Effect Of Corona Discharge Field On Corn Seeds And Development Of Cotton Seeds Dielectric Separator

Dielectric separation is based on the vigor of the seed being separated, and the separator is of simple structure and good adaptability. Dielectric properties and impedance characteristics of cotton seeds was studied in this paper. Results showed that the dielectric constant of grade A cotton seeds after dielectric separation was less than CK, dielectric constant of grade B cotton seeds was slightly higher than CK with the frequency ranging from 0.2 to 0.8 MHz, and then less than CK with the frequency increasing to 2 MHz, dielectric constant of grade C cotton seeds was higher than CK. Both dielectric constant and dielectric loss factor increased with the increasing frequency. However, the real part of impedance characteristics (resistance) increased at first then decreased, while the imaginary part of impedance characteristics (reactance) increased with the increasing frequency, and the amplitude decreased with the increasing frequency, while phase angle showed a basically rising trend. On the basis of single factor experiments of separation voltage and rotating speed, using Deign-expert software to design the orthogonal experiment, and the result showed that germination rate of grade A cotton seeds was almost significantly (P<0.01 or P<0.05) higher than that of CK, and it showed the trend of first increasing then decreasing with the increasing of separation voltage and rotating speed. The germination rate of grade B cotton seeds was substantially higher than that of CK, which was significant difference(P<0.01 or P<0.05), while there also were individual germination rate of grade B cotton seeds lower than that of CK, and it showed the same trend as germination rate of grade A as well. However, the rotating speed had greater impact on it in the view of univariate analysis. Germination rate of grade C cotton seeds was variant, some of which were increasing compared to CK, but most of which was lower than that of CK, and it showed a linear relationship with the increasing of separation voltage and rotating speed, and the univariate analysis indicated that rotating speed had greater impact on it.Corona discharged field was used to treat the corn seeds in this study, and optimal treatment condition was achieved through orthogonal experiments, which was 350 kV/m treating for 5.5 min. Germination rate of corn seeds after being treated was increasing 10.5% (absolute percent) compared to CK, which was significant difference (P<0.01). Corona current and voltage waveform during the experiment were measured and analyzed. On the basis of previous studies, with the corona current being taken into account, treatment energy (TE) was put up to explain the effect of cotton seeds vigor processed by corona discharge field. The result of verification test showed that optimal TE was 1354.32 J, germination rate of corn seeds processed with the optimal TE was significantly (P<0.01)higher than that of CK, increasing by 11.33%(absolute percent). Further more, corona discharge field had little impact on the vigor of corn seeds if the TE was not that much, while if it was too much, inhibitory effect may be generated on the seed germination. Only proper TE could improve the vigor of corn seeds.On basis of dielectric separation principle and analysis of each factor during separation process, a new style of dielectric separation instrument was being developed. The entire separation process was done inside the cylinder, and according to the mechanical and physical properties of cotton seeds, some grooves which were slightly larger than the average particle diameter of cotton seeds were curved in the circumferential direction, and arc-shaped grooves were also curved to place the electrodes. This structure could guarantee that single cotton seeds fall down into the groove, and that the strength of electric field was uniform.