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 airflow were experimentally studied. The region of t he injector position where ignition occurred became gradually narrow with a n increase in the distance between the fuel injector and the plasma torch a nd steeply narrow with an increase in the airflow velocity. This suggests t hat the ignition limit strongly depends on the penetration height of the pl asma torch, which is in inverse proportion to airflow velocity. Nitrogen an d oxygen were compared as feed stocks. Results obtained showed no differenc e in the behavior of the plasma jet itself, the ignition limit, and the fla me shape. Calculations of ignition delay time for an H-2/air mixture with t he addition of N and O radicals showed the same effectiveness and were foun d to be superior to the H and the OH radicals. However, the degree of deter ioration of an anode nozzle made of copper was more severe for oxygen plasm a than for nitrogen.