Ignition of n-hexane-air mixtures by moving hot spheres
2013
会议
Twenty-fourth International Colloquium on the Dynamics of Explosion and Reactive Systems
Assessing the risk of accidental ignition of flammable mixtures is an issue of importance in industry and aviation. In aircraft potential ignition sources include lightning strikes, sparks from electrical equipment, electrostatic discharge in fuel tanks, and overheated pumps. In the case of a lightning strike, hot particles are ejected from the surface that is struck. Such hot particles represent a potential ignition hazard if they are ejected into the ammable vapor space of a fuel tank. Fuel tank makers employ multiple design techniques to prevent or contain such showers, even though there is still much that is unknown about the threshold conditions for hot particle ignition. Quantifying the ignition hazard as a function of particle material, temperature, size and velocity is a key issue for both engineering design and safety analyses. In the current study, small titanium alloy (Ti-6Al-4V) spheres are heated using high current and injected with an average velocity of 2.4 m/s into n-hexane-air mixtures at phi = 0.9. The initial temperature and initial pressure were 298 K and 100 kPa, respectively. Ignition was achieved using moving hot spheres. A narrow probability of ignition distribution was obtained, with an overlap region of 1150-1170 K. The results suggest that a sphere traveling at 2.4 m/s requires a surface temperature of 1200 K for a 90% probability of ignition which is 32% higher than the surface temperature of a stationary glow plug required for ignition.
