In this paper, results are presented from an experimental investigation of propane-air combustion in a stationary microwave (MW) discharge at different conditions. In these experiments, a deeply undercritical discharge is initiated in the base of an electromagnetic vibrator, which is immersed in cold supersonic airflow. Two schemes for mixing propane with air are considered. In the first scheme, a propane-air mixture is delivered through the vibrator and is ignited at the outlet from the vibrator. In the second scheme, propane delivered through the vibrator mixes with air captured by an inlet hole in the vibrator nose prior to being also ignited by the MW discharge at the base of the vibrator. Propane combustion with efficiency of approximately 60% was demonstrated at a mixture velocity up to 200 m/s in the combustion region. The heat release reaches approximately 1 kW at a propane mass flow rate of 2 · 10 −2 g/s and discharge power of approximately 200 W.Index Terms-High-speed combustion, microwave (MW) gas discharge, plasma-assisted burning.

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Pulse detonation engines are considered to be one of effective propulsion systems for future space missions. Significant efforts are being spent on acceleration of fuel combustion and rising is efficiency. Existing studies have mainly focused on optimizing fuel injection and mixing, repetitive initiation of detonation and integration of detonation tubes with fuel inlets. Understanding of streamer propagation mechanism is of essential importance for the studies of electrical breakdown phenomena and their related applications. In this study, a subcritical microwave streamer discharge is used to initiate ignition of air-fuel mixtures. Ignition of lean fuel mixtures by a streamer has been demonstrated at atmospheric pressure. The speed of streamer-initiated combustion has been shown to be higher compared to that initiated by a spark. The combustion efficiency has also been shown to be higher when using the microwave streamer ignition.

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