<title>Fiber Optics As Light-Detector Probes In The Accurate Measurement Of Detonation Velocities In Two-Phase Fuel-Air Explosions</title>

Abstract

Fiber-optic probes can be placed directly into solid explosives in order to obtain accurate measurement of the detonation velocity. In the case of two-phase fuel-air explosions, however, such measurements become difficult as the fiber optics can receive radiant energy from the reaction front well before and after the passage of the reaction front. Nevertheless, appropriate design and placement of the fiber-optic probes and discrimination of the signals makes this technique useful. Furthermore, a5 the distance between the shock and reaction fronts becomes significant in two-phase fuel-air detonations, the concomitant measurement of arrival times at co-located fiber-optic probes and piezoelectric pressure gages of the reaction and shock fronts, respectively, allows characterization of induction time/distance information as a function of the system parameters. Application of this technique to the detonation of aluminum powder in air resulted in induction times of 14 to 48 lisec. Such variation was attributed to variations in the concentration of aluminum powder in air. This compares with an induction time of about 3 psec in the case of ethylene-air homogeneous gas-phase detonations.