Vortex/flame interaction is an important mechanism for unsteady combustion in a swirl combustion system. Technology of low emission stirred swirl （TeLESS）, which is characterized with stratified swirl flow, has been...Vortex/flame interaction is an important mechanism for unsteady combustion in a swirl combustion system. Technology of low emission stirred swirl （TeLESS）, which is characterized with stratified swirl flow, has been developed in Beihang University to reduce NOx emission. However, large-scale flow structure would be induced in strong swirl flow. Experiments and computational fluid dynamics （CFD） simulation were carried out to investigate the unsteady flow feature and its mechanism in TeLESS combustor. Hotwire was firstly applied to testing the unsteady flow feature and a distinct mode with 2244 Hz oscillation frequency occurred at the pilot swirl outlet. The flow mode amplitude decayed convectively. Large eddy simulation （LES） was then applied to predicting this flow mode and know about its mechanism. The deviation of mode prediction compared with hotwire test was 0.8%. The spiral isobaric structure in pilot flow passage indicates that precessing vortex core （PVC） existed. The velocity spectrum and phase lag analysis suggest that the periodic movement at the pilot outlet was dominated by precessing movement. Negative tangen- tial momentum gradient reflects that the swirl flow was unstable. Another phenomenon was found out that the PVC movement was intermittently rotated alon~ the symmetric axis.展开更多
This paper studies the flame dynamics near lean blowout(LBO)conditions in a stratified swirl burner.The novel BASIS burner is used and fueled with premixed methane/air mixture at atmospheric conditions.In the experime...This paper studies the flame dynamics near lean blowout(LBO)conditions in a stratified swirl burner.The novel BASIS burner is used and fueled with premixed methane/air mixture at atmospheric conditions.In the experiments,only the pilot flame works with four different equivalent ratios.It is found that as the flame changes from stable combustion to near LBO,the flame macrostructure changes from V-shape to M-shape.Meanwhile,a characteristic frequency of 405 Hz is found in the spectrum of heat release signal.The closer to LBO,the higher amplitude is found at the frequency peak.Post-processing of flame images illustrates that the 405 Hz comes from the circumferential movement of the flame.Large-eddy simulations(LESs)via OpenFOAM reproduce the flame dynamics near LBO,which agrees with the experimental results.LESs provide more insights into the flow fields,showing that the characteristic frequency of 405 Hz comes from the flame-vortex interaction.This study reveals the mechanism of flame and vortex interactions in a stratified swirl burner near LBO.The heat release signal is also found can be used as a candidate precursor for LBO.展开更多
基金AVIC Commercial Aircraft Engine Co.Ltd.’s support on combustion instability investigation
文摘Vortex/flame interaction is an important mechanism for unsteady combustion in a swirl combustion system. Technology of low emission stirred swirl （TeLESS）, which is characterized with stratified swirl flow, has been developed in Beihang University to reduce NOx emission. However, large-scale flow structure would be induced in strong swirl flow. Experiments and computational fluid dynamics （CFD） simulation were carried out to investigate the unsteady flow feature and its mechanism in TeLESS combustor. Hotwire was firstly applied to testing the unsteady flow feature and a distinct mode with 2244 Hz oscillation frequency occurred at the pilot swirl outlet. The flow mode amplitude decayed convectively. Large eddy simulation （LES） was then applied to predicting this flow mode and know about its mechanism. The deviation of mode prediction compared with hotwire test was 0.8%. The spiral isobaric structure in pilot flow passage indicates that precessing vortex core （PVC） existed. The velocity spectrum and phase lag analysis suggest that the periodic movement at the pilot outlet was dominated by precessing movement. Negative tangen- tial momentum gradient reflects that the swirl flow was unstable. Another phenomenon was found out that the PVC movement was intermittently rotated alon~ the symmetric axis.
基金This work was financially supported by the National Science and Technology Major Project(2017-III-0004-0028)National Natural Science Foundation of China(91641109).
文摘This paper studies the flame dynamics near lean blowout(LBO)conditions in a stratified swirl burner.The novel BASIS burner is used and fueled with premixed methane/air mixture at atmospheric conditions.In the experiments,only the pilot flame works with four different equivalent ratios.It is found that as the flame changes from stable combustion to near LBO,the flame macrostructure changes from V-shape to M-shape.Meanwhile,a characteristic frequency of 405 Hz is found in the spectrum of heat release signal.The closer to LBO,the higher amplitude is found at the frequency peak.Post-processing of flame images illustrates that the 405 Hz comes from the circumferential movement of the flame.Large-eddy simulations(LESs)via OpenFOAM reproduce the flame dynamics near LBO,which agrees with the experimental results.LESs provide more insights into the flow fields,showing that the characteristic frequency of 405 Hz comes from the flame-vortex interaction.This study reveals the mechanism of flame and vortex interactions in a stratified swirl burner near LBO.The heat release signal is also found can be used as a candidate precursor for LBO.
基金This work was supported by the National Natural Science Foundation of China(No.52206222,No.22227901)State Key Laboratory of Laser Interaction with Matter Foundation(SKLLIM2009).
