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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society of Marine Engineering
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Journal DOI :
Korean Society of Marine Engineers
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Volume & Issues
Volume 23, Issue 6 - Nov 1999
Volume 23, Issue 5 - Sep 1999
Volume 23, Issue 4 - Jul 1999
Volume 23, Issue 3 - May 1999
Volume 23, Issue 2 - Mar 1999
Volume 23, Issue 1 - Jan 1999
Selecting the target year
Stall Phenomena of Large Axial-Flow Fan in Ship and Its Countermeasure
Journal of the Korean Society of Marine Engineering, volume 23, issue 4, 1999, Pages 419~431
SENSORLESS SPEED CONTROL OF INDUCTION MOTOR WITH SPEED ESTIMATOR
Journal of the Korean Society of Marine Engineering, volume 23, issue 4, 1999, Pages 432~439
Several methods of induction motor drives which used speed estimators instead of shaft encoders have been reported. However those speed sensorless systems with estimators employing stator voltates and currents usually deteriorates as the speed gets lower because it is difficult to calculate the accurate rotor flux under the influence of DC-offset and saturation of integrators. In this paper to calculate rotor flux at low speed the new rotor flux estimator which replaces integra-tors with two lag circuits is proposed. Simulation and experiment results confirm the validity of this control scheme.
A Study on the Evaluation of the Friction and Wear Properties for Normalized Ductile Cast Iron
Journal of the Korean Society of Marine Engineering, volume 23, issue 4, 1999, Pages 440~446
This study is mainly concerned with the friction and wear properties for the specimens of crank shaft which are made of ductile cast iron. The friction and wear tests were carried out for the nor-malized ductile cast iron specimens and their properties were compared with each other at reheat-ing temperatures(
) and in dry condition at different friction velocity(0.94 m/s 1.88m/s 2.83m/s) range. After austenized at
it is observed that the higher the reheating temperature is the hardness becomes decrease which is supposedly attributed to the fact that the amount of pearlite austenite matrix is rduced by reheating after normalizing and that as the reheating temperature goes up the pearlite generated is less and the interval between the pearlites were widened at last to make pearlite globular. At the low velocity the friction coefficient increase in the beginning and gets stabilized as the sliding distance increases. As the friction velocity grows the friction coefficient decreases suppos-edly since the abrasive wear is heavier at low velocity than at the high velocity as the friction tem-perature at low velocity is lower than at high velocity.
Cycle performance of refrigeration and air-conditioning system using the hydrocarbon refrigerant R-290
Journal of the Korean Society of Marine Engineering, volume 23, issue 4, 1999, Pages 447~452
This paper describes the cycle performance of heat-pump system using R-22 and R-290. Experi-ments were performed in the smooth tube with inside diameter of 10.07mm and outside diameter of 12.07 mm and grooved inner tube having 75 fins with a height of 0.25mm Condensing temper-atures were held constantly between 318K and 328 K while evaporating temperatures were var-ied from 257 K to 288 K mass velocities from 51 to
From the experiments it was known that the evaporating temperature and condensing tempera-ture had moer affected by the compressor shaft power than the tube geometries. Cooling capacity of the R-22 and R-290 had similar values in the smooth and grooved inner tubes. The coefficient of per-formance(COP) was calculated using the compressor shaft power volumetric refrigeration capacity compression ratio and cooling capacity. The COP of the R-290 had slightly higher values than that of R-22 The major parameters affecting the heat pump cycle performance wee the refrigerant proper-ties and operating conditions rather than the geometric shapes of the heat exchanger
A Study on the Prediction of Fatigue Life by use of Probability Density Function
Journal of the Korean Society of Marine Engineering, volume 23, issue 4, 1999, Pages 453~461
The estimation of fatigue life at the design stage is very important in order to arrive at feasible and cost effective solutions considering the total lifetime of the structure and machinery compo-nents. In this study the practical procedure of prediction of fatigue life by use of cumulative damage factors based on Miner-Palmgren hypothesis and probability density function is shown with a
LNG tank being used as an example. In particular the parameters of Weibull distribution taht determine the stress spectrum are dis-cussed. At the end some of uncertainties associated with fatigue life prediction are discussed. The main results obtained from this study are as follows: 1. The practical procedure of prediction of fatigue life by use of cumulative damage factors expressed in combination of probability density function and S-N data is proposed. 2. The calculated fatigue life is influenced by the shape parameter and stress block. The conser-vative fatigue design can be achieved when using higher value of shape parameter and the stress blocks divded into more stress blocks.
