Heterogeneous detonation supported by fuel fogs or films

Abstract

Experimental results on the propagation of detonations in decane fogs (∼2μ) and detonations along layers of decane or hexadecane on the walls of tubes filled with gaseous oxygen are presented. The effect of fuel-to-oxygen mixture ratio and tube diameter on the detonation velocity is investigated. Self-sustaining detonation of decane fogs propagates at near Chapman-Jouguet velocities. The thickness of the reaction zone is estimated from the detonation velocity in various size tubes to be 4 times the thickness of gas-phase detonations. The process of transition to detonation in fogs is found to be similar to gaseous detonations. Self-sustaining detonation of a layer of decane or hexadecane on the walls of a tube containing oxygen propagates at 2.2 to 1.0 mm/μsec depending upon the mixture ratio and tube diameter. This corresponds to a Mach number of 6.75 to 3.1, respectively. No rich limit exists; rather, a plateau velocity is reached where an increase in the thickness of the fuel layer does not influence the propagation velocity. Under certain conditions, frozen layers of hexadecane exhibit detonation velocities nearly twice as fast as that observed when the layer is in liquid form.