• Research Article

    A Numerical Study on NOX Emission of Swirl Premix Burner Affected by Air Fuel Ratio and Air Slit Area in a Model Gas Turbine Combustor

    스월 예혼합 버너를 장착한 가스터빈 연소실에서 공연비와 공기 슬릿 면적 변화에 따른 NOX 배출에 관한 수치적 연구

    Yuan Gang Wang, Jun Ho Park and Chae Hoon Sohn

    왕위엔강, 박준호, 손채훈

    Two factors that affect NOX emission of swirl premix burner are investigated numerically in the present study. The first one is ... + READ MORE
    Two factors that affect NOX emission of swirl premix burner are investigated numerically in the present study. The first one is air fuel ratio which is changed from 31.7 to 38.7 by keeping the air flow rate and decreasing the fuel flow rate. As the air fuel ratio increases, the mixing is enhanced and temperature of a model combustor decreases. Then, the NOX emission decreases. The second factor is the air slit area of the burner. Air slit area is reduced by changing the width of slit with 3 methods depending on the position, i.e., width decrease in the upper-side, the lower-side, and both sides. The velocity of air inflow increases as the air slit width decreases. Then, unmixedness inside the burner will be reduced, which results in reduction of NOX emission. This strong correlation between unmixedness and NOX emission verifies that NOX reduction can be attained by mixing enhancement of fuel and air inside the burner. - COLLAPSE
    December 2020
  • Research Article

    The Extinction Characteristics of Interacting SNG-Air Lean Premixed Asymmetric Flames

    상호작용하는 SNG-Air 희박 예혼합 비대칭 화염의 소화 특성

    Yeon Se Kang, Jih Wan Ahn, Keun Seon Sim and Kee Man Lee

    강연세, 안지환, 심근선, 이기만

    Experimental and numerical studies were conducted to clarify the extinction mechanism in mutually interacting SNG (synthetic natural gas) - air premixed asymmetric counter-flow ... + READ MORE
    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-1 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). - COLLAPSE
    December 2020
  • Research Article

    Effects of Insulation Thickness on Flame Spread over Electrical Copper Wire with Applied AC Electric Fields

    AC 전기장이 인가된 구리 전선을 통해 전파하는 화염에 대해 피복재의 두께에 따른 화염 거동에 대한 실험적 연구

    Min Sung Kang, Chun Sang Yoo, Jeong Park, Suk Ho Chung and Oh Boong Kwon

    강민성, 유춘상, 박 정, 정석호, 권오붕

    Effects of insulation thickness on flame spread over electrical copper wires with applied AC electric fields were experimentally investigated. The AC volrage ... + READ MORE
    Effects of insulation thickness on flame spread over electrical copper wires with applied AC electric fields were experimentally investigated. The AC volrage and frequency varied in ranges of 0-5 kV and 10-1000 Hz, respectively. A one electrode configuration was used such that the electric potential was applied to one wire end and thus the infinite ambience could be a ground. The results showed that the flame shape and the tilting direction were significantly influnced by applied voltage and frequency. The flame spread rate decreased in an increase of insulation thickness as well as varied sensitively with applied votage and frequency. Additionally, the molten polyethylene (PE) experienced various dynamic behaviors such as dripping of molten PE, electrospray, di-electro-phoresis, and rotation of molten PE, essentially affecting the flame spread rate. These complicated phenomena were systematically analyzed and discussed. - COLLAPSE
    December 2020
  • Research Article

    Effects of Biomass Particle Size on Flame Structure and Combustion Characteristics using Blended Coal/Biomass Fuel in a Pulverized Coal Swirl Burner

    미분탄 스월버너에서 석탄/바이오매스 혼소시 바이오매스 입자 크기가 화염구조 및 연소특성에 미치는 영향

    Ye Seul Park, Min Sung Choi, Xin Zhuo Li, Chan Ho Jeong, Ji Hoon Lee and Gyung Min Choi

    박예슬, 최민성, 리신줘, 정찬호, 이지훈, 최경민

    The flame structure and combustion characteristics of co-firing coal and LPG with different sizes of biomass were investigated in a dual swirl ... + READ MORE
    The flame structure and combustion characteristics of co-firing coal and LPG with different sizes of biomass were investigated in a dual swirl pulverized coal burner by using a high-speed camera with bandpass filter and PIV system. Three sizes of spent mushroom compost (<45, 45~90, 90~150 µm) were cofired with pulverized coal (45~90 µm) at a blending ratio of 20%. When the biomass of the same size with coal was used, the turbulence intensity had the highest uniformity while other cases exhibited locally strong turbulent intensity. The combustion using <45 µm biomass was terminated early compared to other conditions, whereas the reaction region was the widest for 45~90 µm biomass. The flame had uniform turbulent intensity with wide and strong reaction when the biomass size was equal to that of coal. When using 45~90 µm of biomass, high velocity was maintained in the overall region and CH* radical was observed in a wide region with the highest radical intensity. - COLLAPSE
    December 2020
  • Research Article

    Effect of Low Temporal Resolution on the Uncertainty of Resolving Flame Speed of Moving Flames

    저시간 분해능으로 인한 화염 속도 분석의 불확실성

    Dong Hyuk Shin

    신동혁

    This paper analyzes the effect of low temporal resolution on the accuracy of determining the local flame speed for experimental measurements and ... + READ MORE
    This paper analyzes the effect of low temporal resolution on the accuracy of determining the local flame speed for experimental measurements and simulations. Flame speed measurement of moving flames requires the evaluation of a temporal derivative of flame front motion. Measurements have limited temporal resolution, which can lead to a bias error in the calculation of flame speed. The error associated with the temporal resolution was derived in the leading order effect on sampling time. In order to demonstrate the error term, we employed numerical examples. Artificial flame solutions are generated by solving the G-equation with prescribed flow fields and fine spatial/temporal resolutions. By varying the sampling time step, we demonstrated the error can lead to negative values of the measured flame speed. Furthermore, when coarse sampling time steps are used, the calculated flame speed also exhibits a spurious curvature dependency. Lastly, the associated error can be estimated by spatial gradients of the flame front for convection dominated flows. - COLLAPSE
    December 2020
  • Research Article

    Investigation on the Effect of the Burner Outlet Configuration on the Combustion Characteristics of a Swirl-premixed Burner

    스월-예혼합 버너의 출구 형상 변화에 따른 연소 특성 분석

    Hae Ji Ju, Ju Hyeong Cho, Jeong Jae Hwang, Min Kuk Kim, Han Seok Kim and Won June Lee

    주해지, 조주형, 황정재, 김민국, 김한석, 이원준

    This study investigated the effect of the outer recirculation zone(ORZ) on the combustion characteristics and NOX emissions. Numerical simulation and ... + READ MORE
    This study investigated the effect of the outer recirculation zone(ORZ) on the combustion characteristics and NOX emissions. Numerical simulation and experimental test were conducted for the combustors with two types of the burner outlet. The ORZ is formed conspicuously for a flat type with sudden expansion outlet while it is formed in a negligible size for a curved type with gradual expansion outlet. In a higher adiabatic flame temperature(AFT) condition of 2020 K, the NOX emission of the flat type is increased by 19% compared with the curved type as the ORZ has long residence time and high temperature enough to produce the thermal NOX. On the other hand, the NOX emission of the flat type is decreased slightly in a lower AFT of 1850 K as the temperature of the ORZ is not high enough to significantly produce the thermal NOX. The tendency of the calculated NOX emission is consistent with the experiment results. - COLLAPSE
    December 2020