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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Experimental Assessment of the Emissions Control Potential of a Rich/Quench/Lean Combustor for High Speed Civil Transport Aircraft Engines

In support of Pratt & Whitney efforts to define the Rich burn/Quick mix/Lean burn (RQL) combustor for the High Speed Civil Transport (HSCT) aircraft engine, UTRC conducted a flametube-scale study of the RQL concept. Extensive combustor testing was performed at the Supersonic Cruise (SSC) condition of a HSCT engine cycle, Data obtained from probe traverses near the exit of the mixing section confirmed that the mixing section was the critical component in controlling combustor emissions. Circular-hole configurations, which produced rapidly-, highly-penetrating jets, were most effective in limiting NOx. The spatial profiles of NOx and CO at the mixer exit were not directly interpretable using a simple flow model based on jet penetration, and a greater understanding of the flow and chemical processes in this section are required to optimize it. Neither the rich-combustor equivalence ratio nor its residence time was a direct contributor to the exit NOx. Based on this study, it was also concluded that (1) While NOx formation in both the mixing section and the lean combustor contribute to the overall emission, the NOx formation in the mixing section dominates. The gas composition exiting the rich combustor can be reasonably represented by the equilibrium composition corresponding to the rich combustor operating condition. Negligible NOx exits the rich combustor. (2) At the SSC condition, the oxidation processes occurring in the mixing section consume 99 percent of the CO exiting the rich combustor. Soot formed in the rich combustor is also highly oxidized, with combustor exit SAE Smoke Number <3. (3) Mixing section configurations which demonstrated enhanced emissions control at SSC also performed better at part-power conditions. Data from mixer exit traverses reflected the expected mixing behavior for off-design jet to crossflow momentum-flux ratios. (4) Low power operating conditions require that the RQL combustor operate as a lean-lean combustor to achieve low CO and high efficiency. (5) A RQL combustor can achieve the emissions goal of EINOX = 5 at the Supersonic Cruise operating condition for a HSCT engine.

Rosfjord, T. J.↗
NASA NTRS2001

Experimental Assessment of the Emissions Control Potential of a Rich/Quench/ Lean Combustor for High Speed Civil Transport Aircraft Engines

In support of Pratt & Whitney efforts to define the Rich burn/Quick mix/Lean burn (RQL) combustor for the High Speed Civil Transport (HSCT) aircraft engine, UTRC conducted a flametube-scale study of the RQL concept. Extensive combustor testing was performed at the Supersonic Cruise (SSC) condition of an HSCT engine cycle. Data obtained from probe traverses near the exit of the mixing section confirmed that the mixing section was the critical component in controlling combustor emissions. Circular-hole configurations, which produced rapidly-, highly-penetrating jets, were most effective in limiting NO(x). The spatial profiles of NO(x) and CO at the mixer exit were not directly interpretable using a simple flow model based on jet penetration, and a greater understanding of the flow and chemical processes in this section are required to optimize it. Neither the rich-combustor equivalence ratio nor its residence time was a direct contributor to the exit NO(x). Based on this study, it was also concluded that: (1) While NO(x) formation in both the mixing section and the lean combustor contribute to the overall emission, the NOx formation in the mixing section dominates. The gas composition exiting the rich combustor can be reasonably represented by the equilibrium composition corresponding to the rich combustor operating condition. Negligible NO(x) exits the rich combustor. (2) At the SSC condition, the oxidation processes occurring in the mixing section consume 99 percent of the CO exiting the rich combustor. Soot formed in the rich combustor is also highly oxidized, with combustor exit SAE Smoke Number <3. (3) Mixing section configurations which demonstrated enhanced emissions control at SSC also performed better at part-power conditions. Data from mixer exit traverses reflected the expected mixing behavior for off-design jet to crossflow momentum-flux ratios. (4) Low power operating conditions require that the RQL combustor operate as a lean-lean combustor to achieve low CO and high efficiency. (5) An RQL combustor can achieve the emissions goal of EINO(x) = 5 at the Supersonic Cruise operating condition for an HSCT engine.

