Plasma Assisted Cooling of Hot Surfaces on Hypersonic Vehicles

Hanquist, Kyle M.; Boyd, Iain D.

doi:10.3389/fphy.2019.00009

Cited by 23 publications

(4 citation statements)

References 29 publications

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“…Additional research with CFDs could consider the potential effect of positive surface charge in reducing the air density in front of the vehicle. Using a positive surface charge to reduce the perceived freestream density of the flow would have significant and already quantified effects on drag and convective heat transfer (12). However, since the temperature in front of the vehicle is considerably lower than the temperatures inside the boundary layer, much higher speeds would be necessary to produce the same density reduction.…”

Section: Table 2 Data and Results For Determination Of Maximum Potent...mentioning

confidence: 99%

Analysis of the effects of positive ions and boundary layer temperature at various hypersonic speeds on boundary layer density

Selvakumar,

Palanisamy

2020

J Emerg Invest

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Vehicles traveling at hypersonic speeds ionize the air around them. This ionization leads to the possibility of utilizing an induced positive surface charge to lower the density of the boundary layer flow electrostatically. Reducing the boundary layer's density would have several positive effects, such as lowering the drag and heat transfer. The study's goal was to identify the Mach numbers for which the electrostatic drag and heat transfer manipulation would be most applicable inside the stratosphere. We hypothesized that the potential to use induced positive surface charge repulsion to lower boundary layer density would increase with speed, and there will be greater (>10%) potential to decrease boundary layer density at a lower bound estimate of Mach 18-19. We also explored the extent to which extrapolation through a quadratic model based on Dr. Jesse R. Maxwell's data in Morphing Waveriders for Atmospheric Entry could be used to approximate maximum boundary layer temperature values. The experiments were conducted using computational fluid dynamics software. The study demonstrated that, on average, higher Mach speeds resulted in a considerably higher potential decrease in density. Also, as predicted by the hypothesis, a significant potential reduction in density occurred near Mach 19. The study also supported using the quadratic model based on Maxwell's data for approximating the maximum boundary layer temperature up to at least Mach 26. This study highlights that further research on the surface charge method is warranted as we seek to explore higher hypersonic speeds within the stratosphere.

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Section: Table 2 Data and Results For Determination Of Maximum Potent...mentioning

confidence: 99%

Analysis of the effects of positive ions and boundary layer temperature at various hypersonic speeds on boundary layer density

Selvakumar,

Palanisamy

2020

J Emerg Invest

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“…This means that the surface electron emission will be at most 97% of the flowfield electron current. Furthermore, using the current balance through the sheath to define the ratio of space-charge limited current to that of the flowfield ions, γ, in terms of Γ, Hanquist and Boyd have shown that [18],…”

Section: Floating Surfacementioning

confidence: 99%

“…Tests were conducted in a plasma arc tunnel at the Sandia Corporation for various geometries, material properties and flow conditions [16]. More recently, Hanquist and Boyd simulated the experiments using various modeling options [17,18]. Overall, the simulations were able to encompass the experimental results but uncertainties in the measurements made it difficult to draw any direct conclusions on which modeling options were most accurate.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Computational Models for Electron Transpiration Cooling

et al. 2021

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Recent developments in the world of hypersonic flight have brought increased attention to the thermal response of materials exposed to high-enthalpy gases. One promising concept is electron transpiration cooling (ETC) that provides the prospect of a passive heat removal mechanism, rivaling and possibly outperforming that of radiative cooling. In this work, non-equilibrium CFD simulations are performed to evaluate the possible roles of this cooling mode under high-enthalpy conditions obtainable in plasma torch ground-test facilities capable of long flow times. The work focuses on the test case of argon gas being heated to achieve enthalpies equivalent to post-shock conditions experienced by a vehicle flying through the atmosphere at hypersonic speed. Simulations are performed at a range of conditions and are used to calibrate direct comparisons between torch operating conditions and resulting flow properties. These comparisons highlight important modeling considerations for simulating long-duration, hot chamber tests. Simulation results correspond well with the experimental measurements of gas temperature, material surface temperature as well as measured current generated in the test article. Theoretical methods taking into consideration space charge limitations are presented and applied to provide design suggestions to boost the ETC effect in future experiments.

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“…For the first 2D case, we simulate a plasma bounded by a square equipotential conducting surface that emits electrons from a small part of its length, see figure 1(a). Practical examples of partially-emitting conducting surfaces include arcs [42,43], divertor plates with local hot spots [44], and hypersonic vehicles [45]. Spacecraft contain conducting surfaces where photoelectron emission occurs from the components exposed to sunlight [46].…”

Section: Plasma Bounded By a Surface With An Emitting Segmentmentioning

confidence: 99%

Effects of emitting surfaces and trapped ions on the sheath physics and current flow in multidimensional plasma systems

Johnson¹,

Campanell²

2021

Plasma Sources Sci. Technol.

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Recent one-dimensional simulations of planar sheaths with strong electron emission have shown that trapping of charge-exchange ions causes transitions from space-charge limited (SCL) to inverse sheaths. However, multidimensional emitting sheath phenomena with collisions remained unexplored, due in part to high computational cost. We developed a novel continuum kinetic code to study the sheath physics, current flow and potential distributions in two-dimensional unmagnetized configurations with emitting surfaces. For small negatively biased thermionic cathodes in a plasma, the cathode sheath can exist in an equilibrium SCL state. The SCL sheath carries an immense density of trapped ions, neutralized by thermoelectrons, within the potential well of the virtual cathode. For further increases of emitted flux, the trapped ion cloud expands in space. The trapped ion space charge causes an increase of thermionic current far beyond the saturation limit predicted by conventional collisionless SCL sheath models without ion trapping. For sufficiently strong emission, the trapped ion cloud consumes the entire 2D plasma domain, forming a mode with globally confined ions and an inverse sheath at the cathode. In situations where the emitted flux is fixed and the bias is swept (e.g. emissive probe), the trapped ions cause a large thermionic current to escape for all biases below the plasma potential. Strong suppression of the thermionic emission, required for the probe to float, only occurs when the probe is above the plasma potential.

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Plasma Assisted Cooling of Hot Surfaces on Hypersonic Vehicles

Cited by 23 publications

References 29 publications

Analysis of the effects of positive ions and boundary layer temperature at various hypersonic speeds on boundary layer density

Analysis of the effects of positive ions and boundary layer temperature at various hypersonic speeds on boundary layer density

Evaluation of Computational Models for Electron Transpiration Cooling

Effects of emitting surfaces and trapped ions on the sheath physics and current flow in multidimensional plasma systems

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