• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.4
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• pp.920-932
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• 1994

The combustion phenomena of a reciprocating engine is one of the most important processes affecting performance and emissions. One effective way to improve the engine combustion is to control the motion of the charge inside a cylinder by means of optimum induction system design, because the flame speed is mainly determined by the turbulence at compression(TDC) process in S.I. engine. It is believed that the tumble and swirl motion generated during intake breaks down into small-scale turbulence in the compression stroke of the cycle. However, the exact nature of their relationship is not well known. This paper describes cycle resolved LDV measurement of turbulent flow inside the cylinder of a 4-valve engine under motoring(non-firing) conditions, and studies the effect of intake port configurations on the turbulence characteristics using following parameters ; Eulerian temporal autocorrelation coefficient, turbulence energy spectral density function, Taylor micro time scale, integral time scale, and integral length scale.

• Journal of the Korea Furniture Society
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• v.23 no.3
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• pp.261-270
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• 2012

Nowadays, kitchen are not for the housewives who were independent themselves in the past but for the functional spaces. Kitchen spaces are not only the main function in the residence but also changing spaces which provide the mutual understanding communication between the family members. Although the primary function of the kitchen is food preparation, it is commonly a gathering spot for family and friends, especially if it includes an informal eating area. With so much time spent in the kitchen, and can easily become tired do the decorating scheme. But, for fear of high remodeling costs, it is often unchanged for many years. Surprisingly, there are many changes that can de made to the decorating scheme of a kitchen without either the expense or the inconvenience of remodeling. Between materials on the market, materials for kitchen interior were chosen for this study. Following results came from the materials after combustion. Among boards, MDF showed the highest score in these four categories; residual inflame time, residual glow time, carbonization length, carbonization area. Also, among finishing materials (interior materials), MDF + Poly Coating showed the highest score in those categories. Therefore, it seemed that interior materials need flame retardancy.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.490-495
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• 2003

In steel-making process of iron and steel industry, the purity and quality of steel can be dependent on the amount of CO contained in the molten metal. Recently, the supersonic oxygen jet is being applied to the molten metal in the electric furnace and thus reduces the CO amount through the chemical reactions between the oxygen jet and molten metal, leading to a better quality of steel. In this application, the supersonic oxygen jet is limited in the distance over which the supersonic velocity is maintained. In order to get longer supersonic jet propagation into the molten metal, a supersonic coherent jet is suggested as one of the alternatives which are applicable to the electric furnace system. It has a flame around the conventional supersonic jet and thus the entrainment effect of the surrounding gas into the supersonic jet is reduced, leading to a longer propagation of the supersonic jet. In this regard, gasdynamics mechanism about why the combustion phenomenon surrounding the supersonic jet causes the jet core length to be longer is not yet clarified. The present study investigates the major characteristics of the supersonic coherent jet, compared with the conventional supersonic jet. A computational study is carried out to solve the compressible, axisymmetric Navier-Stokes equations. The computational results of the supersonic coherent jet are compared with the conventional supersonic jets.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.125-130
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• 2004

Experimental study on combustion characteristics of double swirl coaxial injectors has been conducted for the assessment of critical injector design parameters. A reusable, unielement thrust chamber has been fabricated with a water-cooled copper nozzle. Two principle design parameters, a swirl angle and a recess length, have been investigated through hot firing tests for the understanding of their effects on high pressure combustion. Clearly, both parameters considerably affect the combustion efficiency, dynamics and hydraulic characteristics of an injector. Internal mixing of propellants in a recess region increases combustion efficiency along with the increase of a pressure drop required for flowing the same amount of mass flow rates. It is concluded that pressure buildup due to flame can be released by the increase of LOx flow axial momentum or the reduction of a recess length. Dynamic pressure measurements of the thrust chamber show varied dynamic behaviors depending on injector configurations.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.2
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• pp.1-8
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• 2013

This study presents relations between the time lag and interaction index of the impinging-jet injectors using the time lag model in a model chamber. The response of the flame is analyzed to artificial perturbation with 5% amplitude of oxidizer speed at a resonance frequency. At the mixing point of fuel and oxidizer, which determines the characteristic length, the relationship between velocity perturbation and heat release rate is quantified by combustion parameters of interaction index and time lag. In this method, time lag or delay is calculated by the characteristic length and the average velocity obtained from numerical results. The tendency that the time delay decreases with axial jet velocity has been observed.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 1996.11a
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• pp.43-48
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• 1996

It is considered that automobile inner space is dangerous due to its combustion characteristics. (Automobile interior is largely made by plastic materials.) At last it is necessary to study on combustion characteristics of automobile interior. we could obtain its rapid combustion velocity and high smoke density by using ASTM D 2863 apparatus, DSC (Differential Scanning Calorimetry), Smoke density apparatus and so on. The study is summerized by following conditions and results. 1. Sample size was 150mm(length)$\times$60mmwidth). 2. Combustion velocity appeared peak point in the 2cm point. 3. PVC and foam layers are important factors in the face of smoke density. 4. Using DSC, we obtained the point that automobile interior was melted. 5. Automobile interior should be improved because of its low L.O.I value and rapid flame propagation velocity.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.169-174
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• 2014

Detonation propagation studies is recently getting more attention in these days for its feasibility in aerospace application. Another motivation for this study is the safety concern in industries, since the detonation can cause failure to the mechanical components particularly when the flame accelerates within a pipe or tubes. In this study we numerically simulated a Moderately unstable detonation case with various grid systems and fluid dynamic length scales and have compared in the contents. Moderately Unstable detonation case was selected for this study and detailed Hydrogen-Air Reaction Mechanisms proposed by Jachimowski was used in this study with N2 as inert species.

• Journal of the korean Society of Automotive Engineers
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• v.11 no.6
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• pp.48-56
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• 1989

A shock tube technique was developed in which a freely falling droplets column produced by an ultrasonic atomizer was ignited behind reflected shock. In the present study, the effects of turbulent mixing on the ignition delay of a cetane was decided, also, ignition process was investigated. For the purpose of disturbance of droplets column and mixing, authors installed turbulent lattice in shock tube. Usually, the ignition delay is so called Arrhenius plot which found break point in the Arrhenius plot on the high temperature side. The rate of misfiring increased rapidly below 1080K, but ignition took place from 838k and luminous flame was seen to spread over the whole section by turbulent lattice. Length, from end plate to turbulent lattice, was varied with 60,40,20mm. Also, ignition process was detected by Photo transistor. As a result, it was found that physical factors changed ignition delay greatly and turbulent mixing had a considerable effects in the ignition process.

• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.5-7
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• 2012

This study presents relations between the time lag and interaction index of the impinging-jet injectors using time lag model in a model chamber. To analyze the response of the flame, 5% amplitude of oxidizer velocity is artificially perturbed at a resonance frequency. At the mixing point of fuel and oxidizer, which determines the characteristic length, the relationship between velocity perturbation and heat release rate is quantified by combustion parameters of interaction index and time lag. As the improved method to apply the time-lag, the method using the average velocity obtained from numerical results is suggested.

• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.19-22
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• 2012

Experimental study in coflow jet flames has been conducted to investigate effects of adding Helium to coflowing air-side in self-excitation. The Differences between buoyancy-driven and diffusive-thermal self-excitations with the same order of O(1.0 Hz) in self-excitation are explored and discussed in laminar coflow jet flames.