Numerical assessment of MILD combustion enhancement through plasma actuator

One promising solution to achieve moderate or intense low-oxygen dilution (MILD) combustion under lower temperatures may be using non-equilibrium plasma discharge. Plasma assisted combustion can extend the flammability limits by reducing the auto-ignition temperature of the reactants and can be a great approach to achieve steady MILD combustion under extreme conditions through decreasing ignition delay time. In particular, the influence of the outlet flows from a co-flowing cylindrical dielectric barrier discharge (DBD) on the CH4/N2 combustion under MILD combustion has been investigated numerically through some simplifications on plasma discharge. A three streams coaxial burner are modeled in a 2D-axisymmetric computational domain by a steady state approach. On the whole, different effects of simplified non-equilibrium plasma discharging, fuel dilution, and oxygen concentration of the preheated oxidizer on MILD combustion regimes are studied. It is found that applying the plasma discharge to the flame region, leads to an intensification of the reaction zone, increment of the rate of heat release by around a factor of 3, and 30% reduction of flame lift-off. Different aspects of plasma effect through chemical kinetics, mixing, and thermal heating on MILD combustion are investigated. Apart from all the benefits of plasma such as improving the mixing, it has a momentous impact on both the reaction zone length and its diameter via improving the ignition delay time.