Impact of air humidity on streamer length of a Tesla coil
We have two students who will work on alternative gases for replacement of SF6. Shruthi and Ewout. Their work is about investigating impact of air relative humidity and other contamination on breakdown strength and PD behavior of air, technical air, and C4F7N/CO2. That was the motivation to make this video. It seems we can directly observe that increase level of humidity increases the breakdown strength of air and hence lower the length of the streamer. Even though demonstration in this video is not as solid as possible, but qualitatively we could investigate the effect.
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Nice !!! I never thought about it
So cool!! First time I've seen such a humidity affected discharge test method. Nice discharge photos. I think your home can be considered a small high voltage laboratory now.😃
@HVE
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😅 Lots of unknown regarding the nature of this type of discharges. I would like to write a few paper about them, maybe i ask you to contribute Yiming.
@YimingZang
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@@HVE No problem. I am very happy to try my best to do some contribution with you. Actually, I am recently planning to do some experiments on the effect of environmental factors on discharge. Looking forward to communicate with you.😃
That's an interesting looking monitor in the background.
If you make the background color and texture uniform it will be easier and more consistent to record and observe. Black is not as useful as a uniform pattern with sharp contrasting fine detail. If you also show what is above the spark generator, that would help, The streams extend beyond the top of the viewing area. There might be convection. Probably is, and it might be slow but strongly affect the curvature of the equipotential surfaces over the spark source, and that will focus and strongly affect the channels. You might try finding an infrared camera. Your spark source is not smooth, so the electric field varies from place to place. You are spraying droplets, not just water vapor. Water vapor in air is "humidity" The droplets are something else. The size of the droplets strongly affects the electric field close to the droplets. You do not seem to be careful about contaminants for the spray. Tiny bits of electrolyte or oil can changes the surface tension of the droplets. Water vapor mostly affects pressure. Smaller molecules travel faster. Polar molecules (H2O and CO2 and ions) interact more. You can put up electrode arrays to monitor "between electrode" voltages. There are 16 channel and 64 channel high sampling rates ADCs for the Raspberry Pi. Most of them can be run by Arduino and ESP32 and similar small processors. You might try Schlieren methods to visualsize and record air flows, rising heat, surface flows around the spark source. The spark source power supply is likely high frequency, and not stable. You should record the current and voltage of the power going to the spark generator. Some external sound cards work well for that, or USB oscilloscopes. You could record the sound from several separate microphone at high sampling rates. At least 96000 sps and check the FFT for trends and patterns in the sound. Particularly mixtures of high frequency that vary slowly at sub-audible rates. Most of the SDR (software defined radio programs) will have FFT displays and waterfalls that let you see the spectrum for sound cards. Some of the oscilloscope programs will too. You could record the electromagnetic "sounds" from the device. The low cost RTL_SDR are the most stable. They are 16 bit at 3.32 MegaSamples per second. They use I Q detectors. That is simultaneous 8 bit ADCs for cos(omega*t) and sin(omega*t). You can find how that works searching "I" "Q" "SDR". The SDRPlay RSP1A is 14 bit and 10 MegaSamplesPerSecond (Msps). If you turn down the voltage so there are no visible sparks, monitor with SDRs and sound, and record and analyze for a long time, you should find that much of the spark behavior is predictable from much lower voltages than those needed to make big sparks that humans can see and hear. The shape of the field above the spark source will vary strongly with air currents, rising convection, local temperature variations. You ought to turn off the lights. You ought to carefully place the cameras and try to find some that take higher frame rates. Even the earliest Raspberry Pi MIPI cameras can handle regions of interest (smaller areas) at up to 1000 frames per second. I can think of a few more things. Especially networking with everyone in the world working on similar experiments. Back when electrostatics was found, they did not have the ability to record fast and precisely, But beyond getting data for your eyes and observation, if you share with people world-wide and use similar methods so the data and algorithms are all compatible and complementary, you might have a chance to make it a science, not a toy or forever obscure. Same with candles and flames. Most of what you are trying in air can also be done in gases. But more inportantly, they can also be done in liquids of many sorts, and powders, nanoparticle "liquids" and electrolytes of many sorts. Richard Collins, The Internet Foundation