Effect of porosity and element thickness on flame quenching for in-line crimped-ribbon flame arresters

An experimental system consisting of a pipe with a variable length and diameter and different types of crimped-ribbon flame arresters, was set up to investigate the effect of physical parameters on the flame propagation and quenching processes of propane, ethylene and hydrogen/air mixtures. The results indicated that the quenching mechanism for gases with different reactivities is related to the porosity and thickness of the arrester element, as well as L/D aspect ratio of the pipe. As the porosity increased and the element thickness decreased, the number of failures increased under conditions with L/D greater than 50 for propane, ethylene/air mixtures and L/D greater than 30 for hydrogen/air mixtures. The flame speed tended to increase progressively as the porosity decreased, and it became the highest when the porosity was 0.5. Under the condition with L/D equal to 50, as the porosity decreased, both the flameproof speed and explosion pressure tended to increase progressively when the flame was close to the arrester. As L/D increased, the flame speed tended to increase progressively with decreased thickness of the arrester element. It became the highest when the thickness was 50 mm for propane, ethylene/air mixtures, and 30 mm for hydrogen/air mixtures. However, the explosion pressure tended to decrease progressively. Successful quenching has been observed in some experiments even though the explosion pressure was low and the flame speed was high when the thickness of the arrester element decreased.