# The Simulation of Dielectric Barrier Discharge for Breakdown Voltage in Starch Modification
## 3 Results and Discussion
### Effect of Starch Thickness Layer  
Our further studies worked on examining the impact of starch thickness on the breakdown voltage. The starch layer had a sphere-like form, a 150-micron diameter,  
Figure 14: Schemes of the Paschen curves of different starch shapes using (**a**) parallel plate electrode and (**b**) mesh-plate electrode.  
Figure 13: The breakdown voltage with the product of the pressure and gap distance (\(pd\)) for each type of granule.  
3.1 relative permittivity values, and a 0.6 mm thickness. The thickness was then changed to 1.0 and 1.5 mm, respectively. Table 5 illustrates how the thickness of the starch layer affects the breakdown voltage at atmospheric pressure for a gap distance of 0.2 to 1.0 cm.  
Following the data presented in Table 5, Figure 15 compares the breakdown voltage versus the product of pressure and gap distance (_pd_) between different electrodes for 0.6, 1.0, and 1.5 mm thicknesses.  
The effect of varying starch thicknesses at a short gap (_pd_ = 152 torr cm) is depicted in Figure 15 as a sparking potential of the mesh electrode that is lower than that of the parallel plate electrode by 5.8%, 4.2%, and 3.0% for thicknesses of 0.6, 1.0, and 1.5 mm, respectively. On the other hand, for a wide gap (_pd_ = 760 torr cm), it was less than 2.0% for all thicknesses.  
A comparison of the results for electrodes with different thicknesses of starch shows that the breakdown voltage increases with increasing thickness of the used starch, as depicted in Figure 16. When the thickness was increased from 0.6 mm to 1.0 and 1.5, respectively, for regular electrodes, the results for the corresponding values were about 1.3 and 2.5% and 3.1 and 5.6% for mesh electrodes.  
While the electric field in the gap is stronger than its maximum field strength, discharges happen as the applied voltage increases, which leads to more of these charges building up on the starch surface. They create an electrical field within the gap that is the opposite of the applied field, which causes the total electric field in the gap to decrease rapidly. The breakdown voltage is increased when this electric field is decreased.  
Figure 15: The breakdown voltage with the gap distance and pressure product (_pd_) for each starch thickness.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & & & \multicolumn{4}{c}{**Breakdown Voltage (V)**} \\ \cline{4-9}
**Gap Distance** & _pd_ & & \multicolumn{2}{c}{**0.6 mm**} & \multicolumn{2}{c}{**1.0 mm**} & \multicolumn{2}{c}{**1.5 mm**} \\ \cline{4-9}
**(cm)** & **(torr cm)** & & **Plate** & **Mesh** & **Plate** & **Mesh** & **Plate** & **Mesh** \\ \hline
0.2 & 152 & 6006 & 5659 & 6083 & 5832 & 6158 & 5978 \\
0.3 & 228 & 7307 & 7185 & 7400 & 7259 & 7493 & 7355 \\
0.4 & 304 & 8865 & 8701 & 8976 & 8809 & 9086 & 8937 \\
0.5 & 380 & 10,570 & 10,369 & 10,699 & 10,496 & 10,829 & 10,623 \\
0.6 & 456 & 11,968 & 11,749 & 12,116 & 11,904 & 12,265 & 12,038 \\
0.7 & 532 & 13,464 & 13,221 & 13,629 & 13,396 & 13,798 & 13,549 \\
0.8 & 608 & 14,947 & 14,662 & 15,129 & 14,857 & 15,318 & 15,011 \\
0.9 & 684 & 16,399 & 16,086 & 16,597 & 16,265 & 16,801 & 16,465 \\
1.0 & 760.0 & 17,839 & 17,473 & 18,053 & 17,674 & 18,273 & 17,907 \\ \hline \hline \end{tabular}
\end{table}
Table 5: The breakdown voltage varies depending on the starch thickness layer at 760 torr of pressure.  
This could be happening because, when the starch is very close to the electrode, the electric field produced by the residual surface charges over the barrier is so small that it cannot affect the distribution of the electric field in the gap, changing the breakdown voltage [45]. These results agree with the work reported by [PERSON] et al. [49], [PERSON] et al. [54], and [PERSON] et al. [55].