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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 38, Issue 10 - Dec 2014
Volume 38, Issue 9 - Nov 2014
Volume 38, Issue 8 - Oct 2014
Volume 38, Issue 7 - Sep 2014
Volume 38, Issue 6 - Jul 2014
Volume 38, Issue 5 - Jun 2014
Volume 38, Issue 4 - May 2014
Volume 38, Issue 3 - Mar 2014
Volume 38, Issue 2 - Feb 2014
Volume 38, Issue 1 - Jan 2014
Selecting the target year
Performance characteristics of hot-gas bypass refrigerator with the variation of operation conditions
Baek, Seung-Moon ; Son, Chang-Hyo ; Heo, Jeong-Ho ; Choi, In-Soo ; Yoon, Jung-In ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1021~1026
DOI : 10.5916/jkosme.2014.38.9.1021
In this paper, among various systems applying hot-gas bypass control, outdoor temperature, outlet temperature of water cooler, superheating and subcooling degree, which are the factors affecting the performance of the system bypassing hot-gas to evaporator inlet were analyzed. The main results were summarized as following. Frist of all, performance of refrigeration system bypassing hot-gas to evaporator inlet was affected by outdoor temperature, outlet temperature of water cooler, superheating and sub cooling degree. Thus, providing basic planning date of refrigeration system obtained through optimization of variables is expectable. Thus, providing the basic design data of refrigeration system can be offered by performing the optimization of these variables. Also, the feasibility of this refrigeration system proposed in this paper was obtained by analyzing operating characteristics of the system bypassing hot-gas to evaporator inlet.
A study on design for free cooling system using dry cooler
Yoon, Jung-In ; Baek, Seung-Moon ; Heo, Jeong-Ho ; Kim, Young-Min ; Son, Chang-Hyo ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1027~1031
DOI : 10.5916/jkosme.2014.38.9.1027
Free cooling system is used to reduce energy consumption of cooling system. Free cooling system is consisted of cooling group and dry-cooler in which heat exchange of chilled water and out air is conducted. Although this system has an excellent energy saving effect in place having cooling load regularly, data or material of design for free cooling system is lacked. In this study, characteristics analysis of free cooling system is conducted through software HYSYS with changing some facts. The main result is following as : Dry-cooler capacity is influenced by out air temperature, required chilled water temperature and LMTD(Logarithmic Mean Temperature Difference) of heat exchanger. As out air temperature is more low, dry-cooler capacity become increased. in addition, as required chilled water temperature is more high and LMTD is more low, the out air temperature range is widened for using dry-cooler. If out air temperature is below
, antifreeze need to be used because freeze and burst can be occurred. In case of South Korea, antifreeze of 34% of ethylene glycol concentration is proper. When compressor load of R22, R134a and R407C is compared, considering environmental regulation and energy consumption, R134a is best working fluid.
Boiling heat transfer characteristics of FC-72 in parallel micro-channels
Choi, Yong-Seok ; Lim, Tae-Woo ; You, Sam-Sang ; Kim, Hwan-Seong ; Choi, Hyeung-Sik ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1032~1038
DOI : 10.5916/jkosme.2014.38.9.1032
In this study, an experimental study was performed to understand the boiling heat transfer characteristics of FC-72 in parallel micro-channels. The parallel micro-channels contained channels having a
] cross section and length of 60 mm. And heat flux was varied from 16.4 to
and mass fluxes from 300 to
. The measured heat transfer coefficient was sharply decreased at lower vapor quality and then it was kept approximately constant as the vapor quality is increased. From the experimental results, the boiling heat transfer mechanism of FC-72 was confirmed and the measured heat transfer coefficient was compared and analyzed with the existing correlations to predict the heat transfer coefficient.
The effect of lubricant containing diamond nano-powder on performance
Son, Kwun ; Lee, Jung-Seok ; Park, Tae-Hee ; Park, Kweon-Ha ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1039~1044
DOI : 10.5916/jkosme.2014.38.9.1039
Many research works have been conducted to improve a lubrication performance on diesel engines working in severe conditions. In this study the lubricant containing diamond nano-powder is applied on a diesel engine, and the engine performance is analyzed. The concentration of nano-diamond lubricant fabricated by the matrix synthesis dispersion method is varied. The test results with the nano lubricants are compared with the base oil. The result shows the improvement of efficiency with friction reduction and exhaust emissions reduction of CO, smoke and so on.
