Ignition Characteristics of Plasma Torch for Hydrogen Jet in an Airstream

The ignition characteristics of a plasma torch for a hydrogen jet injected parallel to a subsonic aire ow were experimentally studied. Theregion of the injector position whereignition occurred became gradually narrow with an increase in the distance between the fuel injector and the plasma torch and steeply narrow with an increase in the aire ow velocity. This suggests that the ignition limit strongly depends on the penetration height of the plasma torch, which is in inverse proportion to aire ow velocity. Nitrogen and oxygen were compared as feed stocks. Results obtained showed no difference in the behavior of the plasma jet itself, the ignition limit, and the e ame shape. Calculations of ignition delay time for an H 2/air mixture with the addition of N and O radicals showed the sameeffectivenessand werefoundto besuperiorto theHandtheOHradicals.However,thedegreeofdeterioration of an anode nozzle made of copper was more severe for oxygen plasma than for nitrogen.