Shock Tube Testing of the Transpiration-Cooled Heat Shield Experiment AKTiV

Boehrk, Hannah; Wartemann, Viola; Eggers, Thino; Schramm, Jan Martinez; Wagner, Alexander; Hannemann, Klaus

doi:10.2514/6.2012-5935

Cited by 11 publications

(11 citation statements)

References 4 publications

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“…Experimental studies mainly focused on flat plate, cone and wedge geometries in order to study the development of the coolant film and the associated cooling effectiveness. Figure 1 summarises mostly recent work conducted for a flat plate geometry at hypersonic conditions [13,21,[24][25][26][27][28]. The Reynolds number refers to the axial flow distance between model leading edge and location of injection, and the blowing ratio is defined as the ratio between coolant mass flux (subscript f ) and external boundary layer edge mass flux (subscript g),…”

Section: Introductionmentioning

confidence: 99%

Performance of Transpiration-Cooled Heat Shields for Reentry Vehicles

2020

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This paper presents results of a system study of transpiration cooled thermal protection systems for Earth re-entry. The cooling performance for sustained hypersonic flight and transient re-entry of a blunt cone geometry is assessed. A simplified numerical model is used to calculate the transient temperature of a transpiration cooled heat shield. The performance of transpiration cooling is assessed by calculating the overall required coolant mass for different steady state and transient flight scenarios. Spatially and temporally optimised mass injection is presented for various flight conditions. The majority of the injection is required on the spherical nose segment of the blunted cone. Carbon/Carbon composite ceramic and the ultra high temperature ceramic Zirconium diboride are considered as wall materials. Both materials require similar amounts of coolant injection. In continuous hypersonic cruise, transpiration cooling is highly effective for flight conditions with velocities below 8 km s −1 and altitudes above 40 km. For transient re-entry, transpiration cooling is most viable for trajectories of entry velocities below 8.5 km s −1 and ballistic coefficients below 2.1 kg m −2. Nomenclature A Area, m 2 C D Drag coefficient c p Specific heat capacity, J kg −1 K −1

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Section: Introductionmentioning

confidence: 99%

Performance of Transpiration-Cooled Heat Shields for Reentry Vehicles

2020

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“…In the laminar case, no intrusion of the surrounding hot atmospheric gas is assumed, and the heat transfers for both hot gas to film and film to wall are each determined by Crocco's model. Comparison of HEATS results to former experiments have proven that the model is valid [6,7]. As an approach, the velocity of the film is set to u F 0.1 × u ∞ , and the temperature of the film outside the boundary layer is determined, for example, by calculating the heat exchange during transpiration.…”

Section: B Surface Blockingmentioning

confidence: 99%

“…This way, the temperature response of the structure is determined for the uncooled case as well as for the coupled film-and convection-cooled conditions. It has been validated by comparison to experiments in both a steady-state arc-heated wind tunnel under laminar inflow and short-duration measurements in a shock tube [6,7]. Complementary to the flight data evaluation, a comparison of the measurement and results from HEATS is introduced and discussed.…”

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confidence: 97%

Transpiration-Cooled Hypersonic Flight Experiment: Setup, Flight Measurement, and Reconstruction

