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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

The Ferrofluids Story

A new Ferrofluidics exclusion seal promises improvement in controlling "fugitive emissions" -vapors that escape into the atmosphere from petroleum refining and chemical processing facilities. These are primarily volatile organic compounds, and their emissions are highly regulated by the EPA. The ferrofluid system consists of a primary mechanical seal working in tandem with a secondary seal. Ferrofluids are magnetic liquids - fluids in which microscopic metal particles have been suspended, allowing the liquid to be controlled by a magnetic force. The concept was developed in the early years of the Space program, but never used. Two Avco scientists, however, saw commercial potential in ferrofluids and formed a company. Among exclusion seal commercial applications are rotary feedthrough seals, hydrodynamic bearings and fluids for home and automotive loudspeakers. Ferrofluidics has subsidiaries throughout the world.

Source record↗
NASA NTRS1999

Study the Effects of Charged Particle Radiation on Gravitational Sensors in Space

Space-flight charging of free floating masses poses an unusual problem-- how can one control charge on the object without exerting a significant force on it? One approach is to make contact to the object with a fine wire. However, for many precision applications no physical contact is permissible, so charge must be conveyed in, a more sophisticated manner. One method has already been developed: Gravitational Probe B (GP-B) uses an ultraviolet photo-emission system described in ref 1. This system meets the experiment requirements, yet poses a number of constraints, including high power dissipation (approximately 10 W peak, approximately 1 W average), low current output (approximately 10(exp -13) A), and potential reliability problems associated with fiber optics system and the UV source. The aim of the current research is to improve this situation and, if possible, develop a more rugged and lower power alternative, usable in a wide range of situations. An potential alternative to the UV electron source is a Spindt-type field emission cathode. These consist of an array of extremely sharp silicon tips mounted in a standard IC package with provision for biasing them relative to the case potential. They are attractive as electron sources for space applications due to their low power consumption (10(exp -5) W), high current levels (10(exp -9) to 10(exp -5) A), and the absence of mechanical switching. Unfortunately, existing cathodes require special handling to avoid contamination and gas absorption. These contaminants can cause severe current fluctuations and eventual destruction of the cathode tips. Another potential drawback is the absence of any data indicating the possibility of bipolar current flow. This capability is needed because of the large uncertainties in the net charge transfer from cosmic rays to a free floating mass in space. More recent devices reduce the current fluctuations and destructive arcing by mounting the tips on a resistive substrate rather than a good conductor. This effectively wires a resistor to each individual tip, providing a current limit and thus greatly reducing the possibility of destructive arcing through an individual tip. An issue with this resistive layer is its range of operating temperatures. From the experience with the GP-B system, we hypothesized about using secondary electron emission for control of net charge transfer to an object. An important goal of the testing described below was to demonstrate the ability to apply both positive and negative charges to the test object from a single emitter.

Lipa, John A.↗
NASA NTRS2000

Reduced-Noise Gas Flow Design Guide Developed as a Noise-Control Design Tool for Meeting Glenn's Hearing Conservation and Community Noise Goals

A Reduced-Noise Gas Flow Design Guide has been developed for the NASA Glenn Research Center at Lewis Field by Nelson Acoustical Engineering of Elgin, Texas. Gas flow systems are a significant contributor to t he noise exposure landscape at Glenn. Because of the power of many of these systems, hearing conservation and community noise are importan t issues. The purpose of the Guide is to allow Glenn engineers and de signers to address noise emission and control at the design stage by using readily available system parameters. Although the Guide was deve loped with Glenn equipment and systems in mind, it is expected to hav e wide application in industry.

