유압관로내의 동특성을 이용한 비정상 유량계측에 관한 연구

이홍구,윤석주,박성규,박길문 朝鮮大學校 機械技術硏究所 1998 機械技術硏究 Vol.1 No.1

This paper describes an approach for estimating the unsteady flowrate through a hydraulic pipe lines and a components in real time. Concerning the dynamic characteristics of a hydraulic pipe lines, experimental research from the view point of focusing on the unsteady flowrate through a pipe is insufficient because of the lack of adequate flowmeters. In this experiment, a new instantaneous flowrate measurement system making use of a sharp-edged cylindrical choke and LDV has been proposed and developed by the authors. The unsteady flowrate is obtained from the measurements center-line velocity of a circular pipe using LDV and the pressure difference using a sharp-edged cylindrical choke, and experiments on the frequency characteristics are carried out. The results show a good agreement between the estimated and directly measured flowrate waveforms illustrates the validity of the method proposed here.

90˚ 曲管에서 振動流의 流動特性에 關한 實驗的 硏究

朴吉文,羅基大 조선대학교 생산기술연구소 1985 生産技術硏究 Vol.7 No.2

The pressure distribution, the velocity profiles, and the seperation of steady flows and oscillatory flows in 90 degree curved tubes were studied experimentally. The variables for curvature ratio (a/R), Reynolds number(Re), Dean nurnber(De), frequency parameter (α), and amplitude ratio(K) have been determined. The experimental results are abtained as follows : (1) The peripheral pressure distributions show the maximum near the inside wall of the tested curved tubes. (2) The maximum velocity of the horizontal plane is near the outside wall and that of vertical plane is both outside wall of the tested curved tubes. (3) The pressure distributions of oscilatory flows is higher than that of steady flows. (4) The maximum pressure is the frequency parameter of about 15 for oscillatory flows.

원형관로내 층류 맥동유동의 속도와 압력 분포에 관한 연구

박길문,유영태,위광환,이충주,정지철 조선대학교 생산기술연구소 1996 生産技術硏究 Vol.18 No.2

In this study basic equations for the pulsatile laminar flow in a circular rigid pipe containing a slightly compressible fluid are derived and analytical solutions for the distributions of wave propagation factor K, cross-sectional mean velocity u_(m) and pressure P are schematically developed and confirmed experimentally. The pulsatile flow with 0 ≤ f ≤ 48Hz and 0 ≤ Re ≤ 2500 generated by summing the oscillatory flow made by ball valve into steady one. The wave form of pulsatile flow is described as a longitudinal wave and particle velocities measured experimentally are group velocities of the wave packet which are always smaller than phase velocities which are approximate to the sonic velocity C when the radial dispersion and wall friction are negligible. Therefore wave number is approximated to k = ω/c for high angular velocity region. The axial pressures and centerline velocities were measured by strain-gage type pressure transducers and Pito-static tubes, respectively. The cross-sectional mean velocities calculated from centerline velocities with the parabolic distributions of the laminar flow and confirmed by using the ultrasonic flowmeter. We knew that axial distributions of oscillatory velocity and pressure coincide with thoeretical and depend on the Reynolds number and angular velocity.

기체 방사성 물질 제거를 위한 첨착 활성탄 필터 시스템 성능에 관한 연구

김대욱,손현철,이명석,이석범,박길문 朝鮮大學校 機械技術硏究所 1999 機械技術硏究 Vol.2 No.1

This paper presents an application of impregnated activated carbon and impregnated activated carbon filters. They are used for the removal of gaseous radioactive materials at radioactive material handling facilities such as nuclear power plants and research facilities. High adsorption efficiencies as well as stability are required for them to remove hazardous radioactive gases such as activated free iodine released during normal operation or accident condition. This research was initiated to enhance the independence of nuclear industry and raise the level of nuclear technology to that of the leading nuclear nations. By attaining the capability of design and development of HVAC system, national technological competitiveness can be achieved. Also, the ground for technology export will be hardened. Therefore, it is well timed to initiate the project to develope those filter systems domestically utilizing all the relevant technologies available.

180。 정사각단면 곡관덕트의 입구영역에서 층류 비정상유동의 유동특성에 관한 연구 ( A Study on Flow Characteristics of Laminar Unsteady Flows in Square-section 180。 Curved Duct )

박길문,조병기 대한기계학회 1994 대한기계학회 춘추학술대회 Vol.- No.-

曲管部 뒤에 이어진 直管部의 流動現象에 對한 考察

朴吉文 조선대학교 생산기술연구소 1978 生産技術硏究 Vol.1978 No.-

Flow phenomena in straight parts after helically coiled capillary tubes is studied experimentally. Coiled capillary copper tubes are 1.7mm I.D and 942mm length, and then experimental curvature ratio are d/D =O.0340(D×n=50mm×6 turns), 0.0170(100×3), O.0057(300×1). The Secondary flow was attributed of the effect of the centrifugal pressure gradient in the main flow of coiled tubes, and these variations are due to the oscillatory changes in the secondary circulation discovered here. Since the damping effect of viscous and main flow on the oscillation is large, it tends to decrease the period. The secondary circulation was sometime disappeared in the straight regions after coiled capillary tubes. The experimental results with water agreed with White formula in the laminar rigions and Ito formula in the Tubulent regions.

