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 the injector position where ignition 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 airflow velocity. This suggests that the ignition limit strongly depends on the penetration height of the plasma torch, which is in inverse proportion to airflow 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 flame shape. Calculations of ignition delay time for an H₂/air mixture with the addition of N and O radicals showed the same effectiveness and were found to be superior to the H and the OH radicals. However, the degree of deterioration of an anode nozzle made of copper was more severe for oxygen plasma than for nitrogen.