Tacina, Robert R.↗
NASA NTRS1985

Recent developments in polyimide and bismaleimide adhesives

Research on high temperature resin systems has intensified. In the Aerospace Industry, the motivation for this increased activity has been to replace heat resistant alloys of aluminum, stainless steel and titanium by lighter weight glass and carbon fiber reinforced composites. Applications for these structures include: (1) engine nacelles involving long time exposure (thousands of hours) to temperatures in the 150 to 300 C range, (2) supersonic military aircraft involving moderately long exposure (hundreds of hours) to temperatures of 150 to 200 C, and (3) missile applications involving only brief exposure (seconds or minutes) to temperatures up to 500 C and above. Because of fatigue considerations, whenever possible, it is preferable to bond rather than mechanically fasten composite structures. For this reason, the increased usage of high temperature resin matrix systems for composites has necessitated the devlopment of compatible and equally heat stable adhesive systems. The performance of high temperature epoxy, epoxy phenolic and condensation polyimide adhesives is reviewed. This is followed by a discussion of three recently developed types of adhesives: (1) condensation reaction polyimides having improved processing characteristics; (2) addition reaction polyimides; and (3) bismaleimides.

Politi, R. E.↗
NASA NTRS1978

Theoretical models for Mars and their seismic properties

Theoretical seismic properties of the planet Mars are investigated on the basis of the various models which have been proposed for the internal composition of the planet. The latest interpretation of gravity-field data, assuming a lower value of the moment of inertia, would require a less dense mantle and a larger core than previous models. If Mars is chondritic in composition, the most reasonable models are an incompletely differentiated H-chondrite or a mixture of H-chondrites and carbonaceous chondrites. Seismic profiles, travel times, and free oscillation periods are computed for various models, with the aim of establishing which seismic data is crucial for deciding among the alternatives. A detailed discussion is given of the seismic properties which could - in principle - help answer the questions of whether Mars' core is liquid or solid and whether Mars has a partially molten asthenosphere in its upper mantle.

Okal, E. A.↗
NASA NTRS1982

The composition of ultra-heavy cosmic rays

Preliminary results on the composition of ultraheavy nuclei in the cosmic rays are now available from experiments on HEAO-3 and Ariel-VI satellites. These results are compared with the composition predicted for reasonable propagation models using source abundances similar to those of solar system material. The effects of varying model parameters and of preferential acceleration are discussed. Discrepancies between predicted and observed abundances are larger than can be accounted for solely by first ionization potential effects and are interpreted in terms of a nucleosynthesis process.

Protheroe, R. J.↗
NASA NTRS1992

Pulse propagation in a laminated composite plate and nondestructive evaluation

The surface response of a laminated composite plate with delamination cracks has been studied in this paper. The objective of this study is to analyze the surface response both in the time and frequency domains due to delamination cracks at different depths in a cross-ply composite plate. For reasons of simplicity, attention has been focused here on two-dimensional (plane-strain) motions. The source of excitation is taken to be a line vertical force acting perpendicular to the fibers in a lamina. Numerical results are presented, showing peak responses at certain resonance frequencies. A comparison of these results with those for a uniaxial graphite epoxy plate shows characteristic differences.

Ju, T. H.↗
NASA NTRS1994

The spectrum of the planetary nebula IC 418

A detailed high-spectral-resolution study of the spectrum of IC 418 is made for the region 3650 to 10050 A, using the Hamilton echelle spectrograph of Lick Observatory, and of the UV spectral region with archival International Ultraviolet Explorer (IUE) data. From high-resolution images in both the near- and mid-infrared, Hora et al. (1993) showed that IC 418 probably has a compact shell interior to the detached, well-known, main shell emission. If one assumes a black body or Hubeny (or standard LTE) model atmosphere energy distribution, it does not appear possible to construct a fully satisfactory nebula model that will simultaneously represent the H-beta flux, the (O III) 5007/H-beta ratio, and the scale of this planetary nebula (PN). Fortunately, IUE and IR data supply information on ions in addition to those optically observed so that the chemical composition can be reasonably well established by summing over concentrations of observed ions. In spite of the fact that IC 418 is carbon rich in sense of having a C/O ratio exceeding the solar value, it is a 'metal-poor' object. Possibly it resembles IC 4997 but in a more advanced evolutionary phase. The central star is variable and has a strong wind.

