Numerical Study On Non-equilibrium Plasma Discharge Of Methane-air Mixture

The increasingly stringent requirements for energy saving and environmental protection gives higher requirements for combustion technology.How to get higher fuel economy and reduce pollutant emissions has become a common concern.Lean-burn is a new combustion technology.Compared with the traditional engine combustion technology,the lean combustion technology which adopts low equivalence ratio has the advantage of high efficiency and clean emissions.However,with the increase of air flow rate,the combustion speed gradually slows down,and in extreme cases it may lead to the normal combustion.In order to ensure a reliable ignition and normal combustion,special ignition measures must be taken to strengthen combustion.At present,the non-equilibrium plasma combustion supporting technology is widely recognized as one of the most effective and efficient combustion methods,because it can increase the concentration of active radicals in the mixed gas,shorten ignition delay and improve the combustion process.This paper is devoted to the study of the law of the active particles generated by the effect of gas discharge.Firstly,the ionization process of methane air mixture under external electric field is studied.The one-dimensional model of methane air is solved by finite element method,and the electron density and the mole fraction of active particles with the equivalent ratio and discharge gap are obtained.The results show that the smaller distance near the cathode position?0.05⁰.4mm?maximum electron density first increased and then decreased,and reached the peak at the 0.1mm position;the discharge greatly increased the concentration of active particles of CH₃,NO,H and O₃;as the equivalent ratio decreased,the activity of the mole fraction of particles decreased slightly,however,it also can produce enough active particles even at the lowest equivalence ratio 0.4.Secondly,the two-dimensional axisymmetric model of argon is established,and the electron density,velocity,ion concentration and temperature change of argon are obtained through coupled flow and heat transfer.The results show that the discharge can greatly increase the activity of argon,while the temperature rise in the ionization space is only0.15K.Finally,a preliminary exploration of the change of the particle two-dimensional methane air conditions has been carried out.The results show that the ionization concentration of CH₃ has increased;the plasma discharge experimental platform was built,the change of electron density has been measured and calculated,the results show that the electron density and the experimental simulation was consistent.