Numerical Simulation of Spark Discharges for Gas Turbine Applications

Abstract This study investigates the energy distribution and shape evolution of the spark within a surface-discharge igniter using a magnetohydrodynamic (MHD) model. The model integrates an arc root model within a local thermal equilibrium framework and decomposes the supplied energy into energy fed into the air, energy dissipated at the arc roots, and energy loss in the electrodes. The results show that a significant portion of the supplied energy is dissipated at the arc roots, highlighting the importance of including the arc root model in the study of the arc discharge process. The ionization degree of air, evaluated through volume-weighted electrical conductivity, strongly influences energy distribution. At the initial stage, the low ionization degree results in high plasma electrical resistance, leading to a larger fraction of energy being deposited into the air. As ionization increases, however, arc root losses become predominant. While the pressure wave dominates the early stages, the Lorentz force plays a critical role in the later stages, significantly influencing the shape and size of the arc.