• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.996-999
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• 2011

The flow and combustion dynamics in the ignition and ramjet sustainer phase of an integrated rocket-ramjet(IRR) engine are investigated. The physical model includes the entire engine flowpath, from the freestream in front of the inlet to the exit of the exhaust nozzle. The flowfield obtained from a rocket booster study is used as the initial condition for the present analysis, so that the complete operation history of the engine can be obtained. The analysis for the primary factor governing flame propagation during the ignition and the key mechanisms for driving and sustaining the flow oscillations are performed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.6
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• pp.778-787
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• 1999

In this study, the autoignition process of liquid fuel, injected into hot and stagnant air in a 2-D axisymmetric confined cylindrical combustor, has been investigated. Eulerian-Lagrangian scheme was adopted to analyze the two-phase flow and combustion. The unsteady conservation equations were used to solve the transition of the gas field. Interactions between two phases were accounted by using the particle source in cell (PSI-Cell) model, which was used for detailed consideration of the finite rates of transports between phases. And infinite conduction model was adopted for the vaporization of droplets. The results have shown that the process of the autoignition consists of heating up of droplets, vaporization, mixing and ignition. The ignition criteria could be determined by the temporal variations of temperature, reaction rate and species mass fraction. And the effects of various parameters on ignition phenomena are examined. These have shown that the increasing the reaction rate and/or the vaporization rate can reduce the ignition delay time.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.5
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• pp.1218-1226
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• 1994

The shock tube is a useful device for investigating shock phenomena, spray combustion, unsteady gas dynamics, etc. Therefore, it is necessary to analyze exactly the flow phenomena in shock tube. In this study, the mechanics of its reflected shock zone has been investigated by using of the one-dimensional gas dynamic theory in order to estimate the transition from initial reflection of shock wave region. Calulation for four kinds of reflected shock tube temperature (i.e. (a) 1388 K (b) 1276 K (c) 1168 K (d) 1073 K) corresponding to the experimental conditions have been carried out sumarized as follows. (1) The qualitative tendency is almost the same as in that conditions in region of reflected wave region. (2) High temperature period (reflected shock wave temperature) $T_{5}$, exists 0-2.65 ms. (3) Transition period from temperature of reflection shock wave is far longer than the calculated one. This principally attributed to the fact that the contact surface is accelerated, also, due to the release of energy by viscoity effect. This apparatus can advance the ignition process of a spray in a ideal condition that involved neither atomization nor turbulent mixing process, where, using a shock tube, a column of droplets freely from atomizer was ignited behind a reflected shock.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2010.04a
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• pp.166-170
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• 2010

Six different size of torch-ignition device were applied in a constant volume combustion chamber for evaluating the effects of torch-ignition on combustion. The torch-ignition device was designed six different volumes and same orifice size. The combustion pressures were measured to calculate the mass burn fraction and combustion enhancement rate. In addition, the flame propagations were visualized by shadowgraph method for the qualitative comparison. The result showed that the combustion pressure and mass burn fraction were increased when using the torch ignition device. And the combustion duration were decreased. The combustion enhancement rates of torch-ignition cases were improved in comparison with conventional spark ignition. Finally, the visualization results showed that the torch-ignition device the torch-ignition induced faster burn than conventional spark ignition due to the earlier transition to turbulent flame and larger flame surface, during the initial stage. And the initial flame propagation was effected torch-ignition volume.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.1
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• pp.100-108
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• 2006

Time-resolved current and voltage measurements for an inductive automotive spark system were made. Also presented are measurements of the total energy delivered to the spark gap. The measurements were made in air for a range of pressures from 1-18atm, at ambient temperatures. The measured voltage and current characteristics were found to be a function of many ignition parameters; some of these include: spark gap distance, internal resistance of the spark plug and high tension wire, and pressure. The voltages presented were measured either at the top of the spark plug or at the spark gap. The measurements were made at different time resolutions to more accurately resolve the voltage and current behavior throughout the discharge process. This was necessary because the breakdown event occurs on a time scale much shorter than the arc and glow phases. The breakdown, are, and glow voltages were found to be functions of spark plug resistance, gas density, and spark plug gap as expected from the literature. Spark duration was found to decrease as either pressure or gap was increased. The transition from the arc to glow phase is usually distinguished by a sudden rise in the voltage across the gap. At pressures above about 7atm this transition was not observed suggesting that a glow phase was not present. Energy delivered to the gap increased with increasing pressure. The effective resistance of the spark gap during discharge was about twice as large for the glow phase as the arc phase.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.6
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• pp.472-479
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• 2013

