Influence of gas bubbles on electrical discharges in small working gaps

In the paper the first investigations on gas bubble evolution are presented. The research is based on video recording (VR) and high speed framing camera (HSFC) pictures, as well as theoretical considerations. Violent changes of gas bubbles generated in the consequence of single discharges are analyzed in the time interval of 100 μs (dissolving time) after the end of the pulse. This time corresponds approximately to moving the "deformed" gas bubble from the actual point of origin (transfer time). The investigations were carried out in two typical eroding liquids (n-dodecane and de-ionized water). The variety of the gas bubble evolution depending on the current amplitude and the pulse duration of the electrical discharge shows that the gas bubble growth can be influenced purposefully by controlled pulse parameters of the process energy source. The investigation with double pulses allows to recognize that the replacement of the gas bubble does not occur before the end of the pulse sequence. The ignition conditions for the following pulse are changed considerably by the gas bubble size and its distribution.