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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Stresses in dome-shaped shells of revolution with discontinuities at the apex

Asymptotic solutions of Novozhilov's equations of shells of revolution are derived for axisymmetric and first harmonic loadings. The solutions obtained are valid throughout the shallow and nonshallow regions. Stresses in dome shaped shells of revolution with a discontinuity in the form of a circular hole, a circular rigid insert, or a nozzle at the apex have been investigated. Numerical results are obtained for spheres, ellipsoids, and paraboloids, containing a discontinuity under a internal pressure and moment. Curves depicting stress distributions are given. The influence of three types of discontinuity on the stresses of the shells is also given.

Chen, C. H.↗
NASA NTRS1977

Quantitative mapping of suspended solids in wastewater sludge plumes in the New York Bight apex

The purpose of this investigation was to apply the previously reported methodology to remotely sensed data that were collected over wastewater sludge plumes in the New York Bight apex on September 22, 1975. Spectral signatures were also determined during this study. These signatures may be useful in the specific identification of sludge plumes, as opposed to other plumes such as those created by the disposal of industrial acid wastes.

Johnson, R. W.↗
NASA NTRS1980

Remote sensing and spectral analysis of plumes from ocean dumping in the New York Bight Apex

The application of the remote sensing techniques of aerial photography and multispectral scanning in the qualitative and quantitative analysis of plumes from ocean dumping of waste materials is investigated in the New York Bight Apex. Plumes resulting from the dumping of acid waste and sewage sludge were observed by Ocean Color Scanner at an altitude of 19.7 km and by Modular Multispectral Scanner and mapping camera at an altitude of 3.0 km. Results of the qualitative analysis of multispectral and photographic data for the mapping, location, and identification of pollution features without concurrent sea truth measurements are presented which demonstrate the usefulness of in-scene calibration. Quantitative distributions of the suspended solids in sewage sludge released in spot and line dumps are also determined by a multiple regression analysis of multispectral and sea truth data.

Johnson, R. W.↗
NASA NTRS1984

Development of partially fluorinated resin apex seals

Partially fluorinated polyimides were prepared and molded in the form of discs and pins for test as potential apex seal materials for advanced rotary combustion engines. The polyimides were formulated from the diamine 2,2-bis 4-(4-aminophenoxy)phenyl hexafluoropropane (4-BDAF) and the dianhydrides of pyromellitic acid (PMDA) and benzophenonetetracarboxylic acid (BTDA). Tribological testing was performed at sliding speeds of 0.31 to 11.6 m/s and at temperatures of from 298K to 573K. It is shown that the carbon fiber filled polyimides, particularly the 80/20 compositions, have an excellent balance of wear/friction at 573K. The unfilled, 80/20 and 60/40 compositions indicate an unusual combination of high friction and low wear which may be advantageous in such applications as brakes and traction drives.

Green, H. E.↗
NASA NTRS1993

Microfossils of the Early Archean Apex chert - New evidence of the antiquity of life

Eleven taxa (including eight heretofore undescribed species) of cellularly preserved filamentous microbes, among the oldest fossils known, have been discovered in a bedded chert unit of the Early Archean Apex Basalt of northwestern Western Australia. This prokaryotic assemblage establishes that trichomic cyanobacteriumlike microorganisms were extant and morphologically diverse at least as early as about 3465 million years ago and suggests that oxygen-producing photoautotrophy may have already evolved by this early stage in biotic history.

Schopf, J. W.↗
NASA NTRS1993

Hard apex transition in quasi-periodic oscillators - Closing of the accretion gap

We propose that the 'hard apex' transition in the X-ray two-color diagrams for low-mass X-ray binaries exhibiting quasi-periodic oscillation is associated with closure of a gap between the accretion disk and the star. At low accretion rates, gas crosses this gap intermittently. However, when the mass accretion rate increases, the disk thickens and its inner edge touches the star, thus forming a boundary layer through which the gas flows steadily. This explanation is viable provided that the equation of state of nuclear matter is not significantly harder than the Bethe-Johnson I prescription. Accretion gap scenarios are possibly distinguishable from models which invoke a small magnetosphere around the neutron star, in that they preclude large stellar magnetic fields and associate the high-frequency (horizontal-branch) oscillations with different sites.

