• 대한기계학회논문집B
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• 제33권9호
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• pp.699-708
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• 2009

To understand hydrogen jet liftoff height, the stabilization mechanism of turbulent lifted jet flames under non-premixed conditions was studied. The objectives were to determine flame stability mechanisms, to analyze coexistence of two different flame structure, and to characterize the lifted jet at the flame stabilization point. Hydrogen flow velocity varied from 100 to 300 m/s. Coaxial air velocity was changed from 12 to 20 m/s. Simultaneous velocity field and reaction zone measurements used, PIV/OH PLIF techniques with Nd:YAG lasers and CCD/ICCD cameras. Liftoff height decreased with the increase of fuel velocity. The flame stabilized in a lower velocity region next to the faster fuel jet due to the mixing effects of the coaxial air flow. The flame stabilization was related to turbulent intensity and strain rate assuming that combustion occurs where local flow velocity and turbulent flame propagation velocity are balanced. At the flame base, two different flame structures were found that was the partial premixed flames and premixed flame.

• 한국안전학회지
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• 제16권1호
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• pp.1-8
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• 2001

All objects emit thermal radiation and this radiation is the basis of the techniques used to detect flames. The usual phenomena occurring in the initial stage of the fire are generally invisible products of a combustion and visible smoke. Liquid or gaseous materials do not undergo a smoldering stage so that fires develop very rapidly. Also, the heat generated by the initial flames is usually not sufficient to activate a heat detector. In this case the most effective criterion for automatic fire detection is the flame. According to the fire regulation of korea, the compulsory standard provided that a flame detector shall be installed in a place that the attachment height of detector is higher than 20 m, chemical plants, hangar, refinery, etc.. The results of the research and development are discriminated between a flame and other radiant emitters, developed a UV detector tube contains an inert gas which absorbs UV radiation, developed PZT pyroelectric element is based on the use of photovoltanic cell, developed IR band-pass filter that only allow a 4.3 $\mu\textrm{m}$ radiation wavelength to reach the sensors and developed UV-IR combination flame detector combined into a single detection device.

• 한국안전학회지
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• 제31권5호
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• pp.54-60
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• 2016

In this study, tank truck incidents of road transport of hazardous materials to experimental investigated the potential fire hazard. Real scale fire was to perform experiments for on this qualitative and quantitative data collection and analysis. Particularly affected by radiant heat from the flames caused and damage estimates range investigated accordingly. Flame temperature, internal temperature of tank and emitted radiation from the flames was investigated. The flame of light oil spill caused a fire at a temperature of about $300^{\circ}C$ high in comparison with the methanol by combustion of diesel and methanol, according to the difference, the flame duration changes varies depending on the Burning rate. Depending on spill rate(30, 60, 90 and $120{\ell}/min$) and the longer the duration of the flame important factors for the internal temperature of tank lorry rise was found. Road accident in a fire caused by leakage of hazardous was could the higher the damaged. Therefor, Fire suppression activities should be required in particular to be around.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제37회 추계학술대회논문집
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• pp.258-262
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• 2011

실험용 분젠 연소기를 사용하여 예혼합된 메탄-산소 층류화염전파속도를 연구하였다. 이를 위해 $CH^*$ 자발광 측정기법과 슐리렌 사진술이 사용되었다. 실험결과는 CHEMKIN 3.7을 이용한 수치해석 결과와 비교하였다. 층류화염전파속도를 측정하기 위하여 층류여역 내에서 전체 당량비는 0.5에서 2.0까지 조절하였다. 동축 화염에서 화염전파속도는 각도측정법을 사용하였으며 슐리렌 사진에서는 3.1 m/s로 $CH^*$ 자발광 사진에서는 2.9 m/s로 측정되었다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2005년도 제31회 KOSCO SYMPOSIUM 논문집
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• pp.320-327
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• 2005

An experimental study was performed to investigate the effects of partially premixing, varying the equivalence ratios from $1.36{\sim}{\infty}$, and swirlers with swirl numbers of 0, 0.28, 0.64, and 1.32, on the characteristic of radical ($OH^{\ast}$, $CH^{\ast}$, and $C_2^{\ast}$) and pollutant emission in partially premixed swirling flames. The signal from the electronically excited state of $OH^{\ast}$, $CH^{\ast}$, and $C_2^{\ast}$ was detected through a band pass filter with a photo multiplier tube, and flow fields images were detected through a schlieren system. The results demonstrated that the flame height decreases and jet spreading angle increase with increasing a swirl number. The more momentum ratio and swirl number increase, the more decrease flame height, and the generation of sooting flame is promoted.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2007년도 제34회 KOSCO SYMPOSIUM 논문집
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• pp.191-196
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• 2007

