet side of main engine has been more widely adopted to ships these days for the purpose to reduce fuel consumption rate. But If the temperature sensor for the control loop is placed at the outlet of engine, it brings more difficulties in attaining stable and desirable properties due to dead times included in pipe length and engine itself comparing to the case where the measuring point is at the inlet side of main engine. In relation with this problem, Feed-forward control could be one of realistic solutions as it reveals good properties and requires less cost for system configuration. This study suggests a forward control system which leads to improved temperature control performances to disturbance signals which could arise from variation of engine load or weather condition. Two dead times in the modelling were described, considering pipe length between the actuator and the engine as well as the thermal process inside the engine. The results of analysis were shown by simulations to confirm responses under different conditions.
Noise Attenuation of Marine Seismic Data with a 2-D Wavelet Transform
Kim, Jin-Hoo ; Kim, Sung-Bo ; Kim, Hyun-Do ; Kim, Chan-Soo ;
Journal of the Korean Society of Marine Engineering, volume 32, issue 8, 2008, Pages 1309~1314
DOI : 10.5916/jkosme.2008.32.8.1309
Seismic data is often contaminated with high-energy, spatially aliased noise, which has proven impractical to attenuate using Fourier techniques. Wavelet filtering, however, has proven capable of attacking several types of localized noise simultaneously regardless of their frequencies. In this study a 2-D stationary wavelet transform is used to decompose seismic data into its wavelet components. A threshold is applied to these coefficients to attenuate high amplitude noise, followed by an inverse transform to reconstruct the seismic trace. The stationary wavelet transform minimizes the phase-shift errors induced by thresholding that occur when the conventional discrete wavelet transform is used.