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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 847 records · Page 47
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

An experimental study of a three lifting surface configuration

The aerodynamic ramifications of utilizing three lifting surfaces as opposed to the conventional or canard lifting configurations have been studied on a theoretical basis by previous researchers. This paper presents an experimental investigation of various configuration modifications for an unyawed typical business jet at a Reynolds number of 1.3 million. The three surface has better lift and high-lift drag characteristics than either the canard or tail-aft configurations, but the cruise drag is more. The induced drag at cruise is highest for the canard and lowest for the tail-aft configuration. The pitching moment characteristics are somewhat between those of the canard and tail-aft configurations. A decrease in gap adversely affects the pitching moment characteristics. A smaller stagger leads to better aerodynamic and stability characteristics. A decrease in span of the forward wing gives better cruise drag and longitudinal stability characteristics, but has adverse effects on high-lift drag. A variation in the incidence angles of either or both the forward and aft wings changes the zero-lift moments of the configuration, while marginally affecting overall lift and drag. At cruise, the lift to drag ratio is highest for the conventional and lowest for the three surface. For high lift conditions, the order is reversed.

Ostowari, C.↗
DOE OSTI2023

High resolution, high conductivity components by aerosol jet printing

Highly conductive electrical traces formed over mechanical steps or on non-planar surfaces with linewidths of 10 to 100 μm and a method for forming such electrical traces are disclosed. The method employs two steps, with the first step using an aerosol jet printing (AJP) process to form thin electrical traces that serve as the seed layers for the second step. The first step preferably employs multiple passes with the AJP to create multiple seed sub-layers with improved continuity and conductivity. In the second step, the seed layers are subjected to an electrodeposition process that forms the bulk of the thickness of the electrical traces. The electrodeposition process may include one, two, or three phases at corresponding low or high biases, with low biases providing denser, more highly conductive plating sub-layers, while high biases provide plating sub-layers having better gap bridging properties.

Lavin, Judith Maria↗
NASA NTRS1977

Aerodynamics of a finite aspect ratio jet flap at low flight speeds

A theoretical treatment of inviscid incompressible flow over a thin wing equipped with a part-span jet flap is given; the treatment is capable of describing low-speed flight regimes where nonlinear problems may be significant. The induced flow fields of the jet and the wing are characterized separately, and a fully coupled solution is reached through iteration. A lifting surface theory is employed for the wing aerodynamics, and the vorticity associated with the jet is also taken into account. Calculations are presented for the case of a rectangular wing. Comparisons with existing linear or nonlinear theories and experimental data suggest that the treatment is capable of accurate analyses in situations involving small angles of attack, jet deflection angles and jet momentum coefficients. In addition, the theory may be a better means of evaluating subsidiary aerodynamic variables, such as downwash aft of the wing, than existing treatments.

Addessio, F. L.↗
NASA NTRS2013

Methodology for Flight Relevant Arc-Jet Testing of Flexible Thermal Protection Systems

A methodology to correlate flight aeroheating environments to the arc-jet environment is presented. For a desired hot-wall flight heating rate, the methodology provides the arcjet bulk enthalpy for the corresponding cold-wall heating rate. A series of analyses were conducted to examine the effects of the test sample model holder geometry to the overall performance of the test sample. The analyses were compared with arc-jet test samples and challenges and issues are presented. The transient flight environment was calculated for the Hypersonic Inflatable Aerodynamic Decelerator (HIAD) Earth Atmospheric Reentry Test (HEART) vehicle, which is a planned demonstration vehicle using a large inflatable, flexible thermal protection system to reenter the Earth's atmosphere from the International Space Station. A series of correlations were developed to define the relevant arc-jet test environment to properly approximate the HEART flight environment. The computed arcjet environments were compared with the measured arc-jet values to define the uncertainty of the correlated environment. The results show that for a given flight surface heat flux and a fully-catalytic TPS, the flight relevant arc-jet heat flux increases with the arc-jet bulk enthalpy while for a non-catalytic TPS the arc-jet heat flux decreases with the bulk enthalpy.

Mazaheri, Alireza↗
NASA NTRS1993

Electromagnetically driven relativistic jets - A class of self-consistent numerical solutions

We explore the generalized Grad-Shafranov (GS) equation (Lovelace et al. 1986), which describes the cross-field balance of the magnetic flux surfaces in a stationary, axisymmetric, cold relativistic MHD wind. We construct a family of self-consistent, jet-type, non-self-similar solutions in which flux surfaces thread the equatorial plane vertically and are eventually collimated into nested cylinders. These solutions conserve the total energy and angular momentum along each flux surface and satisfy the relativistic GS equation in the cross-field direction. We find that the total specific energy in the flow depends primarily on a dimensionless combination of the poloidal magnetic flux, the rotation, and the mass loading rate, which reduces to Michel's (1969) magnetization parameter for radial winds. The final width of the flow and its ratio of kinetic energy flux to Poynting flux depend sensitively on the pressure distribution of the ambient medium, which is required to contain the jet at its outer edge when no jet-confirming external toroidal magnetic field is present. Furthermore, we show that the magnetic pressure in the flow can be much higher near the axis than close to the edge, reflecting the 'pinching' effect of the toroidal magnetic field.

