Ignition Characteristics of Methane and Hydrogen Using a Plasma Torch in Supersonic Flow

Ignition and flame-holding characteristics of methane and hydrogen using a plasma torch igniter were experimentally investigated in a supersonic airflow. The main airflow Mach number was 2.3, and the stagnation pressure and temperature corresponded to atmospheric conditions. Nitrogen, oxygen, a hydrogen/nitrogen mixture, and a methane/nitrogen mixture were used as feedstocks for the torch. The fuel was vertically injected from the wall where the plasma torch was attached. The wall pressure and the total temperature at the exit of the test section were measured. Ignition was confirmed for hydrogen injected both upstream and downstream of the torch. No strong dependence on the kind of feedstock of the torch for effectiveness of ignition of the hydrogen fuel was evident in a supersonic flow. By contrast, ignition of the methane fuel was confirmed only when it was injected upstream of the torch. In addition, the wall-pressure increase of the methane fuel was about half that of the hydrogen fuel. An important result for methane fuel was that using oxygen as a feedstock resulted in the most remarkable increase of the total temperature and the wall pressure.