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Lean-burn is the most attractive way to lower emissions of NOx while improving the fuel consumption simultaneously in spark ignition engines. A Pulsed Combustion Jet (PCJ) ignition system has a great potential to enhance ignition reliability and burning rate of lean fuel-air mixtures. Its action is based on the utilization of turbulent plumes formed by jets produced by generators, in the shape and size of an ordinary spark plug, that embody a small (500 mm3 or less) cavity, capped with an orifice plate and outfitted with a hollow electrode. Performance characteristics of PCJ were established by combustion tests carried out in a diskshaped, constant volume combustion chamber using lean methane-air mixtures. The results were compared to those obtained with Pulsed Plasma Jet (PPJ) an standard spark plug ignition systems. Lean limit was extended most by PCJ ignition under both quiescent and swirl conditions.

In internal combustion engines, lean-burn is particularly attractive for minimizing pollutant emissions, in particular NOx, with a concomitant improvement in fuel economy. For combustion in lean fuel-air mixtures, achievement of adequate reliability of ignition and sufficiently high burning rate requires special devices. The most effective among them is the injection of active radicals by means of PFJ (Pulsed Flame Jet) ignition system. Presented here is an experimental proof of the action of the hydroxyl (OH) radical produced by such an ignition system. The measuring apparatus used for this purpose was based on PLIF (Planar Laser-Induced Fluorescence), and the effects of equivalence ratio of the mixture in the cavity, cavity volume, and orifice diameter on the variation of OH fluorescence area in the jet and their intensity were revealed quantitatively.