An intense luminescence flash can be induced during the collapse phase of bubbles generated by pulsed discharge in water. To gain insight into this special phenomenon, we experimentally investigated the optical characteristics and luminescence temperature inside collapsing bubbles. The duration of the luminescence flash generated by pulsed discharge was around tens of microseconds, which was confirmed by high-speed recording and the photodiode output, and the inception time of the luminescence flash was approximately 32.5 μs before the bubble collapsed to its minimum size. The temperatures of the luminescence flash at discharge energies of 25 and 30 J/pulse calculated according to the two-line radiance ratio method were 6673 and 6728 K, respectively.
We investigated the behavior of single bubbles generated by spark discharge under different electric fields and water properties. A higher discharge energy is known to generate a larger bubble. However, our results show that the hydraulic efficiency decreases with increasing charging voltage, but increases with increasing charging capacitance. We found that the water conductivity has little influence on the bubble behavior, whereas a higher water temperature generates a larger bubble with higher hydraulic efficiency. The experimental results agreed well with those of the Rayleigh–Plesset model. Overall, the hydraulic efficiency for spark-induced bubble ranges from 3.5% to 7.5%. This work helps to advance our understanding of spark-induced bubble dynamics and their applications.
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