A Study on the Flue Gas Mixing for the Performance Improvement of De-NOx plant
Journal of the Korean Society of Marine Engineering, volume 23, issue 4, 1999, Pages 462~472
De-NOx facility using Selective Catalytic Reduction method is the most widely applied one that removes NOx from flue gas emitted from combustion facility such as boiler for power generation engine incinerator etc. Reductant
is sprayed into flue gas to convert NOx into
Good mixing between flue gas and
is the most important factor to increase reduction in catalytic layer and to reduce unreacted NH3 slip. Therefore the development of mixer device for mixing effect is one of the important part for SCR facility. Objectives of this study are to investigate the relation between flow and concentration field by observation at the wake of delta-wing type mixer. At the first stage qualitative measurement of flow field is conducted by flow visualization using laser light sheet in lab. scale wind tunnel. Also we have conducted the quantitative analysis by comparing flow field measurement using LDV with numerical simulation. On the basis of qualitative and quantitative analysis we investigate the dis-tribution of flow and concentration in flow model facility. The results of an experimental and compu-tational examination of the vortex structures shed from delta wing type vortex generator having
angle of attack are presented, The effects of vortex structure on the gas mixing is discussed, too.
An Experimental Study of the Application of the Sound-Intensity Technique on the Detection of Defect in Rolling Bearings
Journal of the Korean Society of Marine Engineering, volume 23, issue 4, 1999, Pages 473~479
The two-microphone sound-intensity technique has been used for the detection of defects in ra-ally loaded ball bearings. The difference in the sound-intensity levels measured for bearings with no defect and for those with intentionally introduced defects of different sizes n heir elements under various operating conditions of loads and speeds is demonstrated. The results show that of an inner-race or ball defect. It is difficult to detect defects at lower speeds. Sound-pressure measurements were also performed for comparison and it shown that the detectability of defects by sound-intensity measurements is better than that by sound-pressure measurements.
Application of Neural Network Precompensated PID Controller for Load Frequency Control of Power Systems
Journal of the Korean Society of Marine Engineering, volume 23, issue 4, 1999, Pages 480~487
In this paper we propose a neural network precompensated PID(NNP PID) controller for load frequency control of 2-area power system. While proportional integral derivative(PID) controllers are used in power system they have many problems because of high nonlinearities of the power system So a neural network-based precompensation scheme is adopted into a conventional PID controller to obtain a robust control to the nonlinearities. The applied neural network precompen-sator uses an error back-propagation learning algorithm having error and change of error as inputand considers the changing component of forward term of weighting factor for reducing of learning time. Simulation results show that the proposed control technique is superior to a conventional PID controller and an optimal controller in dynamic responses about load disturbances. The pro-posed technique can be easily implemented by adding a neural network precompensator to an existing PID controller.
