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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 1,603 records · Page 89
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Secondhand Exposure to Simulated Cannabis Vaping Aerosols

Emissions from cannabis vaping degrade indoor air quality and expose non-users to secondhand pollutants. We investigated how the vaping mixture composition affects indoor aerosol characteristics and exposures. Simulated cannabis vaping aerosol was produced by flash evaporation in a 20 m3 chamber of mixtures containing terpenoids, cannabinoids, cannabis extract constituents, and the adulterant vitamin E acetate (VEA). Aerosol time- and size-resolved concentrations (8 nm-2.5 μm at 1 Hz) were measured, and a dosimetry model was used to evaluate the intake of secondhand aerosols. The results showed peak particle number (PN) concentrations between 0.7 × 106 and 13 × 106 cm-3 and peak mass concentration (PM1.0) between 65 and 1191 μg m-3 at t = 5 min after emission. Concentrations decreased to 21-57% of peak PN and 33-69% of peak PM1.0 at t = 60 min. The PM1.0 yield was 0.06 for a terpenoid-only mixture, 0.22-0.36 for tetrahydrocannabinol (THC)-terpenoid mixtures, and >1 for mixtures containing high concentrations of cannabidiol (CBD) or VEA. For intake deposition, the highest aerosol fraction was deposited in the pulmonary region, followed by the tracheobronchial and head regions. Deposition increased in the presence of THC, CBD, or VEA, with aerosols <100 nm contributing the majority of particles deposited in all regions.

Tang, Xiaochen↗
NASA NTRS1962

Jet Interference Effects on a Model of a Single-Engine Four Jet V/STOL Airplane at Mach Numbers from 0.60 to 1.00

An investigation was conducted in the Langley 16-foot transonic tunnel to determine the interference from four exhaust jets on the aerodynamic characteristics of a model of a V/STOL airplane. The single- engine four-jet turbofan power plant of the airplane was simulated by inducing tunnel airflow through two large side inlets and injecting the decomposition products of hydrogen peroxide into the internal flow. The heated gas mixture was exhausted through four nozzles located on the sides of the fuselage under the wing, two near the wing leading edge and two forward of the trailing edge; the nozzles were deflected downward 1.5 deg and outward 5.0 deg to simulate cruise conditions. The wing of the model was a clipped delta with leading-edge sweep of 40 deg, aspect ratio of 3.06, taper ratio of 0.218, thickness-chord ratio of 0.09 at the root and 0.07 at the tip, and 10 deg negative dihedral. Aerodynamic and longitudinal stability coefficients were obtained for the model with the tail removed, and for horizontal-tail incidences of 0 deg and -5 deg. Data were obtained at Mach numbers from 0.60 to 1.00, angles of attack from 0 deg to 12 deg, and with jet total-pressure ratios up to 3.1. Jet operation generally caused a decrease in lift, an increase in pitching-moment coefficient, and a decrease in longitudinal stability at subsonic speeds. The jet interference effects on drag were detrimental at a Mach number of 0.60 and favorable at higher speeds for cruising-flight attitudes.

Schmeer, James W.↗
NASA NTRS2002

Multiple Component Event-Related Potential (mcERP) Estimation

We show how model-based estimation of the neural sources responsible for transient neuroelectric signals can be improved by the analysis of single trial data. Previously, we showed that a multiple component event-related potential (mcERP) algorithm can extract the responses of individual sources from recordings of a mixture of multiple, possibly interacting, neural ensembles. McERP also estimated single-trial amplitudes and onset latencies, thus allowing more accurate estimation of ongoing neural activity during an experimental trial. The mcERP algorithm is related to informax independent component analysis (ICA); however, the underlying signal model is more physiologically realistic in that a component is modeled as a stereotypic waveshape varying both in amplitude and onset latency from trial to trial. The result is a model that reflects quantities of interest to the neuroscientist. Here we demonstrate that the mcERP algorithm provides more accurate results than more traditional methods such as factor analysis and the more recent ICA. Whereas factor analysis assumes the sources are orthogonal and ICA assumes the sources are statistically independent, the mcERP algorithm makes no such assumptions thus allowing investigators to examine interactions among components by estimating the properties of single-trial responses.

