Plasma-assisted ignition and combustion of lean and rich air/fuel mixtures in low- and high-speed flows

A stabler ignition and combustion of the premixed air/fuel mixture remains a topic of great interest due to the high demand for effective and efficient propulsion systems in aerospace applications. Extensive experimental studies and numerical simulations have been carried out to understand and develop ignition systems using cold and non-thermal plasma in microwave streamer discharges. Use of sub-critical streamer discharge allows to ignite air/fuel mixture by an external electric field whose intensity is significantly lower than the intensity required to induce air breakdown. Ignition and combustion of air/propane mixture by microwave sub-critical streamer discharge in low- and high-speed flows is studied experimentally. Qualitative (flame structure) and quantitative (size of combustion region, temperature distributions) characteristics of the flame zone are provided for different flow speeds and equivalence fuel/air ratios, and conditions of discharge initiation with metallic microwave vibrator are studied. The streamer discharge makes it possible to create multiple ignition points providing almost instantaneous ignition of entire volume of the mixture. The results show that the sub-critical streamer discharge can potentially be used in various applications providing more rapid and efficient combustion. •Stable ignition of lean/rich mixtures in air flows is demonstrated•Streamer discharge provides instantaneous volumetric ignition of the mixture.•Effect of fuel/air ratio on combustion efficiency is investigated.•Streamer discharge yields improvement of combustion speed and efficiency.