Search NASA⌕ Search

SEARCH · Search NASA

Results for “Methane emissions”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Gaseous abundances and methane supersaturation in Titan's troposphere

Various properties of Titan's troposphere are inferred from an analysis of Voyager I infrared spectrometer (IRIS) data between 200 and 600/ cm. Two homogeneous spectral averages acquired at widely separated emission angles are chosen for the analysis. Both data sets are associated with northern low latitudes very close to that of the radio science ingress occultation point. Solutions require simultaneous nonlinear least-squares fits to the two IRIS data sets, coupled with iteration of the radio occultation refractivity data. Values and associated 1-sigma uncertainties of several parameters are inferred from our analysis. These include mole fractions for molecular hydrogen (approx. 0.0011), argon (small), and methane near the surface ( approx. 0.057). Solutions are also obtained for the hydrogen parafraction (close to equilibrium, with considerable uncertainty), air temperature near the surface ( approx. 93 K), surface surface temperature discontinuity (approx. 1 K), and maximum degree of methane supersaturation in the upper troposphere (approx. 1.5). Actual values for the above-mentioned parameters depend on the amount of ethane cloud near the tropopause. There is no evidence for methane clouds in the upper troposphere, nor is their presence compatible with large degrees of supersaturation. A wave number dependence for the stratospheric haze opacity is inferred similar to that found for a polymeric residue created in laboratory discharge experiments. This haze appears to be uniformly distributed with latitude between altitudes of 40 and 160 km, provided those nighttime data at southern high latitudes that are discounted.

Samuelson, Robert E.↗
NASA NTRS1997

Shapes of Buoyant and Nonbuoyant Methane Laminar Jet Diffusion Flames

Laminar gas jet diffusion flames represent a fundamental combustion configuration. Their study has contributed to numerous advances in combustion, including the development of analytical and computational combustion tools. Laminar jet flames are pertinent also to turbulent flames by use of the laminar flamelet concept. Investigations into the shapes of noncoflowing microgravity laminar jet diffusion flames have primarily been pursued in the NASA Lewis 2.2-second drop tower, by Cochran and coworkers and by Bahadori and coworkers. These studies were generally conducted at atmospheric pressure; they involved soot-containing flames and reported luminosity lengths and widths instead of the flame-sheet dimensions which are of Greater value to theory evaluation and development. The seminal model of laminar diffusion flames is that of Burke and Schumann, who solved the conservation of momentum equation for a jet flame in a coflowing ambient by assuming the velocity of fuel, oxidizer and products to be constant throughout. Roper and coworkers improved upon this model by allowing for axial variations of velocity and found flame shape to be independent of coflow velocity. Roper's suggestion that flame height should be independent of gravity level is not supported by past or present observations. Other models have been presented by Klajn and Oppenheim, Markstein and De Ris, Villermaux and Durox, and Li et al. The common result of all these models (except in the buoyant regime) is that flame height is proportional to fuel mass flowrate, with flame width proving much more difficult to predict. Most existing flame models have been compared with shapes of flames containing soot, which is known to obscure the weak blue emission of flame sheets. The present work involves measurements of laminar gas jet diffusion flame shapes. Flame images have been obtained for buoyant and nonbuoyant methane flames burning in quiescent air at various fuel flow-rates, burner diameters and ambient pressures. Soot concentrations were minimized by selecting conditions at low flowrates and low ambient pressures; this allows identification of actual flame sheets associated with blue emissions of CH and CO2. The present modeling effort follows that of Roper and is useful in explaining many of the trends observed.

Sunderland, Peter B.↗
NASA NTRS1992

Measurements of fugitive hydrocarbon emissions with a tunable infrared DIAL

A tunable infrared differential absorption lidar (DIAL) system has been designed and developed at the National Physics Lab (NPL) which is capable of making measurements throughout the spectral region 3.0 to 4.2 micro-m. It is ideally suited to measuring a range of organic and inorganic species including methane, propane, and butane. The system also has an ultraviolet channel that is capable of making simultaneous measurements of aromatic hydrocarbons such as Toluene and benzene. This paper describes the source and detection system, together with some measurements of fugitive hydrocarbon emissions performed at various petrochemical plants.