Effect of fuel component on nitrous oxide emission characteristics in diesel engine
Yoo, Dong-Hoon ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1045~1050
DOI : 10.5916/jkosme.2014.38.9.1045
(Nitrous Oxide) is known as the third major GHG(Green House Gas) following
(Carbon Oxide) and
(Methane). The GWP(Global Warming Potential) factor of
is 310 times as large as that of
in the atmosphere is very stable, and it becomes a source of secondary contamination after photo-degradation in the stratosphere. Investigation on the cause of the
formation have been continuously reported by several researchers on power sources with continuous combustion form, such as a boiler. However, in the diesel engine, research on
generation which has effected from fuel components has not been conducted. Therefore, in this research, author has investigated about
emission rates which was changed by nitrogen and sulfur concentration in fuel on the diesel engine. The test engine was a 4-stroke direct injection diesel engine with maximum output of 12 kW at 2600rpm, and operating condition of that was set up at a 75% load. Nitrogen and sulfur concentrations in fuel were raised by using six additives : nitrogen additives were Pyridine, Indole, Quinoline, Pyrrol and Propionitrile and sulfur additive was Di-tert-butyl-disulfide. In conclusion, diesel fuels containing nitrogen elements less than 0.5% did not affect
emissions in the all concentrations and kinds of the additive agent in the fuel. However, increasing of the sulfur additive in fuel increased
emission in exhaust gas.
Investigation on emission characteristics of nitrous oxide from marine diesel engine
Yoo, Dong-Hoon ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1051~1056
DOI : 10.5916/jkosme.2014.38.9.1051
Nitrous oxide (
) is naturally generated from biological activity, such as bacteria`s material exchange. However, recent
concentration in the atmosphere has being increased by the human activities such as industrial growth. One of factors to increase
concentration in the atmosphere is a
emission caused by the combustion of marine fuel oils. The marine transportation presently handles over 99 percent of the international freight cargoes and the number of ship is continuously increasing with increment of cargoes. In this study, author conducted a series of the experimental investigations on which combustion of fuels containing different element concentrations used in a 4-stroke marine diesel engine affect
emissions in the exhaust gas. Moreover, it is assessed on the extent to which fuel combustion patterns in the combustion chamber affect
A study on the comparision of effects and application of marine fuel reduction methods
Park, Goryong ; Cho, Kwonhae ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1057~1063
DOI : 10.5916/jkosme.2014.38.9.1057
reduction from International Societies, lots of laboratories and relevant societies suggest many reports on how to reduce fuel consumption from their specific ways. Undoubtedly, cutting costs is the final desired destination for owner outcome, but many questions there are on the way yet: how is this measure working? how efficient is it? On what size of ship would it work best and be the most effective? etc. Fuel cost is one of the major cost elements for ship owners and/or operators. And by reducing fuel consumption owners and/or operators will reduce both their costs and the environmental impact from their ship. This paper is aim to address how the measures work for saving fuel consumption through improve propulsion efficiency, installation cost and benefit can be calculated easily in the return on investment for estimated one year operation, and finally their compatibility with other fuel saving measure devices.
Influence of fuel injection pattern on combustion and emissions characteristics of diesel engine by using emulsified fuel applied with EGR system
Yoo, Dong-Hoon ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1064~1069
DOI : 10.5916/jkosme.2014.38.9.1064
The use of emulsified fuel and EGR (Exhaust gas recirculation) system are effective methods to reduce NOx emission from diesel engines. In general, it is considered that EGR method influences diesel engine combustion in three different ways: thermal, chemical and dilution effect. Among others, the thermal effect is related to the increase of specific heat capacity due to the presence of
in inlet air. Meanwhile, emulsified fuel method of utilizing latent heat of vaporization and miro-explosion has been recognized as an effective technique for reducing diesel engine emissions. In this paper, an author studied on combustion and emission characteristics by using emulsified fuel (EF, Light oil : 80% + Water : 20%) and EGR (30% EGR ratio) system. And the effect of fuel injection pattern control was investigated.