Hyung, Siek↗
NASA NTRS1996

REE Partition Coefficients from Synthetic Diogenite-Like Enstatite and the Implications of Petrogenetic Modeling

Determining the petrogenesis of eucrites (basaltic achondrites) and diogenites (orthopyroxenites) and the possible links between the meteorite types was initiated 30 years ago by Mason. Since then, most investigators have worked on this question. A few contrasting theories have emerged, with the important distinction being whether or not there is a direct genetic link between eucrites and diogenites. One theory suggests that diogenites are cumulates resulting from the fractional crystallization of a parent magma with the eucrites crystallizing, from the residual magma after separation from the diogenite cumulates. Another model proposes that diogenites are cumulates formed from partial melts derived from a source region depleted by the prior generation of eucrite melts. It has also been proposed that the diogenites may not be directly linked to the eucrites and that they are cumulates derived from melts that are more orthopyroxene normative than the eucrites. This last theory has recently received more analytical and experimental support. One of the difficulties with petrogenetic modeling is that it requires appropriate partition coefficients for modeling because they are dependent on temperature, pressure, and composition. For this reason, we set out to determine minor- and trace-element partition coefficients for diogenite-like orthopyroxene. We have accomplished this task and now have enstatite/melt partition coefficients for Al, Cr, Ti, La, Ce, Nd, Sm, Eu, Dy, Er, Yb, and La.

Schwandt, C. S.↗
NASA NTRS2006

Europa: Processes and Habitability

This viewgraph presentation reviews the known and possible geologic processes of Europa. It shows slides of Europa, with different terrains (ridged plains and molten plains), and a possible view of the interior. Europa's eccentric orbit is reviewed. The presentation also reviews Europa's composition. The possible reasons for Europa's geology are reviewed. Also the possiblity that life exists on Europa is raised. The planned Europa Geophysical Explorer mission is also reviewed.

Europa↗
NASA NTRS2018

Comparison of Several Global Mixing Performance Metrics for High-Speed Fuel Injectors

To experimentally assess and compare the mixing performance of high-speed fuel injectors for scramjet engines, quantitative global metrics are needed. The one-dimensional metric most commonly used to assess the degree of mixing completeness at a given downstream station is the mixing efficiency parameter. The experimental determination of the mixing efficiency parameter requires measurement of the spatial distributions of both the fuel mass fraction and the mass flux. Standard in-stream gas sampling techniques can be used to measure the fuel mass fraction distribution, however the mass flux distribution is not easily determined experimentally because it requires the measurement of three independent aerothermodynamic variables in addition to the mixture composition. For this reason, several metrics that can be calculated from the fuel distribution alone are commonly used to assess mixing performance. Because these other metrics do not provide a mass flux-weighted measure of the local degree of mixing completeness, they may not correlate well with the mixing efficiency parameter. Therefore, if the substitute metrics are to be used to compare the mixing performance of candidate fuel injector concepts, it is important to understand their relationships to the mixing efficiency parameter in a representative scramjet combustor flowfield. This work investigates the relationships between the mixing efficiency parameter and several substitute metrics that are able to be measured with the current experimental setup of the Enhanced Injection and Mixing Project at the NASA Langley Research Center for baseline strut and ramp injectors. The results of these comparisons have revealed that it is possible to glean different (i.e., incorrect) conclusions about which injector is the better mixer when the substitute mixing performance metrics are used instead of the mixing efficiency parameter, thereby highlighting the importance of mass flux-weighted mixing performance metrics.

Ground, Cody R.↗
NASA NTRSDate not supplied

Mixed-Domain Charge Transport in S-Se Alloys as a Li-S Battery Cathode Material

Lithium-sulfur batteries are emerging candidate systems for the next-generation long-range electric aircraft application owing to their potential to deliver high energy density per weight. Their cathodes are to be made primarily with sulfur, but sulfur by itself has much too low electron conductivity to serve as a useful cathode. An idea that has been suggested to overcome this bottleneck is to alloy sulfur with selenium in the hope that electron mobility, which is thought to improve charge transport at some expense of increased weight and reduced energy density. However, understanding of these alloy structures and their transport mechanism is insufficient, and electron mobility at varying degrees of selenium content is not well charted, which are critical for determining the optimum selenium content and testing whether this strategy is generally feasible. The difficulty of computationally characterizing these alloy systems is rooted in the structure. The structures of both sulfur and selenium exhibit eight-atom rings that pack together in various orientations to form their respective crystals. For one, because these crystals (and presumably their alloys as well) feature multiple polymorphs such that their structural coherence is rather unclear. Secondly, these are also relatively large systems (32 atoms per cell) with low-symmetry, which complicate computation both in terms of accuracy and efficiency. Thirdly, such semi-molecular, semi-crystalline structures lead to a combination of band-transport characteristics and hopping-transport characteristics, each of which is a domain with its own physics and set of computational, theoretical challenges. In addition, there is a general dearth of experimental transport data for sulfur-selenium alloys. In this study, we make a comprehensive attempt to tackle this problem using a wide array of first-principles methods. We generate special quasirandom structures to simulate alloy structures, and compute their first-principles Raman spectra for comparison with experimental data to ensure their structural soundness. We then proceed to use recently developed, state-of-the-art tool (AMSET) in order to efficiently compute electronic mobilities under band transport of pure sulfur, pure selenium, as well as their alloys of various compositions at a reasonable accuracy. We then sample numerous dimer configurations of nearest-neighbor eight-atom-ring-pairs and compute electronic hopping rates between them, which yields hopping mobility. A combination of these efforts lead to a general mapping of electron transport behaviors throughout the alloy range. Preliminary results show that introduction of selenium into sulfur initially damages electron mobility due to disorder but eventually improves it beyond that of pure sulfur with additional selenium content, ultimately peaking at the pure-selenium limit. Band transport dominates for holes in sulfur and electrons in selenium, but in all other cases, hopping transport is dominant. Ongoing efforts include determination of charge concentration and conductivity, as well as performing multiphysics modeling to determine the optimum selenium content for best tradeoff between conductivity and energy density for aircraft range.

