The principal component analysis （PCA） is used to analyze the high dimen- sional chemistry data of laminar premixed/stratified flames under strain effects. The first few principal components （PCs） with larger cont...The principal component analysis （PCA） is used to analyze the high dimen- sional chemistry data of laminar premixed/stratified flames under strain effects. The first few principal components （PCs） with larger contribution ratios axe chosen as the tabu- lated scalars to build the look-up chemistry table. Prior tests show that strained premixed flame structure can be well reconstructed. To highlight the physical meanings of the tabu- lated scalars in stratified flames, a modified PCA method is developed, where the mixture fraction is used to replace one of the PCs with the highest correlation coefficient. The other two tabulated scalars are then modified with the Schmidt orthogonalization. The modified tabulated scalars not only have clear physical meanings, but also contain passive scalars. The PCA method has good commonality, and can be extended for building the thermo-chemistry table including strain rate effects when different fuels are used.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Project supported by the National Natural Science Foundation of China(Nos.91441117 and51576182)the Natural Key Program of Chizhou University(No.2016ZRZ007)
文摘The principal component analysis （PCA） is used to analyze the high dimen- sional chemistry data of laminar premixed/stratified flames under strain effects. The first few principal components （PCs） with larger contribution ratios axe chosen as the tabu- lated scalars to build the look-up chemistry table. Prior tests show that strained premixed flame structure can be well reconstructed. To highlight the physical meanings of the tabu- lated scalars in stratified flames, a modified PCA method is developed, where the mixture fraction is used to replace one of the PCs with the highest correlation coefficient. The other two tabulated scalars are then modified with the Schmidt orthogonalization. The modified tabulated scalars not only have clear physical meanings, but also contain passive scalars. The PCA method has good commonality, and can be extended for building the thermo-chemistry table including strain rate effects when different fuels are used.
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.
