Voltage, and Energy Deposition Characteristics of Spark Ignition Systems

Time-resolved current and voltage measurements for an inductive automotive spark system were made. Also presented are measurements of the total energy delivered to the spark gap. The measurements were made in air for a range of pressures from 1-18 atm, at ambient temperatures. The measured voltage and current characteristics were found to be a function of many ignition parameters; some of these include: spark gap distance, internal resistance of the spark plug and high tension wire, and pressure. The voltages presented were measured either at the top of the spark plug or at the spark gap. The measurements were made at different time resolutions to more accurately resolve the voltage and current behavior throughout the discharge process. This was necessary because the breakdown event occurs on a time scale much shorter than the arc and glow phases. The breakdown, arc, and glow voltages were found to be functions of spark plug resistance, gas density, and spark plug gap as expected from the literature. Spark duration was found to decrease as either pressure or gap was increased. The transition from the arc to glow phase is usually distinguished by a sudden rise in the voltage across the gap. At pressures above about 7 atm this transition was not observed suggesting that a glow phase was not present. Energy delivered to the gap increased with increasing pressure. The effective resistance of the spark gap during discharge was about twice as large for the glow phase as the arc phase.