• Research Article

    Analysis of CH2O, CH, and C2 Species in a Single Droplet Flame and the Droplet Combustion Characteristics using a Short Wavelength Filtering

    단파장 필터링을 통한 단일 액적 화염 내 CH2O, CH, C2 화학종 분석 및 액적 연소 특성

    Young Chan Lim and Hyun Kyu Suh

    임영찬, 서현규

    This paper was performed to observe the flame behavior of the biodiesel, diesel, and n-heptane single fuel droplets and analyze the CH ... + READ MORE
    This paper was performed to observe the flame behavior of the biodiesel, diesel, and n-heptane single fuel droplets and analyze the CH2O, CH, and C2 species in a single droplet flame included combustion characteristics experimentally. In order to visualize the combustion process of test fuel droplets, droplet combustion visualization and analysis were conducted using a high-speed camera and a CCD camera coupled with a short wavelength filter. A single fuel droplet was formed on the stainless wire using a syringe and ignited by a heat source provided from the power supply equipment. It was shown that the ignition delay of an n-heptane fuel droplet was shorter than those of biodiesel and diesel fuel droplets due to a higher evaporation rate in the liquid phase. A longer flame extinction and the flame life-time were also observed in the biodiesel and diesel fuel droplets than most n-heptane fuel droplets. In the case of the diesel fuel droplet, it was found that the flame life-time was slightly increased than the biodiesel fuel droplet. The C2 species produced in the flame during combustion of all fuel droplets were distributed throughout the flame, while the CH and CH2O chemical species tended to be located in the flame front and center area. As a result of combustion analysis, the biodiesel, diesel, and n-heptane fuels were shown the changes of the CH2O mole fraction according to the two-stage combustion characteristics, and the mole fraction of CH species was decreased by CH + O2 and CH + H2O chemical reactions. - COLLAPSE
    September 2021
  • Research Article

    Numerical Study on Ideal Combustion Condition and NOx Emission for Natural Gas Replacing COG in a Ladle Burner of Steel Making Process

    제강공정 래들 버너의 COG 대체를 위한 천연가스의 적정 연소 조건및 NOx 배출 영향에 대한 전산해석 연구

    Jongmin Park, Woosuk Kang, Ryang-Gyoon Kim, Ho Lim and Changkook Ryu

    박종민, 강우석, 김량균, 임호, 류창국

    Because of increasing demand to utilize the coke oven gas (COG) for hydrogen production, there is a need to replace COG with ... + READ MORE
    Because of increasing demand to utilize the coke oven gas (COG) for hydrogen production, there is a need to replace COG with natural gas (NG) in the steel making industry. In this study, ideal combustion condition and impact on NOx emission were evaluated in a burner to preheat a ladle used for transport of molten iron. Computational fluid dynamics (CFD) were employed to analyze the distribution of temperature and heat flux in the refractories of an existing ladle. Then, different combustion conditions were assessed for the burner introducing NG. It was found that the same thermal condition of the refractories with the reference case can be achieved for NG combustion by reducing the excess air ratio to match the adiabatic flame temperature. A major NOx reduction was expected by the fuel switching because of lower peak temperatures and reduced contribution of NNH mechanism, which agreed with the field data. Increasing the thermal input of the burner led to a linear increase in the wall temperature and decrease in the thermal efficiency while NOx emission remained steady. Further investigations are required to improve the thermal efficiency by utilizing the enthalpy of the hot flue gas. - COLLAPSE
    September 2021
  • Research Article

    The Study of Turbulent Flame Characteristics by Plate Shape of Turbulence Generator

    난류생성기 판 형상에 의한 난류화염 특성 연구

    Yeonse Kang and Keeman Lee

    강연세, 이기만

    The cross-shaped fractal grids which have RRBT(reduced ratio of bar thickness) and the hexagonal grid were used to generate various turbulent ... + READ MORE
    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(U¯) and highest turbulent fluctuation(u') 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 u'/SL0 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. - COLLAPSE
    September 2021
  • Research Article

    A Numerical Study on NOx Emission by Using Micro Hydrogen Jet Flames

    마이크로 수소제트 화염을 이용한 NOx 배출 저감 특성에 관한 수치해석 연구

    Changhyun You and Sangsoon Hwang

    유창현, 황상순

    As exhaust gas regulations has become strick, interest in hydrogen used as a renewable energy has been increased. Recently research on low ... + READ MORE
    As exhaust gas regulations has become strick, interest in hydrogen used as a renewable energy has been increased. Recently research on low NOx emission through micro jet flame combustion methods has been carried out. In this study, multiple micro flame formation in the jet in the flow condition was assessed numerically. Particulary the flame shape and NOx emission characteristics according to the fuel-air momentum ratio were analyzed by changing the internal fuel cylinder diameter giving effects on the pressure drop and the size of the recirculation zone. Among the five momentum ratio (J) modes classified in jet in the flow geometry, the strong jet and jet dominated modes were studied in this study. In the strong jet mode, large J hardly makes the hydrogen jet deflected. On the other hand, In the case of the jet dominated mode the relatively high cross-flow momentum tends to make mixing rate suitable for making micro hydrogen flame. And the most important factor for NOx generation and emission in combustion using hydrogen fuel is considered to maintain a micro-flame using an appropriate momentum ratio. - COLLAPSE
    September 2021
  • Research Article

