Spectral Diagnostics of Emissions from an Alternating Current Plasma Igniter

This study investigates the effects of operating conditions on the ignition performance of a plasma igniter through spark morphology and emission spectral analyses under varying air pressures and flow rates. The effect of airflow rate at 0.2 MPa on the types of active particles, spectral intensity variations, and electron temperature in the plasma jet is analyzed. The results reveal that igniter performance is significantly influenced by the nozzle airflow rate. Emission spectral analysis identifies active species, including OI, OII, OIII, NI, NII, NIII, NIV, and NO radiation bands, with the strongest peak intensities at 520.18 (NI) and 776.28 nm (NII). Increasing the air pressure from 0.2 to 0.6 MPa without flow restriction has a minimal effect on the emission spectra, spark length, and brightness. At 0.2 MPa, higher airflow rates significantly increase the spark length and spectral intensity. However, the emission intensity varies with wavelength. The emission spectra are dominated by ultraviolet and visible light bands, with the visible band proportion decreasing as the flow rate increases. Electron temperatures, calculated from integrated photon counts, range from 10035.34 to 16474.83 K and increase with higher flow rates. These findings provide insights for optimizing plasma ignition performance under varying operating conditions.