Turbulent jet flow generated downstream of a low temperature dielectric barrier atmospheric pressure plasma device

Whalley, Richard D.; Walsh, James L.

doi:10.1038/srep31756

Cited by 31 publications

(45 citation statements)

References 27 publications

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“…The resulting temperature profile where the maximum is located downstream instead of at the exit of the capillary is often not incorporated in numerical models. This is important to take properly into account the effect of local heating in the modification of gas flow dynamic induced by plasma jet as discussed in 42,43 . The observed heat exchange was also present without any plasma (0 kV or 0 kHz) while still operating a constant 1 slm helium flow.…”

Section: Discussionmentioning

confidence: 99%

“…However when the plasma is on, the rising of the flow at a given distance is less than without plasma (about 1 mm instead of 1.8 mm without plasma at 16 mm distance from the nozzle). The modification of the gas flow dynamics by the plasma is a well known fact and several observations have been made stressing the importance of heating and/or ion wind, causing these changes in the helium flow 42,[44][45][46][47][48] . No consensus has been reached yet whether heating or ion-wind is dominant.…”

Section: Discussionmentioning

confidence: 99%

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Revealing Plasma-Surface Interaction at Atmospheric Pressure: Imaging of Electric Field and Temperature inside the Targeted Material

Slikboer

Acharya

Sobota

et al. 2020

Sci Rep

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The plasma-surface interaction is studied for a low temperature helium plasma jet generated at atmospheric pressure using Mueller polarimetry on an electro-optic target. The influence of the AC kHz operating frequency is examined by simultaneously obtaining images of the induced electric field and temperature of the target. The technique offers high sensitivity in the determination of the temperature variation on the level of single degrees. Simultaneously, the evolution of the electric field in the target caused by plasma-driven charge accumulation can be measured with the threshold of the order of 105 V/m. Even though a specific electro-optic crystal is used to obtain the results, they are generally applicable to dielectric targets under exposure of a plasma jet when they are of 0.5 mm thickness, have a dielectric constant greater than 4 and are at floating potential. Other techniques to examine the induced electric field in a target do not exist to the best of our knowledge, making this technique unique and necessary. The influence of the AC kHz operating frequency is important because many plasma jet designs used throughout the world operate at different frequency which changes the time between the ionization waves and hence the leftover species densities and stability of the plasma. Results for our jet show a linear operating regime between 20 and 50 kHz where the ionization waves are stable and the temperature increases linearly by 25 K. The charge deposition and induced electric fields do not increase significantly but the surface area does increase due to an extended surface propagation. Additionally, temperature mapping using a 100 μm GaAs probe of the plasma plume area has revealed a mild heat exchange causing a heating of several degrees of the helium core while the surrounding air slightly cools. This peculiarity is also observed without plasma in the gas plume.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Revealing Plasma-Surface Interaction at Atmospheric Pressure: Imaging of Electric Field and Temperature inside the Targeted Material

Slikboer

Acharya

Sobota

et al. 2020

Sci Rep

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“…Oil with a nominal size of 1 µm was used to seed the air within the enclosure. The Stokes numbers of the seeding particles used throughout the study was < 0.1, thus ensuring that the seeding particles followed the fluid flow closely with tracing errors being < 1% 20,21 . The velocity vectors were computed on a square grid with spatial resolution of 56 µm using a recursive cross-correlation technique.…”

Section: Methodsmentioning

confidence: 99%

Directional mass transport in an atmospheric pressure surface barrier discharge

Dickenson

Morabit

Hasan

et al. 2017

Sci Rep

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In an atmospheric pressure surface barrier discharge the inherent physical separation between the plasma generation region and downstream point of application reduces the flux of reactive chemical species reaching the sample, potentially limiting application efficacy. This contribution explores the impact of manipulating the phase angle of the applied voltage to exert a level of control over the electrohydrodynamic forces generated by the plasma. As these forces produce a convective flow which is the primary mechanism of species transport, the technique facilitates the targeted delivery of reactive species to a downstream point without compromising the underpinning species generation mechanisms. Particle Imaging Velocimetry measurements are used to demonstrate that a phase shift between sinusoidal voltages applied to adjacent electrodes in a surface barrier discharge results in a significant deviation in the direction of the plasma induced gas flow. Using a two-dimensional numerical air plasma model, it is shown that the phase shift impacts the spatial distribution of the deposited charge on the dielectric surface between the adjacent electrodes. The modified surface charge distribution reduces the propagation length of the discharge ignited on the lagging electrode, causing an imbalance in the generated forces and consequently a variation in the direction of the resulting gas flow.

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“…It has been widely reported that the generation of plasma in a buoyant axisymmetric jet configuration leads to a rapid transition from laminar to turbulent flow. [6][7][8][9][10] It is commonly assumed that gas heating and electrohydrodynamic (EHD) forces play a role in creating turbulence within the flowing gas channel, with the latter being considered as the dominant mechanism. Indeed, Park et al [11] used a pulsed plasma jet to demonstrate that EHD forces are primarily exerted by space charge drifting in the applied electric field following streamer propagation, confirming the modeling results of Hasan and Bradley.…”

Section: ------------------------------------------------------------mentioning

confidence: 99%

“…[12] Whalley and Walsh demonstrated that the spatially developing velocity fields in an inhomogeneous axisymmetric plasma jet flow are turbulent and self-similar, with characteristics matching the turbulent velocity fields which develop naturally with increasing distance from the jet exit. [8] Using an order-ofmagnitude analysis, it was predicted that the presence of a discharge should only increase the jet exit velocity by approximately 10%. Many studies in the field of fluid dynamics have indicated that the generation of turbulence in an axisymmetric jet flow is related to smallamplitude body forces causing perturbations in the unstable shear layers at the jet exit, which grow as they move downstream.…”

Section: ------------------------------------------------------------mentioning

confidence: 99%

Turbulence and entrainment in an atmospheric pressure dielectric barrier plasma jet

Morabit

Whalley

Robert

et al. 2019

Plasma Processes & Polymers

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Particle image velocimetry, laser-induced fluorescence, and computational modeling are used to quantify the impact of plasma generation on air entrainment into a helium plasma jet. It is demonstrated that discharge generation yields a minor increase in the exit velocity of the gas. In contrast, the laminar to turbulent transition point is strongly affected, attributed to an increase in plasma-induced perturbations within the jet shear layer. The temporal decay of laser-induced fluorescence from OH is used as an indicator of humid air within the plasma. The results show that plasma-induced perturbations increase the quenching rate of the OH-fluorescent state;indicating that shear-layer instabilities play a major role in determining the physicochemical characteristics of the plasma.

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Turbulent jet flow generated downstream of a low temperature dielectric barrier atmospheric pressure plasma device

Cited by 31 publications

References 27 publications

Revealing Plasma-Surface Interaction at Atmospheric Pressure: Imaging of Electric Field and Temperature inside the Targeted Material

Revealing Plasma-Surface Interaction at Atmospheric Pressure: Imaging of Electric Field and Temperature inside the Targeted Material

Directional mass transport in an atmospheric pressure surface barrier discharge

Turbulence and entrainment in an atmospheric pressure dielectric barrier plasma jet

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