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This work investigates the microstructure and oxidation response of finders and binder to better understand the phenomena of spoliation in rigid, low density charring ablators. Varcum and fibers are the two main constituents combi...
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This work investigates the microstructure and oxidation response of finders and binder to better understand the phenomena of spoliation in rigid, low density charring ablators. Varcum and fibers are the two main constituents combined in a slurry to manufacture FiberForm, the substrate of PICA. A combination of electron microscopy, X-ray analysis, and surface area analysis techniques are used to characterize the materials at various scales. Results show increasing the processing temperature of the binder increases the structural order and size of the crystallite structure. The macro-pore size increases due the pyrolysis process, but pores at the micro-scale level decrease in volume. At higher oxidation temperatures, the oxidation rate of the binder also increases but is determined to be mostly reaction-limited.
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Inductively coupled plasma wind tunnels accurately replicate the harsh conditions that hypersonic vehicles experience during the atmospheric reentry phase. With the ability to reproduce aerothermal heating and the chemistry of hyp...
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Inductively coupled plasma wind tunnels accurately replicate the harsh conditions that hypersonic vehicles experience during the atmospheric reentry phase. With the ability to reproduce aerothermal heating and the chemistry of hypersonic flight, phenomena such as gas-surface interactions, heat shield ablation response, aero-optics, and non-equilibrium plasma can be investigated in a pristine and flexible test environment. This paper describes the new Plasmatron X inductively coupled plasma (ICP) facility developed by the Center for Hypersonics & Entry Systems Studies (CHESS) at the University of Illinois Urbana-Champaign. At 350 kW, Plasmatron X is currently the largest ICP facility in the United States, which allows near-continuous operation, dedicated to aerothermal testing for hypersonic flight and reentry environments. A description of the facility's unique capabilities, characterization of the operating conditions, and a survey of the aerothermal test environment are provided, focusing on cold-wall stagnation-point heat flux and stagnation pressure characterization, as well as plasma jet unsteadiness through high-speed imaging under different operating conditions.
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Reentry and hypersonic vehicles are exposed to high temperatures during flight that require the use of thermal protection systems to protect the internal structure, payload, and crew. Simulating the response of a thermal protectio...
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Reentry and hypersonic vehicles are exposed to high temperatures during flight that require the use of thermal protection systems to protect the internal structure, payload, and crew. Simulating the response of a thermal protection system to different flight conditions provides time dependent, spatial information for all regions of the material, but such simulations are diflicult to perform accurately and can incur large computational expense for geometrically and thermochemically complex materials. In this paper, we present a new high-order material response solver, named the Coupled Hypersonic Protection System (CHyPS) solver, based on the discontinous Galerkin formulation. CHyPS is shown to match results generated using the Porous material Analysis Toolbox based on OpenFOAM (PATO) for standard ablation test cases, including the effects of pyrolysis, ablation, and material recession.
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During atmospheric re-entry applications, thermal protection systems (TPS) are not only submitted to high thermal and mechanical stresses, but also to a variety of highly reactive chemical species inside the boundary layer that ca...
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During atmospheric re-entry applications, thermal protection systems (TPS) are not only submitted to high thermal and mechanical stresses, but also to a variety of highly reactive chemical species inside the boundary layer that can trigger heterogeneous reactions with the protection components. For carbon fibers based material, the depletion of carbon atoms by oxygen molecules induces high ablation rates of the protection system, that in turn reduce material performances. To protect the fibers from hostile environments, composite materials have been introduced, in particular composite ceramics, which have the advantage to present good thermal and mechanical properties for hypersonics applications. In this study, a mathematical model for the oxidation of this class of material is presented and implemented within the Porous material Analysis Toolbox based on OpenFOAM (PATO) framework to evaluate the protective role of the matrix phase under oxidation, and the ceramics composite response under a variety of external environments.
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Oxidation is a prominent factor in degradation of carbon based ablative materials at high temperatures, resulting in mass loss and material recession through chemical and mechanical erosion. In this work, a finite rate carbon oxid...
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Oxidation is a prominent factor in degradation of carbon based ablative materials at high temperatures, resulting in mass loss and material recession through chemical and mechanical erosion. In this work, a finite rate carbon oxidation model coupled with surface recession is implemented in the Porous Ablation and Thermal Response (Panther) software to investigate carbon oxidation by atomic oxygen over a range of temperatures and pressures. Panther is utilized to investigate the finite rate oxidation model proposed by Swaminathan-Gopalan et al. at conditions of higher pressure and flux relative to the experiments it was built on.
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Experiments to measure the oxidation rates of carbon by molecular and atomic oxygen were conducted using a non-thermal, radio frequency generated plasma exposed to a resis-tively heated graphite rod at surface temperatures between...
