International audienceOxyfuel combustion with exhaust gas recycle coupled with CO 2 capture and storage (CCS) is a promising way to meet low CO 2 emission standards in industrial facilities with limited economical impact. In such systems, the flame stability is very sensitive to the dilution by injection of exhaust gases, particularly in configurations where they are not premixed with the oxygen, making the design of the burners more complex but offering a larger operation flexibility and a better control of flame heat transfer. In order to study the strategies of injection of the oxygen and exhaust gases, this paper presents an experimental study of the aerodynamic mechanisms influencing the stabilization of CO 2-diluted oxy-fuel flames, for four different configurations of 23 kW quadri-coaxial burners with separated injections for oxygen and carbon dioxide. The four burners have same axisymmetric geometry consisting in injections of methane in the center surrounded successively by a first oxygen (O 2i) inner annular jet, the CO 2 co-flow and a second oxygen (O 2e) outer annular jet. Dimensions of burners are chosen to keep constant CH 4 and O 2i injections and to be able to change independently CO 2 and O 2e velocities for constant thermal power, total equivalence ratio, oxygen repartition and dilution ratio. The interaction between combustion and the aerodynamic features is investigated by CH* chemiluminescence imaging and Particle Image Velocimetry (PIV). Mean tomographic images of the flame structure are obtained by Abel's inversion of averaged chemiluminescence images. PIV measurements are performed for two fields of view in order to obtain the global aerodynamic features of the turbulent oxyfuel flames and a more precise characterization in the vicinity of the burner exit. For the latter, the spatial resolution of the measurements is optimized by the development of a specific multi-step PIV processing. Low flow-velocity and high flow-velocity configurations are tested at maximum CO 2 dilution allowed by the burners. Different structures of flames are obtained with a long continuous annular shape or with local extinction for some operating conditions. The intensity of the mixing processes and the resulting stability of the flame depend largely on the shear constraints between CO 2 and O 2e jets. A better stabilization is found for low CO 2 velocity, which favors its mixing with outer oxygen annular jet prior to direct dilution of the flame. An increase of O 2e velocity further improves centrifugal entrainment of CO 2 and then reduces the radial stratification around the flame. These results obtained in a reference configuration are useful guides for the design of flexible and efficient oxy-fuel industrial burners for CCS units
