• Title/Summary/Keyword: Pressure

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A Study About Critical Flow Characteristics and the Pipeline Network Modeling of a Pressure Regulator (I) - The Influence of a Pressure Ratio - (정압기의 임계유동 특성과 배관망해석 모델링에 관한 연구 (I) - 압력비 영향 -)

  • Shin Chang Hoon;Ha Jong Man;Lee Cheol Gu;Her Jae Young;Im Ji Hyun;Joo Won Gu
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.12 s.243
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    • pp.1291-1298
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    • 2005
  • Since the interior shape of a pressure regulator is complex and the change of fluid resistance at each operation condition is rapid and big, the pressure regulator can become the major factor that causes big loss in pipelines. So the suitable pressure regulator modeling by each operation condition is important to obtain reliable results especially in small scale pipeline network analysis. And in order to prevent the condensation and freezing problems, it is needed to confirm both whether temperature recovery is achieved after passing by the pressure regulator's narrow neck and how much amount of low temperature area that can cause condensate accumulation is distributed by various PCV models at every inlet-outlet pressure ratio. In this research, the numerical model resembling P company pressure regulator that is used widely for high pressure range in commercial, is adopted as the base model of CFD analysis to investigate pressure regulator's flow characteristics at each pressure ratio. Additionally it is also introduced to examine pressure regulator's critical flow characteristics and possibility of condensation or freezing at each pressure ratio. Furthermore, the comparison between the results of CFD analysis and the results of analytic solution obtained by compressible fluid-dynamics theory is attempted to validate the results of CFD modeling in this study and to estimate the accuracy of theoretical approach at each pressure ratio too.

A Study on the Characteristic of Contact Pressure for CPB (Cold Pad Batch) Padder Roll Controlled by Hydraulic Single Cell (단일 유압 Cell로 제어되는 CPB(Cold Pad Batch)용 패더롤의 접촉압력 특성 연구)

  • Cho, Kyung-Chul;Lee, Eun-Ha;Jo, Soon-Ok;Park, Si-Woo;Hwang, Youn-Sung;Kim, Soo-Youn
    • Textile Coloration and Finishing
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    • v.29 no.2
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    • pp.86-96
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    • 2017
  • To make uniform pressure distributed over the contact surface was necessary to cold pad batch dyeing machine. In this study, to confirm characteristic of flexibility and the contact pressure distribution through experimental analysis of padder roll were controlled by hydraulic cell. When there were no load pressure only inner pressure, the value of displacement in the center of padder were greater than the end of the padder. The results of this study showed that the padder had the optimum value of inner pressure for uniform contact pressure distribution. Measuring the contact pressure in a padder system were driven by using a pre-scale film. Uniform contact pressure distribution of cell padder were a linearly with load pressure and inner pressure. When the load pressure was less than 8 tons, the inner pressure for the uniform contact pressure was 1~4 bar. The padder roll performance curves proposed in this study were available for practical production environments and various roll designs.

The Change of Children's Blood Pressure and Factors Affecting the Level of Blood Pressure In Children (아동혈압의 시계열 변화 양상 및 평균혈압에 관련된 요인 분석)

  • Suh, Il;Kim, Il-Soon;Nam, Chung-Mo;Lee, Soon-Young;Oh, Hee-Chul;Kim, Chun-Bae;Park, Eun-Cheol
    • Journal of Preventive Medicine and Public Health
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    • v.22 no.3 s.27
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    • pp.303-312
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    • 1989
  • To show the distribution and change of blood pressure according to age and to find factors affecting the level of blood pressure in primary school children, a follow-up study was conducted from 1986 to 1989 on 401 first grade children attending primary school in Kangwha County in 1986 and their parents. The blood pressure of the children was significantly increased according to age. The average annual increase was 1.8mmHg in systolic blood pressure and 2.5mmHg in diastolic blood pressure. The level of blood pressure did not show any significant difference in both sexes. Among children who were at or above the 80th percentile of blood pressure in the first grade, 35 and 30% of them have remained at the same level of systolic and diastolic blood pressure respectively in the fourth grade. But we could not find any significance in the tracking of blood pressure of children who were at or above the 90th percentile of blood pressure in the first grade. Weight and pulse rate were shown to be significant factors affecting systolic blood pressure in children of both sexes and mother's blood pressure and skinfold thickness were also affected systolic blood pressure in girls. The variables significantly affecting diastolic blood pressure were arm circumference and pulse rate for boys and height and pulse rate for girls.

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A Study on Fluctuating Pressure Load on High Speed Train Passing through Tunnels

  • Seo Sung-Il;Park Choon-Soo;Min Oak-Key
    • Journal of Mechanical Science and Technology
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    • v.20 no.4
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    • pp.482-493
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    • 2006
  • The carbody structure of a high speed train passing through a tunnel is subjected to pressure fluctuation. Fatigue strength of the carbody structure against the fluctuating pressure loading should be proved in the design stage for safety. In this study, to get the useful information on the pressure fluctuation in the tunnel, measurement has been conducted during test running of KHST on the high speed line for two years. The measured results were analyzed and arranged to be used for carbody design. A prediction method for the magnitude and frequency of pressure change was proposed and the propagating characteristics of pressure wave was investigated. By statistical analysis for the measured results, a pressure loading spectrum for the high speed train was given. The proposed method can also be used to estimate the pressure loading spectrum for new high speed line at design stage combined with the results of train performance simulation.

