doi:10.3850/978-981-08-7724-8_10-02

ABSTRACT

The present work aimed to separate the turbulence generation by venting from that of self acceleration, by undertaking venting experiments on a very small scale with free venting, where self acceleration of flames and vent flow turbulence and pressure wave generation could be considered not to occur. A vented explosion vessel of 0.0067 m³ volume (L = 0.324 and D = 0.162 m) was used, which was a cylinder with length to diameter ratio, L/D, of 2. Free venting was studied with K_v varied from 2.11 to 16.4 for methane, propane, ethylene and hydrogen. Laminar explosion theory was applied using the assumption of the worst case explosion occurring when the flame area was the surface area of the vessel, A_s. This was shown to over-predict the measured vent overpressure and there was no need for any turbulence parameter. It was concluded that the higher overpressure measured in larger vessels was due to self acceleration of flames and not to the generation of turbulence. The European venting standard was shown to grossly over-predict the measured overpressures for methane and propane, but to under-predict for hydrogen at low K.

Keywords: Gas explosions, Venting, Vent design, Mixture reactivity, Laminar venting theory, Flame speeds.

© 2011 CPD Unit, University of Leeds