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When a fluid is subject to an electric field, it usually processes unique features compared to the conventional fluid that arises from coupling between charged particles and fluid interface. Based on this commonality, we defined the concept of “charged multiphase flow” and constructed a generalized charged multiphase flow system using the “Tai Chi Diagram” to analyze the properties and features of different study objects, with an emphasis on the bubble dynamics on the charged liquid–gas flow object, covering the processes of bubble generation, motion, and interaction, as well as the important dynamic behaviors, involved such as bubble deformation, coalescence, and breakup. Furthermore, in light of the special plasma–liquid interface phenomenon formed by the ionization of the gas/vapor phase in the liquid phase in strong electric fields, the traditional gas–liquid–solid three-phase flow system is expanded into a broader range of multiphase flow systems involving plasma, which enriches the theoretical and frontier scientific problems of the multiphase flow. In addition, technical innovations, remaining work, and future trends in the development of the charged liquid–gas flow, and their potential applications are discussed.

The conical breakup behavior of droplets in immiscible dielectric liquids under non-uniform alternating current (AC) electric fields is experimentally investigated using high-speed photography. The optical-microscopic morphological characteristics of the dynamic behavioral process of charged droplets under different electric field conditions are precisely captured. Two distinct conical breakup configurations, called the trident vibration and lotus vibration modes, are proposed, and their detailed structural parameters are discussed. The extremely small stable conical meniscus (semi-angles range of 11°–18.6°) is found in the liquid–liquid system. The distribution of cone angles under various spatial conditions is determined. In addition, the multilevel asymptotic characteristics of conical fragmentation are found due to the variances in spatial and temporal scales. The diameters of the droplets produced under the cone-jet mode could be as small as a few micrometers. The differences between the droplet breakup mode of AC and DC electric fields are also discussed. Overall, several interesting features are reported for the axisymmetric multi-cone broken morphology when droplets undergo breakup.

Electric field has the potential to influence the combustion characteristics of hydrocarbon fuel. In this paper, the atomization and combustion characteristics of the droplets of biodiesel and biodiesel–ethanol blend in a uniform direct-current electric field were investigated using photography. It was revealed that a certain electric field strength could induce droplet deformations and cone jets. For the droplet blended with 10 vol. % ethanol, the sizes of the secondary droplets from bubble breakups decreased with the increase in electric field strength, possibly due to the Coulomb repulsion in the ligament. The high breakup intensity of the droplet blended with 30 vol. % and 50 vol. % ethanol covered up the effect of electric field on the sizes of secondary droplets from bubble breakups. During the entire range of electric field strength, cone jets generated smaller secondary droplets in comparison with bubble breakups. Moreover, the electric field distorted the flame morphology, especially the flame width increased at the electric field strength of 50 kV/m. The maximum droplet temperature decreased with the electric field strength, in addition to the biodiesel droplet. Overall, the electric field ameliorates fuel droplets' atomization and combustion characteristics.

Droplet impact on a hot substrate under an electric field is fundamental and crucial for electrospray cooling. However, the involved thermal–electric coupling impact electrohydrodynamic has not been well understood. In this study, the effects of an electric field on the droplet impact behavior in different thermal regimes and the subsequent dynamic mechanisms were experimentally investigated. The results showed that the vertical electric field would result in an upward liquid ejection in the film evaporation regime. In the nucleate boiling regime, the liquid pinch-off phenomenon was observed. In addition, the droplet evaporation rate was increased by approximately 23% with an electric field of 6 kV/cm. In the film boiling regime, both the residence time and bounce-off droplet height were significantly increased. The various impact phenomena were mainly explained by the competition between electrostatic and capillary pressures. The comprehensive effects of surface free charges and temperature variation on the droplet surface tension coefficient were discussed. Moreover, according to the thermal analysis, the heat transfer in the film boiling regime with an electric field was enhanced by approximately 137%. This work contributed to the development of the droplet impact dynamics under the coupling temperature and electric fields and demonstrated great promise for the electric field for thermal-fluid manipulation.

To better promote the development of lead-free dielectric capacitors with high energy-storage density and efficiency, we comprehensively review the latest research progress on the application to energy storage of several representative lead-free dielectric materials, including ceramics (ferroelectrics–relaxor ferroelectrics–antiferroelectrics), glass-ceramics, thin and thick films, and polymer-based composites. The results indicate that lead-free dielectric materials with large maximum polarization, high breakdown electric field, small remnant polarization, and slim polarization-electric field loops are more appropriate for developing dielectric capacitors with high energy density and efficiency. However, some significant drawbacks in current lead-free dielectric materials hinder the energy storage performance of these materials. Based on this, we review herein some new strategies to improve the energy-storage capacity of dielectric materials.

Electrocoalescence is an energy-efficient and environmentally friendly process for separating water-in-oil emulsions. In this study, nanoparticle-laden drop–interface electrocoalescence behaviors under direct current (DC) and alternating current (AC) electric fields were numerically investigated using molecular dynamics methods. Good qualitative agreement was obtained between numerical results and experimental validation work. In this report, the influences of the electric field strength, nanoparticle concentration, and electric field frequency on the electrocoalescence process are systematically examined, analyzed, and discussed from the perspective of intermolecular interactions. The coupling of the hydration effect of ions and the strong interactions between silicon dioxide (SiO2) nanoparticles and water molecules was found to give rise to partial drop–interface electrocoalescence. The critical cone angle at which a transition from complete to partial electrocoalescence occurs was found to be 34.41°. A larger water intermolecular distance and a greater tendency for partial coalescence was observed in the nanoparticle-laden (NP-laden) droplets than in a pure water drop. Compared to a DC electric field, an AC electric field tended to cause complete drop–interface electrocoalescence, and the efficiency of complete coalescence was found to increase with increasing frequencies ranging from 10 to 200 gigahertz (GHz). The results of this work will be potentially useful for optimizing the design of compact and efficient oil–water separators.