Study On Coupling Mechanism Of Swirl Induced Flamemacrostructure And Flow Field

Lean Premixed Combustion(LPC)is a clean combustion technique that reduces the emission of contaminant by reducing the equivalent ratio.However,the problem of LPC combustion instability has become a key problem to be solved.The macroscopic change of flame structure in burner is considered to be a precursor to the occurrence of combustion instability.The induced mechanism is complex,not only related to the equivalent ratio,the swirl number,the structure of the burner,but also the coupling of flame and flow field.At present,for scientific issue that the correlation behavior between the coupling mechanism of flame and flow field and the transformation of flame structure,the frontiers are based on planar laser diagnostic technology and carry out experimental research.Based on the full literature research and the planar 3D laser diagnostic experiment,this paper further expands the threedimensional spatial diagnosis technology of the swirling flow field,realizes the innovation of the measurement method,and lays an important role for further exploration of the instability mechanism of the swirling combustion.basis.The main work and achievements of this paper include:(1)Constructed a lean premixed swirl combustion experimental platform,including 2D/3D laser diagnostic system,swirl combustion model combustion chamber,seeder,data acquisition and control system,and gas supply system.The platform can perform a variety of flow field measurements including 2D-PIV(2D2C)/ Stereo-PIV(2D3C)/ Tomographic PIV(3D3C),OH-Chemiluminescence and flow field reconstruction,data and image post-processing capabilities.(2)2D diagnosis of the swirling combustion chamber.Studies have shown that both the cold and the hot state,the flow field presents a "two-zone two-layer" structure,namely the central recirculation zone,the outer recirculation zone,the inner shear zone and the outer shear layer.At the same time,compared with the transient flame-flow field macroscopic structure,it is found that the swirling flame is distorted and curled by the vortex structure in the flow field,and it is found that the fluid flowing back in the outer recirculation zone due to flow instability cause the flame to escape from the shear layer causes the flame to change from a compact type to an M type.(3)3D diagnosis of the swirling combustion chamber.The research shows that the threedimensional flow field in the swirling combustion chamber has a spiral structure.As the number of swirler increases,the pressure difference causes the central flow of the combustion chamber to flow counter,which forms a central recirculation zone,which can act as an ignition source;Under the same conditions,two large-scale vortices are generated near the combustion chamber nozzle.These large-scale vortices are gradually attenuated and broken by the stretching and shearing action of the flow field.These vortices decompose downstream as the flow develops downstream.The work of this paper provides some reference value for the research and design of industrial lean-burn premixed combustion chambers,and lays a foundation for further exploration of the instability mechanism of three-dimensional space swirl combustion.