In-Depth Study on Propane–Air Combustion Enhancement With Dielectric Barrier Discharge

Low-temperature plasmas generated from dielectric barrier discharges (DBDs) play an important role in hydrocarbon combustion reactions. In this paper, two different arrangements of coaxial cylindrical DBD reactors are designed to investigate the enhancement processes of plasma-assisted propane combustion through activating propane and air, respectively. Each reactor corresponds to one kind of activation method. With plasma being on and off, the physical appearances of the propane combustion flame are observed and compared, and the spatial distributions of the flame temperature are measured and comparatively investigated under each activation approach. In addition, some major components such as OH, CH, and C₂ in the combustion flame are identified using flame/plasma emission spectroscopy. The relationship of OH radical concentration with flame position is studied when plasma is on and off, and concentration profiles as well as densities of these major components in the main combustion zone are qualitatively measured and analyzed. Possible physical and chemical reaction mechanisms in the plasma and flame zones are discussed in detail under both activation ways. Experimental results suggest that propane combustion be enhanced with plasma applied on either propane or air stream. A temperature rise of about 30°C is achieved for the activation of propane, but about 50°C is achieved for the activation of air with a 30-W plasma being applied. It denotes that some active species like O-atoms, N-atoms, and excited molecular oxygen and nitrogen produced by activating air components play a greater role than those smaller fragments and radicals generated by cracking propane in plasma-assisted combustion in our experimental conditions.