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Space-Filling Square Fractal 격자에서 발달된 난류 유동 내 자유 전파하는 저선회 화염의 특성에 관한 연구
강연세(Yeonse Kang),이기만(Keeman Lee) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
The turbulent flow generated by applying the space-filling square fractal grid to the shape of the central turbulence generating plate, which plays a key role in forming the lifted flame of the low swirl injector, was observed in the nonreacting and reacting flow fields. Through the study of the non-reacting flow field, the turbulent mean velocity profile before and after the nozzle was investigated, and it was observed that the characteristic of divergent flow without an inner recirculation region was observed. Furthermore, the development and dissipation region of turbulent energy induced by the fractal grids were classified through the turbulent intensity, which is expected to generate various interactions between the turbulent flow and the turbulent flame front in the lifted flame configuration.
강연세(Yeonse Kang),이기만(Keeman Lee) 한국연소학회 2021 한국연소학회지 Vol.26 No.3
The cross-shaped fractal grids which have RRBT(reduced ratio of bar thickness) and the hexagonal grid were used to generate various turbulent flow properties for low swirl flames. In the non-reacting flow field with the fixed bulk velocity at 10 m/s, decreasing RRBT induces the increasing turbulent intensity(IU) with the delay in the location of lowest turbulent mean velocity(Ū) and highest turbulent fluctuation(ú) due to vortex shedding from the bar thickness. This phenomenon was well explained by a wake interaction theory using axial velocity profiles at the centerline. At various equivalence ratios for Hexa. and fractal grids, the characteristics of low swirl flames could be identified to a thin reaction zone regime in the Borghi – Peter regime diagram. Decreasing RRBT increases IU in front of flame brush with increasing turbulent local displacement speeds (ST,LD) via a linear correlation. The turbulent Reynolds number, ReT composed of the ratio of length scale and velocity components induced the proportional trends in non linear relationship showing that the influence of the length scale ratio. The empirical correlation study of ST,LD as a function of ReT and ú/S<SUP>0</SUP>L was investigated to compare the influence of velocity and turbulent length scales ratio. The result of linear correlation equation with ST,LD indicates the influence of velocity factors greater than ReT through the exponential factor.
강연세(Yeonse Kang),이기만(Keeman Lee) 한국연소학회 2019 KOSCOSYMPOSIUM논문집 Vol.2019 No.5
The Synthetic Nature Gas(SNG) generated by the gasification process of coal were concerned for another major energy sources. but unlike a single fuel, its characteristics are complex and has a lot of difficulty for control the flame. The SNG C11 fuel has high hydrogen contents(H₂: 11%) for advantage of extending the extinction boundary which caused by H₂’s preferential diffusion effect. The thermal and chemical interaction between the asymmetric twin flames using a counterflow burner was looked using the structure of the 1D flame. The extinction phenomena of LEB and REB according to the starting point of the extinction boundary was observed. In the case of the LEB was possible to observe the sustain of the weaker flame through the continuous consumption of H₂, while REB’s the weaker flame showed a phenomenon of concentrating on thermal interaction than the chemical’s effects. To figure out difference of interaction phenomenon in LEB, REB, the tendency of the major, key, intermediate species will be observed in detail structure of the sustained flame.
상호작용하는 SNG-Air 희박 예혼합 비대칭 화염의 소화 특성
강연세(Yeonse Kang),안지환(Jihwan Ahn),심근선(Keunseon Sim),이기만(Keeman Lee) 한국연소학회 2020 한국연소학회지 Vol.25 No.4
Experimental and numerical studies were conducted to clarify the extinction mechanism in mutually interacting SNG (synthetic natural gas) - air premixed asymmetric counter-flow flames. The detailed kinetic mechanism of UC San Diego with which the priority of predicting measured extinction boundaries was validated was adopted to analyze various aspects via up and downstream interactions on extinction boundaries in the flame stability map. The flame stability map was presented with a functional dependency on methane mole fractions in the cold stream ejecting from upper and lower nozzles by varying the global strain rate. Increasing global strain rate lead gradually slanted and configuring of island flammable region and finally only one flammable condition at 740 s<SUP>-1</SUP> through the shrinkage of flammable region. The interacting lean-lean asymmetric flames of extinction boundaries have flame speed of positive (negative) depending on the deviation of methane mole fraction for two reactants. The extinction mechanism of those flames was explained and discussed by emphasizing important role of downstream chemical interaction (via H and CO) and upstream thermal interaction (via conductive heat loss from stronger flame to unburned mixture).