• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.6
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• pp.1669-1678
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• 1990

The annular and coaxial swirl flows between which LPG is supplied was selected to study the swirling flames in double co-swirl flows. The objective of this study is to research into the effects of double co-swirl flow conditions on the stability limit, the reverse flow boundary, and the time mean temperature distributions of the swirling flames. The increase of swirl intensity of axial flow makes the stability limit decrease, but the annular swirl flow (SM>0.5) makes stability and swirl intensity of axial flow increase, And the existence of axial swirl flow makes flame intensive and small in size, and this may be applicable to the design of high power compact combustor.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.3
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• pp.1028-1039
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• 1996

This study was focused on the examination of the flame structure and the combustion characteristics of diffusion flame which was formed the turbulent shear flow of a double coaxial air jet system. The shear flow was formed by the difference velocity of surrounding air jet(U$\_$s/) and center air jet (U$\_$c/). So experimental condition was divided S-type flame (.lambda. > 1) and C-type flame (.lambda. < 1) by velocity ratio .lambda. (=U$\_$s//U$\_$c/). For examination of the flame structure and the combustion characteristics in diffusion flame, coherent structure was observed in flame by schlieren photograph method. We measured fluctuating temperature and ion current simultaneously and accomplished the statistical analysis of its. According to schlieren photograph, the flame was stabilized in the rim of the direction of lower velocity air jet, coherent eddy was produced and developed by higher velocity air jet. The statistical data of fluctuating temperature and ion current was indicated that reaction was dominated by higher velocity air jet. The mixing state of burnt gas and non-burnt gas was distributed the wide area at Z = 100 mm of C-type flame.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.04a
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• pp.9-9
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• 1998

가스터빈 연소기의 난류유동장을 구성하는 기본적인 유동형태는 크게 밀폐관내의 돌연 확대를 가지는 동축제트, 선회유동, 그리고 연소공기공 및 회석공기공을 통해 연소실에 수직방향으로 유입되는 제트유동 등으로 분류할 수 있다. 실제 가스터빈 연소기내의 난류유동장을 수치해석하기 위해서는 임의의 형상을 갖는 3차원 유동장을 모사할 수 있는 수치해석법과 고차정확도를 유지하면서도 수렴안정성을 만족시키는 대류항 처리기법 등과 같은 수치모델의 개발이 선행되어야 하며, 이와 함께 복잡한 난류연소유동장을 정확히 묘사할 수 있는 난류모델 및 난류연소모델의 개발 및 검증이 가장 중요한 요인이 된다. 또한 가스터빈 연소기의 최적 설계는 넓은 작동구간에서 높은 효율, NOx 및 CO 배기량의 저감, 희박연소 가연한계의 확장, 연소계통에서의 낮은 압력강하, 낮은 연소벽면온도와 온도구배를 유지시키기 위한 공기에 의한 충분한 냉각 같은 서로 상충되는 설계조건을 만족해야 한다. 그리고, 이러한 상충된 연소설계조건들을 충족시키는 최적 연소기의 설계를 위해서는 실험적인 연구뿐만 아니라 연소기내의 물리적인 현상을 잘 반영할 수 있는 물리적 모델을 바탕으로 한 연소유동의 해석적인 연구를 필요로 한다. 본 연구에서는 원통형 가스터빈 연소기의 등온 및 연소유동장, 그리고 연소기와 연결되는 Scroll 내부의 난류유동장에 대한 수치해석을 수행하여 수치 및 물리모델의 예측능력을 검증하였고, 가스터빈 연소유동장 해석에 관련된 중요 논점들에 대하여 심도있게 분석하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.3
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• pp.285-291
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• 2012

A lot of research on the stability of nonpremixed flames has focused on the fuel-nozzle and quarl geometries. Of the work carried out, only a small amount has focused on the stability of the nonpremixed flame according to the recession distance and air-nozzle geometry. Therefore, in this study, a coaxial-diffusion-type gas burner with a swirler is designed for the systematic investigation of the combustion characteristics of a $CH_4$ flame depending on the recession distance and secondary air-nozzle geometry. 1st air is flowed through the swirler, and 2nd air is flowed through each nozzle. It is shown that the secondary air velocity greatly influences the flame length and shape. There is an optimum recession distance for each nozzle for the best combustion efficiency. In this study, it is shown that the optimized recession distance is nearly half the outer diameter of the air-supply nozzle.