• Research Article

    Digital Twin for Prediction of the Steady State Temperature Field of a Natural Gas Boiler

    천연가스 보일러 내부 정상상태 온도장 예측을 위한 디지털 트윈 구축에 대한 연구

    Jinwoo Park, Woojin Lee, Sungbum Kim and Kang Yul Huh

    박진우, 이우진, 김성범, 허강열

    In this study, a simulation-based digital twin is developed for large-scale industrial natural gas boiler. The digital twin can predict temperature distribution ... + READ MORE
    In this study, a simulation-based digital twin is developed for large-scale industrial natural gas boiler. The digital twin can predict temperature distribution under unexplored operating conditions by a regression model and a limited number of sensor data. The former is generally known as a surrogate model and the latter is known as sparse reconstruction. Proper orthogonal decomposition method is employed together with a kriging regression model for the surrogate model and gappy proper orthogonal decomposition for sparse reconstruction. Three-dimensional simulation data of the natural gas boiler are collected in the parameter space, which consists of excess air rate and swirl vane angle of the device. The surrogate model provides prediction performance within 5% least squared error. With sparse reconstruction, more than 32 measuring points provides prediction performance within 10% least squared error. The results show that the proper orthogonal decomposition has high potential as an analysis method for digital twin and prediction of reacting scalars in industrial combustion devices. - COLLAPSE
    June 2021
  • Research Article

    An Experimental Study on the Characteristics of Bottom Ashin Biomass Boiler

    바이오매스 전소 보일러 내의 바닥재 연료 특성 연구

    Kyeong-Ho Kim, Tae-Yong Jeong, Seung-Mo Kim, Ha-young Park, Nam-gu Han and Chung-Hwan Jeon

    김경호, 정태용, 김승모, 박하영, 한남구, 전충환

    This study focused on the characteristics of bottom ash produced in the combustion process in the biomass boiler furnace, measuring the possibility ... + READ MORE
    This study focused on the characteristics of bottom ash produced in the combustion process in the biomass boiler furnace, measuring the possibility of re-combustion, and considering its availability as a new renewable energy alternative to coal. This study examined the availability of renewable energy as fuel and selected bottom ash, wood pellet, pre-treated torrefied wood pellet and AVRA coal with physical properties similar to those of bottom ash. From the results obtained by conducting experiments in thermo-gravimetric analysis, the reaction rate constant for each sample was derived by coates-redfern method. A drop tube furnace experiment compared the predicted generation results of nitrogen oxides and unburned carbon compounds in the combustion furnace. thermally treated biomass grindability index experiment determined the grindability between bottom ash and each sample. - COLLAPSE
    June 2021
  • Research Article

    Critical Effects of Temperature and Relative Humidity on Thermal Performance on Aging of NASA Standard Pyrotechnic Initiator ‘ZPP’

    NASA 표준 파이로테크닉 개시제 ‘ZPP’의 노화에 대한 온도 및 습도가 열 성능에 끼치는 영향과 효과

    Juyoung Oh and Jai-ick Yoh

    오주영, 여재익

    The aging of the pyrotechnic materials, which is usually referred to as oxidation of metal fuels, causes chemical composition changes that can ... + READ MORE
    The aging of the pyrotechnic materials, which is usually referred to as oxidation of metal fuels, causes chemical composition changes that can result in performance degradation. In this study, critical aging effects on zirconium potassium perchlorate (ZPP), one of the representative materials among NASA standard pyrotechnic initiators were provided. Especially, the hygrothermal aging effects on the thermal performance and lifespan of ZPP were identified via thermal analysis. In addition, reaction kinetics considering the hygrothermal aging effects is newly presented for the first time and the fact that high relative humidity (RH) conditions can lead to major chemical composition changes such as 'fuel oxidation' and 'oxidizer decomposition' in ZPP was found by using the X-ray photoelectron spectroscopy (XPS) technique. Such chemical composition changes gave rise to inadequate performance and led to negative feedback after all. Meanwhile, by substituting the extracted kinetic parameters and heat of reactions into the van't Hoff equation, we have found that a high moisture environment (RH 100%) can reduce the lifespan of ZPP by up to 85%. In conclusion, the RH condition can act as one of the essential variables that critically affect the thermal performance of pyrotechnics. - COLLAPSE
    June 2021
  • Research Article

    An Experimental Study on the Combustion Kinetics and Ash Melting Characteristics of Two Kinds of South Korean Coal Gangue using TGA and TMA

    TGA, TMA를 이용한 국내 석탄 폐석의 연소 동특성 및 회 용융 특성에 관한 실험적 연구

    Yijie Zeng, Kyeong-Ho Kim, Viet Thieu Trinh, Dongfang Li and Chung-Hwan Jeon

    쩡이제, 김경호, 찐비엣티에우, 이동방, 전충환

    Coal gangue has a potential to be used as fuel in a circulating fluidized bed boiler. However, there are few studies on ... + READ MORE
    Coal gangue has a potential to be used as fuel in a circulating fluidized bed boiler. However, there are few studies on it in South Korea. In this study, the combustion characteristics and kinetics of coal gangue were investigated by thermogravimetric analysis at different heating rates (20, 30, and 40°C/min) under air atmosphere. The experimental results indicated that a higher heating rate would improve the oxidation reaction ratio of coal gangue. And the combustion characteristic index (S) indicates that coal has better combustion performance than coal gangue. The kinetic behavior was evaluated with the model-free (Flynn-Wall-Ozawa methods) and model-fitting (Coats-Redfern methods). The activation energy values obtained from the Flynn-Wall-Ozawa method showed the activation energy of coal is less than coal gangue. This result is the same as that of the Coats-Redfern methods. In addition, ash melting temperature, slagging, and fouling are related to ash deposition. In order to predict the ash deposition characteristics of coal gangue in this study was researched by using Thermo-Mechanical Analysis. The results showed that coal gangue has higher ash melting temperature than coal. However, coal gangue has a higher K2O content of ash. Therefore, as a circulating fluidized bed fuel should pay attention to the occurrence of slagging. - COLLAPSE
    June 2021
  • Research Article

    Analysis of Turbulent Premixed Flames in V-shape Flames with Fractal Turbulence Generators: Part. I Turbulent Flow Characteristics in a Non-Reacting Field

    프랙탈 난류생성판을 갖는 V-shape 화염에서 난류 예혼합 화염 분석: Part. I 비반응장의 난류유동 특성

    Juhan Kim and Keeman Lee

    김주한, 이기만

    In this study, various fractal grids are used to investigate the non-reacting turbulent flow characteristics of a circular fractal turbulence generator. The ... + READ MORE
    In this study, various fractal grids are used to investigate the non-reacting turbulent flow characteristics of a circular fractal turbulence generator. The types of fractal grids used as turbulence generators are cross and square, and a total of 24 grids produced by changing the shape parameters are investigated. Also, to compare the characteristics of turbulent flow, a general perforated plate with the same blockage ratio is used together. In the center axis turbulence component results, the two types of fractal grids show different turbulence component tendency depending on their shape parameters, and are investigated individually. As a result of quantitatively confirming the difference in turbulence intensity using the percentage difference method, the two types of fractal grids produced stronger turbulence than the conventional grids (perforated plate and mesh). The results of (r, z) plane measurements show that the shape of the turbulent generator significantly affects the turbulent component after nozzle exit. The inhomogeneity of the turbulence component was more severe in the square grid than in the cross and conventional grids, but as the blockage ratio of the square grid increased, the homogeneity of the turbulence component showed a tendency to improve. - COLLAPSE
    June 2021