Knuth, K. H.↗
DOE OSTI2021

Effects of non-thermal termolecular chemistry on detonation development in hydrogen (H2) / methane (CH4) - air mixtures

In combustion simulations, it is usually assumed that highly-energized collision complexes (either radical or stable species) formed in exothermic reactions are always under thermal equilibrium as they evolve through competing networks of reactions. However, in practical flames, non-trivial amounts of reactive radicals such as H, O and OH are present apart from O2. As a result, collisions of these reactive species with the energized collision complexes have been shown in recent studies to induce non-thermal reactivity. These studies have also demonstrated that such non-thermal reactions can be suitably represented in macroscopic kinetics models as chemically termolecular reactions. The present work was focused on identifying and quantifying the effects of including such reactions on the evolution of an initial deflagration front to a developing detonation in H2/CH4-air mixtures under boosted internal combustion (IC) engine conditions. Specifically, fully resolved simulations, with and without non-thermal reactivity, were performed for a constant volume reactor containing stoichiometric H2/CH4-air mixture. It was found that inclusion of termolecular chemistry resulted in a delayed onset of end-gas auto-ignition. Concurrently, the developing detonation intensity was observed to be significantly higher. Chemical explosive mode analysis (CEMA) was performed to identify the dominant species/reactions responsible for the observed variation in the results.

Detonation↗
DOE OSTI2020

Experimental and numerical investigation of sands and Geldart A biomass co-fluidization

This study investigated the fluidization of sands and small Geldart A biomass mixtures. The mixture fluidized like Geldart A type particles with a uniform bed expansion regime before bubbling. The video recorded color distance between pure sands and sands–biomass mixtures was used to estimate the sands–biomass mixing. The coarse-grained computational fluid dynamics–discrete element method with a hybrid drag model which couples the Syamlal–O'Brien drag and a filtered drag can capture the mixing while the simulation with Gidaspow drag predicted a segregated bed. The simulations were further validated with experimental measured pressure drops. The time averaged pressure drop equals the weight of the bed material, however, its fluctuation is about three times of the bed material fluctuation.

42 ENGINEERING↗
DOE OSTI2024

Segmentation of RDX and TNT in X‐Ray Computed Tomography Reconstructions of Melt‐Cast Explosives

ABSTRACT Three‐dimensional mesoscale characterization of heterogeneous melt‐cast high explosives is challenging because of the difficulty differentiating binder from explosive crystals: two functionally different materials which are typically similar in density by design. Here, we report an algorithm which can differentiate hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX) from 2,4,6‐trinitrotoluene (TNT) in x‐ray computed tomography (CT) volumes with tens of microns resolution. This method allows us to quantify RDX/TNT content, porosity, and RDX domain size. We calibrated the segmentation algorithm using simulated x‐ray CT volumes containing object models of RDX crystals within a TNT matrix. We then segmented and analyzed CT data for Composition B (Comp B), a 60/40 RDX/TNT mixture, and Cyclotol, a 75/25 RDX/TNT mixture. We examined melt‐cast samples fabricated with 100% theoretical maximum density (TMD) and 85% TMD. For the 100% TMD Comp B and Cyclotol samples, the RDX content values calculated by segmentation were 3% and 9% lower, respectively, than the values measured by high‐performance liquid chromatography on material from the same synthesis lots. This result is consistent with the expected underreporting of RDX content resulting from x‐ray CT resolution limits on RDX particles with diameters smaller than 25 µm. The 85% TMD samples were less accurately segmented with our algorithm due to the confounding presence of voids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Plasma processing of SRF cavities at Jefferson Lab: Experiment results and simulation insight