Two-Parameter Characterization for the Resistance Curves of Ductile Crack Growth
Journal of the Korean Society of Marine Engineering, volume 23, issue 4, 1999, Pages 488~503
The present paper considers the constraint effect on J-R curves under the two-parameter
controlled crack growth within a certain amount of crack extension. Since the parameter
three-term solution is independent of applied loading under fully plasticity or large-scale defor-mation
is a proper constraint parameter uring crack extension. Both J and
are used to char-acterize the resistance curves of ductile crack growth using J as the loading level and
are used to char-acterize the resistance curves of ductile crack growth using J as the loading level and A2 as a con-straint parameter. Approach of the constraint-corrected J-R curve is proposed and a procedure of transferring the J-R curves determined from standard ASTM procedure to non-standard speci-mens or real cracked structures is outlined. The test data(e.g. initiation toughness JIC and tearing modulus
) of Joyce and Link(Engineer-ing Fracture Mechanics 1997, 57(4) : 431-446) for single-edge notched bend[SENB] specimen with from shallow to deep cracks is employed to demonstrate the efficiency of the present approach. The variation of
with the constraint parameter
is obtained and a con-straint-corrected J-R curves is constructed for the test material of HY80 steel. Comparisons show that the predicted J-R curves can very well match with the experimental data for both deep and shallow cracked specimens over a reasonably large amount of crack extension. Finally the present constraint-corrected J-R curve is used to predict the crack growth resistance curves for different fracture specimens. over a reasonably large amount of crack extension. Finally the present constraint-corrected J-R curve is used to predict the crack growth resistance curves for different fracture specimens. The constraint effects of specimen types and specimen sizes on the J-R curves can be easily obtained from the constrain-corrected J-R curves.
A Study on the Axial stiffness of Bellows
Journal of the Korean Society of Marine Engineering, volume 23, issue 4, 1999, Pages 504~513
Usually bellows are designed for the purpose of absorbing axial movement. To find out axial stiffness of bellows the axisymmetric shell theory using the finite element method is adopted in this paper. Bellows can be idealised by series of conical frustum-shaped elements because it is axisymmetric shell structure. The force required to deflect bellows axilly is a function of the dimensions of the bellows and the materials from which they are made. The displancements of nodal points due to small increment of force are calculated by the finite element method and the calculated nodal displacements are added to r-z cylinderical coordinates of nodal points. The new stiffness matrix of the system using the new coordinates of nodal points is adopted to calculate the another increments of nodal dis-placements that is the step by method is used in this paper. spring constant is analyzed according to the changing geometric factors of u-shaped bellows. The FEM results were agreed with experiment. Using developed FORTRAN PROGRAM spring constant can be predicted by input of a few factors.
Evaporating Particle Behaviors and plasma Parameters by Spectroscopic Method in laser Welding
Journal of the Korean Society of Marine Engineering, volume 23, issue 4, 1999, Pages 514~522
The laser-induced plasma affects greatly on the results of welding process. moreover selective evap-oration loss of alloying elements leads to change in chemical composition of weld metal as well as the mechanical properties of welded joint. this study was undertaken to obtain a fundamental knowledge of pulsed laser welding phenomena especially evaporation mechanism of different aluminum alloys. The intensities of molecular spectra of AlO and MgO were different each other depeding on the power density of a laser beam Under the low power density condition the MgO band spectrum was predomi-nant in intensity while the AlO spectra became much stronger with an increase in the power density. These behaviors have been attributed to the difference in evaporation phenomena of Al and Mg metals with different boiling points and latent heats of vaporization. The time-averaged plasma temperature and electron number density were determined by spectroscopic methods and consequently the obtained temperature was
and the electron number density was
Chemical Compositio and Structure of Evaporated Alloying Element by Laser Welding Condition
Journal of the Korean Society of Marine Engineering, volume 23, issue 4, 1999, Pages 523~532
This study is aimed to obtain fundamental knowledge of pulse laser welding phenomena the authors investigated the structure and composition of evaporated particles of Al alloys in air and in the Ar atmosphere during pulsed laser welding. The ultra-fine particles of 5 to 100nm diameter in a globular or irregular shape were formed in laser-induced plasma and the main structure was
The composition of particles was ifferent depending on the power density of a laser beam; namely under the low power density conditions magnesium was predominant in the parti-cles while aluminium content increased with an increase in the power density. These results were attributed to evaporation phenomena of metals with different boiling points and latent heats of vaporization. On the other hand the number density of laser-induced plasma species was obtained by Saha's equation. it was confirmed that the number density depends upon the plasma tempera-ture and total pressures.
