湍动稳定环形分层火焰特性的实验研究
A burner for investigating lean stratified premixed flames propagating in intenseisotropic turbulence has been developed. Lean pre-mixtures of methane at differentequivalence ratios are divided between two concentric co-flows to obtain annularstratification. Turbulence generators are used to control the level of turbulence intensityin the oncoming flow. A third annular weakly swirling air flow provides the flamestabilization mechanism. A fundamental characteristic is that flame stabilization doesnot rely on flow recirculation. The flames are maintained at a position where the localmass flux balances the burning rate, the result is a freely propagating turbulent flamefront. The absence of physical surfaces in the vicinity of the flame provides free accessfor laser diagnostics.Stereoscopic Planar Image Velocimetry (SPIV) has been applied to obtain the threecomponents of the instantaneous velocity vectors on a vertical plane above the burneroutlet where the flames propagate. The instantaneous temperature fields have beendetermined through Laser Induced Rayleigh (LIRay) scattering. Planar Laser InducedFluorescence (PLIF) on acetone has been used to calculate the average equivalence ratiodistributions. Instantaneous turbulent burning velocities have been extracted from SPIVresults, while flame curvature and flame thermal thickness values have been calculatedusing the instantaneous temperature fields. The probability distributions of thesequantities have been compared considering the separate influence of equivalence ratiostratification and turbulence.