Non-Normality and Internal Flame Dynamics in Premixed Flame-Acoustic Interaction

2010 ◽  
Author(s):  
Priya Subramanian ◽  
Raman Sujith
Keyword(s):  
Premixed Flame ◽  
Acoustic Interaction ◽  
Flame Dynamics

Impact of the Precessing Vortex Core on NOx Emissions in Premixed Swirl-Stabilized Flames: An Experimental Study

2020 ◽  
Author(s):  
Finn Lückoff ◽  
Moritz Sieber ◽  
Christian Oliver Paschereit ◽  
Kilian Oberleithner
Keyword(s):  
Flow Control ◽  
Large Scale ◽  
Active Flow Control ◽  
Premixed Flame ◽  
Nox Emissions ◽  
Precessing Vortex Core ◽  
Flame Dynamics ◽  
Swirl Flows ◽  
Active Flow ◽  
The Impact

Abstract 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.

Effect of Nanosecond Repetitively Pulsed Discharges on the Dynamics of a Swirl-Stabilized Lean Premixed Flame

2013 ◽  
Author(s):  
D. A. Lacoste ◽  
J. P. Moeck ◽  
D. Durox ◽  
C. O. Laux ◽  
T. Schuller
Keyword(s):  
Transfer Function ◽  
Thermal Power ◽  
Premixed Flame ◽  
Plasma Discharges ◽  
Chemical Effects ◽  
Flame Dynamics ◽  
Lean Premixed ◽  
Flame Response ◽  
Order Of Magnitude ◽  
Pulsed Discharges

The effects of Nanosecond Repetitively Pulsed (NRP) plasma discharges on the dynamics of a swirl-stabilized lean premixed flame are investigated experimentally. Voltage pulses of 8-kV amplitude and 10-ns duration are applied at a repetition rate of 30 kHz. The average electric power deposited by the plasma is limited to 40 W, corresponding to less than 1 % of the thermal power of 4 kW released by the flame. The investigation is carried out with a dedicated experimental setup that allows for studies of the flame dynamics with applied plasma discharges. A loudspeaker is used to perturb the flame acoustically, and the discharges are generated between a central pin electrode and the rim of the injection tube. Velocity and CH* chemiluminescence signals are used to determine the flame transfer function assuming that plasma discharges do not affect the correlation between CH* emission and heat release rate fluctuations. Phase-locked images of the CH* emission were recorded to assess the effect of the plasma on the oscillation of the flame. The results show a strong influence of the NRP discharges on the flame response to acoustic perturbations, thus opening interesting perspectives for combustion control. An interpretation of the modifications observed in the transfer function of the flame is proposed by taking into account the thermal and chemical effects of the discharges. It is then demonstrated that by applying NRP discharges at unstable conditions, the oscillation amplitudes can be reduced by an order of magnitude, thus effectively stabilizing the system.

scholarly journals Premixed flame dynamics in presence of mist

2018 ◽  
Vol 191 (2) ◽  
pp. 197-207 ◽  
Author(s):  
Colette Nicoli ◽  
Pierre Haldenwang ◽  
Bruno Denet
Keyword(s):  
Premixed Flame ◽  
Flame Dynamics

scholarly journals Effect of the Inclination Angle on Premixed Flame Dynamics in Half-Open Ducts

ACS Omega ◽  
2020 ◽  
Vol 5 (38) ◽  
pp. 24906-24915
Author(s):  
Zhifeng Yao ◽  
Haoxin Deng ◽  
Jianfei Dong ◽  
Xiaoping Wen ◽  
Weilong Zhao ◽  
...  
Keyword(s):  
Inclination Angle ◽  
Premixed Flame ◽  
Flame Dynamics
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