Motofumi Tanaka

Application of radio-frequency thermal plasmas to treatment of fly ash

RF thermal plasma systems for treatment of fly ash have been proposed in order to recover the useful metals and materials from fly ash discharged from a melting furnace. The fundamental investigations for recovering the detoxified and useful materials from fly ash by means of RF thermal plasma process were performed. In terms of the numerical analysis and the experimental results, it is verified that fly ash is decomposed by RF thermal plasmas and heavy metal species separate from fly ash by means of the effects of temperature control and hydrogen.

Temperature Dependence of Toluene Decomposition Behavior in the Discharge-Catalyst Hybrid Reactor

Temperature dependence of toluene decomposition behavior was investigated with a two-stage discharge and ozone-catalyst hybrid reactor. Temperature was varied from 20 to 200degC because VOC exhausts from painting and printing facilities reach this temperature level. A synergistic effect of discharge and catalysts was observed for toluene conversion at temperatures lower than 200degC. In the hybrid reactor, COx formation was promoted compared to discharge alone, and toluene was completely oxidized to COx at higher than 100degC.

Lift Enhancement of a Pitching Airfoil in Dynamic Stall by DBD Plasma Actuators

A dielectric barrier discharge (DBD) plasma actuator was applied to control leading-edge flow separation on periodically oscillated NACA 0012 airfoil. The effectiveness of flow control by the plasma actuator was investigated through pressure measurements on the surface of the airfoil. All of the cases exhibited a higher cycle-integrated lift and an improvement in the lift cycle hysteresis. The lift enhancement by the plasma actuator was sensitive to frequency of unsteady actuator operation. The maximum peak of efficiency of lift enhancement was observed around F=0.5. The time-resolved PIV measurement was also conducted to understand the flow control mechanism by the plasma actuator. The clear vortices appeared at the leading-edge at high angle of attack, and moved along the airfoil surface toward trailing edge. These vortices bring entrainment of main flow and the lift enhancement of the oscillating airfoil can be achieved.

Preparation and characteristic evaluation of hydrophobic epoxy-based nanocomposites

Nanocomposite techniques are used to improve the electrical properties of epoxy materials, for example, insulation breakdown strength and partial discharge resistance. In the first step, we prepared epoxy-based nanocomposites by using hydrophobic epoxy as the base resin and 10wt% of titanium dioxide or 5wt% of layered silicate as nano fillers, and measured the partial discharge resistance and insulation breakdown strength. It was confirmed that the depth of the hole caused by partial discharge exposure was decreased to half and one-fourth and the insulation breakdown strength was increased by about 0.8% and 4% with the addition of titanium dioxide or layered silicate, respectively, as compared to the base resin. In the second step, we fabricated impregnated mica tapes, which have been widely used in high-voltage equipment, using nanocomposite epoxy as binder resins. We can see that, although the erosion depth was not changed significantly, the insulation breakdown strength was increased by about 35% and 8.7% in mica tapes containing titanium and layered silicate, respectively, compared with mica tape without nano-fillers.

Airflow produced by dielectric barrier discharge between asymmetric parallel rod electrodes

We observed a novel type of airflow produced by an atmospheric rf discharge between asymmetric parallel rod electrodes. The electrodes were a bare metal rod 1 mm in diameter and a glass-coated metal rod 3.2 mm in diameter. The thrust, measured by a pendulum, increased with discharge input power.