Milton, M. J. T.↗
NASA NTRS1992

A preliminary study of the variability and magnitude of the flux of biogenic sulfur gases from a New Hampshire salt marsh

Salt marshes have highly variable spatial and temporal fluxes of hydrogen sulfide, carbonyl sulfide, methane thiol, dimethyl sulfide, and carbon disulfide (H2S, COS, MeSH, DMS, and CS2, respectively). This variability was tested at nine emission sites in a New Hampshire, USA salt marsh: three replicates in each of three vegetation zones, Spartina alterniflora, S. patens, and a transition zone. Three sites were sampled simultaneously, either within or across vegetation zones, using a dynamic flux chamber technique. Difficulties with calibration and field equipment resulted in fluxes with maximum absolute uncertainties of greater than plus or minus 200 percent. However, the relative uncertainty between subsequent samples was closer to plus or minus 20 percent. Chambers are expected to affect the natural flux of gases by altering the humidity, temperature, and composition of the gas inside the chamber. Summertime fluxes are highest for all gases except COS which demonstrated evidence of a springtime peak. A summertime background flux of 5 to 100 x 10(exp -9) g S/m(sup -2) min was observed for all gases, while S alternifora fluxes of MeSH and DMS were approximately 8 fold and approximately 100 fold higher than S. patens, respectively. DMS and MeSH fluxes were higher during the day than at night. Evidence of COS uptake by plants was observed. CS2 appeared to be the quantitatively least important sulfur gas emitted. Improved laboratory and sample collection techniques and further data collection in the field will yield information on the details of salt marsh variability, will improve estimates of the error associated with single flux measurements, and will allow a more accurate estimation of sulfur fluxes from salt marshes based on vegetation and area coverage data. Inability to control the temperature and humidity inside of the chamber remain significant problems with the chamber design.

Morrison, Michael Cope↗
NASA NTRS2010

High-Resolution Spectroscopy of Stratospheric Ethane Following the Jupiter Impact of 2009

We report on high-resolution infrared spectroscopy of ethane (C2H6) performed at the latitude of an impact site on Jupiter discovered on 19 July 2009 by A. Wesley from a location in Murrumbateman, Australia. The observations used the NASA Goddard Space Flight Center's Heterodyne Instrument for Planetary Wind and Composition (HIPWAC) at the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. HIPWAC is a mid-infrared (9-12 microns) heterodyne spectrometer operating at the highest limit of spectral resolving power (lambda\Delta\lambda > l06), providing information on atmospheric constituent abundance and temperature through fully resolved tine shapes. Ethane is a stable trace product of methane photochemistry that is nearly uniformly mixed in Jupiter's stratosphere, providing an effective probe of that altitude region. Ethane emission line profiles near 11,74 microns in the Ug band were measured in Jupiter's stratosphere at 25 MHz (11.00083/cm) resolution. A sequence of spectra of ethane acquired over a range of longitude at the impact latitude (56S planetocentric) probes constituent abundance and temperature profile, both on and off the impact region. Near the site of the impact, ethane emission increased above levels measured well outside the impact region. Radiative transfer analysis indicates increased ethane mole fraction (30% greater). Variation in the measured continuum level and line intensities within 75deg of the impact longitude indicate the presence of an opacity source (haze) at altitudes near and above the tropopause and as high as the 10-mbar level near the impact site. The indication of possible haze opacity up to the 10-mbar level in the atmosphere is consistent with measurements made by HIPWAC's predecessor as part of the IRTF Shoemaker Levy-9 campaign in 1994.

Fast, Kelly↗
NASA NTRS2014

Airborne In-Situ Trace Gas Measurements of Multiple Wildfires in California (2013-2014)

Biomass burning emissions are an important source of a wide range of trace gases and particles that can impact local, regional and global air quality, climate forcing, biogeochemical cycles and human health. In the western US, wildfires dominate over prescribed fires, contributing to atmospheric trace gas budgets and regional and local air pollution. Limited sampling of emissions from wildfires means western US emission estimates rely largely on data from prescribed fires, which may not be a suitable proxy for wildfire emissions.We report here in-situ measurements of carbon dioxide, methane, ozone and water vapor from the plumes of a variety of wildfires sampled in California in the fire seasons of 2013 and 2014. Included in the analysis are the Rim Fire (August October 2013, near Yosemite National Park), the Morgan Fire (September 2013, near Clayton, CA), and the El Portal Fire (July August 2014, in Yosemite National Park), among others. When possible, fires were sampled on multiple days.Emission ratios and estimated emission factors will be presented and discussed in the context of fuel composition, plume structure, and fire phase. Correlations of plume chemical composition to MODISVIIRS Fire Radiative Power (FRP) and other remote sensing information will be explored. Furthermore, the role of plumes in delivery of enhanced ozone concentrations to downwind municipalities will be discussed.