Flows Characteristics of Developing Turbulent Pulsating Flows in a curved Square Duct
Journal of the Korean Society of Marine Engineering, volume 23, issue 4, 1999, Pages 533~542
In this study the flow characteristics of developing turbulent pulsating flows in a square-sec-tional 180。 curved duct are investigated experimentally. The experimental study of air flow in a square-sectional curved duct is carried out to measure axial velocity distribution secondary flow velocity profiles and wall shear stress distributions by using a Laser Doppler Velocimetry system with the data acquisition and processing system of Rotating Machinery Resolver (RMR) and PHASE software at the entrance region of the duct which is divided into 7 sections from the inlet(
) to the outlet (
intervals. The results obtained from the study are summarized as follows: (1) The time-averaged critical Dean number of turbulent pulsating flow(De ta, cr) is greater than
It is understood that the critical Dean number and the critical Reynolds number are related to the dimensionless angular frequency in a curved duct. (2) Axial velocity profiles of turbulent pulsating flows are of an annular type similar to those of turbulent stead flows. (3) Secondary flows of trubulent pulsating flows are strong and complex at the entrance region. As velocity amplitudes(A1) become larger secondary flows become stronger. (4) Wall shear stress distributions of turbulent pulsating flows in a square-sectional
curved duct are exposed variously in the outer wall and are stabilized in the inner wall without regard to the phase angle.
A Study on the Calcuation of NO Formation in Cylinder for Diesel Engines
Journal of the Korean Society of Marine Engineering, volume 23, issue 4, 1999, Pages 543~551
Diesel engine is a major source of the air pollution. In general the concentrations of these pollu-tants in diesel engine exhaust differ from values calculated assuming chemical equibrium. Thus the detailed chemical mechanisms by which these pollutions form and the kinetic of these process-es are important in determining emission levels. In this study the computer program has been developed to calculate the required thermodynam-ic properties of combustion products(10 spacies) for both equilibrium and non-equilibrium in cylin-der for diesel engines. Nitric oxide emissions are calculated by using the extended Zeldovich Kinet-ic mechanism with a steady state assumption for the N concentration and equilibrium values used for H, O,
and OH concentrations. By the results it is confirmed that developed simulations program with the NO prediction model is validated against residual mass fraction combustion index of Wiebe's functions pre-mixed com-bustion ration fuel injection timing.
Heat transfer of Mixed convection in rectangular space with constant heat flux
Journal of the Korean Society of Marine Engineering, volume 23, issue 4, 1999, Pages 552~558
Ventilation of the marine engine room is very important for the health of the workers as well as the normal operation of machines. To find proper ventilation conditions of this engine room numerical simulation with a standard k-
model was carried out. In the present study the marine engine room is considered as a closed space with a heat source and forced ventilation ducts. The injection angle of air supply is found to be important. Injection with a downward angle depresses recirculation flow causing a strong stream in the wider space of the room Ventilation and removal of the released heat are promoted with this pattern, There is a possibility of local extreme heating at the upper surface of the engine when supply and exhaust ports of air are in bilateral symmetry.
Velocity Measurement of PIV Using a General Light Source
Journal of the Korean Society of Marine Engineering, volume 23, issue 4, 1999, Pages 559~564
A particle image velocimetry is the representative technique for measuring flow velocities at whole field simultaneously. The present study adopted the PTV method for velocity acquisition in a square enclosure with initially isothermal fluid by using a general lamp-based sheet light source. The enclosure was composed of hot and cold vertical wall and was confined by two horizon-tal adiabatic walls. The drift velocities were measured and the drift was visualized by PTV for a rayleigh number of
Obtained instant simulataneous velocity vectors show flow pattern and the result of horizontal velocity profile agree well with the numerical result.
