• Proceedings of the Korea Society for Simulation Conference
• /
• 2002.05a
• /
• pp.203-207
• /
• 2002

The dynamic analysis is performed for cold, warm, and hot startups and shutdown. The operating characteristics of an horizontal drum type HRSG are analyzed as well. This analysis was performed by ProTRAX which is a commercial software developed by TRAX Corp.

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.06a
• /
• pp.288-294
• /
• 2009

Various polymer electrolyte membrane fuel cell (PEMFC) startup procedures were tested to explore possible techniques for reducing performance decay and improving durability during repeated startup-shutdown cycles. The effects of applying a dummy load, which prevents cell reversal by consuming the air at the cathode, on the degradation of a membrane electrode assembly (MEA) were investigated via single cell experiments. The electrochemical results showed that application of a dummy load during the startup procedure significantly reduced the performance decay, the decrease in the electrochemically active surface area (EAS), and the increase in the charge transfer resistance ($R_{ct}$), which resulted in a dramatic improvement in durability. After 1200 startup-shutdown cycles, post-mortem analyses were carried out to investigate the degradation mechanisms via various physicochemical methods including FESEM, an on-line $CO_2$ analysis, EPMA, XRD, FETEM, SAED, FTIR. After 1200 startup-shutdown cycles, severe Pt particle sintering/agglomeration/dissolution and carbon corrosion were observed at the cathode catalyst layer when starting up a PEMFC without a dummy load, which significantly contributed to a loss of Pt surface area, and thus to cell performance degradation. However, applying a dummy load during the startup procedure remarkably mitigated such severe degradations, and should be used to increase the durability of MEAs in PEMFCs. Our results suggest that starting up PEMFCs while applying a dummy load is an effective method for mitigating performance degradation caused by reverse current under a repetition of unprotected startup cycles.

• Transactions of the Korean hydrogen and new energy society
• /
• v.20 no.4
• /
• pp.317-322
• /
• 2009

To investigate degradation mechanism of PEMFC operated with repetitive startup/shutdown cycling, i-V characteristics, impedance, cyclic voltamograms were measured. OCV decreased from 0.967 to 0.951 V while the cell voltage at 800mA/$cm^2$ from 0.657 to 0.563V, implying that the electrodes rather than membrane electrolyte was damaged during the cycling operation. Electrochemical analyses supported that the performance degradation could be mainly attributed to degradation of the electrodes such as a decrease in electrochemical active surface area rather than degradation of membrane.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.1144-1147
• /
• 2017

It was reviewed about the pressure oscillation on the inlet of turbo-pump at the moment of engine startup and shutdown. Specially, This research was performed how much is the effect of PSD(Pogo Suppression Device) about the pressure oscillation on the inlet of turbo-pump at the moment of engine startup and shutdown. For analysis, propellant tank PSD and Engine are modelled with Flowmaster which is the commercial 1D program. As the analysis results, even though the PSD is installed in the pipeline, the pressure drop or rising at the moment of engine startup and shutdown is same compared to the case without PSD. However, it was confirmed that PSD reduces the pressure oscillation of the high frequency band as the original purpose of PSD.

• 한국신재생에너지학회:학술대회논문집
• /
• 2007.11a
• /
• pp.137-141
• /
• 2007

The startup behaviour of PEM fuel cells at subfreeze zero is one of the most challenging tasks to be solved before PEM fuel cell vehicle is commercialized. Automotive companies are trying to increase cold statup capability of fuel cell. In this study, we found out the design factor of the stack to increase cold startup capability using 4kW stack and then cold startup test was performed at the various shutdown condition and the various current. In order to test the cold startup possibility and capability in vehicle, we installed 80kW stack in the vehicle and this 80kW fuel cell vehicle was housed in an environmental chamber to investigate the characteristics of cold startup and driving. We found that it is possible for fuel cell vehicle with 80kW stack to self-heated cold startup and drive at $-15^{\circ}C$.

• Korean Chemical Engineering Research
• /
• v.51 no.5
• /
• pp.540-544
• /
• 2013

During start up and shut down of a proton exchange membrane fuel cells (PEMFC), the performance and lifetime of PEMFC were reduced. In this study, effect of startup and shutdown were investigated in dead-end type PEMFC using oxygen as a cathode gas with polarization curve, impedance spectroscopy (EIS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Dummy load which eliminates residual hydrogen and oxygen during startup and shutdown operation should be applied to mitigated the degradation of PEMFC performance. At 50% relative humidity (RH) under the repetitive on/off cycling, the cell performance decayed faster than at 100% RH because of corrosion of the cathode carbon support. Water suppling into cell reduced the degradation rate of dead-end type PEMFC during start up and shut down cycling at 50% RH.

• 제어로봇시스템학회:학술대회논문집
• /
• 2001.10a
• /
• pp.134.3-134
• /
• 2001

The dynamic behavior of heat recovery steam generators for combined cycle power plant is simulated in cases of startup and shutdown conditions. To ensure performance and design data, dynamic model of the HRSG was developed and dynamic simulation was performed. The dynamic analysis will undoubtedly reduce costs which is associated with plant startup and contribute to a smooth commercial plant operation.

• Journal of the Korean Electrochemical Society
• /
• v.13 no.4
• /
• pp.277-282
• /
• 2010

Durability of automotive polymer electrolyte membrane fuel cell (PEMFC) strongly depends the startup/shutdown procedure. Formation of hydrogen/air boundary in the anode gas channel, so-called reverse current condition, particularly induces fast degradation of the cathode. Under the reverse current condition, high voltage is present at the cathode facing air in the anode gas channel and is a function of residual oxygen concentration in the gas channels, that increases with storage time and reaches 21% (air) eventually. In this study, effects of residual oxygen concentration in a PEMFC on degradation of the PEMFC.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 1999.06a
• /
• pp.325-330
• /
• 1999

The dynamic behavior analysis of air-lubricated tilting pad journal bearing which considers start-up, running and shutdown Process were performed. By carrying out the experiment of shaft vibration, measurement of the vibration amplitudes supported by air lubricated tilting pad bearing and analysis of the result, we found more accurate dynamic behavior of the system. There were many investigations in these bearings, but dynamic behavior of startup, shutdown and running process were lacked. By using the experimental data we found the accurate dynamic behavior of the system.

• Nuclear Engineering and Technology
• /
• v.55 no.3
• /
• pp.839-849
• /
• 2023

The development of automation technology to reduce human error by minimizing human intervention is accelerating with artificial intelligence and big data processing technology, even in the nuclear field. Among nuclear power plant operation modes, the startup and shutdown operations are still performed manually and thus have the potential for human error. As part of the development of an autonomous operation system for startup operation, this paper proposes an action coordinating strategy to obtain the optimal actions. The lower level of the system consists of operating blocks that are created by analyzing the operation tasks to achieve local goals through soft actor-critic algorithms. However, when multiple agents try to perform conflicting actions, a method is needed to coordinate them, and for this, an action coordination strategy was developed in this work as the upper level of the system. Three quantification methods were compared and evaluated based on the future plant state predicted by plant parameter prediction models using long short-term memory networks. Results confirmed that the optimal action to satisfy the limiting conditions for operation can be selected by coordinating the action sets. It is expected that this methodology can be generalized through future research.