1 / 18

Exploring streamer variability in experiments

Exploring streamer variability in experiments. T.M.P. Briels , S. Nijdam, G.J.J. Winands, E.M. van Veldhuizen, U. Ebert. [T.M.P. Briels, Ph.D. thesis, Dec. 2007]. Workshop Leiden, 8-12 October 2007. Contents. Experimental setup Streamer start and propagation Positive and negative streamers

briar
Download Presentation

Exploring streamer variability in experiments

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Exploring streamer variability in experiments T.M.P. Briels, S. Nijdam, G.J.J. Winands, E.M. van Veldhuizen, U. Ebert [T.M.P. Briels, Ph.D. thesis, Dec. 2007] Workshop Leiden, 8-12 October 2007

  2. Contents • Experimental setup • Streamer start and propagation • Positive and negative streamers - diameter - velocity - energy • Scaling with pressure (pos. str.) • diameter • branching structure • Conclusions

  3. Experimental setup New parameter ranges: • Gap: 10-160 mm • Voltage: 5-96 kV • Rise time: 15-150 ns • Pressure: 13-1000 mbar • Pos. and neg. streamers • Point-plane • Air

  4. Time resolved photographs 30 kV, air [Ebert et al, PSST, 15 (2006) S118] needle Exposure: 300 ns 50 ns 10 ns 2 ns (0 < t < 300 ns) (50 < t < 100 ns) (50 < t < 60 ns) (46 < t < 48 ns) 40 mm plate

  5. Streamer start from needle electrode 99.8% N2 : 0.2% O2, 15 mbar, 16 cm gap, 5 kV [0,0.2] [0.2,0.4] tє[0,70 us] [0.4,0.6] [0.6,0.8] E/p = 21 kV/(cm*bar) [0.4,0.7] [0.3,0.7]

  6. Start and propagation • E/p = 16 kV/(cm*bar):40 mm gap, 400 mbar, 25 kV, air, Trise = 25ns • E/p = 22 kV/(cm*bar):30 mm, 613 mbar, 40 kV, synt. air, Trise = 12ns, MIPT tє[0,50 ns] [50,100 ns] [125,175 ns] [125,175 ns] tє[5,10 ns] [10,15 ns] [20,25 ns] [80,85 ns]

  7. Positive and negative streamers air, 1 bar, 40 mm gap, texp = 160 ns positive negative Observations: • Channels form - pos: V Vinception - neg: V Vdc-breakdown • Stability field (= voltage/streamer length) - pos: ~5 kV/cm - neg: ~15 kV/cm 20 kV 20 kV 46 kV 47 kV 83 kV 77 kV

  8. Diameter and velocity needle à • Diameter: dx - FWHM - single streamer - in focus - no return stroke • Velocity: dy/dtexp - dtexp large and small enough dx 40 mm dy plate à R2 = 0, R3 = 4 kOhm, Vp=54 kV, Ip=8 A, texp= 2 ns 050815:43

  9. Positive and negative diameter air, 1 bar, 40 mm gap • Positive 10% thicker than negative but within error margins • For V > 25 kV and short rise times ( 30 ns) streamers become fat(factor 10!) ~ factor 10 ~ factor 2

  10. Positive diameter d and v vary factor 10 in one discharge! • Type 1: d ~ 2.5 mm, v > 1 mm/ns, I ~ 12 A. • Type 2: d ~ 1.2 mm, v ~ 0.5 mm/ns, I ~ 1 A. • Type 3: d ~ 0.2 mm, v ~ 0.1 mm/ns, I ~ 10 mA • Thin: - V ~ Vinception - via branching - seriesresistance [Briels et al, J. Phys. D.: Appl. Phys. 39 (2006) 5201] air, 1 bar, 60 kV

  11. 40 mm Positive and negative velocity air, 1 bar, 40 mm gap • Positive 20% faster than negative ~ factor 8 ~ factor 2

  12. Diameter and velocity • v ~ 0.5*d2 (d varies with applied voltage)

  13. Positive and negative dissipated electrical energy air, 1 bar, 40 mm gap • Energy: • Total: positive more energetic than negative • Primary: equally energetic

  14. Scaling with pressure air, 40 mm gap, 10 kV • Scaling away from electrode [preliminary results: Briels et al, IEEE, 33 (2005) 264]

  15. Scaling of diameter 13-1000 mbar, 10-160 mm gap • air: p*d = 0.20 ± 0.02 mm*bar for thinnest (type 3) streamers

  16. Scaling of branching structure 40 mm gap • Air: D/dmin = 11.6 ± 1.5 D d

  17. Conclusions on streamers in air • Evolution of streamers out of initial cloud • Positive and negative streamers become more alike at higher voltages • For 25 < V < 55 kV and short rise times ( 30 ns) streamers become fat(factor 10) and fast (factor 8). • Scaling minimal streamers: (p*d)/T = 0.2 mm*bar/293K

  18. N2 (99.9%), 40 mm gap, 400 mbar, 16 kV

More Related