The safe design and operation of clean fuels like hydrogen require a detailed understanding of their explosion characteristics. An experimental study of the flame propagation behavior influenced by quadrangular, cylindrical, and triangular obstacles was executed in a 530 mm x 82 mm x 82 mm pipe. The results confirm the understanding that obstacles with a tip promote the generation of flow instability and produce a more intense burning behavior of the flame. The shear layers shed fewer larger vortices after the quadrangular obstacle; however, these vortices can be dislodged to form smaller and more vortices after passing through the triangular obstacles. The shear layer has weak shedding properties behind obstacles with curved edges. In the flame propagation process, the quadrangular obstacles have a more obvious promoting effect of the initial explosion, but the degree is weaker than with the triangular obstacles. The effect of the quadrangular obstacles on flame velocity is mainly influenced by gas flow at the flame front. In triangular obstacles, the shear layer became prominent in the later stage of the explosion process and this contributes to enhancing the flame velocity and overpressure.(c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.