Assessment of the impact of nanosecond plasma discharge on the combustion of methane air flames

Abstract

At present, development of plasma assisted ignition and combustion is a very promising research area due to its wide applications in the field of aeronautical engines and power sector. Plasma discharge can improve the combustion because it produces large number of chemically active particles which affects the chemical reaction. Simulation is an effective tool to analyze the interaction between the plasma and the flame through the implementation of plasma-assisted combustion. This study focused on three main objectives. Initially a microscopic plasma model with detailed kinetic plasma mechanisms was developed, then the validation of these mechanisms in air/methane mixture has been performed. Finally, the effects of nano pulsed plasma discharge on combustion have been investigated. In order to accomplish the above task, two numerical tools Chemical Kinetic Solver (CHEMKIN) and Plasma Kinetic Solver (ZDPlasKin) are used. It was found that the kinetic model of plasma provides good overall agreement with experimental data and identify key processes for species (e.g. O atom) generation and decay. The results showed that with the increase of reduced electric field, active particles and intermediate species/radicals (in particular ozone) are increased. ZDPlasKin results were incorporated in CHEMKIN to investigate and compare the flame speed, thermal and chemical effect by using a GRI-Mech scheme modified with the addition of ozone reactions. It has been found that with the adding of plasma flame speed was increased up to 26% at stoichiometric ratio. The chemical heat release also showed increment at low temperatures that confirmed the combustion enhancement. Furthermore, ignition delay timings were significantly reduced with the plasma excitation.