The low-temperature nonequilibrium characteristics of dielectric barrier discharge (DBD) make it an important candidate for the decomposition and conversion of CO₂. In this study, quartz, alumina and zirconia are selected as the dielectrics to investigate the effect of dielectric materials of planar DBD reactor on the discharge and conversion characteristics of CO₂. It is shown that under the same input power conditions, zirconia has the highest CO₂ conversion rate when used as a dielectric, followed by alumina, and quartz has the lowest. Combined with the analysis of the measured electrical characteristics, it is shown that zirconia has the highest transferred charge, thus further increasing the discharge efficiency. Experimental results of the single dielectric barrier layer-metal mesh electrode reactor show that the CO₂ discharge can operate in the lower power range and the CO₂ conversion rate is higher than that of the double dielectric barrier layer reactor. Spectroscopic measurements show that the emission intensity of the discharge in the reactor with high relative permittivity materials is higher than that in the case of low relative permittivity materials, and the emission intensity of the single dielectric layer reactor is also higher than that in the case of the double dielectric layer reactor.

The choice of electrode configuration and dielectric material is critical to the discharge process and plasma characteristics of a dielectric barrier discharge (DBD) reactor. In this study, a new electrode configuration of DBD reactor with copper mesh as electrode inserted between dielectrics is proposed, which has a much higher capacitance than the conventional double-dielectric layer DBD reactor. Two materials with different relative dielectric permittivities, alumina and zirconia, are chosen as dielectrics for an experimental comparison of CO₂ decomposition. The experimental results show that the conversion rate of CO₂ for the reactor with copper mesh inserted between dielectrics are higher than that of the corresponding double dielectric layer reactor under the same discharge power, and the conversion rate of CO₂ with zirconia as a dielectric material is higher than the case of alumina as a dielectric. Further analysis of discharge characteristics shows that for the reactor with copper mesh inserted between dielectrics, the applied voltage required for discharge is significantly reduced, the amount of transferred charge is significantly increased, and the number of micro-discharge current pulses as well as the average lifetime during a single voltage cycle are also considerably increased, leading to an increase in the CO₂ discharge efficiency and conversion rate.

The reasonable thermochemical kinetic model is a key prerequisite for accurately predicting the non-equilibrium flow field and radiation of high-speed atmospheric reentry vehicles. A vibrational and electronic specific State-to-State kinetic model is first established to couple with post-shock flow equations to analyze the thermochemical non-equilibrium flow characteristics. It is found that the vibrational and electronic energy levels non-Boltzmann metric are large at the flight altitude higher than 50 km, which is thus considered a demarcation line for constructing the low- and high-altitude models. Therefore, in this study, two new physics-based thermochemical kinetic models are constructed from the State-to-State model using the multi-group maximum entropy method for low-altitude and high-altitude regions, respectively, across the entire flight velocity domains. By analyzing the differences in post-shock flow physical characteristics under various flight altitudes, single-group and multi-group functions are, respectively, adopted to reconstruct the internal energy levels distributions within the flow field for the low-altitude and high-altitude chemical models. Compared to the State-to-State model, the low-altitude and high-altitude models significantly reduce the number of solved species and chemical reactions, while maintaining computational accuracy of post-shock non-equilibrium flow, with calculated thermodynamic parameters error less than 5% and chemical parameters error below 10%. Finally, the low-altitude and high-altitude chemical models constructed in this study exhibit better predictive capability in reproducing ground experimentally measured electron number density and predicting reentry flight heat flux and radiation compared with the classical Park's and Gupta's models, demonstrating the promising applicability of developed models. This study provides a new, reasonable chemical model for the entire flight altitude and velocity domain that can be used in computational fluid dynamics simulations to predict non-equilibrium flow and radiation in high-speed reentry vehicles.

The pinch-off process of liquid bridges in metal droplet-on-demand printing directly determines printing precision and structural quality. Numerical simulations have investigated the regulation mechanism of the liquid bridge necking process by the positive and negative pressure pulses, namely, the “push–pull effect,” generated by electromagnetic actuation on the molten metal. The results show that the positive pressure pulse dominates the initial necking of the liquid bridge through axial stretching effect, while the negative pressure pulse significantly accelerates the necking process of the liquid bridge through a dual strengthening effect, namely, axial reverse stretching and radial shearing effect. The increase in the negative pulse peak causes the upward movement of the pinch-off position and the dynamic evolution of the morphology from inverted cone, cylinder to positive cone. The scaling law of necking velocity under bidirectional drive clarifies the competitive mechanism of surface tension suppressing necking in the early stage and negative pulse-induced curvature instability triggering self-accelerated breakup and the analysis of axial and radial Weber numbers reveals the competition mechanism between inertial force and capillary force. The droplet generation time, velocity, and size can be controlled by the “pulse intensity-duration” collaborative optimization method, which provides a theoretical basis for high-precision electronic printing and microscale metal 3D printing.