The Effect of H₂ Addition on CNG/H₂-Air Flame Shape Topology in a Lean-Premixed Swirl Stabilized Gas Turbine Combustor

The present study investigates the flame shape topology in a lean premixed swirl stabilized combustor for various hydrogen thermal powers (P_th.H2) and equivalence ratios (ϕ) using CNG/H₂-air mixtures at atmospheric conditions. High-speed OH*-chemiluminescence (OH*-CL) imaging is employed to study flame dynamics. It is found that at a fixed value of hydrogen mole fraction (X_H2), an intense and short flame is found for a higher value of ϕ. Also, at a fixed value of ϕ, flame length shortens, and an enhanced heat release is observed near the burner exit with an increase in X_H2. A V-shaped flame with the flame tip pointing toward the exhaust port is witnessed at low values of ϕ and X_H2. Moreover, the V-shaped flame transitioned into an M-shaped flame with a flickering flame tip near the wall with an increase in ϕ and X_H2. Further, the heat release zone gets extended and distributed over the entire length of the combustion chamber for small values of ϕ and X_H2. Finally, the stable flame topology is correlated to the non-dimensional parameters Damköhler number (Da), and the wall temperatures (T_w).