Spatio-temporally Resolved Emission Spectroscopy of Inductive Spark Ignition in Atmospheric Air Condition

Current transistorized coil ignition (TCI) system consists of ignition coil and spark plug, whose electrical properties, structure and gas composition determine entire discharge processes and therefore the early stage of combustion. In this work, a new measurement and diagnostic technique were developed and tested to investigate the early phases of spark ignition process. The spark discharge of commercial TCI system was analyzed by using spatio-temporally resolved optical emission spectroscopy to find out the Interrelation of the characteristic evolution of discharge with the formation of reactive species inside the activated volume. The emission spectra of inductive spark discharge in atmospheric air were measured at the range of wavelength from 300 to 800 nm, while the secondary voltage and current of spark ignition system were acquired simultaneously. An optical probe with linearly arranged glass fiber bundle was used to achieve spatial distribution of emission intensity vertically along the electrode gap of spark plug. At the same time, the time series of emission spectra were illustrated by using the precise gate shift operation of intensified CCD camera mounted on the spectrograph. ... mehrThe emission of electronically excited species such as molecular nitrogen, atomic oxygen and electrode material were effectively measured with the spectral resolution of 0.2 nm. During the abrupt increase of current in breakdown phase, only molecular nitrogen emission was exclusively detected. It was followed by the atomic oxygen and electrode material, which are closely related to the flame initiation and electrode wear respectively. The activated volume of spark discharge near cathode showed higher emission intensity for all the aforementioned species in comparison with the region near anode. The electronic, vibrational and rotational temperatures of the discharge were calculated by using additional spectra measurement at selective wavelength range with spectral resolution of 0.1 nm. Alongside the calorimetric measurement, the temperature profile over position and time allowed the quantitative evaluation of energy-transfer efficiency of spark discharge into the gas mixture.