Experimental Studies on Nano-Second High Voltage Plasma Ignition in a Constant Volume Combustion Chamber

Conventional automotive ignition systems are known for their ability to ignite fuel-air mixtures with a spark, which is an example of thermal plasma. In recent times it has been demonstrated that compared to thermal plasma, non-thermal plasma is an effective means of enhancing combustion. To establish this point, an experimental setup was built, and experiments were carried out in a Constant Volume Combustion Chamber (CVCC) with a conventional J type spark plug. Under atmospheric conditions, the combustion tests were carried out with methane-air mixtures. A nano-second, high voltage repetitive pulse discharge generator was used as a non-thermal plasma ignition source. To generate thermal plasma, an induction-based automobile ignition system was used. Flame propagation inside the CVCC was captured using a high-speed camera by employing shadowgraph imaging. With Nano-Second Pulse Discharge (NPD), Flame Development Time (FDT) was reduced by 22% with NSD_1ms and by 58% with NPD_5ms configurations respectively. Also, the initial flame kernel size increased up to 20% with NPD_1ms and 50% with NPD_5ms configurations. From the cumulative heat release curve, it was evident that a decrease in FDT led to a steeper pressure rise and early completion of the combustion process