Thermal characteristic and spatial morphology between electrode and phase changing ice during de-icing process of dielectric barrier discharge and critical behavior of the surface charge density

Abstract

Dielectric barrier discharge (DBD) plasma recently has been demonstrated as an effective in situ heating methodology in anti-ice and de-ice applications of the aircraft. However, the thermal stability of this special heat source during the interactions between the plasma and the ice block may pose serious concerns. In this paper, it is found that when the ice blocks of different characteristic locations covered the DBD device with alternative current (AC) power, two different kinds of interaction processes can be resulted: First, the concentration of the heat flow through the local enhancement of the streamers between the electrode and the ice, long-lasting for the glaze ice ended with the partial evaporation of the melted ice block with larger separations, or short-lived intermittent for the rime ice until the boundary is beyond the reach. Second, sparks, very likely to be generated between the electrode and the ice block when the separation and electric field meet the transition conditions, resulting in the fast evaporation of the melted ice block and the severe aging or on-sight burning of the devices, even at the operation voltage safe for the AC-DBD plasma without ice blocks. It is emphasized that the coexistence or the number of the ice blocks of different separations does not alter such behavior. Supported by the calculation of the streamer-to-spark transition criterion, and affected by ice phase change, it is argued that the de-icing AC-DBD plasma is a strong nonlinear heat source, resulting from the surface charge accumulation, melting of the ice blocks, and the enhancement of ionization collision frequency due to the mixing of the evaporated water molecules. A new critical condition, the critical surface charge density was proposed for the initiation of spark, ρsc: Densities higher than ρsc will lead to the catastrophic spark, while the lower will lead to the selective concentration of the heat flow for the faster de-icing process. Due to the random distribution nature of the electrode-to-ice separations during the real-world practice of an AC-DBD heat source for de-icing, the existence of ρsc may be under further scrutiny and considered as a crucial factor for the stable operation of the plasma heat sources for de-icing.