To study the preheating process of pulse discharge in water

an underwater pulse discharge system was designed and built. The maximum charging voltage of the capacitors in this system is 10 kV and maximum storage capacity is 5 kJ. The waveforms of capacitor voltage and circuit current from preheating to main discharge process were obtained by discharge experiments. The distributions of temperature

electrical field

current density

heat dissipation

and voltage waveform between water gap during preheating processs were obtained by numerical simulation. The voltage waveform agrees well with the experimental results. The influences of water conductivity

water gap distance

electrode shape on the preheating process in water were also analyzed by simulation. Under the experimental conditions

the preheating process is at the order of milliseconds. With greater water conductivity

shorter water-gap length and more uneven electric field

the preheating process will be faster. The simulation results indicate that the location of the first boiling point in water is close to the top of the anode

which may provide a beneficial help for studying the initiation of streamers in water.