• Title/Summary/Keyword: Multi-Pressure

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Study on a Multi-pipe Water Hammer Phenomenon by using CFD of Rapid Valve Closing (전산유체해석(CFD)을 이용한 밸브의 급폐쇄에 따른 다중 배관 수격 현상에 관한 연구)

  • Park, No-Suk;Kim, Seong-Su;Kang, Moon-Sun;Choi, Jong-Woong
    • Journal of Korean Society of Water and Wastewater
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    • v.27 no.4
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    • pp.479-487
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    • 2013
  • This study was to investigate characteristics for the pressure wave propagation and the maximum pressure near a rapid closure valve which was installed the end of multi piping network. The multi piping network consists of one inlet and three outlet with straight pipes. The diameter of the pipes including the valve was 100 mm, 80 mm, 80 mm respectively. The valve was rapidly closed with the instantaneous time which was 0.023s in the level for the water hammer. For the simulation, the influence of the pipe thickness and deformation due to pressure-wave-propagation was not considered. CFD was conducted under the following condition : the initial pressure was 1bar in the inlet and the mass flow rate was 7.83 kg/s in the outlet(the velocity in the pipe with 100 mm diameter was 1 m/s). As the valve have conditions that were status with and without fluid flow in the pipe after valve closing, the maximum pressure change and the frequency analysis were examined. As the results, the case that was status with fluid flow appeared the higher maximum pressure than another's, the maximum frequency band was about 10 ~ 11 Hz.

Optimum design of direct spring loaded pressure relief valve in water distribution system using multi-objective genetic algorithm (다목적 유전자 알고리즘을 이용한 상수관망에서 스프링 서지 완화 밸브의 최적화)

  • Kim, Hyunjun;Baek, Dawon;Kim, Sanghyun
    • Journal of Korean Society of Water and Wastewater
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    • v.32 no.2
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    • pp.115-122
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    • 2018
  • Direct spring loaded pressure relief valve(DSLPRV) is a safety valve to relax surge pressure of the pipeline system. DSLPRV is one of widely used safety valves for its simplicity and efficiency. However, instability of the DSLPRV can caused by various reasons such as insufficient valve volume, natural vibration of the spring, etc. In order to improve reliability of DSLPRV, proper selection of design factors of DSLPRV is important. In this study, methodology for selecting design factors for DSLPRV was proposed. Dynamics of the DSLPRV disk was integrated into conventional 1D surge pressure analysis. Multi-objective genetic algorithm was also used to search optimum design factors for DSLPRV.

A Study of Human Gait Discrimination Using Multi-pressure Sensor (다중압력센서를 이용한 보행패턴 추정에 관한 연구)

  • Choi, Dae-Yeong;Kim, Kyung-Ho
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.65 no.4
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    • pp.673-677
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    • 2016
  • In this study, In order to measure foot pressure, it makes analyzing device using multi-pressure sensor. This device was limited frequency band to 5Hz by using low-pass filter and MCU was detected signal every milliseconds. After wearing the device, the result was confirmed by blue-tooth to measure wirelessly. Also, we propose an algorithm to obtain the walking pattern using a time table in each of the detected peak from the pressure sensor. Using the algorithm, right walking pattern and abnormal pattern was detected. The results can be reflected more individual walking patterns than when using a conventional methods and also, developed device was no restriction on the human activity.

The Study on Workload Reducing Effects of Multi-Elastic Insoles (다탄성 Insole의 Workload 감소 효과에 관한 연구)

  • Lee, Chang-Min;Lee, Kyun-Deuk;Oh, Yeon-Ju;Kim, Jin-Hoon
    • Journal of the Ergonomics Society of Korea
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    • v.26 no.2
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    • pp.157-165
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    • 2007
  • The Work-Related Musculoskeletal Disorders (WMSDs) can be occurred by various factors such as repetition, forceful exertions and awkward postures. Especially, occurrences of the WMSDs on the waist and lower limb are reported in workplaces, demanded standing postures for a long time, in service and manufacturing industry. The static and standing postures without movement for a long time increase work loads to the lower limb and the waist. Accordingly, anti-fatigue mat or anti-fatigue insole is used as a preventing device of the WMSDs. However anti-fatigue mats are limited in space and movement. In this study, multi-elastic insoles are designed and shown the effects of the workload reduction for a long time under the standing work. The foot pressures and EMG (Electromyography) are measured at 0 hour and after 2 hours by 6 health students in their twenties. The 6 prototype insoles are designed with three elastic (Low, Medium and High). These insoles are compared with no insole (insole type 7) as control group. The EMG measurement was conducted to waist (erector spinae muscle), thigh (vastus lateralis muscle) and calf (gastrocnemius muscle). The foot pressure is analyzed by mean pressure value and the EMG analysis is investigated through MF (Median Frequency), MPF (Mean Power Frequency) and ZCR (Zero Crossing Rate). The results of the foot pressure show that the multi-elastic insoles had smaller foot pressure value than that of no-insole. Moreover, Insole 2 and Insole 3 have the smallest increasing rate in foot pressure. The EMG results show that the multi-elastic insoles had smaller EMG shift value than that of no-insole in 2 hour, and then shift value shows the smallest value in Insole 2. Therefore, this study presents that the multi-elastic insoles have reducing effects of the work load for a long time standing work in both side of foot pressure and EMG.

