• Nuclear Engineering and Technology
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• 제53권4호
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• pp.1119-1126
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• 2021

Spacer grid with mixing vane had been widely used in nuclear reactor core. One of the main feather of spacer grid with mixing vane was that strong swirl flow was formed after the spacer grid. The swirl flow not only changed the bubble generation in the near wall field, but also affected the bubble behaviors in the center region of the subchannel. The interaction between bubble and the swirl flow was one of the basic phenomena for the two phase flow modeling in fuel assembly. To obatin better understanding on the bubble behaviors in swirl flow, full three dimension numerical simulations were conducted in the present paper. The swirl flow was assumed in the cylindral calculation domain. The bubble interface was captured by Volume Of Fluid (VOF) method. The properties of saturated water and steam at different pressure were applied in the simulation. The bubble trajectory, motion, shape and force were obtained based on the bubble parameters captured by VOF. The simulation cases in the present study included single bubble with different size, at different angular velocity conditions and at different pressure conditions. The results indicated that bubble migrated to the center in swirl flow with spiral motion type. The lateral migration was mainly related to shear stress magnitude and bubble size. The bubble moved toward the center with high velocity when the swirl magnitude was high. The largest bubble had the highest lateral migration velocity in the present study range. The effect of pressure was small when bubble size was the same. The prelimenery simulation result would be beneficial for better understanding complex two phase flow phenomena in fuel assembly with spacer grid.

• Nuclear Engineering and Technology
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• 제54권4호
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• pp.1253-1260
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• 2022

This paper reports the control method for the core power of the China initiative Accelerator Driven System (CiADS) facility. In the CiADS facility, an intense external neutron source provided by a proton accelerator coupled to a spallation target is used to drive a sub-critical reactor. Without any control rod inside the sub-critical reactor, the core power is controlled by adjusting the proton beam intensity. In order to continuously change the beam intensity, an adjustable aperture is considered to be used at the Low Energy Beam Transport (LEBT) line of the accelerator. The aperture size is adjusted based on the Proportional Integral Derivative (PID) controllers, by comparing either the setting beam intensity or the setting core power with the measured value. To evaluate the proposed control method, a CiADS core model is built based on the point reactor kinetics model with six delayed neutron groups. The simulations based on the CiADS core model have indicated that the core power can be controlled stably by adjusting the aperture size. The response time in the adjustment of the core power depends mainly on the adjustment time of the beam intensity.

• 동력기계공학회지
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• 제16권3호
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• pp.16-21
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• 2012

Biodiesel is technically competitive with or offers technical advantages over conventional petroleum diesel fuel. Biodiesel is an environmentally friendly alternative liquid fuel that can be used in any diesel engine without modification. In this study, to investigate the effect of fuel injection timing on the characteristics of performance with DBF in DI diesel engine. The engine was operated at five different fuel injection timings from BTDC $6^{\circ}$ to $14^{\circ}$ at $2^{\circ}$ intervals and four loads at engine speed of 1800rpm. As a result of experiments in a test engine, maximum cylinder pressure is increased with leading fuel injection timing. Specific fuel oil consumption is indicated the least value at BTDC $14^{\circ}$ of fuel injection timing.

• Journal of Information Processing Systems
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• 제13권3호
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• pp.500-517
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• 2017

In this paper, an improved zone-based routing protocol for heterogeneous wireless sensor networks is proposed. The proposed protocol has fixed the sized zone according to the distance from the base station and used a dynamic clustering technique for advanced nodes to select a cluster head with maximum residual energy to transmit the data. In addition, we select an optimal route with minimum energy consumption for normal nodes and conserve energy by state transition throughout data transmission. Simulation results indicated that the proposed protocol performed better than the other algorithm by reducing energy consumption and providing a longer network lifetime and better throughput of data packets.

• 동력기계공학회지
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• 제21권1호
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• pp.63-69
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• 2017

The combustion characteristics of gasoline and diesel were tested in a compression ignition engine. Both fuels were used with same common rail injection system. Combustion experiment showed that low load condition of 0.45 MPa IMEP (indicated mean effective pressure) was tested in metal and optical engines. The gasoline combustion showed higher hydrocarbon and carbon monoxide emissions but lower soot emission compared with diesel combustion. NOx emissions were very high at late injection timing but significantly decreased at early injection timing due to the lean combustion resulted from vigorous mixing process. Direct combustion visualization showed that the diesel combustion was dominated by diffusion combustion exhibiting soot incandescence and the gasoline combustion was mostly consisted of premixed combustion showing blue chemiluminescence.