    Study on Various Catalytic Conditions for the Ignition of Hydrogen/Oxygen Mixture

    촉매의 조건에 따른 수소/산소 혼합 기체의 점화 특성 연구

    Minsig Hwang, Jongmin Shin, Tae Seong Roh and Hyoung Jin Lee

    황민식, 신종민, 노태성, 이형진

    A fundamental study was conducted to develop a combustor system using hydrogen catalyst reaction as an ignition source. Several variable conditions were ... + READ MORE
    A fundamental study was conducted to develop a combustor system using hydrogen catalyst reaction as an ignition source. Several variable conditions were selected to analyze the ignition characteristics using the catalyst; the main catalyst component, reduction temperature and reaction surface area of catalysts, and the equivalent ratio of the mixture gas. The platinum(Pt) catalyst was finally selected because of its excellent reactivity. The ignition performance was best when catalysts were reduced at 300°C. Moreover, the ignition performance was improved with a larger surface area and low equivalence ratio of mixture gas. XRD analysis and SEM photography were performed to identify the formation and crystallization of nano Pt particles. The analysis showed that Pt (111) crystals had the highest distribution at a reduction temperature of 300°C. Nano Pt particles were well-formed in the catalysts, but excessive heating degrades the catalysts' performance. This study identified the ignition characteristics of Pt catalysts, and successful catalytic ignition was observed in the designed experimental system. - COLLAPSE
    September 2021
  • Research Article

    Analysis of Turbulent Premixed Flames in V-shape Flames with Fractal Turbulence Generators: Part. II Characteristics of Turbulent Flame Structures

    프랙탈 난류생성판을 갖는 V-shape 화염에서 난류 예혼합 화염 분석: Part. II 난류화염의 구조 특징

    Juhan Kim and Keeman Lee

    김주한, 이기만

    This study focuses on the characteristics of turbulent flame structures in V-shape turbulent premixed flames to evaluate the turbulent combustion dynamics of ... + READ MORE
    This study focuses on the characteristics of turbulent flame structures in V-shape turbulent premixed flames to evaluate the turbulent combustion dynamics of fractal turbulence generator. The details of the non-reactive turbulent flow characteristics with the fractal turbulence plate were explained in the previous study of Part I. In this work, the integral length scale of non-reactive flow was additionally investigated to obtain a Borghi-Peters diagram. By comparing the Borghi-Peters diagram shown as a result of the non-reactive flow with the reaction OH-PLIF image, it was confirmed that the flame characteristics for each regime were well represented. Also, the irregular turbulence of premixed flame was quantitatively analyzed using the flame brush obtained by the mean progress variable method. As a result, the flame brush of the fractal turbulence generator was wider than the perforated plate and mesh type. Finally, it was found that the thickness and angle of the flame brush were proportional to the turbulence intensity and turbulent Reynolds number, which are dimensionless numbers of turbulent flow. - COLLAPSE
    September 2021
  • Technical Notes

    A Study on the Methodology for the Boiler Combustion Optimization of Thermal Power Plant based on Soft Computing Approach Reflecting Changes in the Operation Environment

    기력발전 운영 환경 변화를 반영한보일러 연소 최적화 기술의 소프트컴퓨팅적 접근 방법론 연구

    Jinsoo Kim and Bumshin Kim

    김진수, 김범신

    In this paper, in order to evaluate the availability of the boiler combustion optimization of MPC technology for the current method of ... + READ MORE
    In this paper, in order to evaluate the availability of the boiler combustion optimization of MPC technology for the current method of thermal power generation operation, two cases of experiment were implemented. Firstly, an experiment was performed using simulator linkage and actual process operation information. As a result, it was possible to obtain effects such as reducing overshooting when the target load was reached when linking the simulator. Secondly, an experiment was performed using actual operation information for optimizing combustion-related variables. However. the result of optimization by MPC solution was difficult to apply to actual process control. This is because the mechanical power generation control system is designed for the purpose of following the demand load, ① it is difficult to define a clear causal relationship between the process operation variables and nitrogen oxides and carbon monoxide, and ② data preprocessing techniques for handling disturbances and time delays. It could be confirmed that this was due to the inadequacy of the optimization technique among the multiple conflicting variables. To supplement this, soft-computing approaches including ① data linearization applying Bayesian optimization method, ② generalization of process situation prediction algorithm through application of multi-stage machine learning prediction structure and incremental data utilization, ③ global optimization method through combination of empirical-heuristic optimization algorithm are introduced to optimize the boiler combustion of thermal power plant. - COLLAPSE
    September 2021