Fig.7 (a) shows the numerical calculation results of the gas flow field, namely the streamline and velocityfield, inside the ion col-lector. In this calculation, the air flow velocity at the ion collector inletwas about 7.073 m/s or the airflowratewas about 3 L/min. It is noted that the domain is represented at the symmetry plane. It was showed that theflowfield has the highest velocity at the inlet and outlet of the ion collector. Theflow velocity generally peaks at the axis and decreases towards the wall of the outer electrode. Uni-formity of the velocityfield was presented in the collecting zone of
the collector.