Effect of Lewis and Zeldovich Numbers on the Flame Acceleration Behavior of Premixed Natural Gas-Hydrogen Flames for Different Obstacles Separation Distances

The present article aims to characterize the acceleration of premixed flames through obstacles. The studied mixtures involve natural gas, hydrogen, helium and air, with Lewis and Zeldovich numbers ranging from 0.60 to 1.36 and 6.09 to 8.45, respectively. The obstacles had a blockage ratio of 0.75 and three different separation distances, based on the hydraulic diameter (D), were tested: 1.0D, 1.5D and 2.0D. It was observed that mixtures with lower Lewis and Zeldovich numbers tend to accelerate with greater intensity through the obstacles. Therefore, the mixtures with the lower Lewis and Zeldovich showed the highest maximum velocities. The flame accelerates with more intensity for the 1.0D obstacles’ separation distance. Finally, the experimental flame tip position and the flame propagation velocity were compared with theoretical calculations showing good agreement at the early stages of flame propagation and inaccuracies at later stages.