• 대한기계학회논문집B
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• 제29권9호
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• pp.988-996
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• 2005

Flame structure and extinction mechanism of counterflow methane/air non-premixed flame diluted with nitrogen are studied by NASA 2.2 s drop tower experiments and two-dimensional numerical simulations with finite rate chemistry and transport properties. Extinction mechanism at low strain rate is examined through the comparison among results of microgravity experiment, 1D and 2D simulations with a finite burner diameter. A two-dimensional simulation in counterflow flame especially with a finite burner diameter is shown to be very important in explaining the importance of multidimensional effects and lateral heat loss in flame extinction, effects that cannot be understood using a one-dimensional flamelet model. Extinction mechanism at low strain rate is quite different from that at high strain rate. Low strain rate flame is extinguished initially at the outer flame edge, the flame shrinks inward, and finally is extinguished at the center. It is clarified from the overall fractional contribution by each term in energy equation to heat release rate that the contribution of radiation fraction with 1D and 2D simulations does not change so much and the overall fractional contribution is decisively attributed to radial conduction ('lateral heat loss'). The experiments by Maruta et at. can be only completely understood if multi-dimensional heat loss effects are considered. It is, as a result, verified that the turning point, which is caused only by pure radiation heat loss, has to be shifted towards much lower global strain rate in microgravity flame.

• 대한기계학회논문집B
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• 제28권4호
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• pp.371-381
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• 2004

Numerical simulation of $CO_2$ addition effects to fuel and oxidizer streams on flame structure has been conducted with detailed chemistry in H$_2$-O$_2$ diffusion flames of a counterflow configuration. An artificial species, which displaces added $CO_2$ in the fuel- and oxidizer-sides and has the same thermochemical, transport, and radiation properties to that of added $CO_2$, is introduced to extract pure chemical effects in flame structure. Chemical effects due to thermal dissociation of added $CO_2$ causes the reduction flame temperature in addition to some thermal effects. The reason why flame temperature due to chemical effects is larger in cases of $CO_2$ addition to oxidizer stream is well explained though a defined characteristic strain rate. The produced CO is responsible for the reaction, $CO_2$＋H=CO＋OH and takes its origin from chemical effects due to thermal dissociation. It is also found that the behavior of produced CO mole fraction is closely related to added $CO_2$ mole fraction, maximum H mole fraction and its position, and maximum flame temperature and its position.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.209-212
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• 2001

A flame detector responds either to radiant energy visible to the human eye or outside the range of human vision. Such a detector is sensitive to glowing embers, coals, or flames which radiate energy of sufficient intensity and spectral quality to actuate the alarm. An infra-red detectors can respond to the total IR component of the flame alone or in combination with flame flicker in the frequency range of 5 to 30 Hz. A major problem in the use of infrared detectors receiving total IR radiation is the possible interference of solar radiation in the infrared region. When detectors are located in places shielded from the sun, such as vaults, filtering or shielding the unit from the sun's rays is unnecessary. In this study, we proposed method for redue a false alarm with using filtering & sensor technology for distinguish of causes of raise a false alarm and pure flame.

• 한국가스학회지
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• 제11권3호
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• pp.33-39
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• 2007

[ $CH_4/air$ ] 예혼합화염에서 EGR 성능개선을 위한 RG의 첨가효과에 대한 수치적 연구가 수행되었다. 일반적으로 EGR은 화염온도 및 NOx 저감을 위해 사용되어지는 반면, RG는 연소속도와 같은 화염안정성 개선을 위해 사용되어질 수 있다. 본 연구는 이들 두 첨가제가 연소특성에 미치는 경쟁적인 효과에 초점이 맞추어졌다. 결론으로서, 적절한 EGR 및 RG 첨가율의 조절은 낮은 NOx 배출의 달성과 동시에 순수 $CH_4/air$ 예혼합화염과 동일한 화염 안정성을 얻을 수 있음을 확인하였다.

• Composites Research
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• 제30권3호
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• pp.223-228
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• 2017

본 연구에서는 폴리프로필렌(PP), 폴리프로필렌 직조섬유를 이용하여 자기강화 복합재료를 제조하고, 자기강화 복합재료에 암모늄 폴리포스페이트(APP) 및 키토산을 첨가하여 난연 자기강화 복합재료를 개발하였으며, 시험을 통하여 기계적 특성 및 난연성을 확인하였다. 시험결과, 자기강화 복합재료의 기계적 강도는 PP에 비해 크게 향상되었으나, 난연제를 첨가하는 양이 증가함에 따라 강도가 점차 감소하였다. 두 난연제 중에서는 키토산을 첨가한 자기강화복합재료가 APP를 첨가한 자기강화복합재료에 비하여 우수한 강도를 보였다. 난연성의 경우, APP를 첨가할 경우, 키토산을 첨가하는 것 보다 더욱 우수하였다. 본 연구의 결과는 자동차 및 포장산업에서 경량화 및 재활용을 위하여 응용이 가능할 것으로 기대된다.

