Corona Discharge in Supersonic Flow

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Corona Discharge in Supersonic Flow
Faculty: Frank K. Lu, Ph.D., George Emanuel, Ph.D., Bernie Svihel (EE Department)
Students: Philip Panicker, U.S. Satyanand, Ph.D.

Conventional high current electric arc discharge ignition for combustion engines has many disadvantages despite its simplicity and low cost. This source of ignition has many disadvantages such as limited discharge size, interference of the flow by the electrodes, and low wall-plug efficiency (low electrical energy being transferred to the gas compared to the energy required to produce the arc discharge).

These difficulties can be somewhat overcome by supplementing the arc discharge with corona discharge. The performance of the corona ignition system is expected to be superior for the following reasons:
The geometry of the corona discharge electrodes can be tailored to have many corona streamers of electrons. This in turn enhances the size and shape of the ignition volume in a given combustion chamber.
Because of the greater electron energy distribution in the plasma, there is better coupling of the discharge with the gases (ions are good chain branching agents). This leads to more rapid and efficient combustion than the arc discharge.
Low anode and cathode voltage drops, low radiation loss and hence more efficient use of energy deposited into gases i.e. high wall-plug efficiency.

All these merits could lead to smaller and lighter engines with higher specific impulse. Initial experiments were conducted with corona discharge producing plasma in a supersonic (M=2) flow of air in a shock tube (see photograph). After testing successfully the efficacy of ionization of air at supersonic speeds, the corona discharge system of ignition would be employed for the combustion of supersonic air-fuel mixtures.

Graduate School ~ Mechanical and Aerospace Engineering