Junsoo Park↗
NASA NTRSDate not supplied

Idunn Mons as the landing site of the Venera-D mission: scientific relevance and possible operational tests on Mount Etna.

Along with the recently selected NASA DAVINCI [1] and VERITAS [2] missions, and with the ESA EnVision mission [3], the Roscosmos Venera-D mission [4,5] opens the new decade of Venus exploration. Among these missions, the Venera-D is the only one to be equipped with a lander which could drill the surface of Venus and analyze its chemical composition. For this reason, it is crucial to select a future landing site based on its scientific relevance, as well as on safety constraints. We propose here Idunn Mons (Figure 1a), a major large volcano of Imdr Regio, as the landing site for the Venera-D mission. We also indicate Mount Etna in Italy (Figure 1b) as a suitable test site on Earth for drilling tests and in-situ elemental and mineralogical analyses [6,7].

venus↗
NASA NTRS2004

Abstraction and Assume-Guarantee Reasoning for Automated Software Verification

Compositional verification and abstraction are the key techniques to address the state explosion problem associated with model checking of concurrent software. A promising compositional approach is to prove properties of a system by checking properties of its components in an assume-guarantee style. This article proposes a framework for performing abstraction and assume-guarantee reasoning of concurrent C code in an incremental and fully automated fashion. The framework uses predicate abstraction to extract and refine finite state models of software and it uses an automata learning algorithm to incrementally construct assumptions for the compositional verification of the abstract models. The framework can be instantiated with different assume-guarantee rules. We have implemented our approach in the COMFORT reasoning framework and we show how COMFORT out-performs several previous software model checking approaches when checking safety properties of non-trivial concurrent programs.

Chaki, S.↗
NASA NTRS1988

Surface compositional and structural aspects of Martian samples

There are many excellent reasons to examine the surface composition of a wide range of Martian samples. The existing spectral data indicate that many dust and soil particles have a thin Fe(+3) layer with a typical particle size in the 10 micrometer to 400 micrometer range. In view of the high CO2 content of the atmosphere, one might expect that surface carbonates should be present. In addition to chemisorbed material there will probably exist physisorbed atmospheric components of the atmosphere including oxygen, nitrogen and water vapor. The latter could possibly give rise to some hydrated minerals. Using ultra-high-vacuum/mass spectrographic techniques it should be possible to detect physisorbed and moderately strong chemisorbed species on the particle surfaces with a temperature programmed degassing procedure. In some instances such an approach is capable of helping distinguish between volcanic and impact generated materials by detecting the presence of fumerolic gases. Such gases typically condense on the exterior of the ejected particles. Additionally surface atomic and chemical compositions should be examined by a combination of modern surface analytical techniques. The combination we currently have in Buffalo at SUNY would appear to be one of the best available including ESCA (150 micrometer spot capability) Auger (SAM) with 300 A focussing for surface compositional surveys, SIMS for high sensitivity trace element detection and ISS for immediate surface layer analysis.

