Modeling spark-plug discharge in humid air

Abstract

Detailed knowledge of the species involved in the oxidation steps during combustion is of interest for technological applications. Using a formerly developed numerical model for a spark-plug discharge in dry air at atmospheric pressure, we studied here the influence of air humidity in the evolution of the densities of neutral and charged species and the gas temperature. The reduced electric field, electronic density, and temperature previously obtained from experimental measurements are parametrically introduced in the model. The effect of relative humidity with the values of 25%, 50%, 75%, and 100% is studied considering the water–air mixture formed by 63 species and coupled by 738 physical and chemical processes. The source term of the chemical reactions is calculated with the ZDPlaskin tool coupled to the numerical model. The analysis of the predominant pathways in the production and consumption of selected species is also carried out. Highly reactive species originated from the inclusion of water in the plasmochemical cycle reach relatively large density values and might play a significant role when considering an air–fuel mixture.