The enhancement of flame stability in coflow jets has been investigated experimentally by observing the liftoff behaviors of nonpremixed propane and methane flames in the electric fields. The liftoff or blowoff velocities has been measured in terms of the applied AC voltages and frequency. The experimental results showed that the liftoff velocity could be extended significantly just by applying the high voltage to the central fuel nozzle both for propane and methane. As increasing the applied voltage, the liftoff velocity increases almost linearly with the applied voltage and have its maximum value at certain applied voltage. After that, the liftoff velocity showed decrease with the applied voltage. Through the experimental observation, we found that the liftoff velocity could be correlated well with the applied voltage and frequency in the linearly increasing regime. And after having maximum in the liftoff velocity, it was observed that the liftoff velocity decreases with the applied voltage irrespective of AC frequencies. To visualize the change of flame structure with electric fields, planar laser induced fluorescence technique was adopted, and the enhancement of flame stability has been explained based on the flame structural change in electric fields.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.569-572
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• 2006

In present study, the influence of changing combustor pressure on flame stabilization and nitrogen oxide (NOX) emission in the swirl flame with secondary fuel injection was investigated. The combustor pressure was controlled by suction at combustor exit. Pressure index ($P^*=Pabs/Patm$), where Pabs and Patm indicated the absolute pressure and atmosphere pressure, was controlled in the range of 0.7~1.15 for each equivalence ratio conditions. It could be observed that flame stable region became narrower with decreasing equivalence ratio and pressure index. In this combustion system, stable flames were formed until $P^*=\;0.7$. Emission index decreased with decreasing pressure index for overall equivalence ratio conditions and NOx reduction rates were almost identical for $P^*<1$ regardless of equivalence ratio though EINOx values showed different level with change of equivalence ratio for $P^*{\geq}1$. It is also observed that EINOx decreased with increasing secondary fuel injection ratio. Emission index of nitric oxide was controllable by adjusting the changing combustor pressure and injecting secondary fuel and this NOx reduction technology is applicable to industrial furnaces and air conditioning system.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.143-148
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• 2001

We measured emission indices for $NO_x$, CO, temperature and radical characteristics for partially premixied flames formed by suction & blow fans air condition. At sufficiently high levels of partial premixing a double flame structure consisting of a rich premixed inner flame and outer diffusion flame was established similar to that previously observed in premixed flames. $NO_x$, Temperature, CO values were experimented with approximately constant air flow rate and decreasing equivalence ratios. The reduction in $NO_x$ and temperature at suction condition as compared with that for blow condition was approximately 20%, but on the contrary, CO emission was increased. In addition, We measured temperature distributions and found that temperature increased continuously with increasing partial premixing. We also estimated CH, $C_2$ radical intensity. CH and $C_2$ radicals provide evidence that, for the present measurement, CH and $C_2$ radicals intensity was associsated with their premixed component. And we observed stronger $C_2$, CH radicals intensity at suction conditions than blow conditions.

• Journal of Mechanical Science and Technology
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• 제18권3호
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• pp.499-512
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• 2004

The effects of swirl intensity on non-reacting and reacting flow characteristics in a flat flame burner (FFB) with four types of swirlers were investigated. Experiments using the PIV method were conducted for several flow conditions with four swirl numbers of 0, 0.26, 0.6 and 1.24 in non-reacting flow. The results show that the strong swirling flow causes a recirculation, which has the toroidal structures, and spreads above the burner exit plane. Reacting flow characteristics such as temperature and the NO concentrations were also investigated in comparison with non-reacting flow characteristics. The mean flame temperature was measured as the function of radial distance, and the results show that the strong swirl intensity causes the mean temperature distributions to be uniform. However the mean temperature distributions at the swirl number of 0 show the typical distribution of long flames. NO concentration measurements show that the central toroidal recirculation zone caused by the strong swirl intensity results in much greater reduction in NO emissions, compared to the non-swirl condition. For classification into the flame structure interiorly, the turbulence Reynolds number and the Damkohler number have been examined at each condition. The interrelation between reacting and non-reacting flows shows that flame structures with swirl intensity belong to a wrinkled laminar-flame regime.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.95-95
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• 2010

An apparatus for generating flames and more particularly the microwave plasma burner for generating high-temperature large-volume plasma flame was presented. The plasma burner was composed of micvrowave transmission lines, a field applicator, discharge tube, coal and gas supply systems, and a reactor. The plasma burner is operated by injecting coal powders into a 2.45 GHz microwave plasma torch and by mixing the resultant gaseous hydrogen and carbon compounds with plasma-forming gas. We in this work used air, oxygen, steam, and their mixtures as a discharge gas or oxidant gas. The microwave plasma torch can instantaneously vaporize and decompose the hydrogen and carbon containing fuels. It was observed that the flame volume of the burner was more than 50 times that of the torch plasma. The preliminary experiments were carried out by measuring the temperature profiles of flames along the radial and axial directions. We also investigated the characteristics for coal combustion and gasification by analyzing the byproducts from the exit of reactor. As expected, various byproducts such as hydrogen, carbon monoxide, carbon dioxide, hydrogen sulfide, etc. were detected. It is expected that such burner cab be applied to coal gasification, hydrocarbon reforming, industrial boiler of power plants, etc.