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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
Journal Basic Information
Journal DOI :
The Korean Society of Mechanical Engineers
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Volume & Issues
Volume 22, Issue 7 - Jul 1998
Volume 22, Issue 6 - Jun 1998
Volume 22, Issue 5 - May 1998
Volume 22, Issue 4 - Mar 1998
Volume 22, Issue 3 - Mar 1998
Volume 22, Issue 2 - Feb 1998
Volume 22, Issue 1 - Jan 1998
Volume 22, Issue 10 - 00 1998
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수직평판 사이를 흐르는 두 점성 유체의 밀도차에 의한 새로운 계면의 불안정성 연구(II) -수치적 비선형 연구-
이철우 ; 주상우 ; 이상천 ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 10, 1998, Pages 1349~1349
DOI : 10.22634/KSME-B.19220.127.116.119
A nonlinear evolution of the interface is observed when two vertical fluid layers of different densities flow between two parallel vertical plates. The existence of Rayleigh-Taylor instability, the effects of the density ratio and total flow rate in the vertical stratified flow are studied. An exact location of the interface is described by Spectral method and Fourier coefficients are recorded to check the evolution of the interface.
온도 보상을 고려한 전달 시간차 방식 초음파 공기 유량계의 개발
황재석 ; 김중일 ; 고상근 ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 10, 1998, Pages 1359~1359
DOI : 10.22634/KSME-B.1918.104.22.1689
In this study, a transit time type ultrasonic flow meter was developed to measure the volumetric air flow rate in a circular tube. To accomplish a high sampling rate, the ultrasonic wave was transm itted and received continuously. The calibration of transit time of the ultrasonic wave with temperature variation is not easy because of the bound effect of the ultrasonic beam at the tube wall. And so, a sound absorbing material was used at the inner surface of the flow meter to reduce ultrasonic echo. And Two sets of ultrasonic sensors were used to measure the flow rate, and the temperature compensation circuit was developed to acquire the flow rate which is not affected by the air temperature.
이산재료 가열공정용 수평채널에서의 혼합대류열전달
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 10, 1998, Pages 1368~1368
DOI : 10.22634/KSME-B.1922.214.171.1248
Mixed convection in a horizontal channel loaded with discrete material and equipped with a top exhaust is studied experimentally and numerically. Experimental measurements are compared with numeric al predictions to validate the two-dimensional numerical model. The observed steady flow is two-dimensional while unsteady convection, triggered at a critical Richardson number, is highly three-dimensional. Measured temperatures and those predicted with a two-dimensional numerical model are in good agreement. Because the steady convection is two-dimensional, the two-dimensional model performs well in predicting temperatures within the system. Even in unsteady three-dimensional flow, the numerical predictions are close to the measured time-mean air and plate temperatures. The model, however, underestimates the critical Richardson number which indicates the onset of the thermally-induced transition to unsteady convection.
전폐형 유도전동기의 프레임 열전달계수에 미치는 유동각의 영향에 관한 연구
윤명근 ; 전창성 ; 고상근 ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 10, 1998, Pages 1378~1378
DOI : 10.22634/KSME-B.19126.96.36.1998
Computer modelling is increasingly used as a design tool, which requires more detailed input data for heat transfer coefficients in various regions of the induction motor. But there are few papers about frame, the main heat transfer surface. The experiments were performed with a carbon coated paper, uniform halt flux generating material. The frame heat transfer coefficients and its correlation equations were obtained with flow rate and rotational direction of cooling fan. The flow angle had an important effect on the frame heat transfer and the maximum heat transfer was existed at some point of it. The results can be used for the cooling fan design as well as thermal analysis program of induction motor.
석유 팬 히터의 연소실 주변 압력 분포 특성
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 10, 1998, Pages 1389~1389
DOI : 10.22634/KSME-B.19188.8.131.529
This paper was studied to understand the characteristics of surface pressure distributions around a circular combustion chamber within the heat-intercept duct of kerosene fan heater. The experiment was carried out in the heat-intercept duct of kerosene fan heater attached to the blow-down-type subsonic wind tunnel with a test section of 240 [mm] × 240 [mm] × 1200 [mm] in condition of the flowrate Q = 2.903, 3.456, 3.94 [m3/min] respectively. Also the drag coefficient and the lift coefficient were obtained from these surface pressure distributions. The purpose of this paper was to determine the position of the air-supply holes for a secondary combustion in order to prohibit unstable flame and local heat concentration on the combustion chamber. Consequently it was found that ( i ) the positive surface pressure distributions occurred in the range of θ = 330°∼90°, but the negative surface pressure distributions occurred in the range of θ = 255°∼340° due to the arrangement between axial fan and the position of surface pressure measurement in the heat-intercept duct when axial fan rotated clockwise, and ( ii ) the optimum position of the air-supply holes for secondary combustion chamber corresponded to the range of θ = 45°∼105° within the height of H = 40 mm under the condition that the flame did not reach on the inner part of a circular combustion chamber directly.
