Flow-Tube Oxidation Experiments on the Carbon Preform of a Phenolic-Impregnated Carbon Ablator

Panerai, Francesco; Martin, Alexandre; Mansour, Nagi N.; Sepka, Steven; Lachaud, Jean

doi:10.2514/1.t4265

Cited by 63 publications

(26 citation statements)

References 34 publications

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“…The ultimate goal of a microscale analysis would be the identification of the carbon fiber intrinsic reactivities. Spatially resolved images could advance such analysis, for instance, by micro-tomography as carried out by Panerai et al 50 . A material code was developed at the VKI using discontinuous Galerkin discretization to simulate the complex in-depth thermal response of ablative composite materials 51 .This code makes use of the new thorough physico-chemical library Mutation ++ , providing the thermal and transport properties of gas mixtures, including the calculation of both finite-rate gas-phase chemistry and homogeneous/heterogeneous gas/gas-solid equilibrium chemistry 52 .…”

Section: Discussionmentioning

confidence: 99%

Emission Spectroscopic Boundary Layer Investigation during Ablative Material Testing in Plasmatron

Helber

Chazot

Hubin

et al. 2016

JoVE

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Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution for future high-speed reentry missions. But despite the advancements made since Apollo, heat flux prediction remains an imperfect science and engineers resort to safety factors to determine the TPS thickness. This goes at the expense of embarked payload, hampering, for example, sample return missions.Ground testing in plasma wind-tunnels is currently the only affordable possibility for both material qualification and validation of material response codes. The subsonic 1.2MW Inductively Coupled Plasmatron facility at the von Karman Institute for Fluid Dynamics is able to reproduce a wide range of reentry environments. This protocol describes a procedure for the study of the gas/surface interaction on ablative materials in high enthalpy flows and presents sample results of a non-pyrolyzing, ablating carbon fiber precursor. With this publication, the authors envisage the definition of a standard procedure, facilitating comparison with other laboratories and contributing to ongoing efforts to improve heat shield reliability and reduce design uncertainties.The described core techniques are non-intrusive methods to track the material recession with a high-speed camera along with the chemistry in the reactive boundary layer, probed by emission spectroscopy. Although optical emission spectroscopy is limited to line-of-sight measurements and is further constrained to electronically excited atoms and molecules, its simplicity and broad applicability still make it the technique of choice for analysis of the reactive boundary layer. Recession of the ablating sample further requires that the distance of the measurement location with respect to the surface is known at all times during the experiment. Calibration of the optical system of the applied three spectrometers allowed quantitative comparison. At the fiber scale, results from a post-test microscopy analysis are presented.

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Section: Discussionmentioning

confidence: 99%

Emission Spectroscopic Boundary Layer Investigation during Ablative Material Testing in Plasmatron

Helber

Chazot

Hubin

et al. 2016

JoVE

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“…Numerous emission lines of Ca and Ca+ are visible both in front of FiberForm and PICA, which is explained by clusters of calcium introduced during the manufacturing process of FiberForm. 15,16 Copper emission lines around 324 nm are almost always present in the spectra due to cathode erosion in the arc-jet. One main difference between PICA and FiberForm is the presence of species containing hydrogen, in particular NH with its peak emission at 336 nm and OH peaking at 306 nm and the H  at 486.1 nm.…”

Section: A Emission Spectroscopy Signatures In the Stagnation Regionmentioning

confidence: 99%

Characterization of Ablation Product Radiation Signatures of PICA and FiberForm

Winter

Butler

Danehy

et al. 2016

46th AIAA Thermophysics Conference

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Emission spectroscopy measurements in the post-shock layer in front of low density ablative material samples of different shapes were obtained in the NASA Langley HYMETS arcjet facility. A horizontal line of measurement positions was imaged on the entrance slit of the spectrometer allowing detection of the entire stagnation line in front of the samples. The stagnation line measurements were used to compare the post-shock layer emission signatures in front of PICA and FiberForm. The emission signatures of H, NH, and OH are characteristic for pyrolysis gases and consequently were only observed in front of the PICA samples. CN and C were found in front of both materials and are mainly due to interactions of the carbon fibers with the plasma. In all tests with instrumented samples, the emission of Mn, Cr, and Ni was observed when the thermocouple temperatures reached or exceeded ~1,500 K, strongly indicating erosion of the molten thermocouple tips. Temperatures in the post-shock layer were estimated from comparing the CN band emission to spectral simulation. The resulting rotational and vibrational temperatures were on the order of 7,000 to 9,000 K and close to each other indicating a plasma condition close to equilibrium. In addition to the stagnation line configurations, off-axis lines of observation were investigated to gather information about spalled particles in the flow. From a comparison of measured continuum emission with simulated Planck radiation, average particle temperatures along the measured line of observation were determined for two cases. Particle temperatures between 3,500 and 2,000 K were found. A comprehensive investigation of the entire amount of data set is ongoing.

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“…Surface reactions will also likely be encouraged due to the relatively large size of the carbon fibers (µm), compared to the PAH molecules (Å), and soot nuclei (nm). Heterogeneous reaction rates are still widely unknown, and previous works have only focused on oxidation reactions with respect to the fibers [68]. The potential for solid carbon deposition, through "soot" or PAH/fiber collisions, and the effect that this has on the pyrolysis gas mixture is a topic that has not received much attention previously.…”

Section: Effect Of Carbon Depositionmentioning

confidence: 99%

Pyrolysis Gas Composition for a Phenolic Impregnated Carbon Ablator Heatshield

Rabinovitch

Marx

Blanquart

2014

11th AIAA/ASME Joint Thermophysics and Heat Transfer Conference

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Published physical properties of phenolic impregnated carbon ablator (PICA) are compiled, and the composition of the pyrolysis gases that form at high temperatures internal to a heatshield is investigated. A link between the composition of the solid resin, and the composition of the pyrolysis gases created is provided. This link, combined with a detailed investigation into a reacting pyrolysis gas mixture, allows a consistent, and thorough description of many of the physical phenomena occurring in a PICA heatshield, and their implications, to be presented.

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Flow-Tube Oxidation Experiments on the Carbon Preform of a Phenolic-Impregnated Carbon Ablator

Cited by 63 publications

References 34 publications

Emission Spectroscopic Boundary Layer Investigation during Ablative Material Testing in Plasmatron

Emission Spectroscopic Boundary Layer Investigation during Ablative Material Testing in Plasmatron

Characterization of Ablation Product Radiation Signatures of PICA and FiberForm

Pyrolysis Gas Composition for a Phenolic Impregnated Carbon Ablator Heatshield

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