S. M. Aithal, "Analysis of the Current Signature in a Constant-Volume Combustion Chamber," Preprint ANL/MCS-P2093-0512, May 2012. [pdf]
Identifying charged species and their relative concentrations as a function of initial mixture composition, temperature, and pressure can play an important role in the diagnostics and control of combustion devices. This paper aims to identify important charged species and their temporal variation in a spark-ignited methane-air mixture using the equilibrium constant method. The equilibrium composition of twenty neutral and seven charged species ((e-), CHO+, H3O+, NO+, OH-, O2-, O) was obtained using a novel adaptation of the Newton-Raphson method for highly stiff nonlinear system of equations. A two-zone combustion model was used to study the effect of air-fuel ratio (AFR), on the temporal variation of charged species concentration. Temporal variation of the current computed from the equilibrium concentration of charged species was found to compare well with experimental data for several AFRs.