암시적 VOF 방법을 이용한 주조공정의 충전과정 해석
김우승 ; 권용복 ; 임익태 ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 10, 1998, Pages 1400~1400
DOI : 10.22634/KSME-B.19184.108.40.2060
In this paper, the well-known VOF method is implicitly modified to analyze the casting process. This modified method incorporated into SIMPLER algorithm is applied to the mold filling analysis in t wo-dimensional cavity casting process. The phase change analysis including the effect of residual flow after the completion of filling has also become performed. The results from the present method are compared with those of the explicit and implicit SOLA-VOF methods to examine the accuracy and efficiency of the present method. The results show that the present method is more efficient than the other two methods in the computational tune. It is also shown that the present method is superior to the SOLA-VOF method in the view of symmetry. The results also indicate that the mushy region is significantly influenced by the residual Bow at the initial slam of solidification.
비압점성유동 해석을 위한 비정렬 유한체적법
강동진 ; 배상수 ; 주상우 ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 10, 1998, Pages 1410~1410
DOI : 10.22634/KSME-B.19220.127.116.110
A flexible and accurate unstructured finite volume method is presented for two dimensions incompressible flows. It allows a mesh of arbitrary polygons, and a higher order upwind scheme, a modified QUICK, is used to discritize the convective terms in the momentum equations. All dependent variables, velocity components and pressure, are stored at the same grid point. A pressure equation is derived from the continuity equation. Present method is validated through calculation of several laminar and turbulent flows. All turbulent flows arc calculated with Baldwin-Lomax model. All numerical solutions show good agreement with previous experiment and/or numerical solutions. Triangular mesh shows better prediction, in terms of accuracy and convergence speed, over quadrilateral mesh in general, and this improvement is believed to come from accurate calculation of flux crossing the control volume
4-밸브 엔진실린더내 연소전 텀블측정 및 거동해석
이진욱 ; 강건용 ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 10, 1998, Pages 1422~1422
DOI : 10.22634/KSME-B.1918.104.22.1682
Many researches have been studied on in-cylinder flow as one of dominant effects for an engine combustion. Specially because the combustion flame speed is mainly determined by the turbulence at the end of compression process, the control of charge air motion inside a cylinder by changing intake system design is very important. This paper describes experimental results of the tumble flow measurement inside the cylinder of 4-valve single cylinder transparent engine using laser Doppler velocimetry. The three intake port configurations and compression ratio were selected for changing the intake tumble motion and turbulence intensity at the compression process. This study are done with some tumble analysis parameters. Averaging tumble velocity, tumble moment, tumble area ratio and eccentricity of tumble center were used as non-dimensional parameters to analyze tumble flow structure behavior during intake and compression process. It was found that there is a correlation between the tumble flow during induction and the turbulence levels at the end of compression process
분사각도변화에 따른 단일 막냉각홀 주위에서의 열/물질전달 및 막냉각효율 특성
이동호 ; 김병기 ; 조형희 ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 10, 1998, Pages 1433~1433
DOI : 10.22634/KSME-B.1922.214.171.1243
The present study investigates local heat transfer coefficients and film cooling effectiveness around a film cooling hole with compound angle orientations entering a cross flow. The film cooling je t is injected through a single hole inclined at 30° to the surface and laterally from 0° to 90° for the blowing rates of 0.5, 1.0 and 2.0. The naphthalene sublimation technique has been employed to determine both local heat/mass transfer coefficients and local adiabatic wall (impermeable wall) film cooling effectiveness near the injection hole. The two parameters are obtained from separate tests using pure air and naphthalene saturated air injections. The results indicate that the injected jet protects the surface effectively at low blowing rates and spreads more widely with the compound angle injections than with the axial injection. However, the film cooling effectiveness is low and the surface area protected by the injected jet is narrow at the high blowing rate.
층류 확산화염에서의 PAH 및 매연생성에 대한 압력의 영향
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 10, 1998, Pages 1445~1445
DOI : 10.22634/KSME-B.19126.96.36.1995
The effects of pressure on PAH and soot formation process in diffusion flames have been experimentally studied. The co-flow burner was housed in a high pressure chamber with optical access. A serie s of ethylene, ethane and propane laminar diffusion flames were studies utilizing a laser light extiction and scattering method for the integrated soot volume fraction and a broad-band LIF technique for the PAH concentration. Increasing operating pressure the soot formation process is enhanced while the soot oxidation process is suppressed, and therefore, soot particles are emitted eventually from a tip of the flame. The pressure dependence of-the soot formation process is greater for earlier residence times, and it was insensitive to the fuel tested in this study(ethylene, ethane and propane). The maximum soot yield appears to be a determining factor for the pressure dependence of the soot formation process. The greater sensitivity was observed when soot yield was less. The PAH concentration increases with pressure, and the pressure dependence of the PAH formation process is greater than that of the soot formation process. The peak soot volume fraction and the peak PAH concentration increases as ∼Pn, where n values are 1.7-2.25 for the soot volume fraction and 2.5 for the PAH concentration. This result implies that the PAH formation and particle inception steps in soot formation are more sensitive to operating pressure than the subsequent surface growth process.