Gas↗
NASA NTRS1978

The effect of anthropogenic carbon monoxide on the methane budget of the troposphere

Photochemical model calculations indicate that significant perturbations in tropospheric OH, CH4, and related compounds may occur in the coming decades due to increased anthropogenic emissions of CO and NO(x). The magnitude and direction of the perturbation depends on future emission rates of CO and NO(x) and also on the efficiency with which urban NO(x) is transported to the ambient atmosphere. If CO and NO(x) emissions increase at comparable rates, the CO effect on OH will dominate and OH will decrease while CH4 increases. The effects of a variation in tropospheric OH, halocarbons, and other compounds include a perturbation to stratospheric ozone and the atmosphere's thermal equilibrium.

Chameides, W. L.↗
NASA NTRS1987

IRAS observations of the Pluto-Charon system

High-signal-to-noise-ratio observations of the Pluto-Charon system at 25, 60, and 100 microns using IRAS are combined with visual-magnitude and mutual-eclipse constraints to evaluate thermal models of Pluto and Charon. These models are consistent with eclipse observation by Dunbar and Tedesco (1986) but not with Reinsch and Pakull (1987). The most likely model for Charon is the standard asteroid model, typical for the icy Galilean and Saturnian satellites. Charon models with a significant atmosphere can be ruled out. Based on currently available radius and albedo constraints, no significant numerical distinction is possible between Pluto models ranging from isothermal spheres with surface emissivity between 0.4 and 0.9. Concerns regarding the viability of an emissivity as low as 0.4 favor the higher-emissivity models. The globally uniform surface temperature of Pluto may thus at present be as low as 45 K, with a methane column abundance of 6.7 cm atm. The most likely models are centered on radii of 1180 and 747 km and albedos of 0.47 and 0.26 for Pluto and Charon, respectively.

Aumann, H. H.↗
NASA NTRS1991

Airborne Ground Penetrating Radar (GPR) for peat analyses in the Canadian Northern wetlands study

The study was conducted as part of the NASA Biospherics Research on Emissions from Wetlands (BREW) program. An important aspect of the program is to investigate the terrestrial production and atmospheric distribution of methane and other gases contributing to global warming. Multi-kilometer transects of airborne (helicopter) Ground Penetrating Radar (GPR) data were collected periodically along the 100 km distance from the coast inland so as to obtain a regional trend in peat depth and related parameters. Global Positioning System (GPS) data were simultaneously collected from the helicopter to properly georeference the GPR data. Additional 50 m ground-based transects of GPR data were also collected as a source of ground truthing, as a calibration aid for the airborne data sets, and as a source of higher resolution data for characterizing the strata within the peat. In situ peat depth probing and soil characterizations from excavated soil pits were used to verify GPR findings. Results from the ground-based data are presented.

Pelletier-Travis, Ramona E.↗
NASA NTRS1972

Soot formation in the methane oxygen and methane/oxygen/hydrogen flame

The feasibility of using methane, recovered from carbon dioxide by the Sabatier-Senderens reaction, was investigated as a fuel in a reaction control engine. A problem to be avoided is the emission of soot particles. It is thought that such particles would remain in the environment of the spacecraft and, thereby, adversely affect optical sightings and possibly have an effect upon communications. The initial studies were of a practical nature. The first was the influence of the spatial arrangement of the fuel and oxygen injectors on soot formation. In the second study, inhibition of soot formation was considered. Considering the given situation, it was impractical to use an additive. However, since methanol combustion does not produce soot, and methanol can be produced from methane in situ, the possibility that methanol could act as an inhibitor was studied. In the third study, since these are restartable engines, the effect of shutdown on the rapidity of soot formation was studied.

Dauerman, L.↗
NASA NTRS1980

The chemistry and transport of methane and carbon monoxide in the troposphere

The present understanding of the physical and chemical behavior of methane, carbon monoxide and the chemical species involved in the conversion of CH4 to CO in the troposphere is reviewed. Following a brief summary of CO and CH4 emission and reactions in urban areas, attention is given to measurements of the spatial and temporal distributions of CO and CH4 in the rural atmosphere, the contribution of the oceans to atmospheric CO and CH4 concentrations, and interactions of CH4 and CO with soils and vegetation. Estimates of the transport of CH4 and CO from the troposphere to the stratosphere are discussed, and photochemical reactions of the constituents are examined. Two- and three-dimensional models for CH4 and CO transport are presented, and possible future variations in atmospheric abundances of the molecules are considered. Finally, present estimates of the global methane and carbon dioxide budgets are summarized, and it is pointed out that, despite the large contribution of anthropogenic sources, the budgets appear to be in balance.