Böhrk

2015

Journal of Spacecraft and Rockets

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The present paper presents the in-flight measurement of the transpiration cooling experiment Aktive Kühlung durch Transpiration im Versuch (often referred to as AKTiV) flown on the suborbital reentry configuration Sharp Edge Flight Experiment II (often referred to as SHEFEX II). Thermal response of the structure is measured just upand downstream of a cooled sample with a noncooled reference setup on the opposite side of the vehicle. The measurement shows that the heat flux is reduced upon coolant exhaust. The maximum temperature reduction with 87 K is observed on the porous sample, while downstream the sample, the temperature is reduced by 75 K by film cooling. This corresponds to cooling efficiencies of 58 and 42% on the sample and downstream, respectively. The evaluation is supported by the semi-analytical tool HEATS, based on a transient heat balance at the surface. Comparison of the results with HEATS shows that the heat flux predicted with HEATS is in good concurrence with the measured temperatures on the cooled sample, as well as upstream and downstream with a maximum deviation by 14%. The analysis suggests that the flow condition around the sharp-edged, faceted vehicle remained laminar longer than expected. Nomenclaturem M = Mach number, -_ m = mass flow rate, kg∕s Nu = Nusselt number, -Pr = Prandtl number p = pressure, Pa R = gas constant, J∕kg · K Re = Reynolds number, -r = recovery factor, -_ q = heat flux, W∕m 2 St = Stanton number, -T = temperature, K t = time, s u = velocity, m∕s α A = heat transfer coefficient, W∕m 2 · K α V = heat transfer coefficient, W∕m 3 · K ϵ = emissivity, -η = cooling efficiency, -κ = isentropic coefficient, -λ = thermal conductivity, W∕m · K μ = dynamic viscosity, Pa · s ρ = density, kg∕m 3 σ = Stefan-Boltzmann constant, W∕m 2 · K 4 ϕ = porosity, -Subscripts C = at panel C c = coolant cond = heat conduction conv = heat convection F = film HG = hot gas p = at constant pressure r = recovery rad = radiation res = reservoir S = surface x, y = coordinates W = wall 0 = plenum ∞ = ambient

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“…In laminar case, no admix of the surrounding hot atmospheric gas is assumed and the heat transfer for both "hot-gas-to-film" and "film-to-wall" is determined each by Crocco's model. Comparison of HEATS results to former experiments had proven that the model is valid [6,7]. As an approach, the velocity of the film is set to u F =0.1×u ∞ and the temperature of the film outside the boundary layer is determined, for example, by calculation of the heat exchange during transpiration.…”

Section: Iiib Surface Blockingmentioning

confidence: 99%

“…This way, the temperature response of the structure is determined for the uncooled case as well as for the coupled film-and convection cooled conditions. It has been validated by comparison to experiments in an arc-heated wind tunnel under laminar in-flow [6,7]. Complementary to the filght data evaluation, a comparison of the measurement and results from HEATS is introduced and discussed.…”

Section: Introductionmentioning

confidence: 98%

Transpiration Cooling at Hypersonic Flight - AKTiV on SHEFEX II

Böhrk

2014

11th AIAA/ASME Joint Thermophysics and Heat Transfer Conference

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The present paper presents the in-flight measurement of the transpiration cooling experiment AKTiV flown on the sub-orbital re-entry configuration SHEFEX II. Thermal response of the structure is measured just up-and downstream of a cooled sample with a non-cooled reference set-up on the opposite side of the vehicle. The measurement shows that the heat flux is reduced upon coolant exhaust. The maximum temperature reduction by transpiration-cooling is observed on the porous sample with 87 K, while downstream the sample, the temperature reduction by film cooling is 75 K. This corresponds to cooling efficiencies of 61% and 46% on the sample and downstream, respectively. The evaluation is supported by the semi-analytical tool HEATS, based on a transient heat balance at the surface. Comparison of the results with HEATS shows that the heat flux predicted with HEATS is in good concurrence with the measured temperatures on the cooled sample, as well as upstream and downstream with a maximum deviation by 14%. The analysis shows that the flow condition around the sharp-edged, faceted vehicle remains longer laminar than expected.

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Shock Tube Testing of the Transpiration-Cooled Heat Shield Experiment AKTiV

Cited by 11 publications

References 4 publications

Performance of Transpiration-Cooled Heat Shields for Reentry Vehicles

Performance of Transpiration-Cooled Heat Shields for Reentry Vehicles

Transpiration-Cooled Hypersonic Flight Experiment: Setup, Flight Measurement, and Reconstruction

Transpiration Cooling at Hypersonic Flight - AKTiV on SHEFEX II

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