Problem generating spark under water for cavitation bubbles

  • #1
Beekeeper
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TL;DR Summary
I cannot consistently generate a spark under water using a High Voltage Generator coil. Can you help explain why?
Hi,

I am trying to do some experiments with cavitation bubbles by generating a spark under water however I am having some trouble and was wondering if anyone would be able to help or offer some advice.

The problem I am having is I cannot generate the spark consistently. I place the electrodes in (distilled) water, apply the high voltage across them, they will usually spark a few times and then stop and fail to spark again after that.

The setup I am using is described in the following (attached) diagram:
1736248947904.png

The electrodes are just copper enameled wire with a gap < 1mm. I am using a small "High Voltage Generator Pulse Generator Coil" (goes by other names see this link) of around 1000kV to generate the high voltage across the electrodes. I am controlling a "High Voltage Pulse Generator Coil" with a trigger switch and an Arduino to precisely set the time for the spark. The electrodes themselves are placed in distilled water rather than tap water to avoid potential electrolysis.

Things I have tried:
- different spark durations from 50ms to 2000ms most have similar results
- different thickness of electrode wire from 0.1 to 0.85mm
- multiple strands of electrode wire 3 x 0.25mm and 2 x 0.63mm
- different quality distilled water (currently settled on high grade conductivity <= 1uS/cm)
- different coils, I also tried a 400kV coil with similar results

Although I have not read or seen anyone generate a spark with this "High Voltage Pulse Generator Coil" I thought it would be possible based on this paper which generated a spark using a small piezo electric igniter. But even so I am not sure if using the "High Voltage Pulse Generator Coil" is the problem so curious to hear thoughts on that.

I could try another circuit or setup, but was hoping to first get some advice and try to understand the problem first.

Thanks for taking the time to read my post.
 
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  • #2
I would guess that after the first few sparks, your "distilled water" will be clouded by copper salts from your electrode. I would also guess that those copper salts are shorting your voltage.

You'll likely have this same problem with almost any electrode material. But I would try carbon rods.
 
  • #3
Ok thanks! Sounds plauseable and thanks for the suggestion to use carbon rods instead. I will give that a try.
 

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