Peters, L. K.↗
NASA NTRS1993

Simplified jet-A kinetic mechanism for combustor application

Successful modeling of combustion and emissions in gas turbine engine combustors requires an adequate description of the reaction mechanism. For hydrocarbon oxidation, detailed mechanisms are only available for the simplest types of hydrocarbons such as methane, ethane, acetylene, and propane. These detailed mechanisms contain a large number of chemical species participating simultaneously in many elementary kinetic steps. Current computational fluid dynamic (CFD) models must include fuel vaporization, fuel-air mixing, chemical reactions, and complicated boundary geometries. To simulate these conditions a very sophisticated computer model is required, which requires large computer memory capacity and long run times. Therefore, gas turbine combustion modeling has frequently been simplified by using global reaction mechanisms, which can predict only the quantities of interest: heat release rates, flame temperature, and emissions. Jet fuels are wide-boiling-range hydrocarbons with ranges extending through those of gasoline and kerosene. These fuels are chemically complex, often containing more than 300 components. Jet fuel typically can be characterized as containing 70 vol pct paraffin compounds and 25 vol pct aromatic compounds. A five-step Jet-A fuel mechanism which involves pyrolysis and subsequent oxidation of paraffin and aromatic compounds is presented here. This mechanism is verified by comparing with Jet-A fuel ignition delay time experimental data, and species concentrations obtained from flametube experiments. This five-step mechanism appears to be better than the current one- and two-step mechanisms.

Lee, Chi-Ming↗
NASA NTRS2011

Methane and Environmental Change during the Paleocene-Eocene Thermal Maximum (PETM): Modeling the PETM Onset as a Two-stage Event

An atmospheric CH4 box model coupled to a global carbon cycle box model is used to constrain the carbon emission associated with the PETM and assess the role of CH4 during this event. A range of atmospheric and oceanic emission scenarios representing different amounts, rates, and isotopic signatures of emitted carbon are used to model the PETM onset. The first 3 kyr of the onset, a pre-isotope excursion stage, is simulated by the atmospheric release of 900 to 1100 Pg C CH4 with a delta C-13 of -22 to - 30 %. For a global average warming of 3 deg C, a release of CO2 to the ocean and CH4 to the atmosphere totalling 900 to 1400 Pg C, with a delta C-13 of -50 to -60%, simulates the subsequent 1 -kyr isotope excursion stage. To explain the observations, the carbon must have been released over at most 500 years. The first stage results cannot be associated with any known PETM hypothesis. However, the second stage results are consistent with a methane hydrate source. More than a single source of carbon is required to explain the PETM onset.

Carozza, David A.↗
NASA NTRS1982

Doppler line profiles measurement of the Jovian Lyman Alpha emission with OAO-C

Observation of Jupiter made with the high resolution ultraviolet spectrometer of the Orbiting Astronomical Observatory copernicus in April and May, 1980, yield a Jovian Lyman alpha emission intensity of 7 + or 2.5 RR. This indicates a decrease by about a factor of two since the Voyager ultraviolet spectrometer measurements, nearly a year earlier. An unusually high column abundance of hydrogen atoms above the methane homopause at the Voyager epoch is indicated. Since the auroral charged particle bombardment of molecular hydrogen is expected to contribute significantly to the global population of the hydrogen atoms, it is suggested that at the time of the Voyager Jupiter encounter unusually high auroral activity existed, perhaps d to the high concentration of the Io plasma torus. The temporal variation of the Saturn lyman alpha emission, when contrasted with the Jovian data, reveals that the auroral processes are not nearly as important in determining the Saturn Lyman alpha intensity in the nonauroral region.

