Microbubble-based model analysis of liquid breakdown initiation by a submicrosecond pulse

Qian, Jun; Joshi, Ravi; Kolb, Juergen F.; Schoenbach, K.H.; Dickens, J.; Neuber, A.; Butcher, M.; Cevallos, M.; Krompholz, H.; Schamiloglu, E.; Gaudet, J.

doi:10.1063/1.1921338

Cited by 82 publications

(46 citation statements)

References 41 publications

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“…Obviously, pressure, temperature and gas composition vary from one phenomenon to the next. In electrical engineering, the higher densities of liquids are desirable for fast switching, but pre-existing microbubbles largely influence streamer properties in fluids [13,14]. For this reason, the operation of spark gaps filled with supercritical fluids is now under investigation [15].…”

Section: Streamers In Different Media At Various Densitiesmentioning

confidence: 99%

Positive streamers in air and nitrogen of varying density: experiments on similarity laws

Briels¹,

Veldhuizen²,

Ebert³

2008

J. Phys. D: Appl. Phys.

139

213

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Abstract. Positive streamers in ambient air at pressures from 0.013 to 1 bar are investigated experimentally. The voltage applied to the anode needle ranges from 5 to 45 kV, the discharge gap from 1 to 16 cm. Using a "slow" voltage rise time of 100 to 180 ns, the streamers are intentionally kept thin. For each pressure p, we find a minimal diameter d min . To test whether streamers at different pressures are similar, the minimal streamer diameter d min is multiplied by its pressure p; we find this product to be well approximated by p · d min = 0.20 ± 0.02 mm · bar over two decades of air pressure at room temperature. The value also fits diameters of sprite discharges above thunderclouds at an altitude of 80 km when extrapolated to room temperature (as air density rather than pressure determines the physical behavior). The minimal velocity of streamers in our measurements is approximately 0.1 mm/ns = 10 5 m/s. The same minimal velocity has been reported for tendrils in sprites. We also investigate the size of the initial ionization cloud at the electrode tip from which the streamers emerge, and the streamer length between branching events. The same quantities are also measured in nitrogen with a purity of approximately 99.9%. We characterize the essential differences with streamers in air and find a minimal diameter of p · d min = 0.12 ± 0.02 mm · bar in our nitrogen.

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Section: Streamers In Different Media At Various Densitiesmentioning

confidence: 99%

Positive streamers in air and nitrogen of varying density: experiments on similarity laws

Briels¹,

Veldhuizen²,

Ebert³

2008

J. Phys. D: Appl. Phys.

139

213

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“…An early simulation model for liquid breakdown uses a lattice to investigate the fractal nature of the streamer structure as a function of the electric field E [28], and has been expanded to incorporate needleplane geometry [29], a 3D-lattice [30], statistical time [31], availability of seed electrons [32], and varying conductance of the streamer channels [33]. Charge generation and transport in an electric field have also been solved by a finite element method (FEM) approach, to simulate streamer propagation in 2D and 3D, adding impurities to generate streamer branching [34][35][36][37]. A major difference between breakdown in gases and liquids is that a phase change is involved when making the streamer channel in liquids.…”

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confidence: 99%

Simulation model for the propagation of second mode streamers in dielectric liquids using the Townsend-Meek criterion