• 한국화재소방학회논문지
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• 제24권6호
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• pp.170-175
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• 2010

동축류버너를 이용한 제트확산화염에서 이산화탄소의 첨가가 매연 생성에 미치는 영향을 조사하였다. R-타입 열전대를 이용하여 화염대 및 황염과 청염의 경계온도를 측정하였다. 광감쇄법을 이용하여 화염이 존재하는 국소부분에서의 상대적인 매연 농도(1-I/$I_0$)를 측정하였다. 광원으로는 파장이 632.8nm인 He-Ne 레이저가 사용되었고 디텍터를 이용하여 매연입자에 의해 산란과 흡수를 겪은 후의 감쇄된 신호를 직접 측정하였다. 또한, 매연 생성에 있어서의 열적 효과를 알아보기 위해 산화제의 유속을 변화시켜 유속에 의한 영항을 알아보았다. 실험 결과로써, 황염과 청염 각각의 온도는 이산화탄소의 첨가에 따라 점차 낮아졌지만 황염과 청염의 경계온도는 거의 일정하였다. 산화제 측에 이산화탄소를 첨가함에 따라 상대적인 매연 농도는 낮아졌고 이는 산화제의 유속을 증가시켰을 때의 효과와 유사했다. 이것은 화염온도의 저하와 매연입자의 체류시간 감소에 기인하는 것으로 생각된다. 또한 이산화탄소의 첨가가 화염의 불안정성을 야기하여 순수 에틸렌/공기 화염에 비해 화염의 길이가 다소 증가하는 것으로 나타났다.

• 한국연소학회지
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• 제12권1호
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• pp.28-37
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• 2007

Numerical study is conducted to grasp the flame structure and NO emissions for a wide range of oxy-fuel combustion (covering from air blown combustion to pure oxygen combustion) and for various mole fractions of recirculated $CO_2$ in $CH4-O_2/N_2/CO_2$ counterflow diffusion flames. Special concern is given to the difference of the flame structure and NO emissions between air blown combustion and oxy-fuel combustion w/o recirculated $CO_2$ and is also focused on chemical effects of recirculated $CO_2$. Air blown combustion and oxy-fuel combustion w/o recirculated $CO_2$ are shown to be considerably different in the flame structure and NO emissions. Modified fuel oxidation reaction pathways in oxygen-enriched combustion are provided in detail compared to those in air blown combustion w/o recirculated $CO_2$. The formation and destruction of NO through Fenimore and thermal mechanisms are also compared for air blown combustion and oxyegn-enriched combustion w/o recirculated $CO_2$, and the role of the recirculated $CO_2$ and its chemical effects are discussed. Importantly contributing reaction steps to the formation and destruction of NO are also estimated in oxygen-enriched combustion in comparison to air blown combustion.

• 한국화재소방학회논문지
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• 제15권1호
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• pp.34-40
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• 2001

가스계 혼합소화약제의 소화성능을 검토하기 위하여 Cup-burner test장치를 설치하고 이성분계 및 삼성분계 혼합물의 불꽃소화농도를 측정하였다. 시험대상 이성분계 혼합물은 이산화탄소/HFC-23, 이산화탄소/HCFC-22, 이산화탄소/HFC-227ea, 이산화탄소/HFC-125, 이산화탄소/FIC-13I1, Hexafluoropropylene/HFC-23이고 삼성분계 흔합물은 이산화탄소/HFC-237HFC-l34a, 이산화탄소/HFC-23/HFC-227ea, 이산화탄소/HFC-23/HFC-125이다. Cup-burner test장치에서 측정된 가스계 혼합물의 소화농도는 단일성분의 소화농도와 혼합물의 구성비로 이루어진 모델에 의해 잘 예측됨을 알 수 있었다. 특히 이 모델은 혼합물의 구성성분이 물리적 소화성능을 지닐 때 잘 적용되며 화학적 소화성능의 영향이 강해질수록 측정값과의 오차가 커진다.

• 한국염색가공학회지
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• 제24권1호
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• pp.33-38
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• 2012

In this study, to increase flame retardation of poly(ethylene terephthalate) (PET) in burning, bisphenol A bis(diphenyl phosphate) (BDP), a well known flame retardant containing phosphorous, was reacted on end groups of PET by radical pathway. End-capping mechanism of PET with BDP was suggested and confirmed by spectroscopic and thermal analysis. From 400 MHz $^{31}P$ solid state FT-NMR spectrum of end-capped PET (PET-BDP), phosphorus spectra peak in BDP was found at ca. -20 ppm. Furthermore, P-C bond stretching vibration peaks were found ca. $600cm^{-1}$ in FT-IR spectrums of PET-BDP. These results showed that BDP can be chemically added on end groups of PET by our method. Thermal characteristics of pure PET (pPET) and PET-BDP were measured and evaluated by TGA analysis. There was not significant changes in thermal characteristics of PET-BDP compared to that of pPET.

• 한국염색가공학회지
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• 제24권1호
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• pp.39-44
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• 2012

To improve flame retardation of poly(ethylene terephthalate) (PET) against burning, resorcinol bis(diphenyl phosphate) (RDP), phosphorous containing flame retardant, was incorporated into PET backbone by radical reaction pathway. Radical endcapping of PET with RDP was confirmed by spectroscopic and thermal analysis. From 400 MHz $^{31}P$ solid state FT-NMR spectrum of PET with RDP (PET-RDP), phosphorus spectra peak in RDP was found at ca. -10 ppm. Furthermore, P-C bond stretching vibration peaks were found ca. $530cm^{-1}$ in FT-IR spectrums of PET-RDP. These results indicated that RDP can be chemically bound at the ends of PET by radical addition method. Thermal characteristics of pure PET (pPET) and PET-RDP were measured and evaluated by TGA thermal analysis. There was not significant changes in thermal characteristics of PET-RDP compared to that of pPET.