Teflon probing for the flow characterization of arc-heated wind tunnel facilities

Gulli, Stefano; Ground, Cody R.; Crisanti, Matthew; Maddalena, Luca

doi:10.1007/s00348-013-1647-7

Cited by 5 publications

(4 citation statements)

References 19 publications

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“…In particular, the equilibrium flow in the plenum chamber is computed by using the enthalpy values derived from the energy balance method (Eq. 9) [22][23] and an iterative process, in which the plenum pressure is varied and the Chemical Equilibrium Application (CEA) applet from NASA repeatedly called, is repeated until the calculated mass flow through the nozzle converges to the one measured by a calibrated mass flow meter.…”

Section: B) Optical Properties Of the High-enthalpy Flowmentioning

confidence: 99%

“…III) can be classified it as low-density plasma based on the maximum density ratios obtainable at the nozzle exit / , 0.3 [21]. The nominal values of the density ratios have been calculated by using a numerical code, developed by the authors, which calculates the flow properties from the plenum chamber of the arc heater up to the specimen surface by using a one-dimensional fluid dynamics analysis [22]. In particular, the equilibrium flow in the plenum chamber is computed by using the enthalpy values derived from the energy balance method (Eq.…”

Section: B) Optical Properties Of the High-enthalpy Flowmentioning

confidence: 99%

“…The thermodynamic properties of the flow from the nozzle's throat up to the bow shock in front of the specimen are calculated assuming frozen flow due to the short length of the nozzle [22][23]. A standard iterative method [22,24] has been used to retrieve the local flow field conditions downstream the normal shock in thermodynamic equilibrium.…”

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confidence: 99%

“…A standard iterative method [22,24] has been used to retrieve the local flow field conditions downstream the normal shock in thermodynamic equilibrium. Both the density ratios and the total temperature values obtained downstream the normal shock (3000 8000 ) for the nominal test conditions used during previous experimental campaigns, allows estimating the air-plasma emissivity in the infrared region based on the emission of nitric oxide (NO is the most emitting species in the IR region for air): 0.1 [21], [25][26].…”

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confidence: 99%

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Design of the Experimental Campaign on Variable Transpiration Cooling for Reusable Thermal Protection Systems

Gulli¹,

Maddalena²,

Moghadam

et al. 2015

20th AIAA International Space Planes and Hypersonic Systems and Technologies Conference

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Reusable thermal protection systems are one of the key technologies that have to be improved in order to enable long-duration hypersonic flights and a more affordable access-to-space by means of single-stage-toorbit vehicles. The transpiration cooling has been demonstrated to be one of the most promising cooling techniques in terms of coolant mass saving and minimum disturbances of the external flow. The coupling of the boundary layer with the thermal response of selected porous materials plays a crucial role in enabling the practical use of the transpiration cooling technique for reusable thermal protection systems. Numerical studies conducted by the authors, on the aforementioned coupling, have introduced the new concept of the variable transpiration cooling which allowed identifying a particular cooling strategy (i.e. saw-tooth wall velocity distribution) able to reduce the total amount of coolant used by 37% with respect to other cooling strategies explored. The current capability of manipulating the natural properties of porous materials (e.g. porosity, permeability and thermal conductivity) renewed the interest on demonstrating experimentally the cooling potential of the transpiration strategies simulated numerically. The design phase of the experimental campaign on variable transpiration cooling for testing a full-scale thermal protection system in the 1.6 MW arc-heated wind tunnel located at the University of Texas at Arlington is presented in this work. The prototype thermal shield to be used for the experiments is an axisymmetric carbon-carbon cone having tailored porosity and variable thickness prescribed at the manufacturing level in order to reproduce a variable blowing profile. An innovative calibration procedure of the infrared camera used to map the temperature of the external surface, which is based on simultaneous measurements of the local temperature and intensity of radiation, is described in detail. The results obtained in this work highlight the potential of using the calibration methodology proposed for retrieving the surface temperatures without using blackbody radiators/cavities and without relying on elaborated tests for emissivity characterization which are both needed in standard calibration procedures for infrared camera systems. A preliminary analysis of the optical properties of the plasma flow is also provided in order to assess the impact of the plasma's emissivity on the surface temperature map that will be obtained during the final experiment on transpiration cooling.

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Section: B) Optical Properties Of the High-enthalpy Flowmentioning

confidence: 99%

Section: B) Optical Properties Of the High-enthalpy Flowmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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