Physical Aspects of Vapor-Mist Dielectrics

In earlier work it was shown that by acoustically cavitating a liquid dielectric, a dense mist (~2 x 105 droplet/cm3) of micron-size droplets could be formed which considerably increased the electrical strength of an insulating gas. The high electrical strength of these vapor-mist dielectrics results from a combination of the vapor from the droplets enhancing the gas strength and the droplets collecting electrons and ions. This latter effect helps prevent the formation of electron avalanches which precede breakdown. Within the vapor-mist dielectrics, complex mechanisms are involved, ranging from the enhanced vapor pressure at the droplet surface to surface tension effects and droplet charge which help prevent droplets from both freezing and evaporating. These aspects of vapor-mist dielectrics are examined and discussed in relation to the acoustic cavitation method used for generating the mist.