Barker, E. S.↗
NASA NTRS1992

The Kuwait oil fires as seen by Landsat

A mosaic of two Landsat thematic mapper images acquired May 30, 1991, reveals a dark smoke plume 30-60 km wide extending hundreds of kilometers south of Kuwait City along the Persian Gulf. Smoke coming from the Raudhatain and Sabriyah oil fields blew across the Gulf of Kuwait and over Kuwait City, joined with smoke from the Greater Burgan and Minagish fields, and continued southward over smaller villages and regions of desert agriculture consisting of hundreds of axially irrigated fields in both Kuwait and Saudi Arabia. One agricultural region in Kuwait was completely obscured by the smoke. The light colored limestone gravel and sand surface was darkened by oil lakes near the wells, and by oil drizzling out of the plume downwind of the wells. Most fires produced either a light or dark plume, and the separate plumes mixed to form a combined plume much darker than the land surface, but slightly more reflective than the Gulf waters. A few of the hottest fires had no visible plume, and are presumably associated with methane combustion. The last of the Kuwait fires was reportedly extinguished in November of 1991. Continued monitoring is needed to assess the impact of emissions from both burning and nonburning oil wells on the region's climate, as well as on the agriculture, fishing, and other activities essential to life in the region.

Cahalan, Robert F.↗
NASA NTRS2012

Global Air Quality and Climate

Emissions of air pollutants and their precursors determine regional air quality and can alter climate. Climate change can perturb the long-range transport, chemical processing, and local meteorology that influence air pollution. We review the implications of projected changes in methane (CH4), ozone precursors (O3), and aerosols for climate (expressed in terms of the radiative forcing metric or changes in global surface temperature) and hemispheric-to-continental scale air quality. Reducing the O3 precursor CH4 would slow near-term warming by decreasing both CH4 and tropospheric O3. Uncertainty remains as to the net climate forcing from anthropogenic nitrogen oxide (NOx) emissions, which increase tropospheric O3 (warming) but also increase aerosols and decrease CH4 (both cooling). Anthropogenic emissions of carbon monoxide (CO) and non-CH4 volatile organic compounds (NMVOC) warm by increasing both O3 and CH4. Radiative impacts from secondary organic aerosols (SOA) are poorly understood. Black carbon emission controls, by reducing the absorption of sunlight in the atmosphere and on snow and ice, have the potential to slow near-term warming, but uncertainties in coincident emissions of reflective (cooling) aerosols and poorly constrained cloud indirect effects confound robust estimates of net climate impacts. Reducing sulfate and nitrate aerosols would improve air quality and lessen interference with the hydrologic cycle, but lead to warming. A holistic and balanced view is thus needed to assess how air pollution controls influence climate; a first step towards this goal involves estimating net climate impacts from individual emission sectors. Modeling and observational analyses suggest a warming climate degrades air quality (increasing surface O3 and particulate matter) in many populated regions, including during pollution episodes. Prior Intergovernmental Panel on Climate Change (IPCC) scenarios (SRES) allowed unconstrained growth, whereas the Representative Concentration Pathway (RCP) scenarios assume uniformly an aggressive reduction, of air pollutant emissions. New estimates from the current generation of chemistry-climate models with RCP emissions thus project improved air quality over the next century relative to those using the IPCC SRES scenarios. These two sets of projections likely bracket possible futures. We find that uncertainty in emission-driven changes in air quality is generally greater than uncertainty in climate-driven changes. Confidence in air quality projections is limited by the reliability of anthropogenic emission trajectories and the uncertainties in regional climate responses, feedbacks with the terrestrial biosphere, and oxidation pathways affecting O3 and SOA.

ozone↗
NASA NTRS1981

Some fundamental acoustic observations in combusting turbulent jets

A study is presented of the possibility of using the acoustic radiation emitted from turbulent combustion zones to characterize the structure, mechanics and properties of turbulent combustion. Theoretical consideration is given to the acoustic characteristics of a nonpremixed open turbulent jet flame and the response of the acoustic spectrum to changes in combustion conditions. Experimental observations made of the acoustic emissions from a laboratory burner that establishes turbulent flames at the exit of a fully developed pipe flow as well as two commercial burners using methane, ethane and propane fuels are then presented which reveal changes in the acoustic amplitudes in three high-frequency bands associated with changes in the air-fuel ratio. Results suggest a means for combustion diagnostics and demonstrate the possibility of using acoustic measurements in investigations of combustion zone processes.

Ramohalli, K.↗
NASA NTRS1982

High-spectral-resolution observations of the 7.7-micron feature in HD 44179

Observations of the moon and HD 44179 were obtained in the wavelength range of 7.5-8.5 microns at a resolving power of approximately 800. The spectrum of the moon shows absorptions caused by telluric methane. Use of the moon as a calibrator is effective in removing these atmospheric lines. The spectrum of HD 44179 shows that the 7.7-micron emission feature does not break up into discrete, resolved emission features. Instead, it must be a broad, apparently continuous, emission feature.

Russell, R. W.↗