Investigation of the effect of electrode geometry on spark ignition

Abstract

High-speed schlieren visualization and numerical simulations are used to study the fluid mechanics following a spark discharge and the effect on the ignition process in a hydrogen-air mixture. A two-dimensional axisymmetric model of spark discharge in air and spark ignition was developed using the non-reactive and reactive Navier-Stokes equations including mass and heat diffusion. The numerical method employs structured adaptive mesh refinement software to produce highly-resolved simulations, which is critical for accurate resolution of all the physical scales of the complex fluid mechanics and chemistry. The simulations were performed with three different electrode geometries to investigate the effect of the geometry on the fluid mechanics of the evolving spark kernel and on flame formation. The computational results were compared with high-speed schlieren visualization of spark and ignition kernels. It was shown that the spark channel emits a blast wave that is spherical near the electrode surfaces and cylindrical near the center of the spark gap, and thus is highly influenced by the electrode geometry. The ensuing competition between spherical and cylindrical expansion in the spark $ Full-length article submitted to Combustion and Flame.

DNS and LES of spark ignition with an automotive coil

“…He evidenced the importance of the initial shock wave on ignition and studied the influence of the deposited energy, initial channel and electrodes diameters. Similarly H2/air [5] and pure air [6] ignition DNS where succesfully 2 compared to experimental Schlieren and temperature. While these studies dealt with short duration sparks not representative of an automotive spark plug, Ishii [7] performed similar simulations for propane/air with one-step chemistry, but including a simplified breakdown and glow phase.…”

Two regime cooling in flow induced by a spark discharge

“…Spark discharges are typically generated by raising the voltage difference between two electrodes, until the breakdown voltage is reached, resulting in ionization of gas in the electrode gap. The spark initiates a kernel of gas at very high temperature and pressure which then expands outward [9], producing a shock wave that lasts on the order of a few microseconds, which then gives rise to a transient three-dimensional flow field [10]. The flow induced by spark discharges have been the focus of a few computational studies [11]- [13] as well as some experimental investigations, e.g., [14], [15].…”

Oxidation of n-hexane in the vicinity of the auto-ignition temperature

“…For example, the National Transport Safety Board investigation pointed out that the explosion of the center wing fuel tank resulting from the ignition of the flammable atmosphere in the tank as the probable cause of the flight TWA 800 accident in 1996 [5]. Possible ignition sources include electrical sparks [1,6,7,8,9], stationary hot surfaces [2,3,4] and moving hot particles [10,11,12]. In 2008, the Federal Aviation Administration published the Fuel Tank Flammability Reduction Rule [13] requiring the installation of a flammability reduction or ignition reductions means for the fuel tanks that are most at risk.…”