Mechanism of flashback in laminar lean premixed H2-air jet flames

Current work aims to computationally explore the flashback mechanism in laminar lean premixed H2-air jet flames. For this, a 2D-axisymmetric jet burner domain was constructed for two burner diameters (2.16 and 4.52 mm). Reactive Naiver-Stokes equations were solved using detailed chemistry along with conjugate heat transfer at the fluid-solid interfaces. The comparison of temperature and reactant contours for the two burners unraveled the different flashback mechanisms with an increase in burner diameter. For the smaller diameter burner (2.16 mm) the flame front achieves a near-flat profile during the flashback, while for the larger diameter burner (4.52 mm) the flame maintains its V-shape profile during the flashback. The comparison of hydrogen mole fraction inside the burner reveals that uneven distribution of hydrogen could lead to such a flame shape transition during flashback with an increase in burner diameter. Further exploration of leading factors for these flame shape transitions is still under investigation.