The interaction mechanism of internally-staged-swirling stratified flame is complex,and the pilot flame has a manifest influence on flame stability.To study this,a series of experimental investigations for the pilot f...The interaction mechanism of internally-staged-swirling stratified flame is complex,and the pilot flame has a manifest influence on flame stability.To study this,a series of experimental investigations for the pilot flame has been carried out in a model swirl combustor by only supplying the pilot fuel.The CH*chemiluminescence images of the pilot flame are acquired by a high-speed camera with a CH*bandpass filter,whose dynamic characteristics are identified by image statistical analysis and proper orthogonal decomposition(POD)analysis.And the fast algorithm based on matrix theory proposed in this paper increases the operation efficiency and operability of POD.With the pilot equivalence ratioΦincrease,the pilot flame gradually shows an unstable state,whose POD energy distribution is significantly different.In the unstable state,the flame dynamics include three modes—spiral motion mode,flame shedding mode,and axial oscillation mode,whose formation reasons have also been further analyzed in combination with the experimental characteristics.And the fast Fourier transform(FFT)analysis of the time coefficients for the first four POD modes indicates all the dominant frequency is 280 Hz,which means the model combustor is in resonance.In addition,a sensitivity analysis based on the different image resolutions further reveals the robustness of the POD method and its optimization direction.These results emphasize the important influence of the pilot fuel flow rate on the stability of the pilot flame.展开更多
The coupling of swirl flame with discrete plasma or particle phases offers promising opportunities in combustion control and nanomaterial synthesis.Over recent years,studies on the dynamics and stabilization of swirl ...The coupling of swirl flame with discrete plasma or particle phases offers promising opportunities in combustion control and nanomaterial synthesis.Over recent years,studies on the dynamics and stabilization of swirl flames have produced significant progress.Starting from swirl-stabilized combustion,we focus mainly on two recent trends in reviewing these new concepts in the field of combustion related to electrically/plasma-assisted dynamics control and flame aerosol synthesis of nanomaterials.We organize the material by four themes:(a)unsteady combustion dynamics and control methods;(b)electrically-and plasma-assisted combustion dynamics control;(c)swirl-flame-based synthesis of nanocomposites;and(d)in situ diagnostic methods for the complex combustion above.展开更多
Lean Blow Out(LBO)poses a significant safety hazard when occurring in aero-engines.Understanding the lower stability limits of gas turbine combustors and the characteristics of spray flame close to LBO are imperative ...Lean Blow Out(LBO)poses a significant safety hazard when occurring in aero-engines.Understanding the lower stability limits of gas turbine combustors and the characteristics of spray flame close to LBO are imperative for safe operation.The objective of this work is to evaluate the effects of fuel decreasing rates and pressure drops of the injector on LBO performances in a multiswirl staged combustor equipped with an airblast injector.A set of hardware and control system was developed to realize a user-defined fuel supply law.High-speed imaging was applied to record complete LBO processes under the conditions of linear fuel reduction and stable airflow.Partical Image Velocimetry(PIV)and Planar Mie(PMie)scattering were used to acquire the flow fields and spray fields under non-reacting conditions.Experimental results have shown that LBO limits extend to leaner conditions as the pressure drop of the injector increases.With an increase of the fuel decreasing rate,the exhaust temperature before flame extinction increases,and the LBO Fuel-to-Air-Ratio(FAR)decreases.The time evolution of the integral CH*intensity conforms to a linear function during the LBO process.Proper Orthogonal Decomposition(POD)was used to analyze the dynamic characteristics of lean-burn flames.Under different fuel decreasing rates and pressure drops of the injector,flames close to LBO present similar modal spatial distributions,alternately appearing axial,radial,high-order axial,and high-order radial oscillations.展开更多
基金Youth Program of National Natural Science Foundation of China(Grant No.51806219)National Science and Technology Major Project(2017-V-0010)。
文摘The interaction mechanism of internally-staged-swirling stratified flame is complex,and the pilot flame has a manifest influence on flame stability.To study this,a series of experimental investigations for the pilot flame has been carried out in a model swirl combustor by only supplying the pilot fuel.The CH*chemiluminescence images of the pilot flame are acquired by a high-speed camera with a CH*bandpass filter,whose dynamic characteristics are identified by image statistical analysis and proper orthogonal decomposition(POD)analysis.And the fast algorithm based on matrix theory proposed in this paper increases the operation efficiency and operability of POD.With the pilot equivalence ratioΦincrease,the pilot flame gradually shows an unstable state,whose POD energy distribution is significantly different.In the unstable state,the flame dynamics include three modes—spiral motion mode,flame shedding mode,and axial oscillation mode,whose formation reasons have also been further analyzed in combination with the experimental characteristics.And the fast Fourier transform(FFT)analysis of the time coefficients for the first four POD modes indicates all the dominant frequency is 280 Hz,which means the model combustor is in resonance.In addition,a sensitivity analysis based on the different image resolutions further reveals the robustness of the POD method and its optimization direction.These results emphasize the important influence of the pilot fuel flow rate on the stability of the pilot flame.
基金funded mainly by the National Natural Science Foundation of China(Grant Nos.91641204 and 51676109)
文摘The coupling of swirl flame with discrete plasma or particle phases offers promising opportunities in combustion control and nanomaterial synthesis.Over recent years,studies on the dynamics and stabilization of swirl flames have produced significant progress.Starting from swirl-stabilized combustion,we focus mainly on two recent trends in reviewing these new concepts in the field of combustion related to electrically/plasma-assisted dynamics control and flame aerosol synthesis of nanomaterials.We organize the material by four themes:(a)unsteady combustion dynamics and control methods;(b)electrically-and plasma-assisted combustion dynamics control;(c)swirl-flame-based synthesis of nanocomposites;and(d)in situ diagnostic methods for the complex combustion above.
基金supported by National Science and Technology Major Project (Nos. 2017-Ⅲ-0007-0032 and J2019-Ⅲ-00020045)
文摘Lean Blow Out(LBO)poses a significant safety hazard when occurring in aero-engines.Understanding the lower stability limits of gas turbine combustors and the characteristics of spray flame close to LBO are imperative for safe operation.The objective of this work is to evaluate the effects of fuel decreasing rates and pressure drops of the injector on LBO performances in a multiswirl staged combustor equipped with an airblast injector.A set of hardware and control system was developed to realize a user-defined fuel supply law.High-speed imaging was applied to record complete LBO processes under the conditions of linear fuel reduction and stable airflow.Partical Image Velocimetry(PIV)and Planar Mie(PMie)scattering were used to acquire the flow fields and spray fields under non-reacting conditions.Experimental results have shown that LBO limits extend to leaner conditions as the pressure drop of the injector increases.With an increase of the fuel decreasing rate,the exhaust temperature before flame extinction increases,and the LBO Fuel-to-Air-Ratio(FAR)decreases.The time evolution of the integral CH*intensity conforms to a linear function during the LBO process.Proper Orthogonal Decomposition(POD)was used to analyze the dynamic characteristics of lean-burn flames.Under different fuel decreasing rates and pressure drops of the injector,flames close to LBO present similar modal spatial distributions,alternately appearing axial,radial,high-order axial,and high-order radial oscillations.