Plasma processing of superconducting radio frequency (SRF) cavities has been an active research effort at Jefferson Lab (JLab) since 2019, aimed at enhancing cavity performance by removing hydrocarbon contaminants and reducing field emission. In this experiment, processing using argon-oxygen and helium-oxygen gas mixtures to find minimum ignition power at different cavity pressure was investigated. Ongoing simulations are contributing to a better understanding of the plasma surface interactions and the fundamental physics behind the process. These simulations, combined with experimental studies, guide the optimization of key parameters such as gas type, RF power, and pressure to ignite plasma using selected higher-order mode (HOM) frequencies. This paper presents experimental data from argon-oxygen and helium-oxygen gas mixture C75 and C100 cavity plasma ignition studies, as well as simulation results for the C100-type cavity based on the COMSOL model previously applied to the C75 cavity.

Accelerator Physics↗
NASA NTRS1973

An injector design model for predicting rocket engine performance and heat transfer

A model is formulated for estimating the performance and chamber heat transfer in rocket injectors/chambers operating with gaseous H2-O2 propellants. The model quantifies the combustion performance and chamber heat flux for variables such as chamber length, element type, element area ratio, impingement angle, thrust/element, mixture ratio, moment ratio, element spacing, and physical size. Design equations are given and curves are plotted for evaluation of combustion performance in injectors comprised of F-O-F triplet, premix, coaxial and swirl coaxial element types. Curve plots and equations are also included for estimation of the chamber wall heat fluxes generated by these element types.

Calhoon, D. F.↗
NASA NTRS1980

User's guide for the computer code COLTS for calculating the coupled laminar and turbulent flow over a Jovian entry probe

A user's guide for a computer code 'COLTS' (Coupled Laminar and Turbulent Solutions) is provided which calculates the laminar and turbulent hypersonic flows with radiation and coupled ablation injection past a Jovian entry probe. Time-dependent viscous-shock-layer equations are used to describe the flow field. These equations are solved by an explicit, two-step, time-asymptotic finite-difference method. Eddy viscosity in the turbulent flow is approximated by a two-layer model. In all, 19 chemical species are used to describe the injection of carbon-phenolic ablator in the hydrogen-helium gas mixture. The equilibrium composition of the mixture is determined by a free-energy minimization technique. A detailed frequency dependence of the absorption coefficient for various species is considered to obtain the radiative flux. The code is written for a CDC-CYBER-203 computer and is capable of providing solutions for ablated probe shapes also.

Kumar, A.↗
NASA NTRS1982

Lunar anorthosite 60025, the petrogenesis of lunar anorthosites, and the composition of the moon

The mineral chemistry of the lunar anorthosite 60025 is investigated, and a model for the differentiation of the moon is proposed based on these findings. Among other results, it is concluded that 60025 is a mixture of pieces from a related sequence of anorthosites, and that this sequence was generated by near-perfect accumulate growth during strong fractional crystallization. The parent liquid of the most primitive anorthosite was saturated with olivine, plagioclase, pigeonite, and chromite, and evolved to one saturated with plagioclase, pigeonite, high-Ca clinopyroxene, and ilmenite. The steep slope of anorthosites on an Mg (mafics) vs. Ab (plagioclase) diagram is a result of the very low alkali content of the magma and of the original magma ocean. The bulk moon had low Al2O3, a sub-chondritic Ca/Al ratio, and REE abundances and patterns which were probably close to chondritic. In addition, mare basalt sources were found to be too magnesian and some contain too much high Ca clinopyroxene to be directly or simply complementary to a floated anorthosite crust.