The Lateral Earth Pressure on Braced Cut Walls Considering Subsoil Condition in Korea (국내 지반조건을 고려한 흙막이 백제에 작용하는 토압)

  • Chae, Young-Su;Moon, Il
    • Proceedings of the Korean Geotechical Society Conference
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    • 1994.09a
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    • pp.129-138
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    • 1994
  • It is well recognized that accurate analysis of lateral earth pressure is very signficant factor which determines the design amount of braced cut walls and braced systems. Many researchers, Peck, Terzaghi-Peck and so on, make a study about lateral earth pressure to act on the flexible walls. But these studies trouble accurate to multy layered systems like inland areas in Korea. This study is compared with the field messurement data to estimate the earth pressure distributions in multy layered areas and the empirical earth pressure distributions. The conclusions are as follows : At final excavation depth, the lateral earth pressure which messured by field instrument is smaller than the empirical earth pressure. (About 1.85~5.32 times). In the case of considering the soft rock layer to the final excavation depth, the messured earth pressure is safe to be compared with empirical earth pressure. The messured earth pressure distributions are like that the upper soil layer is small the middle soil layer is large, the rock mass layer is very small.

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The change of spray characteristics on hydraulic acoustic wave influence and prediction of low combustion instability (수력파동에 의한 분무변화 및 저주파 연소불안정에의 영향 예측)

  • Kim, Tae-Kyun;Lee, Sang-Seung;Yoon, Woong-Sup
    • 한국연소학회:학술대회논문집
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    • 2004.11a
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    • pp.152-160
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    • 2004
  • Studies to investigate the influence on hydraulic acoustic wave were conducted using pressure swirl atomizer under making frequency range from 0 to 60Hz using water as a propellant. Pressure oscillation from hydraulic sources gives a strong influences on atomization and mixing processes. The ability to drive these low frequency pressure oscillations makes spray characteristics changeable. The effect of pressure perturbation and its spray characteristics showed that low injector pressure with pressure pulsation gives more significantly than high injector pressure with pressure perturbation in SMD, spray cone angle, breakup length. Moreover, this data could be used for prediction of low combustion instability getting G factor.

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Pressure Locking and Thermal Binding Analysis of the RHR Motor Operated Valve (잔열제거계통 모터구동밸브의 압력잠김 및 열고착 현상 분석)

  • Song, Eun-Sil;Kim, Tae-Il;Lee, Kwang-Nam
    • Proceedings of the KSME Conference
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    • 2001.06d
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    • pp.630-635
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    • 2001
  • The stem thrust required to unwedging a gate valve is influenced by the pressure and temperature when the valve is closed and by the changes in these conditions between closure and opening. "Pressure Locking" and "Thennal Binding" refer to situations where pressure and temperature effects cause the unwedging load to be much higher than normal. A model of these phenomena has been developed. The effects of pressure and temperature are analyzed to determine the change in this disk-to-seat "interference". Flexibilities or Stiffness of the disk and body strongly influence the unwedging thrust. Calculation and limited comparison to data have been performed for the RHR motor operated valve designs and scenario. Pressure changes can increase the unwedging thrust when bonnet pressure exceeds the pressure in the adjacent piping and temperature changes can increase the unwedging thrust when a temperature change after closure produces an increase in the disk-to-seat interference.

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Numerical study of compression waves passing through two-continuous ducts (두 연속 덕트를 전파하는 압축파의 수치해석적 연구)

  • Kim, Hui-Dong;Heo, Nam-Geon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.6
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    • pp.823-831
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    • 1998
  • In order to investigate the impulsive noise at the exit of high-speed railway tunnel and the pressure transients inside the tunnel, numerical calculations using a Total Variation Dimishing difference scheme were applied to axisymmetric unsteady compressible flow field. Some compression wave forms were assumed to model the compression wave produced in real high-speed railway tunnel. The numerical data were extensively explored to analyze the peak over-pressure and maximum pressure gradient in the pressure wavefront. The effect of the distance and cross-sectional area ratio between two-continuous ducts on the characteristics of the pressure waves were investigated. The peak over-pressure inside the second duct decreases for the distance and cross-sectional area ratio between two tunnels to increase. The peak over-pressure and maximum pressure gradient of the pressure wavefront inside the second duct increase as the maximum pressure gradient of initial compression wave increases. The present results were qualitatively well agreed with the results of the previous shock tube experiment.

The Analysis of Fluid Pressure in Polybutylene Piping System (PB 배관에서의 유체압력에 관한 연구)

  • Lee Yong-Hwa
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.18 no.1
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    • pp.17-23
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    • 2006
  • This study is to investigate the pressure wave characteristics and the maximum pressure rise generated by instantaneous valve closure at the end of the straightening polybutylene piping system. Experiments were conducted under the following conditions: initial pressure $1\~5$ bar, flow velocity $\~0.5-3.0m/s$ and water temperature $25^{\circ}C$. Results indicated that the peak pressure generated by quick valve closure reached Joukowsky's value. We also found that the maximum pressure rise and the pressure history depended on not only initial steady pressure but also flow velocity.

Experimental Study on the Exhaust Pressure Charactieristics in the small motorcycle. (소형 이륜자동차의 머플러 배기압력 특성에 관한 실험적 연구)

  • Yi, C.S.;Choi, S.C.;Bae, J.Y.;Chung, H.S.;Jeong, H.M.;Suh, J.S.
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.678-683
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    • 2004
  • In this study, a experiment has been developed for measuring the exhaust pressure of muffler at inlet and outlet. The main experimental parameters were a engine speed and sound absorbing material in the muffler. The muffler sound absorbing material tested a steel wool and glass wool. The exhaust pressure was measured with pressure sensor. The phase of exhaust pressure with high speed was moved according to increasing engine speed comparing with exhaust pressure with low speed. Also, the distribution of exhaust pressure at the model-1, 2 and 3 are similar with distribution of exhaust pressure at muffler inlet.

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