Ignition limit of lean mixture by hydrogen flame jet ignition

Abstract

A hydrogen flame jet ignition method is proposed to achieve the secure ignition and stable combustion of an ultra lean mixture. The mechanism of enhancement by the jet ignition method, especially the role of radicals in the flame jet, is analyzed first and the lean limit of ignition is investigated by the hydrogen flame jet ignition method. This proved that the effect of radicals on the enhancement of lean mixture combustion is smaller than the turbulent effect. The lean limit of stable ignition at atmospheric pressure is therefore almost the same as that of the inflammability limit, namely around φ=0.5. When gas temperature and pressure are increased to actual engine conditions, the lean limit is widened to around 0.3 which is much lower than conventional lean burn engine conditions.