Microchannel Flow Enhancement by Microplasma Actuation

Shivkumar, Gayathri; Tholeti, Siva Sashank; Alexeenko, Alina

doi:10.1115/icnmm2015-48428

Cited by 4 publications

(16 citation statements)

References 10 publications

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“…For pure H 2 , the peak of period-averaged Joule heating is 19×10 9 W/m 3 . This is similar to the prediction of 20×10 9 W/m 3 reported in similar studies for an FE-DBD in atmospheric pressure N 2 [8,46]…”

Section: Source Terms For the Continuum Modelsupporting

confidence: 90%

“…The force pushes gas around the corner of the exposed electrode with magnitude greatest at the corner: 40×10 6 N/m 3 in pure O 2 and 10.5×10 6 N/m 3 in pure H 2 . Its distribution and magnitude in H 2 match those predicted for the same electrodes in nitrogen [8,46]. This previous study also found a force magnitude of 10×10 6 N/m 3 at the corner of the exposed electrode, matching our magnitude of 10.5× 10 6 N/m 3 .…”

Section: Source Terms For the Continuum Modelsupporting

confidence: 89%

“…Of several electrode configurations tested in a previous study, this FE-DBD design was found to produce the largest force in pure N 2 gas under atmospheric conditions [8,46]. In simulations, Joule heating from this design generated temperatures exceeding 1800 K in the plasma.…”

Section: Fe-dbd Simulation Approachmentioning

confidence: 77%

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Enhancement of hydrogen microcombustion via field-emission dielectric barrier discharge

Mackay

Freund

Johnson

2018

Plasma Sources Sci. Technol.

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A particle-in-cell (PIC) model is constructed for a ∼100 μm field-emission dielectric barrier discharge (FE-DBD) actuator in atmospheric pressure mixtures of oxygen, hydrogen, and water vapor. The discharge is characterized, including the effects of gas temperature and gas composition. Quantities relevant to plasma-coupled combustion, such as Joule heating, Lorenz body force, and radical generation are estimated for gas temperatures and compositions relevant for combustion energy conversion. Due to its low ionization energy, O 2 increases the magnitude of Joule heating and body forces in the discharge. However, water vapor weakens these effects because of its high ionization energy and many excitational degrees of freedom that remove energy from electrons through inelastic collisions. At higher gas temperatures the discharge becomes more diffuse on account of lower gas densities. At room temperature, and operated at an easily achieved 300 V at 10 MHz, the FE-DBD produces both intense local body forces (10 7 N/m 3 ) and Joule heating (10 9 W/m 3 ) at the corner of the exposed electrode. A boundary layer model provides an estimate that the FE-DBD can induce flow velocities of around 10-20 m/s and temperature increases of around 5-20 K in room temperature H 2 /O 2 /H 2 O mixtures. Sources based on the PIC model are applied in continuum simulations of non-premixed hydrogen combustion in a microchannel. Without the FE-DBD, the inflow of fuel and oxygen is hindered by viscous losses, thermal conduction to wall boundaries, and thermal expansion of gasses, leading to flame extinction. The FE-DBD actuators pre-heat and dissociate the fuel and produce body forces that counter viscous resistance, sustaining combustion. In another example, FE-DBD plasma coupling reduces the autoignition time of a stoichiometric, 950 K H 2 -O 2 mixture from 117 μs to 49 μs.

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Section: Source Terms For the Continuum Modelsupporting

confidence: 90%

Section: Source Terms For the Continuum Modelsupporting

confidence: 89%

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Enhancement of hydrogen microcombustion via field-emission dielectric barrier discharge

Mackay

Freund

Johnson

2018

Plasma Sources Sci. Technol.

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“…An electric potential of −300 V is applied at a frequency of 10 MHz to the exposed electrode, and the buried electrode remains grounded. Such a design was found to maximize flow actuation in previous studies [13,29]. The oscillating electric field stimulates FE of electrons from the corner of the exposed electrode, ionizing the gas and dissociating molecules through electron impact.…”

Section: Fe-dbd Arraysmentioning

confidence: 99%

Field-emission plasma enhancement of H₂–O₂ micro-combustion

Mackay

Johnson²,

Freund³

2020

Plasma Sources Sci. Technol.