Li, Zhi-Yun↗
NASA NTRS1977

Static, noise, and transition tests of a combined-surface-blowing V/STOL lift/propulsion system

Efficient thrust vectoring and high levels of circulatory lift were obtained in tests of a half model V/STOL airplane by using a type of externally blown jet flap in which the jet exhaust from wing-mounted cruise fans is directed over both upper and lower surfaces of a flapped wing. Approximately 90% thrust recovery with 87 deg of thrust vectoring was achieved under static conditions using 89 deg of trailing edge flap deflection. The approximately 10% loss appears to be associated primarily with pressure losses due to the flap brackets or slot entries. The jet induced lift was shown to be 55% of the theoretical value for a fullspan jet-flapped wing, even though only 27.5% of the wingspan was immersed in the jet. Steady rate of descent capability in excess of 1,000 feet per minute is predicted. The possibility of significant aerodynamic-noise cancelling when blowing over both surfaces at high velocities is indicated.

Schoen, A. H.↗
NASA NTRS1976

An analytical study of noise generation by subsonic flows in the presence of rigid surfaces

A general analytical method is developed for determination of the radiated noise field from highly sheared, subsonic flows in the presence of rigid surfaces. The method is specifically formulated to use measurable flow field properties as the basis input data for calculations. The governing equations of a viscous, incompressible fluid are employed to determine approximately the so-called shear noise source strength distribution in the flow. Mean rates of strain and fluctuating velocity covariances are the fundamental input data for calculations. The method is applied to the wall jet region of a circular jet impinging at 45 deg to an infinite plane surface. Velocity field measurements of Foss are used to describe the required flow properties. Comparisons of calculated results with measured surface pressures and sound pressure levels are given and discussed.

Wooley, J. P.↗
NASA NTRS2015

The Prediction of Scattered Broadband Shock-Associated Noise

A mathematical model is developed for the prediction of scattered broadband shock-associated noise. Model arguments are dependent on the vector Green's function of the linearized Euler equations, steady Reynolds-averaged Navier-Stokes solutions, and the two-point cross-correlation of the equivalent source. The equivalent source is dependent on steady Reynolds-averaged Navier-Stokes solutions of the jet flow, that capture the nozzle geometry and airframe surface. Contours of the time-averaged streamwise velocity component and turbulent kinetic energy are examined with varying airframe position relative to the nozzle exit. Propagation effects are incorporated by approximating the vector Green's function of the linearized Euler equations. This approximation involves the use of ray theory and an assumption that broadband shock-associated noise is relatively unaffected by the refraction of the jet shear layer. A non-dimensional parameter is proposed that quantifies the changes of the broadband shock-associated noise source with varying jet operating condition and airframe position. Scattered broadband shock-associated noise possesses a second set of broadband lobes that are due to the effect of scattering. Presented predictions demonstrate relatively good agreement compared to a wide variety of measurements.

Miller, Steven A. E.↗
NASA NTRS2012

Emission Spectroscopy and Radiometric Measurements in the NASA Ames IHF Arc Jet Facility

Plasma diagnostic measurement campaigns in the NASA Ames Interaction Heating Facility (IHF) have been conducted over the last several years with a view towards characterizing the flow in the arc jet facility by providing data necessary for modeling and simulation. Optical emission spectroscopy has been used in the plenum and in the free jet of the nozzle. Radiation incident over a probe surface has also been measured using radiometry. Plenum measurements have shown distinct radial profiles of temperature over a range of operating conditions. For cases where large amounts of cold air are added radially to the main arc-heated stream, the temperature profiles are higher by as much as 1500 K than the profiles assumed in flow simulations. Optical measurements perpendicular to the flow direction in the free jet showed significant contributions to the molecule emission through inverse pre-dissociation, thus allowing determination of atom number densities from molecular emission. This has been preliminarily demonstrated with the N2 1st Positive System. Despite the use of older rate coefficients, the resulting atom densities are reasonable and surprisingly close to flow predictions.

Winter, Michael W.↗
DOE OSTI2022

Seasonally and Regionally Dependent Shifts of the Atmospheric Westerly Jets under Global Warming

