IMPACT OF THE PRECESSING VORTEX CORE ON NOX EMISSIONS IN PREMIXED SWIRL-STABILIZED FLAMES: AN EXPERIMENTAL STUDY

被引:0
作者
Lueckoff, Finn [1 ]
Sieber, Moritz [1 ]
Paschereit, Christian Oliver [2 ]
Oberleithner, Kilian [1 ]
机构
[1] Tech Univ Berlin, Lab Flow Instabil & Dynam, Inst Fluid Mech & Tech Acoust, Muller Breslau Str 8, D-10623 Berlin, Germany
[2] Tech Univ Berlin, Chair Fluid Dynam, Inst Fluid Mech & Tech Acoust, Muller Breslau Str 8, D-10623 Berlin, Germany
来源
PROCEEDINGS OF THE ASME TURBO EXPO 2020: TURBOMACHINERY TECHNICAL CONFERENCE AND EXHIBITION, VOL 4A | 2020年
关键词
precessing vortex core (PVC); active flow control; NOx emissions; vortex-flame interaction; finite time Lyapunov exponent (FTLE); COHERENT STRUCTURES; COMBUSTION; GAS; INSTABILITIES; BREAKDOWN; DYNAMICS;
D O I
暂无
中图分类号
O414.1 [热力学];
学科分类号
摘要
The reduction of polluting NOx emission remains a driving factor in the design process of swirl-stabilized combustion systems, to meet strict legislative restrictions. In reacting swirl flows, hydrodynamic coherent structures, such as periodic large-scale vortices in the shear layer, induce zones with increased heat release rate fluctuations in connection with temperature peaks, which lead to an increase of NOx emissions. Such large-scale vortices can be induced by the helical coherent structure known as precessing vortex core (PVC), which influences the flow and flame dynamics of reacting swirl flows under certain operating conditions. We developed an active flow control system, which allows for a targeted actuation of the PVC, to investigate its impact on important combustion properties. In this study, the direct active flow control is used to actuate a PVC of arbitrary frequency and amplitude, which facilitates a systematic study of the impact of the PVC on NOx emissions. In the course of the present work, a perfectly premixed flame, which slightly damps the PVC, is studied in detail. Since the PVC is slightly damped, it can be precisely excited by means of open-loop flow control. In connection with time-resolved OH* -chemiluminescence and stereoscopic PIV measurements, the flame and flow response to PVC actuation as well as the impact of the actuated PVC on flow and flame dynamics are characterized. It turns out that the PVC rolls up the inner shear layer, which results in an interaction of PVC-induced vortices and flame. This interaction considerably influences the measured level of NOx emissions, which grow with increasing PVC amplitude in a perfectly premixed flame. Nearly the same increase is to be seen for a partially premixed flame. This in contrast to previous studies, where the PVC is assumed to reduce the NOx emissions due to vortex-enhanced mixing.
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页数:13
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