Effect of the Boost Pressure on Thermal Stratification on HCCI Engine Using Multi-Zone Modeling (Multi zone Modeling을 이용한 흡기관내의 과급이 온도성층화를 갖는 예혼합압축자기착화엔진에 미치는 영향에 관한 연구)

  • Kwon, O-Seok;Lim, Ock-Taeck
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.33 no.4
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    • pp.248-254
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    • 2009
  • The HCCI engine is a next generation engine, with high efficiency and low emissions. The engine may be an alternative to SI and DI engines; however, a pressure rise rate is a major limitation for high load range and power reduction. Recently, we were able to reduce the pressure rise rate using thermal stratification. Nevertheless, this was insufficient to produce high power. In this study, the reduction of the pressure rise rate using thermal stratification was confirmed and the HCCI engine power was increased using the boost pressure. The rate and engine power were produced by CHEMKIN and modified SENKIN. As a result of increasing the boost pressure, a higher IMEP was attained while the pressure rise rate increased only slightly in the HCCI with thermal stratification.

Rotordynamic Characteristics of High Pressure Multistage Pump (고압 다단펌프 축계 진동 특성 고찰)

  • Song, Ae Hee;Song, Jin Dae;Lim, Woo Seop;Yang, Bo Suk
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2012.10a
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    • pp.592-596
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    • 2012
  • This paper presents numerical analysis result of rotor-bearing system of a multi-stage high pressure pump. Especially resonance possibility, stability and damping factor are estimated for a selected commercial multi-stage high pressure pump. The result shows that it is not easy to avoid resonance of rotor-bearing system against main excitation forces which are residual unbalance force and pressure pulsation. This makes damping effect be more important.

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A Study on Measuring the Coefficient of Earth Pressure at Rest II (정지토압계수 측정에 관한 연구 II)

  • SONG MU-HYO
    • Journal of Ocean Engineering and Technology
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    • v.18 no.6 s.61
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    • pp.58-69
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    • 2004
  • In order to investigate the characteristics of the lateral earth pressure at rest, under hysteretic $K_o-loading/unloading$ conditions, seven types of multi-cyclic models have been studied, using dry sand. For this study, the new type of $K_o-oedometer$ apparatus was developed, and the horizontal pressure was accurately measured. The multi-cyclic models consist of primarily 3 cases: (i) $K_o-test$ under the same loading / unloading condition, (ii) multi-cyclic loading / unloading $K_o-test$ exceeding the maximum pre-vertical stress, and (iii) multi-cyclic loading / unloading $K_o-test$ within the maximum pre-vertical stress. Results fromthe multi-cyclic model indicated that a single-cyclic model could be extended if the exponents for the unloading condition $(\alpha\;and\;\alpha^*)$ and the reloading coefficients $(m_r,\;and\;m_r^{\ast})$ were primarily dependent upon the type of model, number of cycles, and the relative density.

Evaluation of Ubiquitous High Blood-Pressure Demonstration in Sungnam (성남시 유비쿼터스 고혈압 관리에 대한 평가)

  • Lee, Won-Jae;Kim, Hye-Jung;Lee, Jae-Eun
    • Korean Journal of Health Education and Promotion
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    • v.25 no.1
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    • pp.13-23
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    • 2008
  • Objective: The current study was to test if the developed sphygmomanometer was working well and blood pressure information could be collected and monitored systematically through the internet. We tested if the sphygmomanometer and services for blood pressure controlled high blood pressure significantly and the ubiquitous monitoring could be used further. Methods: Kyungwon University, KT Co., Gil Medical Center, LIG Nex1 Co., and Sujeong Health Center conducted an ubiquitous high blood control project in Sujeong-gu, Sungnam, Korea from Mar. 5 to May 16. We developed and applied sphygmomanometer. We distributed the devices to 27 high blood pressure patients. The blood pressures of the residents were monitored through the internet when they measured blood pressures in their homes. A nurse monitored and consulted their blood pressures in the monitoring center in Kyungwon University during the demonstration period. The consultant called them and consulted on their blood pressures in few seconds they used the sphygmomanometers. For the significance of change in blood pressure, we tested statistically with Generalized Additive Model(GAM) and Multi-level Analysis. Results: Both GAM and Multi-level Analysis showed that the blood pressures of persons with ubiquitous blood pressure management decreased significantly as time passed. Conclusions: The internet monitoring and services are considered to be promising because most of the participants were satisfied especially because somebody was caring their health. The decrease of blood pressures was significant by GAM and Multi-level Analysis. Thus, we can apply ubiquitous blood pressure management to health promotion projects.

Study on Pressure Drop Characteristics in Multi-Channel Tubes for Automotive Condenser (자동차 응축기용 다채널관의 압력강하 특성에 관한 연구)

  • Jeon, Chang Duk;Chung, Jae Won;Lee, Jinho;Kang, Shin Hyung
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.23 no.7
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    • pp.881-892
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    • 1999
  • Experiment was performed to study the characteristics of pressure drop of multi-channel tubes for automotive condenser using HFC-134a. Single phase liquid and two phase flow pressure drop were measured in one rectangular plain and three micro-fin tubes with 10 channels. Data are presented for the following range of variables: mass flux(200 to $600kg/m^2s$), and inlet saturation pressure of the refrigerant(1.0 and 1.6MPa). For subcooled flow, pressure drops are 10% and 12% higher than that predicted by the Petukhov equation with hydraulic diameter respectively. Two-phase flow pressure drop are compared with the previously proposed correlations, and well predicted by modified correlation that was derived from Traviss correlation. and correlated within -30~+20%. Also experimental data are correlated within -56%~+18% by Webb's prediction method based on the equivalent mass velocity concept originally proposed by Akers et al.