Numerical Simulation of the Early Flame Development Produced by a Barrier Discharge Igniter in an Optical Access Engine

Currently, conventional spark-ignition engines are unfit to satisfy the growing customer requirements on efficiency while complying with the legislations on pollutant emissions. New ignition systems are being developed to extend the engine stable operating range towards increasing lean conditions. Among these, the Radio-Frequency corona igniters represent an interesting solution for the capability to promote the combustion in a much wider region than the one involved by the traditional spark channel. Moreover, the flame kernel development is enhanced by means of the production of non-thermal plasma, where low-temperature active radicals are ignition promoters. However, at low pressure and at high voltage the low temperature plasma benefits can be lost due to occurrences of spark-like events. Recently, RF barrier discharge igniters (BDI) have been investigated for the ability to prevent the arc formation thanks to a strong-breakdown resistance. In this way, the plasma benefits are maintained over an extended range of operation compared to other LTP corona igniters, like RF corona-streamer igniters (CSI). The aim of the present work is to compare the combustion development of a conventional spark and a barrier discharge igniter through computational fluid dynamics simulations in an optical access SI engine, using RANS approach for the turbulence. Computational results are able to reproduce the faster burn rate generated by the BDI in the initial stage of the combustion compared to the traditional spark.