Ryder, G.↗
NASA NTRS1983

A comprehensive model to determine the effects of temperature and species fluctuations on reaction rates in turbulent reacting flows

Reaction rates in turbulent, reacting flows are reviewed. Assumed probability density functions (pdf) modeling of reaction rates is being investigated in relation to a three variable pdf employing a 'most likely pdf' model. Chemical kinetic mechanisms treating hydrogen air combustion is studied. Perfectly stirred reactor modeling of flame stabilizing recirculation regions was used to investigate the stable flame regions for silane, hydrogen, methane, and propane, and for certain mixtures thereof. It is concluded that in general, silane can be counted upon to stabilize flames only when the overall fuel air ratio is close to or greater than unity. For lean flames, silane may tend to destabilize the flame. Other factors favoring stable flames are high initial reactant temperatures and system pressure.

Goldstein, D.↗
NASA NTRS1983

The structure of evaporating and combusting sprays: Measurements and predictions

The structure of particle-laden jets and nonevaporating and evaporating sprays was measured in order to evaluate models of these processes. Three models are being evaluated: (1) a locally homogeneous flow model, where slip between the phases is neglected and the flow is assumed to be in local thermodynamic equilibrium; (2) a deterministic separated flow model, where slip and finite interphase transport rates are considered but effects of particle/drop dispersion by turbulence and effects of turbulence on interphase transport rates are ignored; and (3) a stochastic separated flow model, where effects of interphase slip, turbulent dispersion and turbulent fluctuations are considered using random sampling for turbulence properties in conjunction with random-walk computations for particle motion. All three models use a k-e-g turbulence model. All testing and data reduction are completed for the particle laden jets. Mean and fluctuating velocities of the continuous phase and mean mixture fraction were measured in the evaporating sprays.

Shuen, J. S.↗
NASA NTRS1988

High-energy continuum emission from solar flares

The properties of solar flare continuum emission at energies of greater than 300 keV have been determined from observations obtained during the 21st solar maximum by gamma-ray detectors aboard the SMM and Hinotori satellites. The temporal structure of the high-energy continuum is modeled by two-step acceleration and particle trapping. The results suggest that the very high-energy emission noted must be a mixture of pion-decay radiation and primary electron bremsstrahlung.

Vestrand, W. Thomas↗
NASA NTRS1990

A time-dependent dusty gas dynamic model of axisymmetric cometary jets

The present time-dependent, axisymmetric dusty gas dynamical model of inner cometary atmospheres solves the coupled and time-dependent equations of continuity, momentum, and energy for a gas-dust mixture between the surface of the nucleus and 100 km, using an axisymmetric 40 x 40 grid structure. A novel numerical method employing a second-order accurate Godunov-type scheme with dimensional splitting is used to solve the time-dependent pde system. It is established that a subsolar dust spike not predicted by previous calculations is generated by narrow axisymmetric jets, together with a jet cone whose opening angle depends on the jet length.

Korosmezey, A.↗
NASA NTRS2004

Symmetric normal mixtures

We consider mixture density estimation under the symmetry constraint x = Az for an orthogonal matrix A. This distributional constraint implies a corresponding constraint on the mixture parameters. Focusing on the gaussian case, we derive an expectation-maximization (EM) algorithm to enforce the constraint and show results for modeling of image feature vectors.

symmetry constraint↗
NASA NTRS2007

An Experimental Investigation of the Laminar Flamelet Concept for Soot Properties

The soot properties of round, nonbuoyant, laminar jet diffusion flames are described, based on experiments at microgravity carried out on orbit during three flights of the Space Shuttle Columbia, (Flights STS-83, 94 and 107). Experimental conditions included ethylene- and propane-fueled flames burning in still air at an ambient temperature of 300 K and ambient pressures of 35-100 kPa. Measurements included soot volume fraction distributions using deconvoluted laser extinction imaging, and soot temperature distributions using deconvoluted multiline emission imaging. Flowfield modeling based on the work of Spalding is presented. The present work explores whether soot properties of these flames are universal functions of mixture fraction, i.e., whether they satisfy soot state relationships. Measurements are presented, including radiative emissions and distributions of soot temperature and soot volume fraction. It is shown that most of the volume of these flames is bounded by the dividing streamline and thus should follow residence time state relationships. Most streamlines from the fuel supply to the surroundings are found to exhibit nearly the same maximum soot volume fraction and temperature. The radiation intensity along internal streamlines also is found to have relatively uniform values. Finally, soot state relationships were observed, i.e., soot volume fraction was found to correlate with estimated mixture fraction for each fuel/pressure selection. These results support the existence of soot property state relationships for steady nonbuoyant laminar diffusion flames, and thus in a large class of practical turbulent diffusion flames through the application of the laminar flamelet concept.