A free piston linear engine could be operated under HCCI combustion due to its variable compression ratios. To obtain HCCI combustion, the free piston linear engine needs a high compression ratio to achieve auto-ignition of the fuel/air mixture. In this study, an idea for obtaining a high compression ratio using the transition from SI combustion to HCCI combustion was proposed. The fuel used in this study is hydrogen, which is considered to be an environmentally friendly fuel. Besides, the effects of key parameters such as equivalence ratio (${\phi}$), load resistance ($R_L$) and intake temperature ($T_{in}$) on the SI-HCCI transition were numerically investigated. The simulation results show that the SI-HCCI transition is successful without any significant reduction of in-cylinder pressure as the intake temperature is increased from $T_{in}$=300K (SI mode) to $T_{in}$=450K (HCCI mode), while the load resistance and equivalence ratio are retained respectively at $R_L=120{\Omega}$ and ${\phi}$=0.6 in both SI mode and HCCI mode.

• 한국전산유체공학회:학술대회논문집
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• 2000.10a
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• pp.78-85
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• 2000

The transient laminar reacting flows around fuel droplet have been numerically analyzed. The physical models used in this study can account for the variable thermophysical properties and the chemistry is represent by the one-step global reaction model. The present study is focused on the vaporization and ignition characteristics, flame structure including wake flame, transition flame and envelope flame, and interaction between droplets. special emphasis is given to the triple flame structure and flame stabilization.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.314-318
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• 2006

The interest on the detonation in small tubes, which can be applied to the ignition devices of propulsion system, is increasing. However, the propagation dynamics of detonation waves in small tubes has not been investigated clearly yet. In the present experiments, propagations of detonation waves in stoichiometric propane-oxygen mixture through transparent tubes were recorded using a high speed camera and average velocities were measured as well. In terms of average velocity, there exists a transition regime where the waves show smooth transition from the normal Chapman-Jouguet(CJ) detonation to the low velocity detonation$(\sim0.5V_{CJ})$ along the decreasing initial pressure. In this transition regime, the detonation waves are highly unstable and show cyclic or intermittent longitudinal velocity fluctuation.

• Fire Science and Engineering
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• v.30 no.5
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• pp.1-8
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• 2016

Safety management in hazardous areas with potentially explosive gas atmospheres (here in after referred to as hazardous areas) in large scale facilities dealing with combustible or flammable materials at home and abroad is very important (significant) for the coexistence of the company and local society based on business continuity management (BCM) and reliance. For the safety management in hazardous areas, two systems are mainly used: (1) the control system for the prevention of combustible or flammable substances and (2) the explosion proof system for the elimination of ignition sources when flammable gases are leaked to inhibit the transition to fire or explosion accidents. While technology and regulations on explosion proof facilities or devices for electrical ignition sources are well developed and defined, those for thermal ignition sources need to be more developed and established. In this study, the internal combustion engine in hazardous areas was investigated to determine the risk of ignition. For this purpose, document searches were conducted on the relevant international standards and accidents cases and risk analysis reports. In addition, this study assessed the application cases of the diesel engine's safety equipment, such as spark arresters regarding the site of process safety management (PSM) system in central Korea. To practically apply these results to the hydrocarbon industry, the safety management method for explosion prevention in hazardous areas was provided by risk identification for ignition sources of internal combustion engines, such as diesel engines.

• Fire Science and Engineering
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• v.18 no.3
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• pp.30-38
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• 2004

An important characteristics during fire growth is the phenomena of flashover, which is the transition from the local combustion to the full-room fire. The aim of this study is to predict the flashover times, the ignition times and HRR(heat release rate) of flashover for building interior materials. By using the literature data and RSM(response surface methodology), the new equations for predicting the flashover time, the ignition time and the HRR of building interior materials are proposed. The A.A.P.E.(average absolute percent error) and the A.A.D.(average absolute deviation) of the reported and the calculated flashover times were 38.74sec and 51.24sec respectively, and the correlation coefficient was 0.975. The A.A.P.E and the A.A.D of the reported and the calculated ignition times were 10.96sec and 1.97sec, and the correlation coefficient was 0.962. Also the A.A.P.E and the A.A.D. of the reported and the calculated the HRR of flashover by means of times were 29.92 and 514, and the correlation coefficient was 0.830. The values calculated by the proposed equations were in good agreement with the literature data. Therefore, it is expected that this proposed equations will support the use of the research for other building interior materials.