Combined Measurements and Computations of High Enthalpy and Plasma Flows for Determination of TPM Surface Catalycity
TITLE: Measurement Techniques for High Enthalpy and Plasma Flows [Techniques de mesure pour les ecoulements de plasma et les ecoulements a haute enthalpie] To order the complete compilation report, use: ADA390586 The component part is provided here to allow users access to individually authored sections f proceedings, annals, symposia, ect. However, the component should be considered within he context of the overall compilation report and not as a stand-alone technical report. The paper presents the method for the TPM catalycity 3,5m/s V prediction on the basis of high enthalpy plasmatron heat 102rn/c transfer tests, performed in subsonic regimes, and 1400 appropriate CFD modeling of the whole plasma flow field in the plasma wind tunnel (1), viscous reacting gas ,5 flows around a test model (2), a nonequilibrium 12=1,0m0s boundary layer near the stagnation point of a test model 1200 (3) and analysis of the the heat transfer for test conditions l • 0m/s at the small Reynolds and Mach numbers (4). In general, the methodology was developed during the study of the 1000 catalytic efficiencies of the Buran TPM-the black 0 1 2 3 X, m ceramic tile and the CC material with antioxidation coating-in dissociated nitrogen and air reacting flows. Fig. 1. Surface temperature distribution along the windward This experimental-theoretical methodology has been center line of the Bor vehicle [ref 8]. Dots-the flight test modified recently for the determination of TPM data: I-CC material with antioxidation coating; 2-ceramic catalycity in subsonic carbon dioxide and pure oxygen tile, 3-ceramic tile covered with black platinum. Curves-flows from high enthalpy tests performed by using the computations at different catalytic recombination rates Kw. 100-kW inductive IPG-4 plasmatron. The interaction between combined ground test measurements and CFD modeling is considered as genesis for catalytic effects Tw, K duplication, plasma flow field rebuilding and the extraction of the quantitative catalycity parameters from the measured high enthalpy flow parameters, surface temperature and stagnation point heat fluxes.
Analysis of differential diffusion phenomena in high enthalpy flows, with application to thermal protection material testing in ICP facilities
This thesis presents the derivation of the theory leading to the determination of the governing equations of chemically reacting flows under local thermodynamic equilibrium, which rigorously takes into account effects of elemental (de)mixing. As a result, new transport coefficients appear in the equations allowing a quantitative predictions and helping to gain deeper insight into the physics of chemically reacting flows at and near local equilibrium. These transport coefficients have been computed for both air and carbon dioxide mixtures allowing the application of this theory to both Earth and Mars entry problems in the framework of the methodology for the determination of the catalytic activity of Thermal Protections Systems (TPS) materials.Firstly, we analyze the influence of elemental fraction variations on the computation of thermochemical equilibrium flows for both air and carbon dioxide mixtures. To this end, the equilibrium computations are compared with several chemical regimes to better analyze the influence of chemistry on wall heat flux and to observe the elemental fractions behavior along a stagnation line. The results of several computations are presented to highlight the effects of elemental demixing on the stagnation point heat flux and chemical equilibrium composition for air and carbon dioxide mixtures. Moreover, in the chemical nonequilibrium computations, the characteristic time of chemistry is artificially decreased and in the limit the chemical equilibrium regime, with variable elemental fractions, is achieved. Then, we apply the closed form of the equations governing the behavior of local thermodynamic equilibrium flows, accounting for the variation in local elemental concentrations in a rigorous manner, to simulate heat and mass transfer in CO2/N2 mixtures. This allows for the analysis of the boundary layer near the stagnation point of a hypersonic vehicle entering the true Martian atmosphere. The results obtained using this formulation are compared with those obtained using a previous form of the equations where the diffusive fluxes of elements are computed as a linear combination of the species diffusive fluxes. This not only validates the new formulation but also highlights its advantages with respect to the previous one : by using and analyzing the full set of equilibrium transport coefficients we arrive at a deep understanding of the mass and heat transfer for a CO2/N2 mixture.Secondly, we present and analyze detailed numerical simulations of high-pressure inductively coupled air plasma flows both in the torch and in the test chamber using two different mathematical formulations: an extended chemical non-equilibrium formalism including finite rate chemistry and a form of the equations valid in the limit of local thermodynamic equilibrium and accounting for the demixing of chemical elements. Simulations at various operating pressures indicate that significant demixing of oxygen and nitrogen occurs, regardless of the degree of nonequilibrium in the plasma. As the operating pressure is increased, chemistry becomes increasingly fast and the nonequilibrium results correctly approach the results obtained assuming local thermodynamic equilibrium, supporting the validity of the proposed local equilibrium formulation. A similar analysis is conducted for CO2 plasma flows, showing the importance of elemental diffusion on the plasma behavior in the VKI plasmatron torch.Thirdly, the extension of numerical tools developed at the von Karman Institute, required within the methodology for the determination of catalycity properties for thermal protection system materials, has been completed for CO2 flows. Non equilibrium stagnation line computations have been performed for several outer edge conditions in order to analyze the influence of the chemical models for bulk reactions. Moreover, wall surface reactions have been examined, and the importance of several recombination processes has been discussed. This analysis has revealed the limits of the model currently used, leading to the proposal of an alternative approach for the description of the flow-surface interaction. Finally the effects of outer edge elemental fractions on the heat flux map is analyzed, showing the need to add them to the list of parameters of the methodology currently used to determine catalycity properties of thermal protection materials.
Multilayer high density flex technology
The industrial trend of shrinking microelectronic devices while increasing the density of interconnections places great demands on the substrates upon which these devices are packaged. Multilayer flex circuits will provide the interconnection densities needed to meet these demands in a wide range of packaging and interconnection technologies. This paper discusses the development of ultra-high density flexible circuits. Processes and materials to fabricate fine line pitches from 12.5 /spl mu/m to 40 /spl mu/m are examined. Various microvia structures, through hole and blind via, are demonstrated. A test vehicle was designed and built for BGA packages to illustrate the density capability. A four-layer structure is demonstrated by using Z-connection to connect two layer pairs. Electrical, mechanical, and reliability test results are presented to show the selection of flex substrate material, Z-connection methodology and fabrication processes. A cost comparison of high-density flex to alternative substrates is discussed to identify potential.