Characteristic of Multi-channel Nanosecond Discharge Plasma Ignition under Sub-atmospheric Pressures

Relight of aircraft engines at high altitudes in the event of flame out is militated against by the extremely low (absolute) pressure and temperature. However, nanosecond repetitive pulsed (NRP) discharge is being increasingly used in ignition field because of its chemical activations, thermal and hydrodynamic expansions. The effect of NRP discharge on ignition kernel explosion is investigated at low initial pressure. The ignition probability, ignition kernel explosion, pressure delay and rise time are compared amount three ignition types at atmosphere and low initial pressure. The results show that the high frequency nanosecond discharge has a cliffy rising edge and a narrow pulse width, which improves the discharge efficiency. The turbulence phenomenon caused by NRP discharge in the static gas accelerates ignition kernel expansion through cellular instabilities on the kernel surface. In the condition of low initial pressure and lean mixture, NRP discharge is more efficient than spark and new actuator produces larger initial kernel making a substantial increase in ignition efficiency. NRP discharge can reduce pressure delay time and the new actuator makes pressure delay time shorten by 24% (with the initial pressure at 0.1 MPa and equivalent at 1.0).