Extinction of Lean Propane/Air Turbulent Premixed Flames in a Stagnation Point Flow

Effects of flame stretch and flame curvature on the extinction of turbulent premixed flames in a stagnation point flow have been studied experimentally. A lean propane/air mixture has been used. The bulk stretch rate was varied from 15 s⁻¹ to 60 s⁻¹, while the turbulent intensity of velocity fluctuation in the approach flow was varied up to 0.6 m/s. In the near extinction limits, the local stretch rate was estimated by measuring the mean centerline velocity with LDV and the local flame curvature was measured by using the laser tomographic method. The local stretch rate decreases, while the stretch rate due to the local flame curvature increases with increasing turbulent intensity. As a result, it is proposed that the sum of these two stretch rates plays a key role in flame extinction.