Effect of Equivalence Ratio and Ignition Location on Premixed Syngas-Air Explosion in a Half-Open Duct

A detailed experimental work is conducted to address the response of premixed syngas-air (H-2/CO = 50%/50%) explosion with the effect of equivalence ratio and ignition location. The equivalence ratio, 45, ranges from 0.8 to 3.0, and three different ignition locations, i.e., left closed end (Ig-1), central duct (Ig-2), and right open end (Ig-3), are considered. Results show that the flame oscillates more violently as the ignition location is set close to the open end. But for a given ignition location, the flame undergoes a similar shape change as the equivalence ratio increases. The pressure dynamics suggest that the pressure waves do a little on the flame propagation as the flame is ignited at Ig-1. But when the flame is ignited at Ig-2 and Ig-3, both the flame tip speed and overpressure oscillate and coincide well with each other, and the pressure waves play an important role in the flame oscillation. What's more, the parameters, including flame propagation time (t), the maximum flame propagation speed (v(max)), and the maximum overpressure (P-max), are obtained. The results indicate that the equivalence ratio and the ignition location are coupled to affect the premixed syngas-air explosion, and the extremum, i.e., minimum t, maximum v(max) and P-max, are attained at Phi = 1.4 for Ig-1, at Phi = 1.6 for Ig-2, and at Phi = 1.8 for Ig-3. Finally, the results suggest that the flame ignited at Ig-3 is less destructive, because it has the longest flame propagation time, but the smallest v(max )and P-max.