Experiments on collapsing cylindrical flames

This article is concerned sith the effect of curvature on laminar flame dyn amics. This topic is of fundamental interest and it has practical implicati ons in turbulent combustion, it is shown that highly curved premixed flames may be obtained by operating a standard axisymmetric burner in a specific pulsed mode. Collapsing cylindrical flames are observed by submitting the b urner to suitably tuned plane pulsations of the flow velocity. The cylindri cal flame pattern collapses in an essentially radial motion. In these circu mstances the flame cylinder separates unburned inner gases from the burned outer flow. The temporal evolution of the flame may be monitored using schl ieren images while the inner flow: velocity is determined from particle ima ge velocimetry (PIV). It is shown that these data yield the stretched lamin ar burning velocity up to very small radii, Models of the stretched laminar burning velocity as a function of curvature are compared to experimental d ata and Markstein lengths are deduced. These experiments indicate hew lamin ar flames respond to large curvature values. The data gathered may be used to guide modeling efforts in the area of turbulent combustion. (C) 2001 by The Combustion Institute.