Characterization of Spark Discharges of Spark Plugs Using Two Different Optical Methods

Spark plugs are used to ignite a petrol-air mixture in the cylinder of an Otto engine. Therefore, an ignition coil which is connected to the spark plug generates a very high voltage, up to 45 kV. The spark discharge is located between the driven center electrode and the grounded counter electrode, which are separated by 0.7 mm and pertains to most automotive applications. The high energy phase of the spark discharge lasts only a few 100 ns. Depending on the engine operation mode, the pressure at the ignition point varies from 5 to more than 40 bars.