Enhancing the mechanical efficiency of electric wind in corona discharges

This paper deals with experimental measurements of the electric wind velocity induced by corona discharges in air at atmospheric pressure. DC coronas are established inside a tube of a few cm in diameter, between a HV needle and a grounded electrode (grid and ring), in order to produce an electric wind for airflow applications or EHD gas pumps. The goal here is to optimize the corona properties to increase its mechanical efficiency, such as electric wind velocity. The influence of the following parameters is investigated: electrode polarity, collecting electrode geometry, electrode gap and tube diameter. Measurements of time-averaged velocity profiles at the tube outlet have allowed us to compute flow rate, induced mechanical power and efficiency of each configuration. This has shown that: (1) the maximum velocity is higher in the case of positive coronas than in the case of negative ones, (2) this is certainly due to the presence of streamers in the case of positive coronas, (3) mesh size plays a fundamental role and using a grid as a collecting electrode is more efficient than a ring, and (4) the most efficient configuration allowed us to produce a 10 m/s electrical wind, a flow rate of about one I/s, a mechanical power of a few mW with an efficiency of about one percent. (c) 2007 Elsevier B.V. All rights reserved.