Experimental study on the premixed syngas-air explosion in duct with both ends open

Premixed flame of stoichiometric syngas-air mixture with various hydrogen volume fractions, 10% <= X (H-2) <= 90%, propagating in a duct with both ends open is experimentally investigated in this study. Two representative ignition locations, i.e., Ig-1, locating at the center of the duct, and Ig-2, locating at the right open end, are considered. Results show that the tulip flame is first attained in the duct with both ends open at 10% <= X (H-2) <= 50% as the flame is ignited at Ig-1. However, the flame maintains the convex shape with the cellular structure on the flame surface as the flame is ignited at Ig-2. The cellular structure results from Darrieus-Landau instability, but the Darrieus-Landau instability cannot invert the convex flame front. The flame tip and pressure dynamics have been examined. When the flame is ignited at Ig-1, the flame oscillates violently, and the overpressure profiles oscillate as a Helmholtz-type. When the flame is ignited at Ig-2, the left flame front propagates in an atmospheric pressure with a nearly constant speed. The prominent flame acceleration and oscillation are not observed at Ig-2 because of lacking flame acoustic interaction. What's more, the characteristic time of flame propagation has been compared. The time t(w) is shorter while the time t(p) is longer than the calculated value, and the time t(e) has been delayed by both open ends. The flame propagation process is moderated as the flame propagates in the duct with both ends open. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study experimentally investigates the premixed flame of stoichiometric syngas-air mixture with various hydrogen volume fractions propagating in a duct with both ends open. Results show that the ignition location affects the flame morphology and propagation speed. The flame propagation process in the duct with both ends open is moderated by various factors.