A distinct feature of the atmospheric circulation response to increasing greenhouse gas forcing is the poleward shift of the zonal-mean westerly jet. The dynamical mechanisms of the zonal-mean poleward jet shift have been extensively studied in literature. At seasonal/regional scales, however, the westerly jets can shift equatorward, such as in the early-summer Asia–Pacific region, the late-winter America–Atlantic region, and the winter/spring east Pacific. These equatorward jet shifts imply climate impacts distinct from those of the poleward shifts, yet their causes are not well understood. In this work, based on a hierarchy of coupled, prescribed-SST, and aquaplanet simulations, we attribute the seasonal/regional equatorward jet shifts to the enhanced tropical upper-level warming (ETUW), which arises from both the tropical moist adiabat and the enhanced equatorial surface warming. By steepening the meridional temperature gradient in the subtropical upper-to-middle level and assisted by positive eddy feedback, the ETUW increases the zonal wind equatorward of the climatological jet. When the regional/seasonal meridional temperature gradients (or equivalently the westerly jets) are weak and peak close to the tropics, the ETUW effect overcomes the poleward jet-shift mechanisms and leads to the equatorward jet shifts. This climatological-state dependency is consistently seen in the decomposed jet responses to uniform warming and surface warming pattern, and further demonstrated through idealized aquaplanet experiments with designed climatological states. For uniform warming, the ETUW arising from moist adiabat makes the general poleward jet shifts insignificant in the aforementioned favorable regions/seasons. For warming pattern, the ETUW from enhanced equatorial warming drives substantial equatorward jet shifts in these favorable seasons/regions.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Air‐Ice‐Ocean Coupling During a Strong Mid‐Winter Cyclone: Observing Coupled Dynamic Interactions Across Scales

Abstract Arctic cyclones are key drivers of sea ice and ocean variability. During the 2019–2020 Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition, joint observations of the coupled air‐ice‐ocean system were collected at multiple spatial scales. Here, we present observations of a strong mid‐winter cyclone that impacted the MOSAiC site as it drifted in the central Arctic pack ice. The sea ice dynamical response showed spatial structure at the scale of the evolving and translating cyclonic wind field. Internal ice stress and ocean stress play significant roles, resulting in timing offsets between the atmospheric forcing and the ice response and post‐cyclone inertial ringing in the ice and ocean. Ice motion in response to the wind field then forces the upper ocean currents through frictional drag. The strongest impacts to the sea ice and ocean from the passing cyclone occur as a result of the surface impacts of a strong atmospheric low‐level jet (LLJ) behind the trailing cold front and changing wind directions between the warm‐sector LLJ and post cold‐frontal LLJ. Impacts of the cyclone are prolonged through the coupled ice‐ocean inertial response. Local impacts of the approximately 120 km wide LLJ occur over a 12 hr period or less and at scales of a kilometer to a few tens of kilometers, meaning that these impacts occur at combined smaller spatial scales and faster time scales than most satellite observations and coupled Earth system models can resolve.

Meteorology & Atmospheric Sciences↗
DOE OSTI2021

Tuning plasma parameters to control reactive species fluxes to substrates in the context of plasma catalysis

The key reactive plasma-produced gas phase species responsible for the enhanced conversion of chemicals in plasma catalysis compared to thermal catalysis have to date not been identified. This outstanding question is mainly due to the inherent large variety of plasma-produced species and the challenge of controlling and measuring the flux of each constituent of the cocktail of reactive species to a (catalytic) substrate. In this paper, we explore the possibility to control the dominant reactive species fluxes, relevant for plasma-catalysis, to a substrate in the effluent of an RF driven Ar-O 2 plasma jet. The absolute species densities of the major reactive species (O, O 2 (a 1 Δ g ), O 3 and ions) were quantified by molecular beam mass spectrometry (MBMS) to assess the possibility of using treatment distance, O 2 admixture concentration, plasma dissipated power, RF modulation frequency and duty cycle as well as the feed gas flow rate to alter the dominant species densities. Selected experimental results were also compared with a pseudo-1D plug flow model. The short-lived and long-lived species can be effectively separated by changing the treatment distance and the RF modulation frequency. Furthermore, adjusting the O 2 admixture concentration enables to change the ratio of the O 2 (a 1 Δ g ) and O 3 density. The changes in the trend of ion and O flux were found to be very similar for nearly all investigated parameters. Nonetheless the gas flow rate was able to significantly change the ratio of the O and ion density in the plasma jet effluent. Here, the impact of the surface-dependent loss probability and boundary layer reactions on the species flux to a substrate and how this qualitatively relates to the MBMS density measurements is further addressed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Upgrading biocrude oil into sustainable aviation fuel using zeolite-supported iron-molybdenum carbide nanocatalysts

Food waste is an underdeveloped source for production of sustainable aviation fuel (SAF). Now, there is no certified conversion process of food waste for SAF by American Society for Testing and Materials (ASTM). We report the use of zeolite-supported molybdenum carbide nanocatalysts in upgrading biocrudes, produced from food wastes through HTL, into SAF precursors. Our data show a complete removal of oxygen from the biocrude through hydrodeoxygenation and a higher heating value of 46.5 MJ/kg, which is comparable to that of Jet A (46.1 MJ/kg). The prescreening tests (tier alpha and beta) show the average carbon number of the distillation cut (150° to 230°C) of upgraded fuel is 10.6, close to the value of 11.4 for average conventional jet fuel, and the specifications of properties including surface tension, viscosity, heating value, flash point, and freezing point were found to meet the standards of SAF. The metal carbide nanocatalysts were reusable in upgrading tests, and the activity of deoxygenation was retained.

10 SYNTHETIC FUELS↗