• Title/Summary/Keyword: Flame length

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Flame Retardancy and Physical Properties of Polyurethane Foam with Expandable Graphite (팽창 흑연을 포함한 폴리우레탄 폼의 난연 및 물성 변화 연구)

  • Bae, Sung-Jun;Park, Ji-Hyeon;Go, Jae-Wang;Choi, Pil-Jun;Lee, Jae-Yeon;Sur, Suk-Hun
    • Journal of Adhesion and Interface
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    • v.20 no.3
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    • pp.96-101
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    • 2019
  • In this study, the flame retardant and physical properties of the expandable graphite/polyurethane foam composites were considered by the addition of expandable graphite. The tensile strength of expandable graphite/polyurethane foam composites decreased with the content of the expandable graphite and the analysis of cell shape by SEM has shown that as the expandable graphite content increases, the cell becomes uneven and collapses. As the results of the compressive strength, density and air permeability tests, it was found that density and as the content of the expandable graphite increased, the compressive strength of the composites increased but air permeability decreased. When the amount of expandable graphite was added at 10 phr or higher, the foam has excellent flame retardation performance. Analysis of the degree of diffraction by X-ray diffraction (XRD) showed that as the content of the expandable graphite increased, the crystal peak of the graphite appeared near $2{\theta}=26^{\circ}$.

Combustion Characteristics and the Modeling of Ionized Methane for Battery Fires (배터리화재를 모사한 이온화 메탄의 연소특성 및 모델링)

  • Ko, Hyuk-Ju;Lee, Eui-Ju
    • Fire Science and Engineering
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    • v.33 no.1
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    • pp.23-29
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    • 2019
  • Rechargeable battery such as lithium-ion battery has been noticed as a kinds of the energy storage system in the recent energy utilization and widely used actually in various small electronic equipment and electric vehicles. However, many thermal runaway caused battery accidents occurred recently, which still is obstacle for advanced application of lithium ion battery. One of the main differences to general fires is the existence of ionized electrolyte with electron during combustion. Therefore, we simply simulated the ion addition effects of battery fires by introducing an ionized fuel in jet diffusion flames. When the ionized methane through a corona discharge was used as fuel, the overall flame stability and shape such as flame length showed no significant difference from normal methane flame, but NOx and CO emissions measured at the post flame region decreased. The ion addition effect of methane oxidation was also numerically simulated with the modeling of hydrogen addition in the mixture. It was confirmed that the hydrogen addition at a fixed temperature had a similar effects on ionization of methane and hence could be modeled successfully.

Combustion Characteristics of CH4 Nonpremixed Flame with Recession Distance (메탄 비예혼합 화염의 후퇴거리에 따른 연소특성)

  • Kim, Jun-Hee;Ku, Kun-Woo;Hong, Jung-Goo;Lee, Choong-Won;Kim, In-Su;Cheong, In-Mo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.36 no.3
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    • pp.285-291
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    • 2012
  • A lot of research on the stability of nonpremixed flames has focused on the fuel-nozzle and quarl geometries. Of the work carried out, only a small amount has focused on the stability of the nonpremixed flame according to the recession distance and air-nozzle geometry. Therefore, in this study, a coaxial-diffusion-type gas burner with a swirler is designed for the systematic investigation of the combustion characteristics of a $CH_4$ flame depending on the recession distance and secondary air-nozzle geometry. 1st air is flowed through the swirler, and 2nd air is flowed through each nozzle. It is shown that the secondary air velocity greatly influences the flame length and shape. There is an optimum recession distance for each nozzle for the best combustion efficiency. In this study, it is shown that the optimized recession distance is nearly half the outer diameter of the air-supply nozzle.

