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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Transactions of the Korean Society of Mechanical Engineers B
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Journal DOI :
The Korean Society of Mechanical Engineers
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Volume & Issues
Volume 25, Issue 12 - Dec 2001
Volume 25, Issue 11 - Nov 2001
Volume 25, Issue 10 - Oct 2001
Volume 25, Issue 9 - Sep 2001
Volume 25, Issue 8 - Aug 2001
Volume 25, Issue 7 - Jul 2001
Volume 25, Issue 6 - Jun 2001
Volume 25, Issue 5 - May 2001
Volume 25, Issue 4 - Apr 2001
Volume 25, Issue 3 - Mar 2001
Volume 25, Issue 2 - Feb 2001
Volume 25, Issue 1 - Jan 2001
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Thermal Performance Simulation of Cogeneration Power Plants
Lee, Dong-Won ; O, Myeong-Do ; Lee, Jae-Heon ; Jo, Yeong-Jin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 4, 2001, Pages 451~460
DOI : 10.22634/KSME-B.2001.25.4.451
An analysis program for the thermal performance prediction of steam turbine cogeneration systems with multi-extraction, reheat and regeneration has been developed on the basis of the thermodynamic heat balance method. Heat balance analyses were performed for a commercial cogeneration power plant using the program. Its appropriateness was verified by comparing its heat balance results with those of other commercial programs and those provided by the original system designer. Further parametric analyses were carried out and performance improvement measures in designing the plant were suggested.
Characteristics of Interacting Lifted Flames
Lee, Seung ; Lee, Byeong-Jun ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 4, 2001, Pages 461~466
DOI : 10.22634/KSME-B.2001.25.4.461
The characteristics of nonpremixed interacting flames are investigated in the parameter of nozzle configuration and nozzle separation distane, s. Three nozzle arrangements - diamond 4 nozzle, linear 5 nozzle and cross 5 nozzle- are used. When s is about 10 nozzle diameter, flames lift from the nozzle at the highest fuel flowrate compared with the other s cases. Normally flames are extinguished at the lifted states. Flowrates when blowout occurs are affected by the nozzle configuration, nozzle seperation distance. Blowout flowrates for the diamond- or cross-shaped nozzle cases are parabolic function of s. For 5 cross nozzle case, flames extinguished at 3.3 times higher flowrate than that of single equivalent area nozzle. Turbulent liftoff heights are not function of flowrates for these cases.
Indoor Temperature Control of an Air-Conditioning System Using Model Predictive Control
Jo, Hang-Cheol ; Byeon, Gyeong-Seok ; Song, Jae-Bok ; Jang, Hyo-Hwan ; Choe, Yeong-Don ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 4, 2001, Pages 467~474
DOI : 10.22634/KSME-B.2001.25.4.467
The mathematical model of a air-conditioning system is generally very complex and difficult to apply to controller design. In this paper, simple models applicable to the controller design are obtained by modeling the air-conditioning system by single-input single-output between compressor speed and indoor temperature, and by multi-input single-output between compressor speed, indoor fan speed and indoor temperature. Using these empirical models, model predictive control(MPC) technique was implemented for indoor temperature control of the air-conditioning system. It has been shown from various experiments that the indoor temperature control based on the MPC scheme yields reasonably good tracking performance with smooth changes in plant inputs. this multi-input multi-output MPC approach can be extended to multi air- conditioning systems where the conventional PID control scheme is very difficult to apply.
Heat Transfer Enhancement by the Perforated Plate of Round Impinging Air Jets
Kim, Yun-Taek ; Lee, Yeong-Min ; Won, Se-Yeol ; Lee, Dae-Hui ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 4, 2001, Pages 475~484
DOI : 10.22634/KSME-B.2001.25.4.475
The purpose of this study is to investigate the heat transfer augmentation using the perforated plate placed in front of a target plate in an axisymmetric impinging air jet system. The new liquid crystal technique using neural networks with median filtering is used to determine the Nusselt number distributions on the target surface. The experiments were made for the jet Reynolds number (Re) 23,000. The effects of the pitch-to-diameter (p/d1) from 1.5 to 2.5 in the perforated plate, the hole diameter on perforated plate (d1) from 4㎜ to 12㎜, the perforated plate to target surface distance (z/d1) from 1 to 3, and the nozzle-to-target surface distance (L/d) from 2 to 10 on the heat transfer characteristics were experimentally investigated. It was found that when the perforated plate was located between the nozzle exit and the target plate, the average heat transfer rate at the stagnation region corresponding to r/d
1.0 was increased up to the maximum 2.3 times compared to the case without the perforated plate.