A study on the arrangement of integrated power system for warship
Baek, Hyun-Min ; Jung, Kyun-Sik ; Lee, Myung-Ho ; Choi, Jae-Sung ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1070~1074
DOI : 10.5916/jkosme.2014.38.9.1070
According to IEEE 1662(2009), IPS is a power system where all prime movers produce electrical power that is shared among propulsion, mission, and ship service loads. Discriminating attributes of integrated power systems are flexibility of movers` arrangements, mechanical decoupling between prime movers and propulsors, an increased level of energy conversion and transmission redundancy, and flexibility of redistributing available electrical power for future electronic weapons. IPS could have various steps of power that can be produced at optimal load of movers. In this study, an evaluation method for optimal arrangement of movers was investigated when an IPS warship is projected. The two factors are utilized for the quantitative analysis which are the weight of system as the fighting power and the fuel consumption per year as the economic feasibility. And also the ways for arrangement of system were studied according to existence of small diesel generator. The evaluation method that decides the optimization level is based on the DEA(Data Envelopment Analysis)
The study on substructure design and analysis for 5MW offshore wind turbine
Sun, Min-Young ; Lee, Sung-Bum ; Lee, Ki-Yeol ; Moon, Byung-Young ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1075~1080
DOI : 10.5916/jkosme.2014.38.9.1075
This study aims at dedicating to relevant technology fields by suggesting design methods of structures and estimating their safety in relation to substructure for offshore wind power requiring high safety to various environment conditions. Especially, with respect to 5MW Offshore Wind Power System, this study will provide information about major wind directions and duration in combination with the developing wave climate at the test field. Therefore, connections between wind fields and approaching wave trains will be estimated and their intensity, direction and time shift will be pointed out. Furthermore, the local pressure distribution of breaking waves will be investigated by physical and numerical modeling. The currently applied structural and fatigue assessment of support structures for offshore wind energy converters is based on common design rules. Normally, constructions in structural engineering are treated as limited, single structures. This means that varying aspects of manufacturing are considered by high safety factors.
Characteristics of canola biodiesel fuel blended with diesel on the combustion and exhaust gas emissions in a compression ignition diesel engine
Yoon, Sam Ki ; Kim, Min Soo ; Choi, Nag Jung ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1081~1086
DOI : 10.5916/jkosme.2014.38.9.1081
An experimental study was performed in order to compare with the case of using pure diesel the characteristics of combustion pressure and exhaust emissions when the engine speed was changed in a CRDI 4-cylinder diesel engine using biodiesel( Canola oil) blended and pure diesel fuel. As a results, the combustion pressure was decreased with increasing biodiesel blended rate when engine speed was 1,000, 1,500, 2000(rpm). but the combustion pressure of the engine speed 2,500rpm was increased with increasing biodiesel blended rate. The emission results show, that CO was decreased with increasing biodiesel blended rate and engine speed. The emission of
, NOx, were increased with increasing biodiesel blended rate and engine speed.
Effects of stabilizing elements on mechanical and electrochemical characteristics of stainless steel in marine environment
Lee, Jung-Hyung ; Choi, Yong-Won ; Jang, Seok-Ki ; Kim, Seong-Jong ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1087~1093
DOI : 10.5916/jkosme.2014.38.9.1087
Stainless steels stabilized with Ti or Nb are largely used in offshore and shipbuilding industries due to its excellent corrosion resistance. In this study, carbide stabilizers, Ti and Nb, were added to stainless steel 304 specimens with different concentrations(Ti: 0.26%, 0.71%, Nb: 0.29%, 0.46%, 0.71%), and their mechanical and electrochemical characteristics were evaluated. Micro-Vickers hardness testing was employed to characterize the mechanical characteristics with alloying elements. Electrochemical evaluation techniques including Tafel analysis, cyclic polarization experiment, galvanostatic experiment were utilized to compare the corrosion characteristics of the specimens. The result of hardness tests revealed that Nb containing specimens showed increasing hardness with increasing alloying contents while adding Ti had little effect on increase in hardness. In the case of electrochemical measurements, the electrochemical characteristics of the specimens were enhanced with increasing Nb contents while they were deteriorated with increasing Ti contents. As a result, different stabilizers and their contents may produce significant differences in electrochemical characteristics, and there such effect must be taken account of in development of stainless steels for marine environment.
