Mechanism Of Non-equilibrium Plasma Formation And Effects On Combustion

Lean combustion technology was widely applied to internal-combustion engine in recent years, lean combustion can increase the efficiency of fuel and decrease the pollutant in exhaust. As the fuel air ratio approaches the lean-burn limit, the energy required to initiate combustion increases dramatically and the flame propagation speed decreases substantially. For these problem, non-equilibrium plasma was applied for ignition and combustion enhancement of engine, the activity of radical and electron can promote chemical reactions.In this paper, non-equilibrium was produced by nanosecond pulse discharge, reduced field strength for electron energy distribution was numerically studied by the EEDF model. Combined with reaction pathway, the direction of energy deposit was analyzed. An air discharge mechanism was combined with a methane discharge mechanism to form a multi-component kinetic of mixture discharge. Discharge progress was numerically calculated by plasma solver ZDPlasKin, the effect of the reduced field strength and the pulse repetition frequency on the particle number densities of CH3, OH, O3, O, CH2O was analyzed. The kinetic of combustion was simulated by a multi-zone solver. Ignition delay time, heat release rate and unburned HC was numerically studied with and without plasma during the combustion processes.Research shows that:(1) large fraction of energy deposited to excitation state of N2and dissociation O2when the reduced field strength is between200-400Td;(2) CH3, H and O acted as the intermediate components for the production of CH2O, OH and O3the particle number density has a proportional with the strength of the reduced field;(3) non-equilibrium can decrease ignition delay time, shorten burning time and reduce the unburned HC of exhaust gas.