Optimization of Plasma Jet Ignition Properties: Ignition of Lean-Quiescent Mixtures of Propane

Abstract

Plasma jet ignition is known to improve the lean operation of spark ignited engines. Design parameters such as orifice and cavity size and operational characteristics such as the energy requirements and fueling have been investigated in order to develop an optimal plasma jet plug design.

The results of the orifice size studies reported here indicate that a unique balance exists between jet penetration and jet mass flow. The correct balance of these two factors produces optimal combustion enhancement. Comparison of data obtained at elevated pressure with that obtained at atmospheric pressure reveals that by increasing the orifice size the plasma jet performance obtained in atmospheric experiments can be duplicated at engine pressures.

Experiments conducted to investigate the energy requirements of the plasma jet indicate that the primary factor influencing jet performance is the total energy input into the gas, while the current and voltage characteristics of the charging supply exert secondary effects. Investigations of the effect of fueling the plug cavity confirms that reduced input energy levels are needed to ignite lean mixtures. In addition, the feasibility of using cavity fuels such as solid hydrides and paraffins has been demonstrated.