Cooper, Beth A.↗
NASA NTRS1976

New potentials for conventional aircraft when powered by hydrogen-enriched gasoline

Hydrogen enrichment for aircraft piston engines is under study in a new NASA program. The objective of the program is to determine the feasibility of inflight injection of hydrogen in general aviation aircraft engines to reduce fuel consumption and to lower emission levels. A catalytic hydrogen generator will be incorporated as part of the air induction system of a Lycoming turbocharged engine and will generate hydrogen by breaking down small amounts of the aviation gasoline used in the normal propulsion system. This hydrogen will then be mixed with gasoline and compressed air from the turbocharger before entering the engine combustion chamber. The paper summarizes the results of a systems analysis study. Calculations assuming a Beech Duke aircraft indicate that fuel savings on the order of 20% are possible. An estimate of the potential for the utilization of hydrogen enrichment to control exhaust emissions indicates that it may be possible to meet the 1979 Federal emission standards.

Menard, W. A.↗
NASA NTRS1986

Effects of salinity on the microwave emission of soils

Controlled plot experiments were conducted to collect L and C band passive microwave data concurrent with ground observations of salinity and soil moisture. Two dielectric mixing models were used with an emission model to predict the emissivity from a bare smooth uniform profile. The models produce nearly identical results when near zero salinity is involved and reproduce the observed data at L band extremely well. Discrepancies at C band are attributed to sampling depth problems. Comparisons of predicted emissivities at various salinities with observed values indicate that the dynamic range of the emissivities can be explained using either of the dielectric mixing models. Evaluation of the entire data set, which included four salinity levels, indicates that for general application the effects of soil salinity can be ignored in interpreting microwave data for estimating soil moisture under most agricultural conditions.

Jackson, T. J.↗
NASA NTRS1987

Salinity effects on the microwave emission of soils

Controlled plot experiments were conducted to collect L and C band passive microwave data concurrent with ground observations of salinity and soil moisture. Two dielectric mixing models were used with an emission model to predict the emissivity from a bare smooth uniform profile. The models produce nearly identical results when near zero salinity is involved and reproduce the observed data at L band extremely well. Discrepancies at C band are attributed to sampling depth problems. Comparisons of predicted emissivities at various salinities with observed values indicate that the dynamic range of the emissivities can be explained using either of the dielectric mixing models. Evaluation of the entire data set, which included four salinity levels, indicates that for general application the effects of soil salinity can be ignored in interpreting microwave data for estimating soil moisture under most agricultural conditions.

Jackson, Thomas J.↗
NASA NTRS1976

New potentials for conventional aircraft when powered by hydrogen-enriched gasoline

Hydrogen enrichment for aircraft piston engines is under study in a new NASA program. The objective of the program is to determine the feasibility of inflight injection of hydrogen in general aviation aircraft engines to reduce fuel consumption and to lower emission levels. A catalytic hydrogen generator will be incorporated as part of the air induction system of a Lycoming turbocharged engine and will generate hydrogen by breaking down small amounts of the aviation gasoline used in the normal propulsion system. This hydrogen will then be mixed with gasoline and compressed air from the turbocharger before entering the engine combustion chamber. The special properties of the hydrogen-enriched gasoline allow the engine to operate at ultralean fuel/air ratios, resulting in higher efficiencies and hence less fuel consumption. This paper summarizes the results of a systems analysis study. Calculations assuming a Beech Duke aircraft indicate that fuel savings on the order of 20% are possible. An estimate of the potential for the utilization of hydrogen enrichment to control exhaust emissions indicates that it may be possible to meet the 1979 Federal emission standards.

