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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

Extending Our Understanding of Compliant Thermal Barrier Performance

Thermal barriers and seals are integral components in the thermal protection systems (TPS) of nearly all aerospace vehicles. They are used to minimize the flow of hot gases through interfaces and protect underlying temperature-sensitive components and systems. Although thermal barriers have been used extensively on many aerospace vehicles, the factors affecting their thermal and mechanical performance are not well-understood. Because of this, vehicle TPS designers are often left with little guidance on how to properly design and optimize these barriers. An ongoing effort to better understand thermal barrier performance and develop models and design tools is in progress at the NASA Glenn Research Center. Testing has been conducted to understand the degree to which insulation density influences structural performance and permeability. In addition, the development of both thermal and mechanical models is ongoing with the goal of providing an improved ability to design and implement these critical TPS components.

high temperature↗
DOE OSTI2020

Operation and turndown of a segmented annular combustion system

The present disclosure is directed to the operation and turndown of a segmented annular combustion system. The method includes injecting, via a fuel nozzle, a combustible mixture into a primary combustion zone between an adjacent pair of integrated combustor nozzles and burning the combustible mixture. The method further includes flowing air and injecting fuel into a premixing channel defined within a first integrated combustor nozzle to produce a second combustible mixture. The second combustible mixture is injected into a secondary combustion zone where it is combusted. The flow of combustion gases is accelerated, via turbine nozzles of the integrated combustor nozzles, toward turbine blades of a downstream turbine section. The method permits turndown of the combustion system by reducing or shutting off fuel to various components of the combustion system.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2023

Device and method for improving specific energy requirement of plasma pyrolyzing or reforming systems

Devices and methods for reducing the specific energy required to reform or pyrolyze reactants in plasmas operating at high flow rates and high pressures are presented. These systems and methods include 1) introducing electrons and/or easily ionized materials to a plasma reactor, 2) increasing turbulence and swirl velocity of the flows of feed gases to have improved mixing in a plasma reactor, and 3) reducing slippage from a plasma reactor system. Such plasma systems may allow plasma reactors to operate at lower temperatures, higher pressure, with improved plasma ignition, increased throughput and improved energy efficiency. In preferred embodiments, the plasma reactors are used to produce hydrogen and carbon monoxide, hydrogen and carbon, or carbon monoxide through reforming and pyrolysis reactions. Preferred feedstocks include methane, carbon dioxide, and other hydrocarbons.

Bromberg, Leslie↗
NASA NTRS1974

Flow properties in expansion tube with helium, argon, air, and CO2

Test flow velocities from 5 to 7 km/sec were generated in a 6-in. expansion tube using helium, argon, air, and CO2 test gases. Pitot pressure profiles across the flow at the test section are presented for the four test gases, and measured flow quantities are compared to computer predicted values. Comparison of predicted and measured flow quantities suggests the expansion to be near thermochemical equilibrium for all test gases and implies the existence of a totally reflected shock at the secondary diaphragm. Argon, air, and CO2 flows were observed to attenuate while traversing the acceleration section, whereas no attenuation was observed for helium.

Miller, C. G.↗
NASA NTRS2005

Bifunctional catalytic electrode

The present invention relates to an oxygen electrode for a unitized regenerative hydrogen-oxygen fuel cell and the unitized regenerative fuel cell having the oxygen electrode. The oxygen electrode contains components electrocatalytically active for the evolution of oxygen from water and the reduction of oxygen to water, and has a structure that supports the flow of both water and gases between the catalytically active surface and a flow field or electrode chamber for bulk flow of the fluids. The electrode has an electrocatalyst layer and a diffusion backing layer interspersed with hydrophilic and hydrophobic regions. The diffusion backing layer consists of a metal core having gas diffusion structures bonded to the metal core.

Cisar, Alan↗
NASA NTRS1985

Carbon films grown from plasma on III-V semiconductors

Dielectric carbon films were grown on n- and p-type GaAs and InP substrates using plasmas generated at 30 KHz from gaseous hydrocarbons. The effect of gas source, flow rate, and power on film growth were investigated. Methane and n-butane gases were utilized. The flow rate and power ranged from 30 to 50 sccm and 25 to 300 W, respectively. AES measurements show only carbon to be present in the films. The relative Ar ion sputtering rate (3 KeV) of carbon depends on the ratio power/pressure. In addition, the degree of asymmetry associated with the carbon-semiconductor interface is approximately power-independent. SIMS spectra indicate different H-C bonding configurations to be present in the films. Band gaps as high as 3.05 eV are obtained from optical absorption studies.