4각덕트의 입구영역에서 난류진동유동의 유동특성에 관한 연구

박길문,조병기,고영하 조선대학교 동력자원연구소 1996 動力資源硏究所誌 Vol.18 No.1

The flow characteristics of developing turbulent oscillatory flow are investigated experimentally in the entrance region of a square duct (40 ㎜ X 40 ㎜ and 4,000 ㎜). Experimental results of mean velocity profiles, turbulence intensity and entrance length are measured by using a hot-wire anemometer system together with data acquisition and processing systems. For turbulent oscillatory flow, the turbulent components in the velocity waveforms increase as the dimensionless transverse position approaches the wall. Velocity distribution are not change fully developed region. Inflow and outflow are nearly symmetrical form in the fully developed region such as x/D_h≥40. Turbulence intensity increases as the dimensionless transverse position increases from the center to the wall of the duct, and is slightly smaller in the accelerating phase than in the decelerating phase for the developing turbulent oscillatory flows. The entrance length of the turbulent oscillatory flow is about 40 times as large as the hydraulic diameter in the present experimental conditions.

직관덕트내에서 정상유동, 진동유동과 맥동유동의 임계레이놀즈수에 관한 연구

박길문,봉태근 한국마린엔지니어링학회 1998 한국마린엔지니어링학회지 Vol.22 No.1

The critical reynolds number in a square-sectional straight duct is investigated experimentally. The experimental study for the air flow in a square-sectional straight duct is carried out to calssify critical Reynolds number on steady flow and unsteady flow. To calssify the critical Reynolds number we obtained velocity waveform by using a hot-wireanemometer and data acquisition system with photocorder.

정사각단면 $180^{\circ}$ 곡관덕트의 입구영역에서 비정상층류유동의 유동특성에 관한 연구

박길문,모양우,조병기,Park, G.M.,Mo, Y.W.,Cho, B.K. 대한의용생체공학회 1996 의공학회지 Vol.17 No.4

The flow characteristics of developing unsteady laminar flow in a square-sectional $180^{\circ}$ curved duct are experimentally investigated by using laser doppler velocimerty (LDV) system with data acquisition and processing system of rotating machinery resolver(RMR) and PHASE software. The major flow characteristics of developing laminar pulsating flows are presented by mean velocity profilel velocity distribution of secondary flow, wall shear stress distributions, entrance lengths according to dimensionless angular frequency($\omega^+$), velocity amplitude ratio($A^1$), and time-averaged Dean number($De_ta$). The velocity profiles and wall shear stress distribution of laminar pulsating flow with dimensionlessangular frequency show the flow characteristics of the quasi-steady laminar flow in a curved duct. The developing region of laminar pulsatile flows in a square-sectional $180^{\circ}$ curved duct is extended to the curved duct angle of approximately $120^{\circ}$ under the present experimental condition.

정사각단면 $180^{\circ}C$ 곡덕트에서 층류진동유동의 유동 특성에 관한 연구

박길문,조병기,봉태근,Park, Gil-Mun,Jo, Byeong-Gi,Bong, Tae-Geun 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.2

In the present study, the flow characteristics of developing laminar oscillatory flows in a square -sectional 180 deg. curved duct are investigated experimentally. The experimental study using air in a square-sectional 180 deg. curved duct is carried out to measure velocity distributions with a data acquisition and LDV (Laser Doppler Velocimetry) processing system. In this system, Rotating Machinery Resolver (RMR) and PHASE program are used to obtain the results of unsteady flows. The major flow characteristics of developing oscillatory flows are found by analyzing velocity curves, mean velocity profiles, time-averaged velocity distribution of secondary flow, wall shear stress distributions, and entrance lengths. In a lower dimensionless angular frequency, the axial velocity distribution of laminar oscillatory flow in a curved duct shows a convex shape in a central part and axial symmetry. The maximum value of wall shear stress in a lower dimensionless angular frequency is located in an outside wall, but according to increasing the dimensionless angular frequency, the maximum of wall shear stress is moved to inner wall. The entrance lengths of laminar oscillatory flows in a square-sectional 180 deg. curved duct is obtained to 90 deg. of bended angle of duct in this experimental conditions.