Investigation on the Lean Stable Limit of a Barrier Discharge Igniter and of a Streamer-Type Corona Igniter at Different Engine Loads in a Single-Cylinder Research Engine

Currently, the Radio-Frequency Corona Ignition systems represent an important solution for reducing pollutant emissions and fuel consumption related to Internal Combustion Engines while at the same time ensuring high performance. These igniters are able to extend the lean stable limit by increasing the early flame growth speed. Kinetic, thermal and ionic effects, together with the peculiar configuration of the devices, allow to start the combustion process in a wider region than the one involved by the traditional spark. In this work two corona igniters, namely a Barrier Discharge Igniter and a Corona Streamer Igniter, were tested in a single-cylinder research engine fueled with gasoline at different engine loads in order to investigate the igniters performance through indicated analysis and pollutant emissions analysis. For each operating point, the devices control parameters have been set to ensure maximum energy releasement into the medium with the aim of investigating, at the extreme operating conditions, the capability of the devices to extend the lean stable limit of the engine. The Corona igniters have been tested on a constant volume calorimeter as well, reproducing the engine pressure conditions at the corresponding ignition timing. The target is to give an estimation of the thermal energy released during the discharge and then to compare their capability to provide high-stability energy.