Characterization of the effects of a dielectric barrier discharge plasma actuator on a coaxial jet in a Bunsen burner

The following work details the experimental and numerical characterization of jet flow control in a coaxial Bunsen burner obtained by an alternate current driven dielectric barrier discharge plasma actuator (AC-DBDPA). Fuel and oxidizer flows could be inverted between the inner circular tube and outer annular tube. Use of the ACDBDPA was intended to improve lean combustion performance. The high voltage (HV) electrode of the ACDBDPA was powered with sinusoidal voltage excitation at 20 kHz frequency and peak-to-peak voltage of about 12 kV. Two burner fueling configurations were tested, characterized by different flow rates in the inner and annular tubes. Values of actuator power dissipation, which were deduced through electrical characterization, ranged between 25 and 28 W. A preliminary analysis of the air-methane flame behavior in presence and absence of plasma actuation was performed. Images of the flame and chemiluminescence emissions showed that the flame luminosity changed and OH radical production increased in presence of the discharge. The thermal and fluid dynamic effects of the plasma actuation on the flow were investigated by means of a non-reacting flow characterization (absence of combustion), where air was used as both fuel and oxidizer. The flow pattern and turbulence in both presence and absence of actuation were studied by laser Doppler velocimetry (LDV) measurements. Flow temperature was acquired using thermocouples. The non-reacting flow experimental results showed that, for a fixed inlet volumetric flow rate, the plasma actuation increased jet velocity and air temperature. Interesting results were obtained from a spectral analysis using the time resolved velocity signals: plasma actuation affected jet mixing and impacted energy distribution between the different flow scales. Complementary numerical simulations identified increasing temperature as primarily responsible for increasing flow velocity. Moreover, numerical predictions permitted better identification of flow regimes under different test conditions.