A Similarity Solution for the Directional Casting of Peritectic Alloys in the Presence of Shrinkage-Induced Flow
Yu, Ho-Seon ; Jeong, Jae-Dong ; Lee, Jun-Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 4, 2001, Pages 485~495
DOI : 10.22634/KSME-B.2001.25.4.485
This paper presents a similarity solution for the directional casting of binary peritectic alloys in the presence of shrinkage-induced flow. The present model retains essential ingredients of alloy solidification, such as temperature-solute coupling, macrosegregation, solid-liquid property differences, and finite back diffusion in the primary phase. An algorithm for simultaneously determining the peritectic and liquidus positions is newly developed, which proves to be more efficient and stable than the existing scheme. Sample calculations are performed for both hypo- and hyper-peritectic compositions. The results show that the present analysis is capable of properly resolving the solidification characteristics of peritectic alloys so that it can be used for validating numerical models as a test solution.
Reduction of Soot Emitted from a
Normal Diffusion Flame with Application of DC Corona Discharge
Lee, Jae-Bok ; Hwang, Jeong-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 4, 2001, Pages 496~506
DOI : 10.22634/KSME-B.2001.25.4.496
The effect of corona discharge on soot emission was experimentally investigated. Size and number concentrations of soot aggregates were measured and compared for various voltages. Regardless of the polarity of the applied voltage, the flame length decreased and the tip of flame spreaded with increasing voltage. For the experimental conditions selected, the flame was blown off toward the ground electrode by corona ionic wind. When the negative applied voltage was greater than 3kV(for electrode spacing = 3.5cm), soot particles in inception or growth region were affected by the corona discharge, resulting in the reduction of number concentration. The results show that the ionic wind favored soot oxidation and increased flame temperature. Number concentration and primary particle size greatly increased, when the corona electrodes were located the region of soot nucleation or growth(close to burner mouth).
A Study on Pressure Distributions in a Centrifugal Compressor Channel Diffuser
Gang, Jeong-Sik ; Gang, Sin-Hyeong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 4, 2001, Pages 507~513
DOI : 10.22634/KSME-B.2001.25.4.507
Time averaged pressure distributions in a high-speed centrifugal compressor channel diffuser at design and off-design flow rates are investigated. Pressure distributions from the impeller exit to the channel diffuser exit are measured for various flow rates from choke to near surge condition, and the effects of operating condition are discussed. The strong non-uniformity in the pressure distribution is obtained over the vaneless space and semi-vaneless space caused by the impeller-diffuser interaction. As the flow rate increases, flow separation near the throat, due to large incidence angle at the vane leading edge, increases aerodynamic blockage and reduces the aerodynamic flow area downstream. Thus the minimum pressure location occurs downstream of the geometric throat, and it is named as the aerodynamic throat. And at choke condition, normal shock occurs downstream of this aerodynamic throat. The variation in the location of the aerodynamic throat is discussed.
Performance Characteristics of a V-type Probe Developed for Wall Vorticity Measurement
Kim, Seong-Uk ; Ryu, Sang-Jin ; Yu, Jeong-Yeol ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 4, 2001, Pages 514~522
DOI : 10.22634/KSME-B.2001.25.4.514
In order to investigate the relation between wall vorticity and streamwise velocity fluctuations in a turbulent boundary layer, a wall vorticity probe has been developed, which consists of two hot-wires on the wall aligned in V configuration. Although the measured intensity of spanwise wall vorticity fluctuations is somewhat lower than previous results, the intensity of streamwise wall vorticity fluctuations is in good agreement with them. It has been shown that the measured intensity of spanwise wall vorticity fluctuations is affected by transverse length of the wall vorticity probe. Instantaneous streamwise and spanwise wall vorticity fluctuations are compared with the results of DNS. Probability density function of spanwise wall vorticity fluctuations shows good agreement with previous results and is different from that of streamwise wall vorticity fluctuations. Energy spectrum of streamwisw wall vorticity fluctuations is lower than that of spanwise wall vorticity fluctuations in low frequency region.
Correlation of Wall Vorticity and Streamwise Velocity Fluctuations in a Turbulent Boundary Layer
Ryu, Sang-Jin ; Kim, Seong-Uk ; Yu, Jeong-Yeol ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 4, 2001, Pages 523~532
DOI : 10.22634/KSME-B.2001.25.4.523
A simultaneous measurement of wall vorticity and near-wall streamwise velocity fluctuations has been performed using a V-type wall vorticity probe and an I-type velocity probe to investigate the relation between them. Long-time averaged space-time correlations show that the wall vorticity is highly correlated with a turbulence structure which is tilted from the wall in the streamwise direction and that there is a streamwise vortex pair near the wall. It is shown that a structure correlated with the streamwise wall vorticity is smaller than and prior to a structure correlated with the spanwise wall vorticity. Tilting angles are obtained from the phase shift between the wall vorticity and streamwise velocity fluctuations. The tilting angle of the structure correlated with the streamwise wall vorticity is larger than that of the structure correlated with the spanwise wall vorticity. The convection velocity of the near-wall streamwise velocity fluctuations obtained from the space-time correlation is in good agreement with previous results.
