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Smith, L. L.

Publications and source records attributed to Smith, L. L..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Emissions Measurements from a Lobed Fuel Injector/Burner

The present experimental study examines NO(x) and CO emissions associated with alternative fuel injector geometries. These injectors mix fuel and air to differing extents and thus create different local equivalence ratios upstream of flame ignition and stabilization. Two of the devices studied are lobed fuel injectors, in which mixing of reactants is associated with stream wise vorticity generation and straining of fuel-air interfaces, while the third is a non-lobed fuel injector which creates relatively little fuel-air mixing prior to ignition.Results show that one lobed injector geometry appears to produce locally lean premixed flame structures, resulting in low NO. emissions when compared with non-lobed injector emissions. The other lobed injector geometry appears to produce a local fuel-air mixture which is closer to stoichiometric conditions, with NO(x) emissions that are actually higher than for the non-lobed injector. For both lobed injector geometries examined here, CO emissions become high for over-all lean operating conditions, consistent with premixed combustion behavior. The present study demonstrates the importance of control of the local equivalence ratio in minimizing burner emissions.

Mitchell, M. G.↗
NASA NTRS1998

Burner Emissions Associated with Lobed and Non-Lobed Fuel Injectors

The present experimental study examines NO(sub x), and CO emissions associated with three alternative fuel-injector geometries. These injectors mix fuel and air and strain their interfaces to differing extents and thus create different local equivalence ratios within flow regions upstream of flame ignition and stabilization. Two of the devices studied are lobed fuel injectors, in which molecular mixing of reactants is associated with streamwise vorticity generation, while the third one is a non-lobed fuel injector. Results show that rapid mixing allowed both lobed injector geometries to produce very lean premixed flame structures, with a lower achievable turn-down or fuel/air mass flux ratio than for the analogous non-lobed injector, which largely, produced distinct diffusion flames. All three injectors exhibited some level of sooting near walls and in the far-field region, with the non-lobed injector sooting to the greatest extent. At low fuel flow rates, in which the lobed injectors created locally very lean premixed conditions, there resulted lower NO(sub x) emissions as compared with non-lobed injector emissions. Yet at higher fuel-air mass flux ratios, NO(sub x) emissions from the lobed injectors were actually higher than for the nonlobed injector, likely due to reduced sooting and hence reduced radiative heat losses associated with enhanced mixing. For both lobed injector geometries examined here, CO emissions became high for low values of the fuel/air mass flux ratio, again consistent with locally premixed combustion behavior, despite the fact that fuel was injected separately from air directly into the burner test section. The present study demonstrates that, for fuel-air mixing enhancement devices, control of the local equivalence ratio is critical in order to optimize burner emissions.

Mitchell, M. G.↗
NASA NTRS1997

Mixing Enhancement in a Lobed Injector

An experimental investigation of the non-reactive mixing processes associated with a lobed fuel injector in a coflowing air stream is presented. The lobed fuel injector is a device which generates streamwise vorticity, producing high strain rates which can enhance the mixing of reactants while delaying ignition in a controlled manner. The lobed injectors examined in the present study consist of two corrugated plates between which a fuel surrogate, CO2, is injected into coflowing air. Acetone is seeded in the CO2 supply as a fuel marker. Comparison of two alternative lobed injector geometries is made with a straight fuel injector to determine net differences in mixing and strain fields due to streamwise vorticity generation. Planar laser-induced fluorescence (PLIF) of the seeded acetone yields two-dimensional images of the scalar concentration field at various downstream locations, from which local mixing and scalar dissipation rates are computed. It is found that the lobed injector geometry can enhance molecular mixing and create a highly strained flowfield, and that the strain rates generated by scalar energy dissipation can potentially delay ignition in a reacting flowfield.

Smith, L. L.↗
NASA NTRS1996

NOx Emissions from a Lobed Fuel Injector/Burner

The present experimental study examines the performance of a novel fuel injector/burner configuration with respect to reduction in nitrogen oxide NOx emissions. The lobed injector/burner is a device in which very rapid initial mixing of reactants can occur through strong streamwise vorticity generation, producing high fluid mechanical strain rates which can delay ignition and thus prevent the formation of stoichiometric diffusion flames. Further downstream of the rapid mixing region. this flowfield produces a reduced effective strain rate, thus allowing ignition to occur in a premixed mode, where it is possible for combustion to take place under locally lean conditions. potentially reducing NOx emissions from the burner. The present experiments compare NO/NO2/NOx emissions from a lobed fuel injector configuration with emissions from a straight fuel injector to determine the net effect of streamwise vorticity generation. Preliminary results show that the lobed injector geometry can produce lean premixed flame structures. while for comparable flow conditions, a straight fuel injector geometry produces much longer. sooting diffusion flames or slightly rich pre-mixed flames. NO measurements show that emissions from a lobed fuel injector/burner can be made significantly lower than from a straight fuel injector under comparable flow conditions.