Menard, W. A.↗
NASA NTRS2010

The Unique OMI HCHO/NO2 Feature During the 2008 Beijing Summer Olympics: Implications for Ozone Production Sensitivity

In preparation of the Beijing Summer Olympic and Paralympics Games, strict controls were imposed between July and September 2008 on motor vehicle traffic and industrial emissions to improve air quality for the competitors. We assessed chemical sensitivity of ozone production to these controls using Ozone Monitoring Instrument (OMI) column measurements of formaldehyde (HCHO) and nitrogen dioxide (NO2), where their ratio serves as a proxy for the sensitivity. During the emission controls, HCHO/NO2 increased and indicated a NOx-limited regime, in contrast to the same period in the preceding three years when the ratio indicates volatile organic carbon (VOC)-limited and mixed NOx-VOC-limited regimes. After the emission controls were lifted, observed NO2 and HCHO/NO2 returned to their previous values. The 2005-2008 OMI record shows that this transition in regimes was unique as ozone production in Beijing was rarely NOx-limited. OMI measured summertime increases in HCHO of around 13% in 2008 compared to prior years, the same time period during which MODIS vegetation indices increased. The OMI HCHO increase may be due to higher biogenic emissions of HCHO precursors, associated with Beijing's greening initiative for the Olympics. However, NO2 and HCHO were also found to be well-correlated during the summer months. This indicates an anthropogenic VOC contribution from vehicle emissions to OMI HCHO and is a plausible explanation for the relative HCHO minimum observed in August 2008, concurrent with a minimum in traffic emissions. We calculated positive trends in 2005-2008 OMI HCHO and NO2 of about +1 x 10(exp 14) Molec/ square M-2 and +3 x 10(exp 13) molec CM-2 per month, respectively. The positive trend in NO2 may be an indicator of increasing vehicular traffic since 2005, while the positive trend in HCHO may be due to a combined increase in anthropogenic and biogenic emissions since 2005.

Witte, J. C.↗
NASA NTRS2000

Laminar Diffusion Flame Studies (Ground- and Space-Based Studies)

Laminar diffusion flames are of interest because they provide model flame systems that are far more tractable for analysis and experiments than more practical turbulent diffusion flames. Certainly, understanding flame processes within laminar diffusion flames must precede understanding these processes in more complex turbulent diffusion flames. In addition, many properties of laminar diffusion flames are directly relevant to turbulent diffusion flames using laminar flamelet concepts. Laminar jet diffusion flame shapes (luminous flame boundaries) have been of particular interest since the classical study of Burke and Schumann because they are a simple nonintrusive measurement that is convenient for evaluating flame structure predictions. Thus, consideration of laminar flame shapes is undertaken in the following, emphasizing conditions where effects of gravity are small, due to the importance of such conditions to practical applications. Another class of interesting properties of laminar diffusion flames are their laminar soot and smoke point properties (i.e., the flame length, fuel flow rate, characteristic residence time, etc., at the onset of soot appearance in the flame (the soot point) and the onset of soot emissions from the flame (the smoke point)). These are useful observable soot properties of nonpremixed flames because they provide a convenient means to rate several aspects of flame sooting properties: the relative propensity of various fuels to produce soot in flames; the relative effects of fuel structure, fuel dilution, flame temperature and ambient pressure on the soot appearance and emission properties of flames; the relative levels of continuum radiation from soot in flames; and effects of the intrusion of gravity (or buoyant motion) on emissions of soot from flames. An important motivation to define conditions for soot emissions is that observations of laminar jet diffusion flames in critical environments, e.g., space shuttle and space station facilities, cannot involve soot emitting flames in order to ensure that test chamber windows used for experimental observations are not blocked by soot deposits, thereby compromising unusually valuable experimental results. Another important motivation to define conditions where soot is present in diffusion flames is that flame chemistry, transport and radiation properties are vastly simplified when soot is absent, making such flames far more tractable for detailed numerical simulations than corresponding soot-containing flames. Motivated by these observations, the objectives of this phase of the investigation were as follows: (1) Observe flame-sheet shapes (the location of the reaction zone near phi=1) of nonluminous (soot free) laminar jet diffusion flames in both still and coflowing air and use these results to develop simplified models of flame-sheet shapes for these conditions; (2) Observe luminous flame boundaries of luminous (soot-containing) laminar jet diffusion flames in both still and coflowing air and use these results to develop simplified models of luminous flame boundaries for these conditions. In order to fix ideas here, maximum luminous flame boundaries at the laminar smoke point conditions were sought, i.e., luminous flame boundaries at the laminar smoke point; (3) Observe effects of coflow on laminar soot- and smoke-point conditions because coflow has been proposed as a means to control soot emissions and minimize the presence of soot in diffusion flames.