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Experiments to measure the oxidation rates of carbon by molecular and atomic oxygen were conducted using a non-thermal, radio frequency generated plasma exposed to a resis-tively heated graphite rod at surface temperatures between 773 and 2073 K. The temperature dependence of oxidation behavior was obtained for pure O_2 and for a mixture of O_2 and O atoms produced by the plasma. Oxygen atom flux to the graphite samples was characterized based on etching rates of reference polyimide films. Mass loss and exposure time of the graphite samples were measured at different test conditions to calculate oxidation rates. Mass spectrom-etry was used to identify the chemical species present in the oxidation products. Experiments were carried out at a pressure of 0.33 kPa which provided carbon oxidation results relevant to atmospheric entry conditions and which will be used to inform Arrhenius rate equations for gas-surface interaction computational models.
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Characterization of the inductively coupled plasma (ICP) torch at the Plasmatron X facility developed by the Center for Hypersonics & Entry Systems Studies (CHESS) was performed by means of optical emission spectroscopy (OES). OES provides a noninvasive method of identifying both atomic and molecular species within the plasma jet without physically perturbing the flow. Additionally, experimental spectra can be compared to simulated spectra to provide estimates of the gas temperature. In this work, we present the preliminary results of a spectroscopic characterization campaign of the newly commissioned 350 kW ICP wind tunnel, identifying the chemical composition and determining the gas temperatures as a function of the tunable parameter spaces (i.e., applied power and static pressure)....
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Characterization of the inductively coupled plasma (ICP) torch at the Plasmatron X facility developed by the Center for Hypersonics & Entry Systems Studies (CHESS) was performed by means of optical emission spectroscopy (OES). OES provides a noninvasive method of identifying both atomic and molecular species within the plasma jet without physically perturbing the flow. Additionally, experimental spectra can be compared to simulated spectra to provide estimates of the gas temperature. In this work, we present the preliminary results of a spectroscopic characterization campaign of the newly commissioned 350 kW ICP wind tunnel, identifying the chemical composition and determining the gas temperatures as a function of the tunable parameter spaces (i.e., applied power and static pressure).
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摘要 :
Characterization of the inductively coupled plasma (ICP) torch at the Plasmatron X facility developed by the Center for Hypersonics & Entry Systems Studies (CHESS) was performed by means of optical emission spectroscopy (OES). OES provides a noninvasive method of identifying both atomic and molecular species within the plasma jet without physically perturbing the flow. Additionally, experimental spectra can be compared to simulated spectra to provide estimates of the gas temperature. In this work, we present the preliminary results of a spectroscopic characterization campaign of the newly commissioned 350 kW ICP wind tunnel, identifying the chemical composition and determining the gas temperatures as a function of the tunable parameter spaces (i.e., applied power and static pressure)....
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Characterization of the inductively coupled plasma (ICP) torch at the Plasmatron X facility developed by the Center for Hypersonics & Entry Systems Studies (CHESS) was performed by means of optical emission spectroscopy (OES). OES provides a noninvasive method of identifying both atomic and molecular species within the plasma jet without physically perturbing the flow. Additionally, experimental spectra can be compared to simulated spectra to provide estimates of the gas temperature. In this work, we present the preliminary results of a spectroscopic characterization campaign of the newly commissioned 350 kW ICP wind tunnel, identifying the chemical composition and determining the gas temperatures as a function of the tunable parameter spaces (i.e., applied power and static pressure).
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A state-to-state two-step binary collision (TSBC) recombination model is developed for the rovibrationally coupled database of cross-sections from quasi-classical trajectory (QCT) calculations. The current work contains two parts....
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A state-to-state two-step binary collision (TSBC) recombination model is developed for the rovibrationally coupled database of cross-sections from quasi-classical trajectory (QCT) calculations. The current work contains two parts. In the first part, the two-step binary collision framework has been extended to include a rovibrationally resolved database from our previous work which can only apply to the vibrationally resolved QCT database. In this framework, only the product of orbiting-pair (OP) lifetime and formation cross-section is included in the model, rather than quantifying these parameters individually, in order to determine the overall recombination probability in DSMC. The probability of recombining two oxygen atoms to a specific rovibrational energy level is then determined by applying microscopic reversibility to the corresponding dissociation cross-section. In the second part, the individual OP lifetime and OP formation cross-section are computed based on the interaction potential of two oxygen atoms, which allows for determination of the recombination cross-section directly from the potential energy surface. Good agreement of the computed recombination rate coefficient from the orbiting pair parameters with the literature values is found within the temperature range from T =3000K to 8000K.
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