Abstract
Stratified methane-air mixtures are formed in the early stages of methane leakage in confined spaces, and an explosion may occur if a source of ignition were to appear at the appropriate time and location. However, this has not been elucidated thus far. The aim of this study is to measure the concentration gradient of methane injected from the top surface of a duct, and to investigate the effects of ignition delay (tig), which is the time interval from methane leakage to ignition, on flame behavior and explosion overpressure. Experimental results show that tig significantly affects flame behavior in stratified methane-air mixtures, including the flame shape and speed. The stratified methane-air mixtures cannot be ignited at tig ≤ 3 min. The horizontal flame speed and maximum overpressure (Pmax) first increase as tig increases from 4 min to 15 min and thereafter remain nearly unchanged with further increase in tig. The value of Pmax at tig in the range 15–25 min is approximately that observed for homogeneous methane-air mixtures. Tulip flames are observed at tig ≥ 10 min. Diffusion and convection flames, which follow the leading premixed flame front, are only formed at tig ≤ 6 min.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call