Plasma Jet Ignition of Lean Mixtures

Single-cylinder and multi-cylinder dynamometer tests and vehicle evaluations of a plasma jet ignition system used in conjunction with a modified combustion cylinder head are reported. Significant nitrogen oxide emission reductions are obtained, though emissions below 2.0 g/mi are not consistently achieved. The NO/sub x/ reduction is attributed to a decrease in gas residence time at high gas temperatures and a lower thermodynamic gas temperature history. The NO/sub x/ reduction, however, is accompanied by an increased hydrocarbon emission level which is attributed to the blind cavity which increases combustion chamber surface area and consequently the total surface quench film mass. Thus, exhaust aftertreatment appears to be required for total emission control with the system.