Pouch, J. J.↗
NASA NTRS1990

Model gases for the detailed study of microscopic chemical nonequilibrium in diatomic gas flows

It is shown that chlorine (Cl2) and iodine (I2) are suitable model diatomic gases to use in theoretical studies of chemical nonequilibrium that account for rotational and vibrational as well as electronic processes in a gas. Because of the low temperature at which significant dissociation can be achieved in iodine, it is a particularly attractive candidate for the study of relatively low temperature chemically reacting flows, permitting detailed knowledge of the nonequilibrium populations of translational, rotational, vibrational and electronic energy levels. A preliminary investigation indicates that a useful iodine flow facility can be constructed and that diagnostic techniques are available to validate in detail prediction techniques for nonequilibrium flows.

Kunc, Joseph A.↗
NASA NTRS2014

Spectroscopic Measurement Techniques for Aerospace Flows

The conditions that characterize aerospace flows are so varied, that a single diagnostic technique is not sufficient for its measurement. Fluid dynamists use knowledge of similarity to help categorize and focus on different flow conditions. For example, the Reynolds number represents the ratio of inertial to viscous forces in a flow. When the velocity scales, length scales, and gas density are large and the magnitude of the molecular viscosity is low, the Reynolds number becomes large. This corresponds to large scale vehicles (e.g Airbus A380), fast moving objects (e.g. artillery projectiles), vehicles in dense fluids (e.g. submarine in water), or flows with low dynamic viscosity (e.g. skydiver in air). In each of these cases, the inertial forces dominate viscous forces, and unsteady turbulent fluctuations in the flow variables are observed. In contrast, flows with small length scales (e.g. dispersion of micro-particles in a solid rocket nozzle), slow moving objects (e.g. micro aerial vehicles), flows with low density gases (e.g. atmospheric re-entry), or fluids with a large magnitude of viscosity (e.g. engine coolant flow), all have low Reynolds numbers. In these cases, viscous forces become very important and often the flows can be steady and laminar. The Mach number, which is the ratio of the velocity to the speed of sound in the medium, also helps to differentiate types of flows. At very low Mach numbers, acoustic waves travel much faster than the object, and the flow can be assumed to be incompressible (e.g. Cessna 172 aircraft). As the object speed approaches the speed of sound, the gas density can become variable (e.g. flow over wing of Learjet 85). When the object speed is higher than the speed of sound (Ma > 1), the presences of shock waves and other gas dynamic features can become important to the vehicle performance (e.g. SR-71 Blackbird). In the hypersonic flow regime (Ma > 5), large changes in temperature begin to affect flow properties, causing real-gas effects to occur (e.g. X-43 Scramjet). At even higher Mach numbers, chemistry and nonequilibrium effects come into play (e.g. Startdust re-entry capsule), further complicating the measurement. These limits can be predicted by calculating the ratio of chemical and thermal relaxation time to the flow time scales. Other non-dimensional numbers can be used to further differentiate types of aerospace flows.

Danehy, Paul M.↗
NASA NTRS1985

Pool fire-ventilation crossflow experiments in a simulated aircraft cabin interior

An experimental facility has been built to study pool fire dynamics and flame spread behavior in a 1/3-scale simulated aircraft interior; attention is presently given to pool fire ventilation crossflow using a 'channel' pool fire subjected to crossflow velocities that replicate postcrash conditions in a wide body aircraft. Crossflow velocity is noted to have a strong effect on visible flame geometry, tilting the flame over sharply. A reverse flow ceiling jet of hot gases was also present in all tests, however, and extended far upstream of the fire, so that despite the appearance of the visible flame, the vertical momentum of the plume was strong enough to establish the reverse flow layer and spread smoke and toxic gases upstream against a significant ventilating flow.

Bankston, C. P.↗
NASA NTRS1976

Infrared band absorptance correlations and applications to nongray radiation

Various mathematical models for infrared radiation absorption spectra for atmospheric gases are reviewed, and continuous correlations for the total absorptance of a wide band are presented. Different band absorptance correlations were employed in two physically realistic problems (radiative transfer in gases with internal heat source, and heat transfer in laminar flow of absorbing-emitting gases between parallel plates) to study their influence on final radiative transfer results. This information will be applied to the study of atmospheric pollutants by infrared radiation measurement.

Tiwari, S. N.↗
NASA NTRS1972

Evaluation of advanced bladder technology

Research conducted during this period is reported. Studies presented include: (1) diffusion and permeation of CO2, O2, N2, and NO2 through polytetra fluoroethylene; (2) diffusion, permeation and solubility of simple gases (CO2, O2, N2, CH4, C2H6, C3H8, and C2H4) through a copolymer of hexafluoro propylene and tetrafluoro ethylene (FEP); (3) viscous flow and diffusion of gases throug small apertures; (4) diffusion and permeation of O2, N2, CO2, CH4, C2H6, and C3H8 through nitroso rubber; and (5) results of gas transport studies with carborane siloxane, nitroso rubber, silicone membrane, krytox coating on teflon, and FEP coated glass cloth. Publications generated under this program are listed.

