Plasma-enhanced combustion of propane using a silent discharge

It is well known that applying an electric field to a flame can affect its propagation speed, stability, and combustion chemistry. External electrodes, arc discharges, plasma jets, and corona discharges have been employed to allow combustible gas mixtures to operate outside their flammability limits or to increase combustion speed. Previously reported experiments have involved silent electrical discharges applied to propagating flames. These demonstrated that the flame propagation velocity can be increased when the discharge is applied to the unburned gas mixture upstream of a flame. In contrast, the work reported here used a coaxial-cylinder, nonthermal, silent discharge plasma reactor to activate a propane gas stream before it was mixed with air and ignited. With the plasma, the physical appearance of the flame changes (increased stability) and substantial changes in mass spectrometer peaks are observed, indicating that the combustion process is enhanced with the application of the plasma.