et al. 2018

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A simulation model for second mode positive streamers in dielectric liquids is presented. Initiation and propagation is modeled by an electron-avalanche mechanism and the Townsend-Meek criterion. The electric breakdown is simulated in a point-plane gap, using cyclohexane as a model liquid. Electrons move in a Laplacian electric field arising from the electrodes and streamer structure, and turn into electron avalanches in high-field regions. The Townsend-Meek criterion determines when an avalanche is regarded as a part of the streamer structure. The results show that an avalanche-driven breakdown is possible, however, the inception voltage is relatively high. Parameter variations are included to investigate how the parameter values affect the model. visible light [3], re-illuminations, from one or more of its branches. Above the breakdown voltage, streamers may change between the 2nd, the 3rd, and the 4th mode during propagation. There are usually more reilluminations in the 3rd mode than the 2nd mode. The inception of the 4th mode is associated with a drastic increase in speed and fewer, more luminous, branches [2].There are numerous mechanisms that can be involved in the streamer phenomena, the challenge is identifying their importance during initiation and propagation. Applying a potential to a needle can cause charge injection, giving a space-charge limited current [16] causing Joule heating [16], which in turn can cause bubble nucleation [17]. A breakdown in the gas bubble can then propagate the needle potential, and the process may repeat. This is one way to explain 1st mode propagation. Electric fields can also cause electrohydrodynamic flow, which could cause streamer formation through cavitation [18]. Electrostatic cracking has also been proposed as a cavitation mechanism [19]. A main topic of discussion is whether a lowering of the liquid density is needed before charge generation can occur. Electron avalanches are important in gas discharge, but their importance in liquid breakdown is still disputed. In water, strong scattering could prevent electrons from forming avalanches in the liquid phase [20]. Therefore, discharges in micro-bubbles can be important for charge generation [10,14,20]. The same mechanism was also proposed for non-polar liquids [19], however, the relative permittivity is about 80 in water and about 2 in a typical oil, and this difference can prove important since the field enhancement within a bubble in oil is much lower than in water. Contrary to water, there are indications of electron avalanches in non-polar liquids [16,21,22], furthermore, while the initiation and the propagation length of 2nd mode streamers are dependent on the pressure, their propagation velocity is not pressure dependent [16,23]. This implies that the mechanism responsible for propagation occurs in the liquid phase and that the gaseous channel follows as a consequence. In very high electric fields, field-ionization can occur [24,25], and this mechanism has been proposed for the fast 3rd and 4th propagation mode...

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“…35 In the case of sub-microsecond discharges, it has been proposed that streamer propagation is triggered by field emission at the interface of pre-existing microbubbles, in which electron impact ionization occurs. 36,37 In the case of microsecond or longer pulsed discharges, a bubble theory associated with thermal effects is most likely to be the main mechanism. A theoretical model has shown that Joule heating leads to the evaporation of liquid and the formation of gas bubbles, in which an electrical discharge propagates.…”

mentioning

confidence: 99%

Initiation process and propagation mechanism of positive streamer discharge in water

Fujita

Kanazawa

Ohtani

et al. 2014

Journal of Applied Physics

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The aim of this study was to clarify the initiation process and the propagation mechanism of positive underwater streamers under the application of pulsed voltage with a duration of 10 μs, focusing on two different theories of electrical discharges in liquids: the bubble theory and the direct ionization theory. The initiation process, which is the time lag from the beginning of voltage application to streamer inception, was found to be related to the bubble theory. In this process, Joule heating resulted in the formation of a bubble cluster at the tip of a needle electrode. Streamer inception was observed from the tip of a protrusion on the surface of this bubble cluster, which acted as a virtual sharp electrode to enhance the local electric field to a level greater than 10 MV/cm. Streak imaging of secondary streamer propagation showed that luminescence preceded gas channel generation, suggesting a mechanism of direct ionization in water. Streak imaging of primary streamer propagation revealed intermittent propagation, synchronized with repetitive pulsed currents. Shadowgraph imaging of streamers synchronized with the light emission signal indicated the possibility of direct ionization in water for primary streamer propagation as well as for secondary streamer propagation.

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Microbubble-based model analysis of liquid breakdown initiation by a submicrosecond pulse

Cited by 82 publications

References 41 publications

Positive streamers in air and nitrogen of varying density: experiments on similarity laws

Positive streamers in air and nitrogen of varying density: experiments on similarity laws

Simulation model for the propagation of second mode streamers in dielectric liquids using the Townsend-Meek criterion

Initiation process and propagation mechanism of positive streamer discharge in water

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