A study on the required energy of a thermal type desalination plant
Song, Chi-Sung ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1094~1100
DOI : 10.5916/jkosme.2014.38.9.1094
TEvaporator is key component in food, seawater distillation and waste water treatment system, which is basically to concentrate the raw liquid by evaporating the pure water under vacuum condition. The liquid concentration is performed through the membrane, electro-dialysis and evaporation. In this study, only the evaporating type was treated for evaluating the economic analysis with the various operating conditions. The results of this study showed that the performance of the OT-MSF desalination system is increased with decreasing the temperature difference between the neighboring evaporators, which means that the number of evaporators is increased, under the determined design conditions.
Design of a 100kW-class radial inflow turbine for ocean thermal energy conversion using R32
Kim, Do-Yeop ; Kim, You Taek ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1101~1105
DOI : 10.5916/jkosme.2014.38.9.1101
Ocean Thermal Energy Conversion(OTEC) which uses the temperature difference between warm surface sea-water and cold deep sea-water to produce electric power is the promising technology. OTEC is able to be utilized as the
reducing technology by using the consistent temperature differential, while the system efficiency is very low. Thus, the design and development of a efficient turbine is essential to improve the system efficiency for OTEC. In this study, a 100kW-class radial inflow turbine using R32 was designed for OTEC and this turbine`s performance was estimated by analysis of CFD. According as the simulation results, turbine`s geometry was corrected. The radial inflow turbine satisfying the requirements is designed by the repeated attempts.
Pressure distribution near truncated POD attached on hydrofoil vessel
Lee, Chun-Ki ; Kim, Hee-Sung ; Moon, Serng-Bae ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1106~1111
DOI : 10.5916/jkosme.2014.38.9.1106
This paper has a purpose to find out the characteristics of pressure distribution according to the POD shape installed in the Hydrofoil vessel, using the CFD. The results showed that as we cut the POD cross-section`s basic shape along the x-axis from 0 to 8cm, the viscous resistance had decreased, but then the pressure resistance had increased modestly. However, the cutoff length of POD cross-section shape has close to 9cm, the viscous drag had increased and the pressure drag had decreased. As a result, we found out that the pressure resistance made more effects in POD shape than the viscous resistance, and the total resistance decreased near the 9cm of cutoff length.
A study on a local descriptor and entropy-based similarity measure for object recognition system being robust to local illumination change
Yang, Jeong-Eun ; Yang, Seung-Yong ; Hong, Seok-Keun ; Cho, Seok-Je ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1112~1118
DOI : 10.5916/jkosme.2014.38.9.1112
In this paper, we propose a local descriptor and a similarity measure that is robust to radiometic variations. The proposed local descriptor is made up Haar wavelet filter and it can contain frequency informations about the feature point and its surrounding pixels in fixed region, and it is able to describe feature point clearly under ununiform illumination condition. And a proposed similarity measure is combined with conventional entropy-based similarity and another similarities that is generated by local descriptor. It can reflect similarities between image regions accurately under radiometic illumination variations. We validate with experimental results on some images and we confirm that the proposed algorithm is more superior than conventional algorithms.
Analysis on transient stability for drilling rigs power system
Kim, Yoon-Sik ; Kim, Chul-Ho ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1119~1124
DOI : 10.5916/jkosme.2014.38.9.1119
This paper describes the emergency situation which occurs in Drilling Rig power system. Especially, we focused on power system transient characteristics on propulsion motor load and generator elimination situation in Drilling Rig operation. We performed numerical simulation and analyzed the result for power system transient stability characteristics on each condition for excitation system and governor control system using ETAP (Electrical Transient Analysis Program).
A study on digital sound reception systems for ships
Kim, Hyungjong ; Kim, Jeongchang ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1125~1130
DOI : 10.5916/jkosme.2014.38.9.1125
In this paper, we propose a sound reception system against surrounding noise for ships based on digital signal processing technologies. In order to suppress unwanted surrounding noises, a digital band-pass filter is designed, which the pass-band of the filter is between 70Hz to 820Hz. Also, we develope a sound direction indicating algorithm with 4 microphones. After filtering the audio signals from 4 microphones, the developed sound direction indicating algorithm can indicate 8 directions. In addition, we implement prototype board for the sound reception using a digital signal processor chip and audio codecs, and verify the proposed algorithm.
