Multi-point ignition of air/fuel mixture by the initiated subcritical streamer discharge

An experimental study of ignition and combustion of a propane/air mixture is carried out, and the efficiency of two ignition systems is compared. The first one is the traditional technology with conventional spark plugs, and the second one is a system with microwave initiated streamer discharges. In both cases, the ignition sources, spark plugs or streamer discharges are distributed along the surface of the combustion chamber. A subcritical streamer discharge is initiated on the surface of the circular tube using a half-wave resonator when the intensity of the electric field is much smaller than the breakdown intensity because ability of electromagnetic vibrators to initiate air breakdown has a resonant character. For the initiated streamer discharge, intensity of microwave radiation is significantly lower than the breakdown intensity. The results obtained for a new microwave ignition system of a fuel/air mixture are presented and compared with an ignition system based on spark plugs. Comparative analysis is given for different initial pressures and composition of fuel/air mixture. The time of propagation of the flame front is compared, as well as the rate of pressure increase in the combustion chamber, depending on the initial pressure and the composition of the mixture. The optimal fuel/air equivalence ratio, which provides the highest pressure and the highest rate of pressure rise in the combustion chamber, is determined. A comparative assessment of the energy efficiency of each of the approaches applied to the ignition of the fuel/air mixture is performed. The results obtained could potentially be useful to improve reliability of plasma-assisted ignition systems and flight safety.