• Journal of Power System Engineering
• /
• v.12 no.1
• /
• pp.20-27
• /
• 2008

수소 추출과 리포밍 과정, 연료 전지, 저장소로 구성된 수소 연료에 대한 연구는 세계적으로 번영하고 있는 중이다. 그러나 한국의 수소 스테이션에 대한 연구는 아직도 개발이 미미한 수준이다. 그리고 역시 수소 스테이션의 가장 중요한 부분인 수소 압축기에 대한 연구도 미흡하다. 수소압축기에서 가장 중요한 부분 중에 하나는 스너버인데 이것의 기능은 수소가스의 맥동압을 줄이고 불순물을 제거한다. 스너버 내부에는 버퍼라고 불리는 기울어진 판이 설치되어 맥동압을 줄이고 불순물을 제거하는 역할을 담당한다. 스너버 내부의 압력 손실과 맥동압이 최소가 될 때 스너버는 적절한 성능을 가졌다고 평가된다. 그러므로 이 연구의 목적은 수치해석을 통하여 스너버의 최적의 기하학적 크기와 버퍼의 각도에 따른 최적의 스너버를 찾는 것이다. 수치해석의 결과에서 다양한 버퍼각도에 따른 스너버의 독특한 특성을 볼 수 있다. 결과적으로 버퍼의 각도가 $35^{\circ}$일때 최소의 압력손실율이 발생했고, 버퍼의 각도가 $10^{\circ}$일 때 최소의 맥동압이 발생하였다.

• Nuclear Engineering and Technology
• /
• v.51 no.2
• /
• pp.546-555
• /
• 2019

Since the first nuclear reactor first critical, nuclear systems has gone through four generations of history, and the fourth generation nuclear system will be truly realized in the near future. The notions of SVBR and lead-bismuth eutectic alloy coolant put forward by Russia were well received by the international nuclear science community. Lead-bismuth eutectic alloy with the ability of the better neutron economy, the low melting point, the high boiling point, the chemical inertness to water and air and other features, which was considered the most promising coolant for the 4th generation nuclear reactors. This study mainly focuses on the structural design optimization of the 4th-generation reactor coolant pump, including analysis of external characteristics, inner flow, and transient characteristic. It was found that: the reactor coolant pump with a central symmetrical dual-outlet volute structure has better radial-direction balance, the pump without guide vane has better hydraulic performance, and the pump with guide vanes has worse torsional vibration and pressure pulsation. This study serves as experience accumulation and technical support for the development of the 4th generation nuclear energy system.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.32 no.8
• /
• pp.29-36
• /
• 2004

Supersonic inlet buzz can be defined as unstable subcritical operation associated with fluctuating internal pressures and a shock pattern oscillating about the inlet entrance. The flow pulsations could result in flameout in the combustor or even structural damage to the engine. An experimental study was conducted to investigate the phenomenon of supersonic inlet buzz on axisymmetric, external-compression inlet. An inlet model with a cowl lip diameter of 30mm was tested at a free stream Mach number of 2.0. Subcritical instability was investigated by considering the frequency of pressure pulsation and shock wave structure at the inlet entrance. The results obtained show that total pressure recovery ratios were varied from 0.42 to 0.78, and capture area ratio from 0.34 to 0.98. The frequency of the subcritical flow increased with decrease in capture area ratios. Frequency was measured at $224{\sim}240Hz$.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.1824-1827
• /
• 2005

For application to micro fluid control systems such as ${\mu}TAS$ (Micro Total Analysis Systems) and DDS (Drug Delivery Systems), it is very significant to handle precise and minute flow rates with low pressure pulsation. In this study, a novel valveless piezoelectric pump using peristaltic motion with three disk type PZT actuators is presented. The newly devised pump with an effective size of $70mm{\times}60mm{\times}55mm$ has three actuator layers connected in series from inlet to outlet. The PZT actuator has a maximum displacement of 240 ${\mu}m$ and a maximum force of 1.6 N. When the driving voltage for PZT actuators is sequentially applied with a certain phase shift, the pumping is performed by peristaltic motion of liquid volume. The working fluid is shut off without the driving voltage. Three methods for sequential driving are proposed and experimentally investigated. First and second methods utilize an intermittent sinusoidal waveform with phase shift of $90{\circ}\;and\;120^{\circ}$, respectively. Third method uses a rectangular waveform with phase shift of $90^{\circ}$. A controller with multi-phase shifter is designed and fabricated. Then, frequency and voltage-flow rate characteristics and load pressure-flow rate characteristics are experimentally investigated to verify the validity of the developed pump.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.9
• /
• pp.1103-1108
• /
• 2012

A main steam pipe system is a branch pipe that connects a boiler with a turbine. Water hammering analysis is very important for limiting the damage caused to pipe systems by operation conditions. Water hammering created by an unsteady flow in pipeline systems can cause excessive change in pressure, vibration, and noise. The main steam pipe structure should be designed to safely maintain the pressure pulsation and several vibrations under operation environments. This study evaluated the structural integrity of a main steam pipe during suspended and normal operation by using the ASME fatigue life methodology and finite element analysis. In the analysis, water hammering was used for transient analysis. The calculated alternating stress and fatigue stress were compared with the applicable limits of ASME fatigue life. All the evaluation results satisfied the requirements of the ASME fatigue life.

