• 한국추진공학회지
• /
• 제21권2호
• /
• pp.1-8
• /
• 2017

본 연구에서는 모델연소실 내부 메탄-산소 확산화염의 연소특성을 분석하기 위해 추진제의 다양한 분사조건에서 연소실험을 수행하여 연소안정한계 측정 및 화염의 형상변이를 관찰하였다. 연구 결과, 추진제가 이론당량비 조건으로 접근할수록 높은 산소 Reynolds 수($Re_o$) 구간에서도 안정적인 부상화염이 관찰되었으며, 가시화염의 길이는 증가하고, 부상높이는 감소하는 경향이 나타났다. 스월 동축형 인젝터에 의한 추진제의 스월효과로 인해 폭이 넓고, 길이가 짧은 화염이 생성되어 연소실 크기가 제한적인 추력기에서의 사용이 적합함을 확인하였다.

• 한국연소학회지
• /
• 제10권2호
• /
• pp.18-25
• /
• 2005

An experimental study has been conducted to evaluate the effects of reburning on $NO_x$ reduction and also to examine heat transfer characteristics from LPG flame. Experiments were performed in flames stabilized by a co-flow swirl burner, which was mounted at the bottom of the furnace. Tests were conducted using LPG gas as main fuel and also as reburn fuel. The effects of reburn fuel fraction and injecting location of reburn fuel are studied. The paper reports data on flue gas emissions, temperature distribution in furnace and various heat fluxes at the wall for a wide range of experimental conditions. In a steady state, the total as well as radiative heat flux from the flame to the wall of furnace has been measured using a heat flux meter. Temperature distribution and emission formation in furnace have been also measured and compared.

• 한국분무공학회지
• /
• 제15권4호
• /
• pp.182-188
• /
• 2010

Significant real fluid behaviors including rapid property changes take place where high pressure combustion devices such as rocket engines. The flamelet model is the reliable approach to account for the real fluid effects. In the present study, the flamelet equations are extended to treat the general fluids over transcritical and supercritical states. The real fluid flamelet model is carried out for the gaseous hydrogen and cryogenic liquid oxygen flames at the wide range of thermodynamic conditions. Based on numerical results, the precise discussions are made for effects of real fluid, pressure, and differential diffusion on the local flame structure.

• 항공우주시스템공학회지
• /
• 제5권1호
• /
• pp.7-12
• /
• 2011

The goal of fire prevention research is to eliminate fires as a cause of fatal accidents and there are two main areas of research. One is to prevent flame propagation during in-flight and it addresses fire hazards. The other is to minimize the possibility of flame penetration or fuselage burn-through and it aims toward post-crash survival include crash protection, emergency evacuation and post-evacuation survival. Civil aviation authorities world-wide are trying to identify threats and measure performance for fire prevention. The results of research are standardized and given as general directions of test methods. This paper has prepared to study and present the means of compliance to the fire prevention requirements and applicable test methods.

• 한국연소학회지
• /
• 제12권1호
• /
• pp.28-37
• /
• 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.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
• /
• pp.201-202
• /
• 2012

The isothermal flow structure and mixing characteristics of a hybrid/dual swirl jet combustor for micro-gas turbine were numerically investigated. Location of pilot nozzle, angle and direction of swirl vane were varied as main parameters with constant fuel flow rates for each nozzle. As a result, the variation in location of pilot nozzle resulted in significant change in turbulent flow field near burner exit, in particular, center toroidal recirculation zone (CTRZ) as well as turbulent intensity, and thus flame stability and emission characteristics might be significantly changed. The swirl angle of $45^{\circ}$ provided similar recirculating flow patterns in a wide range of equivalence ratio (0.5~1.0). Compared to the co-swirl flow, the counter-swirl flow leaded to the reduction in CTRZ and fuel-air mixing near the burner exit and a weak interaction between the pilot partially premixed flame and the lean premixed flame. With the comparison of experimental results, it was confirmed that the case of co-swirl flow and swirl $angle=45^{\circ}$ would provided an optimized combustor performance in terms of flame stability and pollutant emissions.

• 한국연소학회지
• /
• 제19권3호
• /
• pp.34-43
• /
• 2014

The reformer system is a method for hydrogen production from hydrocarbon fuels such as natural gas under high temperature environment($about{\sim}1,000^{\circ}C$). The premixed swirl burner with mixing swirler and combustion swirler designed to deliver fuel cell electric output from 0.5 kW to 1.5 kW. Premixed swirl burner experiments using natural gas and mixture of natural gas and anode off gas were carried out to analyse flame patterns and stability by equivalence ratio respectively. The results show that the stable swirl flame can be established for all cases of fuels type using the premixed swirl burner. The swirl flame had a wide stability region and it showed very low CO(50 ppm) and $NO_x$(20 ppm) emission at different fuel type and various equivalence ratio conditions. The operating range of premixed swirl burner for stable swirl flame is found to exist between equivalence ratio of 0.70 to 0.90 for turn down ratio of 3:1.

