Corona discharge characteristics, ionic wind, and ozone concentration in a multi-needle-to-mesh electrode system for seed drying

Ionic wind and ozone generated by corona discharge have demonstrated considerable potential for applications in nonthermal processing, particularly for low-temperature drying and sterilization of agricultural products. In this study, a corona discharge plasma drying platform was established to evaluate the discharge characteristics of a multi-needle-to-mesh electrode system, as well as the ionic wind and ozone concentration during seed drying. The effects of applied voltage and electrode configuration, including electrode gap (d), mesh aperture (D), and hole spacing (L), on voltage–current (V–I) characteristics, ionic wind velocity, and ozone concentration were systematically investigated. Based on the electrical characteristics, optimal parameters were selected to conduct drying experiments on Capsicum annuum L. seeds, with comparisons made against 50 °C hot-air drying and natural air drying. The findings indicate that positive corona discharge fostered streamer formation at an electrode gap of d = 25 mm. At 15 kV, the positive corona current, ionic wind velocity, and ozone concentration were significantly higher than those under negative polarity. A mesh electrode with an aperture of D = 3 mm and a hole spacing of L = 30 mm was more conducive to generating ionic wind and active species, such as ozone. Drying experiments demonstrate that, under optimal electrical parameters, the initial drying rate of Capsicum annuum L. seeds was 0.11 g/min, approximately 1.8 times that of hot-air drying. This enhancement is primarily attributed to the disruption of the saturated vapor boundary layer on the material surface by the strong ionic wind. In addition, over the same 2-h drying period, the specific energy consumption (SEC) of plasma drying was 18.2 kJ/g, which was substantially lower than that of hot-air drying (33.8 kJ/g). This study confirms the application potential of multi-needle-to-mesh corona discharge technology in the drying of heat-sensitive agricultural products. It provides a theoretical foundation for the design of drying equipment parameters.