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Lightweight Magnesium Bipolar Plates of Direct NaBH4/H2O2 Fuel Cell for AIP Application
Kim, Jihyun,Jang, Bosun,Lee, Taesong,Kwon, Sejin Walter de Gruyter GmbH 2015 International journal of turbo & jet-engines Vol.32 No.3
<B>Abstract</B><P>Fuel cell based power systems have high energy density. However, using H</P>
Lee, Taesong,Park, Junhyeong,Han, Dongsik,Kim, Kyu Tae Elsevier Inc 2019 Proceedings of the Combustion Institute Vol.37 No.4
<P><B>Abstract</B></P> <P>The presence of strong interactions between adjacent flames is inevitable in most practical gas turbine combustion systems. Despite the fundamental and practical importance of this configuration, an accurate description of the dynamics of multiple interacting swirl-stabilized flames is still lacking. To better understand the key processes, we have examined flame transfer/describing functions (FTF/FDF) of two interacting lean-premixed flames in a model gas turbine combustor equipped with two identical fuel nozzles. Unlike non-swirling flames, two adjacent swirl-stabilized flames are defined as having either co-rotating or counter-rotating interaction, depending on the relative direction of azimuthal velocity components. The FTF/FDF of interacting swirl flames for these two impingement conditions are analyzed in reference to the corresponding single nozzle (SN) data to provide physically important insight into the nature of flame–flame interactions in a multi-nozzle (MN) environment. It is first shown that both FTF and FDF are heavily influenced by the combination of swirl rotational directions, since the local flame/flow properties in the interacting region are mainly controlled by the jet impingement patterns. Our results suggest that there is considerable discrepancy between the SN and MN data, implying that the use of SN FTF data for the prediction of the MN flame dynamics can lead to erroneous results. Quantitative analyses of extensive self-excited instability data reveal that the degree of temporal synchronization between adjacent flames is a necessary condition for the onset of the instabilities.</P>
희박 예혼합 메조스케일 다중노즐 수소 화염의 곡률 분포
이태송(Taesong Lee),김규태(Kyu Tae Kim) 한국연소학회 2021 한국연소학회지 Vol.26 No.1
Local structures of lean fully-premixed hydrogen-air flames in a mesoscale multinozzle array were studied in a tunable combustion test facility, using instantaneous OH PLIF measurements and subsequent image processing techniques. We observe that under thermoacoustically stable conditions, pure hydrogen flame ensemble takes on a conical structure and they are stabilized in isolation without strong flame-to-flame interactions. Under unstable conditions, however, marked flame front deformation and cusp formation occur due to high amplitude velocity fluctuations. Our curvature calculation results reveal that the probability density function distribution is characterized by a positive average value, meaning that the formation of convex contours is more pronounced in lean-premixed pure hydrogen combustion environment.
Staggered swirler arrangement in two self-excited interacting swirl flames
Lee, Taesong,Lee, Jiho,Park, Junhyeong,Han, Dongsik,Kim, Kyu Tae Elsevier 2018 Combustion and flame Vol.198 No.-
<P><B>Abstract</B></P> <P>Interference of acoustic and convective disturbances controls the development of self-excited combustion oscillations of a lean-premixed swirl-stabilized flame with a central bluffbody. How this interference mechanism influences the dynamics of multiple interacting flames in a multi-nozzle environment is currently unknown. Here we present observations of a multi-nozzle system's response to staggered swirler arrangements (<I>ξ</I> <SUB>sw, 1</SUB> ≠ <I>ξ</I> <SUB>sw, 2</SUB>) as compared to non-staggered arrangements; the distance between the swirler and the flame is the dominant length scale of vortical disturbances. Our results demonstrate that a slight modification of the swirler arrangement in the streamwise direction – staggered or non-staggered – has a remarkable influence on the stability map of the whole combustion system. Phase-resolved flame imaging measurements indicate that under non-staggered conditions interacting swirl flames feature a coherent motion during a period of oscillation. By contrast, the staggered swirler combination creates significantly non-symmetric flame dynamics, disturbing the development of well-organized motion over the entire reaction zone. Flame surface modulations in the lateral direction are particularly pronounced due to the formation of non-symmetric convection delays of vortical disturbances between adjacent swirl nozzles. For a given swirler arrangement, the system's response to a wide range of combinations of mean nozzle velocities, including symmetric ( <SUB> u ¯ 1 </SUB> = <SUB> u ¯ 2 </SUB> ) and non-symmetric ( <SUB> u ¯ 1 </SUB> ≠ <SUB> u ¯ 2 </SUB> ) conditions, were explored to account for the simultaneous effects of the two convection parameters. Our data show that a major determinant of the onset of the instability is the combination of the Strouhal numbers, 〈St<SUB>1</SUB>, St<SUB>2</SUB>〉, which can be even or uneven depending on the manipulation of the convection time of each nozzle.</P>