Diez, F. J.↗
NASA NTRS2006

Advanced Chemical Propulsion

Advanced Chemical Propulsion (ACP) provides near-term incremental improvements in propulsion system performance and/or cost. It is an evolutionary approach to technology development that produces useful products along the way to meet increasingly more demanding mission requirements while focusing on improving payload mass fraction to yield greater science capability. Current activities are focused on two areas: chemical propulsion component, subsystem, and manufacturing technologies that offer measurable system level benefits; and the evaluation of high-energy storable propellants with enhanced performance for in-space application. To prioritize candidate propulsion technology alternatives, a variety of propulsion/mission analyses and trades have been conducted for SMD missions to yield sufficient data for investment planning. They include: the Advanced Chemical Propulsion Assessment; an Advanced Chemical Propulsion System Model; a LOx-LH2 small pumps conceptual design; a space storables propellant study; a spacecraft cryogenic propulsion study; an advanced pressurization and mixture ratio control study; and a pump-fed vs. pressure-fed study.

Alexander, Leslie, Jr.↗
NASA NTRS2016

Hot-Fire Test Results of an Oxygen/RP-2 Multi-Element Oxidizer-Rich Staged-Combustion Integrated Test Article

As part of the Combustion Stability Tool Development project funded by the Air Force Space and Missile Systems Center, the NASA Marshall Space Flight Center was contracted to assemble and hot-fire test a multi-element integrated test article demonstrating combustion characteristics of an oxygen/hydrocarbon propellant oxidizer-rich staged-combustion engine thrust chamber. Such a test article simulates flow through the main injectors of oxygen/kerosene oxidizer-rich staged combustion engines such as the Russian RD-180 or NK-33 engines, or future U.S.-built engine systems such as the Aerojet-Rocketdyne AR-1 engine or the Hydrocarbon Boost program demonstration engine. For the thrust chamber assembly of the test article, several configurations of new main injectors, using relatively conventional gas-centered swirl coaxial injector elements, were designed and fabricated. The design and fabrication of these main injectors are described in a companion paper at this JANNAF meeting. New ablative combustion chambers were fabricated based on hardware previously used at NASA for testing at similar size and pressure. An existing oxygen/RP-1 oxidizer-rich subscale preburner injector from a previous NASA-funded program, along with existing and new inter-connecting hot gas duct hardware, were used to supply the oxidizer-rich combustion products to the oxidizer circuit of the main injector of the thrust chamber. Results from independent hot-fire tests of the preburner injector in a combustion chamber with a sonic throat are described in companion papers at this JANNAF conference. The resulting integrated test article - which includes the preburner, inter-connecting hot gas duct, main injector, and ablative combustion chamber - was assembled at Test Stand 116 at the East Test Area of the NASA Marshall Space Flight Center. The test article was well instrumented with static and dynamic pressure, temperature, and acceleration sensors to allow the collected data to be used for combustion analysis model development. Hot-fire testing was conducted with main combustion chamber pressures ranging from 1400 to 2100 psia, and main combustion chamber mixture ratios ranging from 2.4 to 2.9. Different levels of fuel film cooling injected from the injector face were examined ranging from none to about 12% of the total fuel flow. This paper presents the hot-fire test results of the integrated test article. Combustion performance, stability, thermal, and compatibility characteristics of both the preburner and the thrust chamber are described. Another companion paper at this JANNAF meeting includes additional and more detailed test data regarding the combustion dynamics and stability characteristics.

Hulka, J. R.↗