Harmonics reduction by accuracy of DC shaping of power converters
Kim, Jongsu ; Ahn, Jaehong ; Kim, Seonghwan ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1131~1136
DOI : 10.5916/jkosme.2014.38.9.1131
Recently, power converters installed on the specialized vessels such as LNG Carrier and Icebreaker and offshore plants mainly use diode rectifier. However, such devices cause distortion of supply voltage waveform by involving much harmonics to input current of non linearity load in rectifying operation. Distortion of supply voltage waveform can be problems such as false operation of generator, transformer and load device and deterioration of power quality. This thesis is focusing with a view to producing accurate sinusoidal AC waveform with certain load through improvement of distortion of current waveform causing under operation of rectifier by using accurate circuit of DC shaping. The result of computer simulation proved that harmonics involved in current and voltage waveform of power system can be reduced.
A study on how to discriminate the polarities of stator windings for 3 phase induction motors by using general purpose multi-testers
Choi, Soon-Man ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1137~1140
DOI : 10.5916/jkosme.2014.38.9.1137
Faulty electric motors onboard vessels with anomalies in windings or poor insulation are usually repaired at land based workshops and reinstalled in place by crew hands after receiving the repaired motors. Especially for 3 phase induction motors which need Y-
starters with 6 lead wires, it would happen that the polarities of stator windings cannot be well distinguished if the original tags of these wires are erased or not visible clearly, resulting in subsequent damage to the repaired motor due to extreme current flow when the power is given to the motor the stator windings of which are wrongly connected in the polarity. This study proposes an easy way to make correct connection in winding polarities without failures based on the electro-magnetically induced voltages on windings when a slight DC current is supplied to a winding coil by using an analog multi-tester. The proposed method is applied to actual motors and delves into the applicability for polarity discrimination through a few measurements onboard vessels.
Polarity discrimination of stator windings for 3 phase induction motors by using DC differential signals between mutual inductive voltages
Choi, Soon-Man ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1141~1145
DOI : 10.5916/jkosme.2014.38.9.1141
When the stator windings of 3 phase induction motors are in wrong condition, the mutual inductive responses between windings can be utilized for the purpose of diagnosing motors in that fault windings affect even the responses by DC excitation. Three phase induction motors are supposed to generate consistent inductive voltages at the remaining windings when exciting DC current is given to one of 3 windings, while the inconsistence of their voltages indicates the existence of disorder at electric motors. This study describes how the exciting current to one of three windings cause the other windings to create induced voltages, analyzing responses by transfer functions, and discloses whether or not the balance relation at two windings is normal in the way of measuring the differential voltage of their outputs. For experiment, common analog multi-testers is used for applying exciting current and measuring the output signal to confirm whether the proposed method is useful enough to be able to discriminate wrong polarities of windings onboard vessels including also the case of exciting current by AC.
A study on how to discriminate the polarities of stator windings for 3 phase induction motors by using induced voltages based on residual magnetism
Choi, Soon-Man ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1146~1149
DOI : 10.5916/jkosme.2014.38.9.1146
To discriminate polarities of stator windings for 3 phase induction motors terminal tags of which are not readable, it is possible to utilize the residual magnetic flux present at their rotors as well as to use the way based on external exciting current. The induced voltages are basically decided by parameters such as the quantity of residual flux, the rotator speed by hand force and the phase properties between stator windings. To adopt induced voltages by residual flux for polarity discrimination at sites, the measured voltages by multi-testers need to be readable in magnitude enough to discriminate winding condition with reasonable phase characteristics. This study focuses on the analysis of various connection cases in the expectation that the summing voltages induced by residual flux shall show zero in case of normal connections while the sum becomes greater indication if the connection is in wrong condition. The proposed method is applied to actual motors to disclose how effective it is for polarity discrimination at sites through comparison of output signals between normal and fault connections.
