Experimental study on the effect of discharge parameters of high-frequency nSDBD on the multi-point ignition characteristics of NH3/air mixture

Multi-point ignition by high-frequency nanosecond surface dielectric barrier discharge (nSDBD) offers the potential to enhance the combustion speed of NH3/air mixtures. This paper investigates the ignition process of high-frequency nSDBD in NH3/air mixture. Firstly, the morphology of the discharge channels is studied, and it is found that before the formation of a clear flame kernel, with the increase of the pulse number, the discharge filament length increases first and then stabilized, while the discharge filament number decreases from about 20 to around 12. Secondly, the influence of the mixed gas state on discharge characteristics is studied, and it is observed that as the gas pressure increases, the single pulse energy decreases and the discharge filament length decreases, but the deposition energy per unit length did not change significantly. The increase in NH3 concentration leads to a slight decrease in discharge energy and length. Finally, the effect of the flame kernel on discharge morphology is studied, and it is found that when the flame kernel is small, the discharge filament trees change from dispersed to coincident, and the discharge energy is concentrated. When the flame kernel is large, the discharge filament trees mostly transform into overlapping types, and the number decreases.