A Study of Measurement and Analysis of Flow Distribution in a Close-Coupled Catalytic Converter
Jo, Yong-Seok ; Kim, Deuk-Sang ; Ju, Yeong-Cheol ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 4, 2001, Pages 533~539
DOI : 10.22634/KSME-B.2001.25.4.533
In this study, results from an experimental and numerical study of flow distribution in a close-coupled catalytic converter (CCC) are presented. The experiments were carried out using a glow measurement system. Flow distribution at the exit of the first monolith in the CCC was measured using a pitot tube under steady and transient flow conditions. Numerical analysis was done using a CF D code at the same test conditions, and the results were compared with the experimental results. Experimental results showed that the uniformity index of exhaust gas velocity decreases as Reynolds number increases. Under the steady flow conditions, flow through each exhaust pipe concentrates on a small region of the monolith. Under the transient flow conditions, flow through each exhaust pipe with the engine firing order interacts with each other to spread the flow over the monolith face. The numerical analysis results support the experimental results, and help explain the flow pattern in the entry region of the CCC.
An Experimental Study on the Flame Characteristics of the Air/
Premixed Flame Using Large Axial Mean Velocity Variation
Kim, Nam-Il ; Lee, Eun-Do ; Sin, Hyeon-Dong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 4, 2001, Pages 540~545
DOI : 10.22634/KSME-B.2001.25.4.540
Many previous researches on the premixed flame in a tube have treated the unsteady flame behaviors in which the shape, position and intensity of the flame varied, but more detail and fundamental research has been necessary. The flame stabilization condition in a tube, a unique steady state, and the unsteady behaviors, using the stabilization condition as an initial condition, were carried out in recent years. In this paper, propane-air premixed flame was stabilized in a tube and the flame behavior was observed when the mean velocity variation was imposed into the opposite direction of the initial mean velocity. The velocity variation is larger than the burning velocity and longer than the reaction time scale. During the period of the velocity variation flame is not extinguished. But after the period of the mean velocity variation the flame could be re-stabilized or be extinguished depending on the experimental conditions: equivalence ratio, period of velocity variation and magnitude of velocity variation. The extinction mechanisms were classified into the two cases, one is caused by the flame stretch in the shear layer near the wall, and the other is caused by the vortices and vortexes, which are generted by the acoustic waves.
Parametric Study of Instability in Obstructed Channel Flow
Hwang, In-Sang ; Yang, Gyeong-Su ; Kim, Do-Hyeong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 4, 2001, Pages 546~553
DOI : 10.22634/KSME-B.2001.25.4.546
A Parametric study is numerically carried out for flow fields in a two-dimensional plane channel with thin obstacles(“baffles and blocks”) mounted symmetrically in the vertical direction and periodically in the streamwise direction. The aim of this investigation is to understand how various geometric conditions influence the critical characteristics and pressure drop. A range of BR(the ratio of baffle interval to channel height) between 1 and 5 is considered. Especially when BR is equal to 3, for which the critical Reynolds number turned out to be minimal, we add blocks in the center region in order to study their destabilizing effects on the flows. It is revealed that the critical Reynolds number is further decreased by the presence of the block.
Effects of Hydrophilic Treatment by IAR Method on the Packing Characteristic Value
Kim, Jin-Ho ; Choe, Chung-Hyeon ; Gang, Byeong-Ha ; Lee, Jae-Heon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 4, 2001, Pages 554~560
DOI : 10.22634/KSME-B.2001.25.4.554
Hydrophilic treatment of the packing materials in a cooling tower has been made by the ion assisted reaction (IAR) method to increase the wettability of the packing materials. The effects of hydrophilic treatment of packing materials on the performance of a cooling tower have been investigated in a wide range of operating parameters, such as water flow rate, air flow rate, and the water inlet temperature. A pilot cooling tower has been designed and built to model a counter-flow cooling tower. The results obtained indicate that the packing characteristic value with hydrophilic packing could be substantially increased by 6∼19.3% than that with conventional packing in the operating ranges considered. The correlations of the packing characteristic value as a function of water-to-air ratio are suggested for a counter-flow cooling tower with hydrophilic packing as well as with conventional packing.