Mitchell, M. G.↗
NASA NTRS1984

NASA: Model development for human factors interfacing

The results of an intensive literature review in the general topics of human error analysis, stress and job performance, and accident and safety analysis revealed no usable techniques or approaches for analyzing human error in ground or space operations tasks. A task review model is described and proposed to be developed in order to reduce the degree of labor intensiveness in ground and space operations tasks. An extensive number of annotated references are provided.

Smith, L. L.↗
NASA NTRS1981

The CAMEO barium release - E/parallel/ fields over the polar cap

Four successive thermite barium releases at an altitude of 965 km over polar cap invariant latitudes 84 to 76 deg near magnetic midnight were conducted from the orbiting second stage of the vehicle that launched Nimbus 7; the releases were made as part of the CAMEO (Chemically Active Material Ejected in Orbit) program. This was the first opportunity to observe the behavior of conventional barium release when conducted at orbital velocity in the near-earth magnetic field. The principal unexpected characteristic in the release dynamics was the high, 1.4 to 2.6 km/s, initial Ba(+) expansion velocity relative to an expected velocity of 0.9 km/s. Attention is also given to neutral cloud expansion, initial ion cloud expansion, convective motion, and the characteristics of field-aligned motion. The possibility of measuring parallel electric fields over the polar cap by observing perturbations in the motion of the visible ions is assessed.

Heppner, J. P.↗
NASA NTRS1980

High-resolution Martian atmosphere modeling

A multilayer radiative transfer, high-spectral-resolution infrared model of the lower atmosphere of Mars has been constructed to assess the effect of scattering on line profiles. The model takes into accout aerosol scattering and absorption and includes a line-by-line treatment of scattering and absorption by CO2 and H2O. The aerosol complex indices of refraction used were those measured on montmorillonite and basalt chosen on the basis of Mars ir data from the NASA Lear Airborne Observatory. The particle sizes and distribution were estimated using Viking data. The molecular line treatment employs the AFGL line parameters and Voigt profiles. The modeling results indicate that the line profiles are only slightly affected by normal aerosol scattering and absorption, but the effect could be appreciable for heavy loading. The technique described permits a quantitative approach to assessing and correcting for the effect of aerosols on lineshapes in planetary atmospheres.

Egan, W. G.↗
NASA NTRS1979

Near-infrared observations of a new molecular feature in IRC + 10216

This letter presents a spectrum of IRC + 10216 in the 3000-4400-kayser region at 9-kayser resolution. A molecular feature at 3400-3600 kaysers has been detected which is attributed to an unspecified N-H bonded molecule; the feature appears to be variable in phase with the infrared light curve. Evidence is given for temperature variations of the emitting dust shell in phase with the infrared light curve. The results suggest that the variability of the molecular feature is due to reversible dissociation of the responsible molecule, which could occur at the higher temperatures accompanying the maxima of the light curve.

Krassner, J.↗
NASA NTRS1979

An analysis of water in galactic infrared sources using the NASA Lear Airborne Observatory

The Michelson interferometer system on the NASA Lear Jet Airborne Observatory is described as well as the data reduction procedures. The objects observed (standard stars, M stars, a nebula, planets, and the moon) are discussed and the observing parameters are listed for each flight date. The spectra obtained from these data flights are presented, grouped by class of object.

Smith, L. L.↗
NASA NTRS1978

Comparison between infrared Martian disk spectra and optical properties of terrestrial analogs

Medium spectral resolution (20 kaysers) infrared measurements of the Martian disk made between 2900 and 5600 kaysers from the NASA Lear Airborne Observatory have been successfully compared with predictions derived from a model of the Martian soil and atmosphere. Modeling of the Martian atmosphere permitted the extraction of Martian soil reflectance in the CO2 bands centered at 3657 kaysers. Three Martian soil analogs previously considered acceptable - limonite, montmorillonite, and basalt - were analyzed to determine the optical complex indices of refraction in the same range as the airborne observations, for mathematical modeling. A characteristic surface particle size approximately 1 to 3 microns diameter is indicated. It is concluded that the Martian soil surface near-infrared optical properties are consistent with a soil composition similar to montmorillonite or limonite, mixed with a basalt.