Dai, Z.↗
NASA NTRS2020

Fuel availability not fire weather controls boreal wildfire severity and carbon emissions

Carbon (C) emissions from wildfires are a key terrestrial–atmosphere interaction that influences global atmospheric composi-tion and climate. Positive feedbacks between climate warming and boreal wildfires are predicted based on top-down controls of fire weather and climate, but C emissions from boreal fires may also depend on bottom-up controls of fuel availability related to edaphic controls and overstory tree composition. Here we synthesized data from 417 field sites spanning six ecoregions in the northwestern North American boreal forest and assessed the network of interactions among potential bottom-up and top-down drivers of C emissions. Our results indicate that C emissions are more strongly driven by fuel availability than by fire weather, highlighting the importance of fine-scale drainage conditions, overstory tree species composition and fuel accumulation rates for predicting total C emissions. By implication, climate change-induced modification of fuels needs to be considered for accu-rately predicting future C emissions from boreal wildfires.

X J Walker↗
NASA NTRS1973

Thermal surveillance of volcanoes of the Cascade Range and Iceland utilizing ERTS DCP systems and imagery

The author has identified the following significant results. Significant results of the thermal surveillance of volcanoes experiment during 1972 included the design, construction, emplacement, and successful operation at volcanic sites in the Cascade Range, North America and on Surtsey, Iceland, of automated thermistor arrays which transmit ground and fumarole temperatures via the ERTS-1 data communication system to Goddard Space Flight Center. Temperature, radiance, and anomalous heat flow variations are being plotted by a U.S. Geological Survey IBM 360/65 computer program to show daily fluctuations at each of the sites. Results are being compiled in conjunction with NASA and USGS aircraft infrared survey data to provide thermal energy yield estimates during the current repose period of several Cascade Range volcanic systems. ERTS-1 MSS images have provided new information on the extent of structural elements controlling thermal emission at Lassen Volcanic National Park.

Friedman, J. D.↗
NASA NTRS1975

Assessing and controlling the effect of aircraft on the environment: Pollution

The air pollution created by aircraft engines around airports and the global atmospheric problem of supersonic aircraft operating in the stratosphere are discussed. Methods for assessing the air pollution impact are proposed. The use of atmospheric models to determine the air pollution extent is described. Methods for controlling the emissions of aircraft engines are examined. Diagrams of the atmospheric composition resulting from exhaust gas emissions are developed.

Poppoff, I. G.↗
NASA NTRS1980

Modification of the ECAS reference steam power generating plant to comply with the EPA 1979 new source performance standards

Detailed capital cost estimates for the ECAS and modified reference plants in mid-1978 dollars for both 250 and 175 F (394 and 353 K) stack gas reheat temperatures based on the cost estimates developed for the ECAS study are presented. The scope of the work included technical assessment of sulfur dioxide scrubber system design, on site calcination versus purchased lime, reheat of stack gas, effect of sulfur dioxide scrubber on particulate emission, and control of nitrogen oxides.

Fogelson, S. A.↗
NASA NTRS1981

Design and performance of resonant-cavity parallel baffles for duct silencing

Resonant-cavity parallel baffles, either empty or with a thin absorbent lining, have been investigated as an alternative to fiberglass-filled baffles commonly used to control noise emission from large ducts. A method for predicting silencer attenuation is described, and it is shown that the new type of baffle is characterized by an acoustic performance similar to that of fibrous baffles, while being virtually immune to such problems as clogging, erosion, or settling. The emphasis of the study is on insertion loss measurements in a 7 by 10 ft wind tunnel.

Soderman, P. T.↗