• 동력기계공학회지
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• 제9권2호
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• pp.50-56
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• 2005

The mechanical properties of glass fiber reinforced polymer reinforcing bars(rebar) in various environment conditions such as moisture, chloride, alkali and freeze-thaw actions at temperature ranging from room temperature($25^{\circ}C$) to high temperature of up to $80^{\circ}C$ have been studied. The test results indicated that tensile strength and interfacial shear strength of GFRP bar were decreased with the increasing of temperature and holding time of each environment condition. The degradation in alkali environment. was more serious than those in the other environments.

• 에너지공학
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• 제12권3호
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• pp.190-196
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• 2003

본 논문에서는 Indolene-MPHA(Methanol Plus High Alcohols)가 엔진성능에 미치는 영향에 관한 연구가 이루어졌다. 본 연구에서는 연료의 성능 인자를 측정하였다. 특히 연료의 성능 인자들인 MBT 점화 시기, 출력, 열효율 등이 측정되었다. 여기에서 알콜 농도는 청정 Indolene의 체적에 따라서 0∼100%까지 변화시켰다. 연료의 성능 인자들은 서로 다른 압축비에서 단기통 스파크점화 엔진을 사용하여 측정하였다. 성능 측정결과에 따르면 Indolene-MPHA 혼합물이 Indolene-Methanol 혼합물보다 빠른 MBT 점화 시기와 유사한 출력 그리고 낮은 열효율을 나타내고 있음을 알 수 있다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.154-159
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• 2005

Low RF power density was used for preparing transparent conducting AI-doped ZnO (AZO) thin films by RF Magnetron Sputtering on Corning 1737 glass. The dependence of films' structural, optical and electrical properties on sputtering gas, film's thickness and substrate temperature were investigated. Low percent of incorporated H2 in Ar sputtering gas has proven to reduce film's resistivity and sheet resistance as low as $4.1\times10^{-3}{\Omega}.cm$. It also formed new preferred peaks orientation of (101) and (100) which indicated that the c-axis of AZO films was parallel to the substrate. From UN-VIS-NIR Spectrophotometer analysis, it further showed high optical transmittance at about $\~ 90\%$ at visible light spectra (400-700nm).

• 한국환경과학회지
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• 제4권2호
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• pp.169-180
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• 1995

This Daper presents effective simulation of the dispersion of thermal discharge which can be relesed at Boryong power plant. Applied numerical models are finite difference method for hydrodynamic analysis and Masch-model comprised of conditions for ambient current velocity. Application of these models is done in Cheonsu Bay Summing up the results of this study are as follows; 1. It is found that the result for measurements of temperature appears high at southwardly Songdo on flood. The reason is that tidal currents which flowed north direction were accompanied with southwardly dispersed thermal discharge. A minute Particle of thermal Plume has a tendency to dispels inward Deacheon Bay. 2. According to the results of numerical experiment, maximum distance for thermal discharge dispersion appeared 10.8 km at lower part and 8.6 km at upper part with power plant outlet as starting point. 3. Comparative the numerical simulation and Airbone Multispectral Scanner indicated that thermal discharge should be verified separative phenomena. The simulated results were compared with field data set showing good agreement. It is concluded that these model can be simulated well.

• 전기학회논문지P
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• 제58권2호
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• pp.214-220
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• 2009

Battery is one of the emergency power and its reliability is a very important to keep up the minimum of building capabilities in case of interruption of electric power. This paper, a comparison was made between three different types of instrument on 30 valve regulated lead acid(VRLA) TYPE 12[V]/100[AH] batteries, and then their indicated measured values(impedance/conductance) were compared with the measured capacity of the battery. As a result, Measured value of instrument is strongly related to battery's capacity in the same group battery and Impedance/Conductance guide line for diagnosis of lead-acid battery's state of health(SOH) is a different from each battery guoup.