Spark discharge ignition process in a spark-ignition engine using a time series of spectra measurements

The spark discharge ignition process was evaluated through simultaneous temperature measurements of the spark discharges and the initial flame kernel. A time series of emission spectra from the spark discharge and initial flame kernel inside a spark-ignition engine was measured using a spectrometer combined with a spark plug and optical fiber. The plasma vibrational temperature of the spark discharge and the gas rotational temperature of the initial flame kernel can be measured through emission spectra from electrically excited CN∗ violet band system and via emission spectra from OH∗ radicals respectively. To eliminate the effects of stratification of temperature and mixture concentrations around the spark plug visualization of the spark discharge and a time series of emission spectra inside a spark-ignition engine were performed simultaneously under homogeneous mixture conditions. The thermal energy transfer from the spark discharge to the combustible mixture was discussed. Results show that CN∗ emission can be detected from the spark discharge visualized through a high-speed camera during the arc discharge phase. Results confirmed the plasma temperature of spark discharge at about 6800 K thermal energy was transferred from the spark plasma channel to the combustible mixture and the gas temperature of the initial flame kernel approached that of the adiabatic flame temperature.