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덤프 연소기에서의 유동 및 음향 조건에 따른 화염특성 연구
황동현(Donghyun Hwang),송윤호(Yoonho Song),안규복(Kyubok Ahn) 한국추진공학회 2015 한국추진공학회 학술대회논문집 Vol.2015 No.11
덤프 연소기는 가스터빈 엔진 및 램제트 엔진에 주로 사용되며, 연소실 내에서의 높은 에너지 밀도로 인해 연소불안정에 취약하다고 알려져 있다. 연소불안정 발생 시 압력섭동과 유동섭동으로 인해 화염의 위치 및 길이가 달라진다. 본 논문에서는 연소불안정과 연소 능동제어를 위한 선행 연구로서 덤프 연소기에서 에틸렌과 공기를 이용해 실험을 수행하였다. 연소불안정 모사를 위해 스피커를 이용한 가진 방법을 사용하였고, 음향가진 조건에 따른 압력섭동을 연소실과 입구에서 측정하였다. CH chemiluminescence 기법을 이용하여 유동 및 음향 조건에 따른 화염길이 및 화염중심 위치의 변화를 측정하였다. Dump combustor is mainly used in gas turbine engines and ramjet engines, and is well known to have encountered combustion instabilities due to high energy density in a combustion chamber. Under combustion instabilities, pressure and velocity fluctuations modify flame lengths and locations. In this paper, experiments using ethylene and air were performed as preceding research for combustion instability and combustion active control. An acoustic driver was used to simulate combustion instabilities, and pressure fluctuations were measured at the inlet and chamber of the dump combustor under several flow and acoustic conditions. Flame lengths and flame center locations were also detected using a CH chemiluminescence technique.
다양한 탄화수소 연료를 이용한 난류 예혼합 화염에서 화염길이 스케일링
황동현(Donghyun Hwang),왕가흠(Kexin Wang),안규복(Kyubok Ahn) 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.5
덤프연소기에서 다양한 탄화수소 계열의 연료를 이용한 화염길이 및 화염중심위치 스케일링이 실험적으로 수행되었다. 덤프연소기는 가스터빈엔진과 램제트엔진에 주로 사용된다. 하지만 높은 에너지 밀도로 인해 연소불안정에 취약하며 연소불안정 발생 시 압력섭동 및 유동섭동으로 인해 화염의 길이 및 중심위치가 변한다. 이번 연구는 에틸렌, 에탄, 프로판 그리고 공기를 사용하였다. 또한 불안정한 유동조건을 모사하기 위해 스피커를 사용하였고, 화염이미지는 CH* chemiluminescence 기법을 적용한 ICCD 카메라를 이용해 촬영하였다. 본 연구의 목적은 입구속도, 당량비, 음향가진에 따른 화염길이 및 화염중심위치의 변화를 조사하고 Reynolds, Strouhal, Damkohler 수와 같은 무차원수들과의 상관관계를 조사하였다. Flame length and flame center length scaling using different hydrocarbon fuels in a dump combustors were conducted experimentally. Generally, dump combustor is used gas turbine engines and ramjet engines. However, it has weakness for combustion instabilities because of high density energy and the flame length and flame center length are changed due to pressure and velocity fluctuation under combustion instabilities. In this work, experiments using ethylene, ethane, propane and air were performed. Also, an acoustic driver was used to simulate unstable flow condition and flame images were taken using ICCD camera with a CH* chemiluminescence technique. The objectives were to investigate about the effects of inlet velocity, equivalence ratio, acoustic forcing frequency on flame lengths and flame center lengths and to examine correlation between normalized flame lengths/flame center lengths and the non-dimensional parameters such as Reynolds, Strouhal, Damkohler number.
황동현 ( Donghyun Hwang ),박재민 ( Jaemin Park ) 한국생산성학회 2018 生産性論集 Vol.32 No.1
This paper describes industrial sector efficiency comparison by technology level through input oriented DEA methodology and shows a differentiated cause-effect relationship by independent variables in each technology level (OECD industrial classification of R&D intensity: low, medium-low, medium-high, and high). In Korea manufacturing industry, sectoral DEA approach of technical efficiency by technology level was un-precedent and could guide productivity improvement idea in a different technology level sector. In the efficiency comparison, medium-high technology sector is more efficient than medium-low and low technology sectors, but high technology sector’s is lower than medium-high sector due to more diverse employee and researcher structure. In a low technology sector, firms could improve efficiency through R&D investment. The other insight is that R&D investment, employee & researchers does not always improve efficiency especially in inefficient firms, which indicated that firms have to optimize their input factors effectively, sometimes reducing or transferring resources such as R&D investment according to its technology level. R&D investment would improve technical efficiency only in low-technology firms. In a cause and effect of efficiency, high tech. firms would have to choose a production scale to improve their scale efficiency. So far, “technology regime” topic of Marlerba & Osenigo(1996, 1997) has been researched with STEPI’s business innovation survey outcome by many researchers and indicated that R&D investment could induce a different outcome based on innovation condition and knowledge basement. In the meantime, Efficiency related research has focused on only firm-level studies without level-up to technology level. Thus, a combination of the both would be a new approach, which would be able to give a benchmarking idea to inefficient firms by technology level. For a future study, it would be meaningful to study an innovation and knowledge basement condition role with sub-industries categorized by sectoral innovation system. But, I also have to acknowledge that R&D investment and revenue at a same year could be a statistical issue of multi-collinearity though it comes from a survey data sample’s restriction.
황동현(Donghyun Hwang),안규복(Kyubok Ahn) 한국추진공학회 2016 한국추진공학회지 Vol.20 No.6
For the active control of a combustion instability, a change should be made in pressure fluctuation or heat release fluctuation using an acoustic driver or a secondary fuel injection. Also, to determine the location and timing of a secondary fuel injection, one needs to know the distribution of heat release fluctuation under combustion instability. In the present research, the distribution of heat release fluctuation has been experimentally measured by changing hydrocarbon fuel, inlet velocity, equivalence ratio, and acoustic forcing condition. It was confirmed that heat release fluctuation with regards to vortex shedding was significantly affected by the Damköhler number. Under the cases of the Damköhler number above approximately 4 – 5, hot spot region was generated in the leading edge of vortex and cold spot region was in the trailing edge. On the contrary, the cases of the Damköhler number below 3 showed the opposite trend.