외경 9.52mm 평활관 및 미세핀관내 R22와 R410A의 증발열전달 특성
김만회 ; 신정섭 ; 임병한 ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 10, 1998, Pages 1454~1454
DOI : 10.22634/KSME-B.19188.8.131.524
An experimental investigation of evaporating heat transfer in 9.52mm horizontal copper tubes was conducted. The refrigerant tested were R22 and near-azeotropic mixture, R410A. The test rig had a st raight, horizontal test section with an active length of 0.92m and was heated by the heat transfer fluid(hot water) circulated in a surrounding annulus. Constant heat flux of 11.0kW/m2 was maintained and refrigerant quality varied from 0.2 to 0.8. The results were reported for evaporation at 15℃ in a 0.92m long test section for 30∼60kg/h mass flow rate. The local and average heat transfer coefficients for seven microfin tubes were presented compared to those for a smooth tube. The average evaporation heat transfer coefficients of R22 and R410A for the microfin tubes were 86∼227% and 64∼199%, respectively, higher than those for the smooth tube. When compared to R22 at the same test conditions, the evaporating heat transfer coefficients for R410A were 97∼129% of R22.
외경 9.52mm 평활관 및 미세핀관내 R22와 R410A의 응축열전달 특성
김만회 ; 신정섭 ; 임병한 ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 10, 1998, Pages 1465~1465
DOI : 10.22634/KSME-B.19184.108.40.2065
An experimental investigation of condensation heat transfer in 9.52mm horizontal copper tubes was conducted using R22 and R410A. The test rig had a straight, horizontal test section with an active length of 0.92m and was cooled by the heat transfer fluid(cold water) circulated in a surrounding annulus. Constant heat flux of 11.0kW/m2 was maintained throughout the experiment and refrigerant quality varied from 0.9 to 0.1. The condensation test results at 45℃ were reported for 40∼80 kg/h mass flow rate. The local and average condensation coefficients for seven microfin tubes were presented compared to those for a smooth tube. The average condensation coefficients of R22 and R410A for the microfin tubes were 1.7∼3.19 and 1.7∼2.94 times larger than those in smooth tube, respectively.
수정 k-ε 모델에 의한 실제 L-형 리블렛의 항력저감 성능예측
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 10, 1998, Pages 1475~1475
DOI : 10.22634/KSME-B.19220.127.116.115
A low-Reynolds-number k-ε turbulence model is applied to predict drag reduction performance for actual L-shaped (blade-type) riblets with finite-thickness in fully-developed flows between i nfinite parallel planes. The present turbulence model is a modified version of the Launder & Sharma''s k-ε model (LS model), in which the gradient production term in ε-equation is modeled to have only the normal derivative terms. The present predictions for drag reduction behavior such as the maximum drag reduction and effects of riblets on turbulence quantities are in good agreement with both the experiments and the recent DNS results: differences in the mean velocity profile and turbulent quantities are found to be limited to the riblet cavity region. Turbulence quantities are also reduced in drag-reducing configurations. Possible shortcomings in the present model using an isotropic turbulent viscosity are also discussed particularly with reference to the absence of any turbulence-driven Secondary motions.
난류확산계수의 수정에 의한 Euerian 확산모델의 개선
김현구 ; 이정묵 ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 10, 1998, Pages 1483~1483
DOI : 10.22634/KSME-B.1918.104.22.1683
In the present article, an improvement of the Eulerian dispersion model based on the gradient diffusion theory (K-theory) by modifying the turbulent diffusivity is presented. The time-dependent eff ective turbulent diffusivity expressed in terms of the Lagrangian time-scale is adopted from the statistical diffusion theory to correct the well-known failure of gradient diffusion theory close to a source in turbulent flow. The modified dispersion model is applied to the dispersion from an elevated continuous source within a turbulent boundary layer on a flat floor. The predicted results of mean concentration field are compared with the associated experiments. It is validated that improvement of the numerical prediction by the modified model in the near vicinity of a source can be achieved.
복잡한 삼차원 형상의 근사적 열해석을 위한 CAD와 열등가회로의 연계
정진수 ; 고상근 ; 유호선 ;
Transactions of the Korean Society of Mechanical Engineers B, volume 22, issue 10, 1998, Pages 1490~1490
DOI : 10.22634/KSME-B.1922.214.171.1240
As a candidate among approximate thermal analyses for complex three-dimensional geometries, attempted is coupling of the thermal network method with a CAD technique. Based on a solid modeling CAD c ombined with the boundary representation, not only thermal regions which describe the system configuration with combinations of primitive geometric elements are generated effectively, but thermal resistances needed for constructing thermal network are also evaluated automatically. The developed method is applied to the thermal analysis of a typical totally-enclosed, fan-cooled induction motor. A representative predicted result, the axial temperature distribution in the motor, agrees favorably with the previously reported experimental data. In addition, this approach facilitates to delineate the overall energy flow of the motor under consideration, which can hardly be obtained from experimental measurements. The proposed method turns out to be an efficient and reliable tool for analyzing complicated thermal systems roughly but quickly.