Research On The Stability Mechanism Of Swirl Premixed Flame Based On Space Laser Diagnosis Technology

Aiming at the instability of Lean Premixed Combustion（Lean Premixed Combustion）blow-out,this paper mainly adopts experimental research methods to study the stability mechanism under the coupling effect of swirling spatial flow field characteristics and flame pulsation characteristics.This paper jointly deals with the interaction between the swirling premixed flame and the space velocity field,and overcomes the previous research methods for this problem:simply carry out the measurement of the flame image or only the test of the flow characteristics.The main work of this paper is as follows:（1）Improved the lean-burn swirl combustion diagnosis platform,which mainly includes the combustion chamber system,the tomographic PIV system and the OH*self-luminous system.And based on this experimental platform,the reaction conditions under various inlet conditions（Reynolds number,swirl number,equivalent ratio）and non-reactive conditions in the swirl field flow experiment were carried out,and the swirl premixed combustion flame image-flow was compiled.Field joint processing procedures.（2）Developed a set of diagnostic test methods for the space velocity field,completed the extraction and characterization of the spatial characteristics of the swirl velocity field,and verified the accuracy and effectiveness of the three-dimensional velocity field.And analyzed the obvious partition structure in the swirling field,the central recirculation zone（IRZ）,the shear zone（SL）and the partial outer recirculation zone（ORZ）located in the combustion chamber close to the nozzle.The influence of Reynolds number on the turbulent flow energy and dissipation rate in the swirling field is studied,and the influence of Reynolds number on the vortex structure in the field is compared.The study found that a high Reynolds number will increase the vortex motion at the entrance of the swirl,which is manifested as an increase in the recirculation velocity and a widening of the central recirculation zone.The distribution of turbulent energy and dissipation rate in the three-dimensional velocity field is studied,and it is found that the The values on both sides of the slice are higher and the Reynolds number is high,the turbulent kinetic energy and dissipation rate in the field will also increase significantly.（3）The diagnosis and extraction of the swirling premixed flame have been completed.The influencing factors of the structure of the lean-burn swirl premixed flame are studied,the instability characteristics of the methane/air premixed flame under different turbulence intensities are studied,and the effect of the swirl intensity on the critical blow-out equivalent ratio of the swirl premixed flame is studied.The law of influence.The study found that the flame macrostructure will go through multiple stages of change as the equivalent ratio decreases,and increasing the swirl intensity can effectively reduce the blow-out equivalent ratio.（4）Analyze the coupling effect of the lean-burn swirl premixed flame and the flow field in combination with the compiled algorithm,and quantitatively analyze the flame structure characteristic parameter extinguishing tensile rate and the tensile strain rate of the flame.The stability law of the lean-burn swirl premixed flame under different equivalence ratios was analyzed in detail,and the mechanism of the influence of flow on the instability of the lean-burn swirl premixed flame was revealed.The equivalent ratio and swirl flow?/?_{e xt} in the field were calculated.The changing law of the intensity,it is found that the value will gradually increase as the equivalence ratio decreases,and a sudden jump will occur when the equivalence ratio is 0.5-0.6.In addition,when the proportion is calculated,it is found that the flame will lose stability when the proportion exceeds 55%.In addition,the law of coupling interaction between vortex and flame is analyzed,and it is found that the maximum strain rate always appears near the high vorticity area,that is,the flame boundary is close to the exit of the bluff body;this indicates that the local extinguishing will weaken the bluff body stabilization mechanism and cause the flame The overall necking.When flame necking occurs,more local flame locations experience high strain rate magnitudes,which further promotes the transition to overall extinction.The work in this paper provides the research foundation and ideas for the blow-out problem of lean-burn swirl premixed flame,and can provide a reference for the prediction of flame instability,and can provide a reference for optimizing the current lean-burn swirl premixed combustion chamber.