A Study on the Measurement Uncertainty of Flowmeter Calibrator
Im, Gi-Won ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 4, 2001, Pages 561~571
DOI : 10.22634/KSME-B.2001.25.4.561
The standard uncertainty of flowrate measurement is obtained by combining that of independent variables. Gravimetric and volumetric method were applied to determine the flowrate and the standard uncertainties of flowrate measurement by both methods were evaluated in accordance with the procedure recommended by International Organization for Standardization. The combined standard uncertainties of determining the flowrate were estimated from the sensitivity coefficient and the standard uncertainty of independent variables. For practical application, the methods for evaluating and expressing uncertainty in flow measurement were discussed. It was found that the uncertainties of the weighing and time measurement in gravimetric method, the volume and time measurement in volumetric method have dominant influence on that of flowrate measurement. With the quantitative analysis of the sensitivity coefficient, the contribution of the each variable uncertainty to the combined standard uncertainty of flowrate measurement is shown clearly.
A Numerical Study on a Prediction of Performance of the Metal Hydride Thermal Conversion System through the Propagation Phenomena of Superadiabatic Thermal Waves
Kim, Gyu-Jeong ; Kim, Gwan-Yeong ; Chae, Jae-U ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 4, 2001, Pages 572~582
DOI : 10.22634/KSME-B.2001.25.4.572
A method of metal-hydride thermal conversion that is an alternative to the traditional method is proposed and investigated. The unit heat pump consists of reactors of two different metal-hydrides are distributed inside parallel channels filled with porous media. The channels are blown through with a heat-transfer agent. Thermal conversion develops as a set of successive heat waves. By a numerical-modeling method it is shown that the maximum thermal effect is attained in synchronous motion of the heat wave and the heat source (or sink) that accompanies the phase transition in the succession of unit metal-hydride pumps. The results are presented in a form convenient for prediction of the thermal and energy efficiency of the proposed thermal-conversion method in real devices.
Numerical Studies on Combustion Characteristics of a Hybrid Catalytic Combustor
Hwang, Cheol-Hong ; Jeong, Yeong-Sik ; Lee, Chang-Eon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 4, 2001, Pages 583~592
DOI : 10.22634/KSME-B.2001.25.4.583
The combustion characteristics of the hybrid catalytic(catalytic+thermal) combustor with a lean methane-air mixture on platinum catalyst were investigated numerically using a 2-D boundary layer model with detailed homogeneous and heterogeneous chemistries. for the more accurate calculations, the actual surface site density of monolith coated with platinum was decided by the comparison with experimental data. It was found that the homogeneous reactions in the monolith had little effect on the change of temperature profile, methane conversion rate and light off location. However, the radicals such as OH and CO were produced rapidly at exit by homogeneous reactions. The effect of operation conditions such as equivalence ratio, temperature, velocity, pressure and diameter of the monolith channel at the entrance were studied. In thermal combustor, the production of N
O was more dominant than that of NO due to the relative importance of the reaction N
O(+M). Finally the productions of CO and NOx by amount of methane addition were studied.
A Numerical Analysis on Flows Around a Moving Body Using a Mesh Transformation Method
Kim, Tae-Gyun ; Heo, Nam-Geon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 4, 2001, Pages 593~599
DOI : 10.22634/KSME-B.2001.25.4.593
A flow analysis is performed in the present study for the moving body problem by proposing a mesh transformation method for the movement of the body in the fluid medium. Unlike other moving mesh techniques, a mesh itself is not moving but changes its property as time marches in a mesh transformation method. The flow field results are compared with those by other moving mesh technique, and showed good agreements. The movement of a floatable body in the flow field caused by the moving body is also studied in the present study by using a mesh transformation technique and a fluid/structure interaction method.
A Study on the Prediction of Self-absorption in Opposed Flames Using WSGGM-Based Spectral Model
Kim, Uk-Jung ; Viskanta, Raymond ; Gore, Jay Prabhakar ; Zhu, Xuelei ;
Transactions of the Korean Society of Mechanical Engineers B, volume 25, issue 4, 2001, Pages 600~609
DOI : 10.22634/KSME-B.2001.25.4.600
WSGGM based low-resolution spectral model for calculating radiation transfer in combustion gases is applied to estimate self-absorption of radiation energy in one-dimensional opposed flow flames. Development of such a model is necessary in order to enable detailed chemistry-radiation interaction calculations including self-absorption. Database of band model parameters which can be applied to various one-dimensional opposed flow diffusion and partially premixed flames is created. For the validation of the model and database, low resolution spectral intensities at fuel exit side are calculated and compared with the results of a narrow band model with those based on the Curtis-Godson approximation. Good agreements have been found between them. The resulting radiation model is coupled to the OPPDIF code to calculate the self-absorption of radiant energy and compared with the results of an optically thin calculation and the results of a discrete ordinates method in conjunction with the statistical narrow band model. Significant self-absorption of radiation is found for the flames considered here particularly for the fuel side of the reacting zone. However, the self-absorption does not have significant effects on the flame structure in this case. Even in the case of the low velocity diffusion flame and the partially premixed flame of low equivalence ratio, the effects of self-absorption of radiation on the flame temperature and production of minor species are not significant.