Browse Publications Technical Papers 2018-01-1727
2018-09-10

Application of Models of Short Circuits and Blow-Outs of Spark Channels under High-Velocity Flow Conditions to Spark Ignition Simulation 2018-01-1727

This report describes the implementation of the spark channel short circuit and blow-out submodels, which were described in the previous report, into a spark ignition model. The spark channel which is modeled by a particle series is elongated by moving individual spark particles along local gas flows. The equation of the spark channel resistance developed by Kim et al. is modified in order to describe the behavior of the current and the voltage in high flow velocity conditions and implemented into the electrical circuit model of the electrical inductive system of the spark plug. Input parameters of the circuit model are the following: initial discharge energy, inductance, internal resistance and capacitance of the spark plug, and the spark channel length obtained by the spark channel model. The instantaneous discharge current and the voltage are obtained as outputs of the circuit model. When two arbitrary spark particles of the spark channel get close, the short circuit occurs if the electric potential differences between the two locations exceed a certain threshold voltage, which is raised with increasing distance between the two particles and decreasing discharge current. When the current falls below a lower limit current for maintenance of discharge, the spark blow-out occurs. A new spark channel is formed if the secondary circuit has the remaining energy which can break the electrical insulation between electrodes. Each line element of the spark channel particles heats and ignites the surrounding mixture gas. The turbulent flame speed and extinction are considered in the flame kernel behavior. The behavior of the spark channel, the current and voltage of the secondary circuit, and the ignition limit due to in-creases in the EGR rate were consistent with data measured from the spark ignition process in a combustion chamber.

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