• 한국안전학회지
• /
• 제19권1호
• /
• pp.124-130
• /
• 2004

수치법을 검증하고 번형률과 연료농도가 무중력 확산화염 구조에 미치는 영향을 파악하기 위해, 무중력에서의 비예혼합 메탄-공기 대향류 화염의 구조를 FDS의 축대칭 모사로 조사하였다. 연료 중의 메탄 몰분율 $X_m$=20, 50, 80%와 각각의 몰분율에서 변형률 $a_g$=20, 50, $90s^{-1}$의 계산결과를 1차원 화염코드인 OPPDIF의 결과와 비교하였다. 축대칭 모사로 계산한 온도와 축방향 유속의 분포가 1차원 모사 결과와 잘 일치하였다. 화염의 두께와 위치, 정체점을 잘 예측함으로써 FDS를 넓은 범위의 변형률과 연료농도의 대향류 화염에 적응할 수 있음을 확인하였다.

• 한국안전학회지
• /
• 제24권6호
• /
• pp.63-71
• /
• 2009

In order to improve flame retardancy, the halogen free organic melamine phosphate(M-P) flame retardant was synthesized from melamine and phosphoric acid by the reaction of precipitation. The ignition test was carried out preparing hybrid flame retardant compound($H_bFRC$) consisting of organic M-P and inorganic Mg$(OH)_2$ as a flame retardant in the polyolefin resins. The flame retardancy and mechanical properties of flame retardant aluminum composite panel($H_bFRC$-ACP) were performed to investigate the possibility of the composite material, which was contained M-P, as a inner core for $H_bFRC$-ACP. For this study, the results of ignition test indicate that a char formation and drip suppressing effect, and combustion time reduced as the content of M-P increased. The limited oxygen index(LOI) values were measured 17.4vol% and 31.5vol% for LDPE only and $H_bFRC$-3(M-P content: 15wt%), respectively. And it was verified that the $H_bFRC$-3 was needed more oxygen quantity with the increase of M-P content when it combustion. Also, the results from thermogravimetric analysis were observed endothermic peak at $350^{\circ}C$ and $550^{\circ}C$, it was confirmed predominant thermal stability though the wide temperature range by the mixture of M-P and Mg$(OH)_2$. The LDPE-ACP (using only LDPE as a inner core), $35.13kW/m^2$ of heat release rate(HRR) and 13.43MJ/m2 of total heat release(THR) were measured while the $H_bFRC$-ACP, $10.44kW/m^2$ of HRR and 1.84MJ/m2 of THR were measured by results of cone calorimeter test. In case of $H_bFRC$-ACP, the average gas emission amount of CO and $CO_2$ could be decreased down to 25% and 20%, respectively, in comparison with LDPE-ACP. The mechanical properties such as tensile strength, bending strength and adhesion strength of $H_bFRC$-ACP were revealed slightly high values $54N/mm^2$, $152N/mm^2$ and 120N/25mm, respectively, compared with LDPE-ACP. It was confirmed that flame retardancy was improved with the synergy effect because of char formation by M-P and hydrolysis by Mg$(OH)_2$. The result of this study suggest that $H_bFRC$ can be applied for an adequate halogen free flame retardant composite material as a inner core for ACP.

• 대한기계학회논문집B
• /
• 제20권8호
• /
• pp.2626-2636
• /
• 1996

A study of soot deposition and reentrainment was carried out both theoretically and experimentally to understand behavior of soot formed by incomplete combustion in a diesel engine. Theoretically, soot deposition on engine cylinder wall and/or piston head was studied with a stagnation point flow approximation. Soot reentrainment occurred upon exhaust gas blowdown was also studied by assuming a long-normal shear velocity distribution. Experimentally, a LPG$O_2/N_2$ flame impinging on a disk, produced by a concentric tubular burner, was chosen as deposition configuration and a shear flow unit with compressed air was installed for the study of reentrainment. For selected flame configuration, soot deposition measurements were conducted and showed that the dominant deposition mechanism was thermophoresis. Distributions of gas temperature and soot number density were estimated by combining data obtained by a B-type thermocouple with a thermophoretic transport theory. Disk temperature distributions were directly measured using a K-type thermocouple. Soot size and morphology were estimated from a TEM photograph. Ratios of soot deposit to reentrained amount were measured for a wide range of shear flow velocities, which showed that the reentrainment model was reasonable.