The characteristics of synags/air mixture explosion in half-open and closed ducts with various hydrogen fractions at the stoichiometric were comparatively studied by a self-made laboratory experimental facility. The results show that there is a significant difference in the premixed flame propagation structure of syngas explosion in open and closed pipelines. In the closed duct

the classic tulip flame is observed from all hydrogen fractions

and the distorted tulip flame can be observed at the hydrogen fraction of 70% and 90%

respectively. In the half-open duct

the classic tulip flame forms at hydrogen fraction of 10%

30%

and 50%

respectively

and the distorted tulip flame can be observed at the hydrogen fraction of 10% and 30%

respectively. Both in half-open and closed duct

the flame propagation speed and maximum pressure increases with the hydrogen fraction increase. When the hydrogen fraction is low (f < 50%)

the flame propagation speed and maximum pressure increase rapidly as hydrogen fraction increases

and at higher hydrogen fraction (f ≥ 50%)

the flame propagation speed and maximum pressure increase slowly with increasing hydrogen fraction.