Christensen, M. V.↗
DOE OSTI2024

Cosmic quenching and scaling laws for the evolution of supermassive black holes and host galaxies

ABSTRACT Observations suggest a co-evolution of supermassive black holes (SMBHs) and host galaxies. In this paper, we consider the mass and energy flow in a near-equilibrium bulge suffused by gases of varying temperatures. By assuming the rate of energy flow independent of the distance r from the bulge center and the local virial equilibrium for permeated gases on scale r, a key parameter $\varepsilon _b$ was identified that quantifies the mass and energy flow in gases and the efficiency of gas cooling (or the "specific" cooling rate per unit mass), and thus regulates the co-evolution of both SMBHs and hosts. With the help of Illustris simulations and observations, we determined the redshift variation $\varepsilon _b\propto (1+z)^{5/2}$. A higher $\varepsilon _b$ in the early Universe means a higher specific cooling rate that allows rapid evolution of SMBHs and hosts. This simple theory, characterized by a single parameter $\varepsilon _b$, provides the dominant mean cosmic evolution of SMBHs and hosts. All other transient phenomena may only contribute to the dispersion around this mean evolution. Based on this theory and relevant assumptions, scaling laws involving $\varepsilon _b$ were identified for the evolution of SMBHs and hosts. For host galaxies, the mass–size relation $M_b\propto \varepsilon _b^{2/3}r_b^{5/3}G^{-1}$, the dispersion–size relation $\sigma _b^2\propto (\varepsilon _b r_b)^{2/3}\propto (1+z)$, or the mass–dispersion relation $M_b\propto \varepsilon _b^{-1}G^{-1}\sigma _b^5$ were identified, where $r_b\propto (1+z)^{-1}$ is the bulge size. For SMBHs, three evolution phases were found involving an initial rapid growth stage with a rising luminosity $L_B\propto (\varepsilon _b M_{\rm BH})^{4/5}$, a transition stage with a declining $L_B\propto \varepsilon _b^2 M_{\rm BH} \propto (1+z)^5$, and a dormant stage with $L_B\propto (\varepsilon _b M_{\rm BH})^{4/3}$. Our results suggest a rapid initial super-Eddington growth in a short period with a new redshift-dependent luminosity limit $L_X\propto\varepsilon _b^{4/5}M_{\rm BH}^{4/5}G^{-1/5}c$, in contrast to the Eddington limit. Analytical solutions were formulated for the BH mass function $\Phi _{\rm BH}$, active galactic nucleus (AGN) mass function $\Phi _{\rm AGN}$, and duty cycle U that predict $\Phi _L\propto L^{-1/5}$ for the faint-end luminosity function, $\Phi _{\rm AGN}\propto M^{-1/5}$ for small-mass-end AGN mass function $\Phi _L$, and $U\propto M^{-1/5}$ at high redshift.

(galaxies:) quasars: supermassive black holes↗
NASA NTRS1975

A comparison of measured and predicted test flow in an expansion tube with air and oxygen test gases

Simultaneous time-resolved measurements of temperature, density, pitot pressure, and wall pressure in both air and O2 test gases were obtained in the Langley pilot model expansion tube. These tests show nonequilibrium chemical and vibrational relaxation significantly affect the test-flow condition. The use of an electromagnetic device to preopen the secondary diaphragm before the arrival of the primary shock wave resulted in an improvement in the agreement between the measured pitot pressure and the value inferred from measured density and interface velocity. Boundary-layer splitter plates used to reduce the wall boundary layer show that this disagreement in the measured and inferred pitot pressures is not a result of boundary-layer effects.

Aaggard, K. V.↗
DOE OSTI2025

Seedless nonresonant gas-flow velocimetry with single-shot coherent Rayleigh-Brillouin scattering

We demonstrate neutral gas-flow velocimetry by exploiting the optical dipole forces exerted by precisely tailored high-intensity laser fields on polarizable particles, in the form of single-shot coherent Rayleigh-Brillouin scattering (CRBS). This enables mapping of the velocity distribution function of the particles in a single laser shot of approximately 200 ns duration, allowing us to perform spectroscopic measurements in the time, rather than the frequency, domain. Importantly, CRBS results in a coherent signal beam, which renders the technique ideal for measurements in optically noisy environments. By correlating the time shift of the resulting spectrum to the Doppler shift caused by the bulk motion of particles, we perform neutral gas-flow velocimetry without the need to seed the flow, nondestructively, for a variety of gases, atomic or molecular. We demonstrate gas-flow velocimetry at flow velocities as low as 1 m ⁢s −1 , with similar velocity resolution, while temperature and gas density can also be estimated from the same single-shot spectra. To prove the effectiveness of the measurement technique, we benchmark it against Pitot tube measurements, which show excellent agreement.

Gerakis, Alexandros [Luxembourg Institute of Scien↗