Showing papers by "Steven G. Buckley published in 1992"

Experimental simulation of premixed turbulent combustion using aqueous autocatalytic reactions

Abstract: Aqueous autocatalytic reactions which produce propagating chemical fronts, analogous to premixed flame-fronts, are used to simulate premixed turbulent combustion in “laminar-flamelet” and “distributed-combustion” regimes. The characteristics of these chemical fronts more nearly match those assumed by current theories of turbulent combustion than do gaseous flames. In this work, proper chemical solutions for this simulation are identified and applied using a Taylor-Couette flow. The effect of the velocity disturbance intensity ( u′ ) normalized by the laminar burning velocity ( S L ) on the front propagation velocity ( S T ) are obtained at values of U≡u′/S L at least 200 times higher than those attainable in gas combustion experiments. At modest U, U T ≡S T /S L data collapse onto a single curve, regardless of S L , indicating stretch-free conditions; these data agree with an approximate theoretical model. Effects of the velocity spectrum are described. At higher U, U T deviates away from this curve, indicating stretch effects which are characterized by a turbulent Karlovitz number (Ka). At high Ka, behavior suggesting distributed-combustion is observed; in this regime U T data are fairly consistent with Damkohler's hypothesis. No quenching is observed, even at Ka≈900, suggesting that the commonly-held view that the quenching of flames in intense turbulence results from mass extinction of flamelets may require reconsideration. It is proposed that instead, heat-loss could be an important factor in extinction.