A comparative study on droplet characteristics and specific charge of ethanol in two small-scale electrospray systems

An investigation on the droplet characteristics of ethanol in small-scale combustors with two different systems was conducted experimentally and theoretically. The classical capillary-mesh electrode arrangement was applied in Type A electrospray system, and for Type B, an additional ring electrode is included. The droplet size and velocity were measured by a Phase Doppler Anemometer. The electric filed intensity was theoretically calculated in the two electrospray systems. Compared with Type A, Type B system has smaller droplet size and velocity in the same spraying mode. Meanwhile the electrospray process in Type B system is more stable than that in Type A with its smaller root mean square velocity. By measuring the spraying current, the average specific charge of the droplets for the two systems was obtained in different spraying modes. And it was found that the addition of the ring electrode can help to increase the droplet charge, which is the fundamental reason for Type B electrospray system to perform better. The corona charge of the droplets was theoretically calculated for the two electrospray systems. It was found that the calculated specific charge generated by corona charging was in good agreement with the experimental results.