A Study on the Fire Spread Risk of Resident Buildings With Pilotis (필로티 건물 이격거리에 따른 화재확산 위험성 연구)

  • Choi, Seung-Bok;Choi, Doo-Chan;Choi, Don-Mook
    • Fire Science and Engineering
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    • v.31 no.4
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    • pp.103-110
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    • 2017
  • With the common tendency in the accordance with the trend, low-stories built edifices that are Pilotis-oriented structured exponentially and constantly increasing its number of buildings. It inevitably contains its risks of facing conflagrations as most of its part is used as parking lots. In the parking lots, the length of the flame has a heavy-weighted possibility that it would get increased because the heat release rate gets relatively high due to the vehicle insulation. Following on top of that, due to the nature of the Pilotisconsisting of pillars, there is a risk of flame spread to the adjacent building if the same Pilotis-structured buildings are adjacent to each other, if the flame spreads to the surroundings due to the influence of the wind. Because the most of the pilotis-structured-buildings have this entrance that makes the residents be able to enter, if the entrance were plugged the resident get a serious risk of a poisonous gas and a flame. Therefore, if the parking-lots of the pilotis-structured-buildings are adjacent to each other it requires a space to prevent the place from the spread of flame. This research studied how far is appropriate to prevent flame spreading with FDS. As a result, the study found that the distance at least 3.0 m is required.

Recess Effects on Spray Characteristics of Swirl Coaxial Injectors

  • Seol, J.H.;Han, P.G.;Jeong, W.H.;Yoon, Y.
    • International Journal of Aeronautical and Space Sciences
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    • v.4 no.1
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    • pp.26-33
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    • 2003
  • Recess is a geometrical configuration shape that the exit surface of an inner injector is located at a certain length inward from that of an outer injector. It is known to have the characteristics that it can augment mixing efficiency and flame stabilization through internal mixing of propellant in it. So, various experiments, such as backlit stroboscopic photography, phase Doppler particle analyzer(PDPA) and mechanical patternator, were performed at several recess lengths to grasp its effect on the spray characteristics of spray angle, breakup length, atomization and' mixing. Recess length was normalized to dimensionless recess number and two principal mechanisms of impingement and swirl recovery were introduced to explain its influence on the spray characteristics. The effect of recess on SMD doesn't appear significantly near the recess number where mixing efficiency attains to the maximum, whereas mass distribution and mixing efficiency are changed considerably. Thus, it can be inferred that a certain optimum recess number exists, where mixing efficiency becomes the maximum.

Study of Fabrication and Improvement of Mechanical Properties of Mg-based Inorganic Fiber using Reflux Process and Silica Coating

  • Yu, Ri;Kim, YooJin
    • Journal of Powder Materials
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    • v.26 no.3
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    • pp.195-200
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    • 2019
  • Whisker-type magnesium hydroxide sulfate hydrate ($5Mg(OH)_2{\cdot}MgSO_4{\cdot}3H_2O$, abbreviated 513 MHSH), is used in filler and flame-retardant composites based on its hydrate phase and its ability to undergo endothermic dehydration in fire conditions, respectively. In general, the length of whiskers is determined according to various synthetic conditions in a hydrothermal reaction with high temperature (${\sim}180^{\circ}C$). In this work, high-quality 513 MHSH whiskers are synthesized by controlling the concentration of the raw material in ambient conditions without high pressure. Particularly, the concentration of the starting material is closely related to the length, width, and purity of MHSH. In addition, a ceramic-coating system is adopted to enhance the mechanical properties and thermal stability of the MHSH whiskers. The physical properties of the silica-coated MHSH are characterized by an abrasion test, thermogravimetric analysis, and transmission electron microscopy.

An Experimental Study on the Effect of Swirler Mass Flowrate and Flare Exit Length on Flow Patterns inside a Model Combustor Chamber (스월러 플레어 출구길이가 모델 챔버내 유동에 미치는 영향에 대한 실험적 연구)

  • Ryu, Gyong Won;Jin, Yu In;Kim, Yeong Ryon;Kim, Hong Jip
    • Journal of the Korean Society of Propulsion Engineers
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    • v.20 no.6
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    • pp.70-75
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    • 2016
  • A swirler is a flame holding device generating recirculation regions in a gas turbine combustor, and the flow pattern due to a swirler has major effects on the flame distributions, combustion efficiency, and characteristics of exhaust gas. An experimental study for a counter-rotating swirler has been conducted to find out effects of the mass flow rate ratio of the inner/outer swirler flow area, the pressure difference between the swirler inlet and outlet, and the flare exit length ratio on the flow patterns in a model combustion chamber by using PIV(Particle Image Velocimetry) technique.