A Study on the Large Deflection Behavior of Ship Plate with Secondary Buckling
Journal of the Korean Society of Marine Engineering, volume 23, issue 4, 1999, Pages 565~573
Hihg Tensile Steel enables to reduce the plate thickness comparing to the case when Mild Steel is used. From the economical view points this is very preferable since the reduction in the hull weight. however to use the High Tensile Steel effectively the plate thickness may become thin so that the occurrence of buckling is inevitable and design allowing plate buckling may be necessary. If the inplane stiffness of the plating decreases due to buckling the flexural rigidity of the cross sect6ion of a ship's hull also decreases. This may lead to excessive deflection of the hull girder under longitudinal bending. In these cases a precise estimation of plate's behavior after buckling is necessary and nonliner analysis of isolated and stiffened plates is required for structural sys-tem analysis. In this connection this paper discusses nonlinear behaviour of thin plate under thrust. Based on the analytical method elastic large deflection analysis of isolated plate is perform and simple expression are derived to evaluated the inplane rigidity of plates subjected to uniaxial compression.
Study on Optimum Modification Method of Dynamic Charcteristics of Ship Structures by Multi-level Optimization
Journal of the Korean Society of Marine Engineering, volume 23, issue 4, 1999, Pages 574~582
This paper discusses the multi-level optimization method in dynamic optimization problems through stiffened plate of ship structures. In structural optimization the computational cost increases rapidly as the number of design variables increases. And we need a great amount of cal-culation and time on problems of modified dynamic characteristics of large and complicated struc-tures. In this paper the multi-level optimization is proposed which decreases computational time and cost. the dynamic optimum designs of stiffened plate that control the natural frequency and minimize weight subjected to constraints condition are derived. The way to apply the multi-level optimization methods in this study follow: In the first step the dynamic characteristics is controlled for the two-dimensional model of stiffened plate by sensitivity analysis and quasi-least squares methods. In the second step the cross-section of the stiffener is decided so that the weight is minimized under needed constraints by the steepest descent or ascent method. In the third the three-dimensional model is made based on the results of the first step and the second step confirmation and finer tuning of the objective function are carried out. It is shown that the results are effective in the optimum modification for dynamic characteristics of the stiffened plate.
Nonlinear Hydraulic System Control using Fuzzy PID Controller
Journal of the Korean Society of Marine Engineering, volume 23, issue 4, 1999, Pages 583~592
In order to control systems which contain nonlinearities control strategies must deal with the effects of them. Since most of control methods based on system mathematical models have been mainly developed focused on stability robustness against nonlinearities or uncertainties under the assumption that controlled systems are linear time invariant they have certain amount of limita-tions to smartly improve control perfomances of systems disturbed by nonlinearities or uncertainties. In this paper the fuzzy PID control law is suggested which can improve control performances of the nonlinear heavy load hydraulic systems disturbed by nonlinearities and uncertainties. Although the derivation process is based on the design process similar to general fuzzy logic con-troller resultant control law has analytical forms with time varying PID gains rather than linguis-tic forms so that implementation using commn-used versatile microprocessors can be achieved easily and effectively in real-time control aspect.
The Structural Analysis of Premixed Turbulent Propagating Flames Utilizing the Image Process Technique
Journal of the Korean Society of Marine Engineering, volume 23, issue 4, 1999, Pages 593~600
The structure of premixed turbulent flames in constant volume vessel was investigated by using a laser tomography. The flame structure was visualized by passing a laser sheet with 0.2mm thick and 2 cm wide through the turbulent flames to obtain their 2-D images. From the obtained images islands of reactants as well as of products were found at least in the 2-D images when the turbu-lence intensity was above 0.4m/s. Moreover in order to obtain the characteristic flamelet thickness the light intensities of them were digitized and processed into three colors incorporating two appro-priate threshold values in the image analysis. As the result the averaged value of charactertistic flamelet thickness was found to be about two times compared to laminar one.