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A detailed three-dimensional computational model is developed to assess the potential of micronscale field emission dielectric barrier discharge (FE-DBD) plasma actuators in non-premixed microburners with channel heights in the range of L z =0.25-0.75 mm. Results for H 2 -O 2 combustion with Reynolds number Re=100 are studied for different configurations of plasma actuator arrays. Without plasma actuation, results agree with corresponding experiments, although in this case the burner typically suffers from incomplete combustion due to thermal quenching, radical quenching, and slow diffusive mixing. For the range of conditions simulated, plasma actuation increases combustion completeness from 25%-70% to 40%-80% by enhancing mixing, generating radicals, and Joule heating. Ionic wind resulting from the FE-DBD plasma disrupts the otherwise simple laminar flow in the burner, accelerating the growth of a mixing layer and enhancing heat transfer to channel walls. The larger, lower temperature flames reduce thermal gradients (and thereby thermal stresses) in the walls. Radical generation due to electron-impact dissociation extends the reaction zone in the diffusion flame and increases combustion completeness. In all cases, the additional heat release with plasma actuation (100-190 W) is significantly larger than the power needed to sustain the plasma (0.1 W), suggesting that plasma actuation may provide a significant advantage in energy generation using realistic portable micro-combustion devices.

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“…The device is driven by an AC voltage of −325 V at a frequency of 10 MHz and operates at atmos pheric pressure. Theoretical and computational studies of flow actuation by 4 such actuators in a microchannel of height 500 µm exhibit an average velocity of 3.8 m s −1 and temperature of 710 K at the exit [20][21][22]. The field emission from such a device can be enhanced by coating the electrode surface with carbon nanopetals [23,24] which creates irregularities to increase the surface roughness.…”

Section: Introductionmentioning

confidence: 99%

Plasma-flow interactions in field-emission discharges with applications in microcombustion

Shivkumar¹,

Li²,

Alexeenko³

2019

J. Phys. D: Appl. Phys.

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Field emission based microplasma actuators generate highly nonneutral surface discharges that can be used to heat, pump, and mix the flow through microchannels and offer an innovative solution to the problems associated with microcombustion. They provide a constant source of heat to counter the large heat loss through the combustor surface, they aid in flow transport at low Reynolds numbers without the use of moving parts, and they provide a constant supply of radicals to promote chain branching reactions. In this work, we present two actuator concepts for the generation of field emission microplasma, one with offset electrodes and the other with planar electrodes. They operate at input voltages in the 275-325 V range at a frequency of 1 GHz which is found to be the most suitable value for flow enhancement. The momentum and energy imparted by the charged particles to the neutrals as modeled by 2D particleincell with Monte Carlo collisions are applied to actuate flow in microchannels using 2D computational fluid dynamics modeling. The planar electrode configuration is found to be more suitable for the purpose of heating, igniting and mixing the flow, as well as improving its residence time through a 10 mm long microcombustor. The combustion of hydrogen and air with the help of 4 such actuators, each with a power consumption of 47.5 mW cm −1 , generates power with an efficiency of 90.5%. Such microcombustors can be applied to all battery based systems requiring micropower generation with the the ultimate goal of 'generating power on a chip'.

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Microchannel Flow Enhancement by Microplasma Actuation

Cited by 4 publications

References 10 publications

Enhancement of hydrogen microcombustion via field-emission dielectric barrier discharge

Enhancement of hydrogen microcombustion via field-emission dielectric barrier discharge

Field-emission plasma enhancement of H₂–O₂ micro-combustion

Plasma-flow interactions in field-emission discharges with applications in microcombustion

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Microchannel Flow Enhancement by Microplasma Actuation

Cited by 4 publications

References 10 publications

Enhancement of hydrogen microcombustion via field-emission dielectric barrier discharge

Enhancement of hydrogen microcombustion via field-emission dielectric barrier discharge

Field-emission plasma enhancement of H2–O2 micro-combustion

Plasma-flow interactions in field-emission discharges with applications in microcombustion

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Product

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Field-emission plasma enhancement of H₂–O₂ micro-combustion