Comparison on the fire performance of additional insulation materials for improving the fire retardancy in engine-room of FRP vessel
Choi, Jung-Min ; Um, Han-Chan ; Jin, Young-Hwa ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1150~1155
DOI : 10.5916/jkosme.2014.38.9.1150
To prevent the flame spread in FRP vessel in fire, the engine-room of the vessel should be constructed additionally with laminated fire-retardant resin over 3 times or equivalent insulation materials to former according to the relevant standard for FRP vessel structure. It is surveyed that insulation materials called `Gel coat` are widely used in FRP fishing vessel, however, test method and its criteria for Gel coat are not clearly establish and have not been evaluated yet, while test method and criteria for fire-retardant resin and fire-retardant polyurethane composite are described in test standard for type-approval. In this study, 3 fire-retardant resins, 4 gel coats, 1 flame-retardant paint and 1 polyurethane composite were selected based on the survey and were evaluated according to both IMO FTP Code part 5 and flame-retardant test. When comparing based on CFE values from flame-spread test, average value for 4 gel coats were lower than that of 3 fire-retardant resins. As for flame-retardant test, there were no significant differences between fire-retardant resin and gel coat, based on charred area.
Change of safety consciousness of passengers onboard ship after the Sewol ferry incident
Hwang, Kwang-Il ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1156~1162
DOI : 10.5916/jkosme.2014.38.9.1156
To prevent the Sewol incident again, by which the victims are 294 dead and still 10 missing, this study analyzed the change of safety consciousness of passengers onboard ship comparatively before and after the Sewol incident. The survey had performed 2 times at Jeju coastal cruise terminal at February 2014 and May 2014, and effective respondents were 394 and 401, respectively. After the Sewol incidents, the answers` ratio that they would follow the routes that the crews show and they would follow the crews` evacuation guides are decreased 24.5% and 18.5%, respectively. This means that the reliability on the crew members were decreased. Although 77.6% passengers responded that they felt nervousness onboard ship, 60% did not take safety lesson(s) and 45% did not know how to wear a life jacket. And also over 50% did not check the evacuation route map and the location of lifeboat, respectively. Meanwhile, 86.9% respondents answered the system of safey lesson should be changed, which has normally done by TV set.
A preliminary study on the development of detection techniques for CO
gas bubble plumes
Kum, Byung-Cheol ; Cho, Jin Hyung ; Shin, Dong-Hyeok ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1163~1169
DOI : 10.5916/jkosme.2014.38.9.1163
As a preliminary study for detection techniques of
gas bubble plumes, we have conducted a comparative experiment on artificially generated
gas bubbles plume by using multibeam echosounder (MBES), single beam echosounder (SBES), and sub-bottom profiler (SBP). The rising speed of artificial gas bubbles is higher than references because of compulsory release of compressed gas in the tank. Compared to single beam acoustic equipments, the MBES detects wide swath coverage. It provides exact determination of the source position and 3D information on the gas bubble plumes in the water column. Therefore, it is shown that MBES can distinctly detect gas bubble plumes compared to single beam acoustic equipments. We can establish more effective complementary detection technique by simultaneous operation of MBES and SBES. Consequently, it contributes to improve qualitative and quantitative detection techniques by understanding the acoustic characteristics of the specific gas bubbles.
A study on the improvement of cavitation inception speed for controllable pitch propeller in the actual warship
Lim, Yong-Su ; Jo, Kwan-Jun ; Yeun, Je-Gil ;
Journal of the Korean Society of Marine Engineering, volume 38, issue 9, 2014, Pages 1170~1174
DOI : 10.5916/jkosme.2014.38.9.1170
If cavitation occurs in propeller, it generates vibration and noise accordingly which results in low efficiency of propeller. It`s important to increase cavitation inception speed(CIS) since the noise of cavitation increases significantly from the beginning of cavitation. This paper describes the result of actual observation and measurement onboard ship with controllable pitch propeller(CPP), so as to verify the first occurrence phenomenon of cavitation. The research suggests new type of controllable pitch propeller with improved CIS at the bolt as it started with bolt cavitation as result of observation. It`s not found bolt cavitation on the CPP proposed in this paper, furthermore its CIS is increased approximately by 4.5 knots than the existing CPP. The result of the research can be used for development of low-noise CPP and improving performance of CIS.