• Journal of the Korean Institute of Gas
• /
• v.23 no.6
• /
• pp.1-7
• /
• 2019

Most oil refineries and chemical plants have flare systems designed to mitigate pressure rises in process facilities in case of emergencies that require the release of large amounts of gas due to sudden process shutdowns such as power outages. However, the rise of the flame of the flare system causes civil complaints from residents around the factory due to visible pollution, and economic loss occurs in the company, which requires constant management. In this study, two items were diagnosed and analyzed in order to derive the optimal operation method of flare system. First, to detect the cause of the rise in flame height, the acoustic leak detector was used to check gas leaks in safety valves and pressure control valves. Second, to identify the cause of flame instability, the pulsation phenomenon was diagnosed through the CFD simulation and modeling experiments of the sealing drum. By confirming the leak at 4.3% of the safety valve and 10% of the pressure control valve, the cause of abnormal sparking was derived. The information presented in this study can be easily applied to any company that has a flare system, and is expected to prevent complaints and product loss.

• The Journal of Korean Physical Therapy
• /
• v.13 no.2
• /
• pp.313-324
• /
• 2001

The 15 male students of T-college which is located in Taegu, who don't have any cardiovascular diseases and skin diseases and agreed to the experiment for finding out the effects of hot and cold therapy. They were divided 5 experimental groups, that is hot therapy in blood Pressures, hot therapy group showed significantly difference of systolic blood Pressure. And the hot therapy group and hot and cold therapy showed the distinctive differences in Scheffes' s analysis after the fact. 3. There was no significant difference in pulsation between before and after experiment and there were no differences in each group. 4. The hot therapy group showed significant difference in WBC and didn't show any difference in RBC(p<.05). 5. Timing does not effect to each group in the changes of HGB and HCT. 6. In the comparison between before and after the experiments in the changes of MCV, cold therapy group showed significant measurement. And in the comparison between before and after one hour the experiment in the changes of MCV, cold therapy group showed significant measurement. The experimental group 1 and 3 showed the distinctive differences in Scheffe' s analysis after the fact(p<.05). 7. In the comparison between before and after one hour experiments in MCV changes, the cold therapy group had significant differences(p<.05). 8. There were no significant differences between before and after the experiments in MCHC changes. 9. In the comparison between before and after one hour experiments in PLT changes, cold therapy group had significant changes(p<.05) and there were no differences among three group.

• The Journal of the Acoustical Society of Korea
• /
• v.15 no.6
• /
• pp.52-58
• /
• 1996

Using the acoustic resonances and oscillatory pulsations considered as the branch of wave technologies, the concept of the acoustic resonance diffusers for waste water treatment which maximize the oxygen transfer efficiency in gas-liquid two phase medium have been proposed, and studies for the principles and performance tests were accomplished. Besides, the design concepts for the low pressure Helmholtz resonator, cylinder and annular type reflection resonator and combined type resonance system have been implemented. The acoustic resonance energy which can speed up the mass transfer process increase the oxygen transfer efficiency, and periodic pulsations generated from the instability of air jet from nozzle make very small air bubbles. Then, the annular type jet resonator(AJR) applying these two principles successfully was evalulated as the most promising device and also the efficiency showing $20{\sim}30%$ better than conventional diffusers has been verified experimentally.

• Journal of Acupuncture Research
• /
• v.19 no.2
• /
• pp.149-163
• /
• 2002

Objective : We have studied literatures of Renying Qi mouth comparison pulse diagnosis theory and distinguished the excess, deficiency and quick-temper of pulse as the measurement parameter of Renying Qi mouth pulse diagnosis. Methods : We have acquired pulse signals of Renying Qi mouth by using diagnostic equipment of Renying Qi mouth pulsation and estimated reappearance of pulse signals. Results : 1. The measurement parameter of Renying Qi mouth pulse diagnosis distinguishes the excess, deficiency and quick-temper of pulse through relative comparison of Renying Qi mouth. 2. When we acquired the pulse singals of Renying Qi mouth by using diagnostic equipment, the property, measuring area, bias pressure, contact or adhesion state of the sensor are considered. 3. As getting the pulse signal of Renying Qi mouth, the sensor of a sound detective mode is effective. 4. The diagnostic equipment of Renying Qi mouth pulse is assessed as being significant reappearance.

• Journal of the Korean Magnetics Society
• /
• v.15 no.2
• /
• pp.125-129
• /
• 2005

Ba-Ferrite thin films were prepared on $A1_2O_3$ substrate by a pulsed laser deposition system and characterized by SEM, $M\ddot{o}$ssbauer spectroscopy and VSM. The appropriate conditions of pulsation in Ba-ferrite was the oxygen pressure of 0.1 Torr at a substrate temperature of $400^{\circ}C$ and the thickness was variable with the deposition time. Ba-ferrite crystals had the forms of hexagonal plate in the 5 minute deposited film and the needle grains coexisted with the increasing film thickness. $M\ddot{o}ssbauer$ spectroscopy assured that the direction of atomic spin in Fe ion tends to normal to the substrate in the hexagonal plate. The VSM curves have the two types hysteresis of hexagonal and needle phase.