Cadenhead, D. A.↗
NASA NTRS2003

Electrically Conducting, Ca-Rich Brines, Rather Than Water, Expected in the Martian Subsurface

If Mars ever possessed a salty liquid hydrosphere, which later partly evaporated and froze down, then any aqueous fluids left near the surface could have evolved to become dense eutectic brines. Eutectic brines, by definition, are the last to freeze and the first to melt. If CaC12-rich, such brines can remain liquid until temperatures below 220 K, close to the average surface temperature of Mars. In the Martian subsurface, in intimate contact with the Ca-rich basaltic regolith, NaC1-rich early brines should have reacted to become Ca-rich. Fractional crystallization (freezing) and partial melting would also drive brines toward CaC12-rich compositions. In other words, eutectic brine compositions could be present in the shallow subsurface of Mars, for the same reasons that eutectic magma compositions are common on Earth. Don Juan Pond, Antarctica, a CaC12-rich eutectic brine, provides a possible terrestrial analog, particularly because it is fed from a basaltic aquifer. Owing to their relative density and fluid nature, brines in the Martian regolith should eventually become sandwiched between ice above and salts beneath. A thawing brine sandwich provides one explanation (among many) for the young gullies recently attributed to seepage of liquid water on Mars. Whether or not brine seepage explains the gullies phenomenon, dense, CaC12-rich brines are to be expected in the deep subsurface of Mars, although they might be somewhat diluted (temperatures permitting) and of variable salt composition. In any case, they should be good conductors of electricity.

Burt, D. M.↗
NASA NTRS2019

Progressive Damage and Failure Analysis of Bonded Composite Joints at High Energy Dynamic Impacts

Both wing and fuselage structures utilize bonded composite joints for structural efficiency in modern commercial and military aircraft. To ensure compliance with certification requirements mechanical fasteners are typically used as a failsafe mechanism for appropriate strength in the event of complete stiffener disbond. However, the use of fasteners decreases the structural efficiency of the structure by adding weight. This establishes the requirement to better exploit the efficiency of bonded structures and fully understand the failure behavior of adhesively bonded composite structures, particularly when subjected to elevated loading rates due to high energy dynamic impacts (HEDI). For this reason, the NASA Advanced Composite Consortium (ACC) HEDI team developed an experimentation and numerical modeling program for high rate loading of composite joints. In the present work, the response of adhesively bonded composite joints subjected to elevated loading rates is studied numerically and validated against experimental results. Due to dynamic considerations of experiments, the idea of wedge insert was extended to use with Split Hopkinson Pressure Bar (SHPB) testing techniques. Mode-I and Mode-II test configurations were simulated to evaluate the capability of two continuum damage material (CDM) models in LS-DYNA, namely MAT162 and MAT261. Three different levels of fidelity were considered to investigate the level of detail required to numerically predict the failure behavior and the results from high fidelity analysis are presented.

MAT261↗
NASA NTRS1996

Finite Element Modeling of the Thermographic Inspection for Composite Materials

The performance of composite materials is dependent on the constituent materials selected, material structural geometry, and the fabrication process. Flaws can form in composite materials as a result of the fabrication process, handling in the manufacturing environment, and exposure in the service environment to anomalous activity. Often these flaws show no indication on the surface of the material while having the potential of substantially degrading the integrity of the composite structure. For this reason it is important to have available inspection techniques that can reliably detect sub-surface defects such as inter-ply disbonds, inter-ply cracks, porosity, and density changes caused by variations in fiber volume content. Many non-destructive evaluation techniques (NDE) are capable of detecting sub-surface flaws in composite materials. These include shearography, video image correlation, ultrasonic, acoustic emissions, and X-ray. The difficulty with most of these techniques is that they are time consuming and often difficult to apply to full scale structures. An NDE technique that appears to have the capability to quickly and easily detect flaws in composite structure is thermography. This technique uses heat to detect flaws. Heat is applied to the surface of a structure with the use of a heat lamp or heat gun. A thermographic camera is then pointed at the surface and records the surface temperature as the composite structure cools. Flaws in the material will cause the thermal-mechanical material response to change. Thus, the surface over an area where a flaw is present will cool differently than regions where flaws do not exist. This paper discusses the effort made to thermo-mechanically model the thermography process. First the material properties and physical parameters used in the model will be explained. This will be followed by a detailed discussion of the finite element model used. Finally, the result of the model will be summarized along with recommendations for future work.

Bucinell, Ronald B.↗
NASA NTRS1984

Nondestructive evaluation of composite materials - A design philosophy

Efficient and reliable structural design utilizing fiber reinforced composite materials may only be accomplished if the materials used may be nondestructively evaluated. There are two major reasons for this requirement: (1) composite materials are formed at the time the structure is fabricated and (2) at practical strain levels damage, changes in the condition of the material, that influence the structure's mechanical performance is present. The fundamental basis of such a nondestructive evaluation capability is presented. A discussion of means of assessing nondestructively the material condition as well as a damage mechanics theory that interprets the material condition in terms of its influence on the mechanical response, stiffness, strength and life is provided.

Duke, J. C., Jr.↗