Flame Retardant Properties of Polymer Cement Mortar Mixed with Light-weight Materials for 3D Printing (3D 프린팅용 경량재료 혼입 폴리머 시멘트 모르타르의 난연특성)

  • Son, Bae-Geun;Song, Hun
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.9 no.3
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    • pp.330-337
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    • 2021
  • 3D printing is not only at the fundamental study and small-scale level, but has recently been producing buildings that can be inhabited by people. Buildings require a lot of cost and labor to work on the form work, but if 3D printing is applied to the building, the construction industry is received attention from technologies using 3D printing as it can reduce the construction period and cost. 3D printing technology for buildings can be divided into structural and non-structural materials, of which 3D printing is applied to non-structural materials. Because 3D printing needs to be additive manufacturing, control such as curing speed and workability is needed. Since cement mortar has a large shrinkage due to evaporation of water, cement polymer dispersion is used to improve the hardening speed, workability, and adhesion strength. The addition of polymer dispersion to cement mortar improves the tensile strength and brittleness between the cement hydrate and the polymer film. Cement mortar using polymer materials can be additive manufacturing but it has limited height that can be additive manufacturing due to its high density. When light-weight materials are mixed with polymer cement mortar, the density of polymer cement mortar is lowered and the height of additive manufacturing, so it is essential to use light-weight materials. However, the use of EVA redispersible polymer powder and light-weight materials, additional damage such as cracks in cement mortar can occur at high temperatures such as fires. This study produced a test specimen incorporating light-weight materials and EVA redispersible polymer powder to produce exterior building materials using 3D printing, and examined flame resistance performance through water absorption rate, length change rate, and cone calorimeter test and non-flammable test. From the test result, the test specimen using silica sand and light-weight aggregate showed good flame resistance performance, and if the EVA redispersible polymer powder is applied below 5%, it shows good flame resistance performance.

Smoke Characteristics of a Small Scale Pool Eire (작은 풀화재에서의 연기 특성)

  • Lee Eui-Ju;Ahn Chan-Sol;Shin Hyun-Joon;Oh Kwang-Chul;Lee Uen-Do
    • Fire Science and Engineering
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    • v.19 no.3 s.59
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    • pp.58-63
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    • 2005
  • Experimental measurements of flames and the product properties were performed for small kerosene pool fires. which is widely used as a fire source of laboratory scale experiments with scaling modeling. The flame length and flickering frequency were investigated for the flame structures, and compared with the theory. Three measurement methods were introduced to clarify the smoke characteristics, i.e. various gas concentrations, smoke density and thermophoretic sampling with transmission electron microscopy (TEM). The yield of carbon dioxide and the consumption of oxygen were proportional to the heat release rate of pool fires, but there is no trend on carbon monoxide emission. Smoke density of turbulent flames was exponentially increased with the heat release rate. The morphology of the soot particle was investigated to address the degree of soot maturing. The results show that the similar smoke morphology between an inverse jet flame and a pool fire exists despite of different combustion controlling mechanisms.

On the Origin of Oscillatory Instabilities in Diffusion Flames (확산화염의 진동불안성의 기원에 대해서)

  • Kim, Jong-Soo
    • Journal of the Korean Society of Combustion
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    • v.10 no.3
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    • pp.25-33
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    • 2005
  • Fast-time instability is investigated for diffusion flames with Lewis numbers greater than unity by employing the numerical technique called the Evans function method. Since the time and length scales are those of the inner reactive-diffusive layer, the problem is equivalent to the instability problem for the $Li\tilde{n}\acute{a}n#s$ diffusion flame regime. The instability is primarily oscillatory, as seen from complex solution branches and can emerge prior to reaching the upper turning point of the S-curve, known as the $Li\tilde{n}\acute{a}n#s$ extinction condition. Depending on the Lewis number, the instability characteristics is found to be somewhat different. Below the critical Lewis number, $L_C$, the instability possesses primarily a pulsating nature in that the two real solution branches, existing for small wave numbers, merges at a finite wave number, at which a pair of complex conjugate solution branches bifurcate. For Lewis numbers greater than $L_C$, the solution branch for small reactant leakage is found to be purely complex with the maximum growth rate found at a finite wave number, thereby exhibiting a traveling nature. As the reactant leakage parameter is further increased, the instability characteristics turns into a pulsating type, similar to that for L < $L_C$.

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