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Technical Paper

RF Plasma Ignition System Concept for Lean Burn Internal Combustion Engines

This paper describes a Radio Frequency (RF) plasma ignitor concept intended for application to internal combustion engines. This system features a high Q quarter-wave coaxial cavity resonator, of simple construction, serving as a tuning element in the RF power supply, a voltage magnifier, and a discharge device attached to the combustion chamber. The resonator is filled with a dielectric and open at the discharge end. The center conductor is terminated with a revolute solid capacitive electrode which concentrates the associated electric field. This non-uniform electric field within the air/fuel mixture creates a corona discharge plasma which is excited at the RF operating frequency and the resulting ionic species recombine to initiate combustion. The RF excitation, relative to DC, reduces breakdown voltage and electrode degradation.
Technical Paper

Analysis of RF Corona Discharge Plasma Ignition

Corona discharge from a RF quarter wave coaxial cavity resonator is considered as a plasma ignition source for spark ignited (SI) internal combustion (IC) engines. The gaseous discharge processes associated with this device are analyzed using principles of gas kinetics and gaseous electronics, with assumed values for the electric field strength. Corona discharge occurs when the electric field shaped and concentrated by a single electrode exceeds the breakdown potential of the surrounding gas. Ambient electrons, naturally present due to ionizing radiation, drift in the direction of the externally applied field, gaining energy while undergoing elastic collisions with neutral molecules. After gaining sufficient energy they dissociate, excite, or ionize the neutral particles through inelastic collision, creating additional electrons. This process leads to avalanche electrical breakdown of the gas within about 10-8 sec.