Egan, W. G.↗
NASA NTRS1978

Airborne infrared interferometric observations and analysis of stratospheric trace constituents

Infrared interferometric observations of key trace constituents of the stratosphere have been obtained. The NASA Lear Airborne Observatory with the Grumman airborne interferometer system was flown in the lower stratosphere at an altitude of 13.7 km to obtain transmission spectra in the 2800-6000 per cm region at a resolution of 2.5 per cm using the moon as a source. An atmospheric modeling program and the AFGL line parameter atlas are used to identify H2O, CH4, O3 and other trace constituents and to derive stratospheric column densities (molecules/sq cm).

Smith, L. L.↗
NASA NTRS1978

Martian atmosphere modeling between 0.4 and 3.5 microns - Comparison of theory and experiment

A model of the lower atmosphere of Mars has been constructed that combines aerosol absorption and scattering with a line-by-line analysis of CO2 and H2O in a multilayer radiative transfer program. Aerosol composition previously inferred from the NASA Lear Jet Observatory data was used to measure the optical complex indices of refraction of appropriate Martian analogs from 0.4 to 2.5 microns. The aerosol vertical particle density scale was deduced using the Viking camera observations of the soil and sky intensities between 0.4 and 1.0 microns in comparison with those modeled using a multilayer Mie scattering program. A comparison of observed Mars atmospheric absorptions was made with those obtained using Lorentz, Voigt, and Doppler line profiles in a multilayer model of the CO2 and H2O. The Voigt line profile of CO2 absorption at approximately 4976 kaysers was then combined in a multilayer aerosol model of the Martian atmosphere. An evaluation of the effect on the line shape was made using several aerosol loadings.

Egan, W. G.↗
NASA NTRS1975

Stability analysis of nonlinear autonomous systems - General theory and application to flutter

The analysis makes use of a singular perturbation method, the multiple time scaling. Concepts of stable and unstable limit cycles are introduced. The solution is obtained in the form of an asymptotic expansion. Numerical results are presented for the nonlinear flutter of panels and airfoils in supersonic flow. The approach used is an extension of a method for analyzing nonlinear panel flutter reported by Morino (1969).

Smith, L. L.↗
NASA NTRS1974

Catalog of data summary of airglow observations obtained at Haleakala, Hawaii

The airglow studies were initiated in July 1961 in response to the discovery of unusual phenomena in the tropical airglow as observed from Algeria. Hawaii, being the southern-most area in the United States and within the tropics, and possessing high mountains with frequent clear skies well isolated from the contaminating light and dust of civilization, appeared to be an ideal location for establishing a tropical airglow station. The University of Hawaii was already developing the Mees Solar Laboratory on Haleakala on the island of Maui, so that the addition of a night sky observatory was a natural development. The collection of data covers a span of about seven and one-half years, including the minimum of the solar cycle in 1963 and just getting into the next maximum in 1968-69. It was unfortunate that financial limitations did not permit the continuation of the observations through one complete solar cycle.

Steiger, W. R.↗
NASA NTRS1972

Observations of the diffuse galactic light.

Systematic observations during five nights were made with a field of 137 arc seconds at a fixed declination of 20 deg 42 min through one arm of the Milky Way over a range of right ascension from 257 to 336 deg. Corrections for zodiacal light, airglow, and integrated starlight leave a residual which is interpreted as the diffuse galactic light. The residual, plotted against galactic latitude, suggests that the diffuse light in the sample studied emanates from several discrete sources.

Roach, F. E.↗
NASA NTRS1972

The evolution of water vapor in the atmosphere of Venus.

Examination of the feasibility of loss of water vapor from the Venus atmosphere, assuming H2O as the sole initial constituent. A steady-state model is constructed, and the photochemistry establishes the distribution of important products in the upper atmosphere. Calculations of exospheric temperatures yield values as high as 100,000 K. Such large temperatures result from the large abundance of atomic hydrogen in the exosphere, and imply a dynamic outflow of all constituents from the upper region of the atmosphere. Such an outflow would cause the escape of all hydrogen and some of the oxygen resulting from dissociation of H2O. Little loss of CO2 would result, due to its low abundance in the upper region, permitting its accumulation to the present observed value. It is concluded that if Venus formed from the same mix of materials as the earth, much tectonic activity and fairly rapid outgassing must have occurred during the early phase of its history to account for the loss of water vapor.

Smith, L. L.↗