Biehle, Garrett T.↗
NASA NTRS1949

Investigations at supersonic speeds of 22 triangular wings representing two airfoil sections for each of 11 apex angles

Data obtained from wind tunnel investigations of two series of 11 triangular wings conducted at Mach numbers of 1.62, 1.92, and 1.40 to determine the effect of leading-edge shape and to compare actual test values with the nonviscous linear theory are presented. The two series of wings had identical plan forms, a constant thickness ratio of 8 percent, a constant location of maximum-thickness point of 18 percent, and a range of apex half-angles from 10 degrees to forty-five degrees. The first series has an elliptical leading edge and the second series a wedge leading edge. Measurements were made of lift, drag, pitching moment, and pressure distribution, the latter being confined to three wings at one Mach number.

Love, Eugene S↗
NASA NTRS1955

Investigations at Supersonic Speeds of 22 Triangular Wings Representing Two Airfoil Sections for Each of 11 Apex Angles

The results of tests of 22 triangular wings, representing two leading-edge shapes for each of 11 apex angles, at Mach numbers 1.62, 1.92, and 1.40 are presented and compared with theory. All wings have a common thickness ratio of 8 percent and a common maximum-thickness point at 18 percent chord. Lift, drag, and pitching moment are given for all wings at each Mach number. The relation of transition in the boundary layer, shocks on the wing surfaces, and characteristics of the pressure distributions is discussed for several wings.

Love, Eugene S↗
NASA NTRS2002

APEX 3D Propeller Test Preliminary Design

A low Reynolds number, high subsonic mach number flight regime is fairly uncommon in aeronautics. Most flight vehicles do not fly under these aerodynamic conditions. However, recently there have been a number of proposed aircraft applications (such as high altitude observation platforms and Mars aircraft) that require flight within this regime. One of the main obstacles to flight under these conditions is the ability to reliably generate sufficient thrust for the aircraft. For a conventional propulsion system, the operation and design of the propeller is the key aspect to its operation. Due to the difficulty in experimentally modeling the flight conditions in ground-based facilities, it has been proposed to conduct propeller experiments from a high altitude gliding platform (APEX). A preliminary design of a propeller experiment under the low Reynolds number, high mach number flight conditions has been devised. The details of the design are described as well as the potential data that will be collected.

Colozza, Anthony J.↗
NASA NTRS2006

Aircraft Particle Emissions eXperiment (APEX)

APEX systematically investigated the gas-phase and particle emissions from a CFM56-2C1 engine on NASA's DC-8 aircraft as functions of engine power, fuel composition, and exhaust plumage. Emissions parameters were measured at 11 engine power, settings, ranging from idle to maximum thrust, in samples collected at 1, 10, and 30 m downstream of the exhaust plane as the aircraft burned three fuels to stress relevant chemistry. Gas-phase emission indices measured at 1 m were in good agreement with the ICAO data and predictions provided by GEAE empirical modeling tools. Soot particles emitted by the engine exhibited a log-normal size distribution peaked between 15 and 40 nm, depending on engine power. Samples collected 30 m downstream of the engine exhaust plane exhibited a prominent nucleation mode.

Wey, C. C.↗
NASA NTRS2010

Analysis of Apex Seal Friction Power Loss in Rotary Engines

An analysis of the frictional losses from the apex seals in a rotary engine was developed. The modeling was initiated with a kinematic analysis of the rotary engine. Next a modern internal combustion engine analysis code was altered for use in a rotary engine to allow the calculation of the internal combustion pressure as a function of rotor rotation. Finally the forces from the spring, inertial, and combustion pressure on the seal were combined to provide the frictional horsepower assessment.

Handschuh, Robert F.↗
NASA NTRS2014

A Survey of Jet Aircraft PM by TEM in APEX III

Based upon field testing during the NASA led APEX III campaign conducted in November 2005 at the NASA Glenn Research Center in coordination with Continental Airlines and Cleveland Hopkins International Airport. This paper reports observations of particulate emissions collected from a suite of jet engine aircraft to assess differences and similarities in soot macro- micro- and nanostructure using transmission electron microscopy (TEM). Aggregates are compact, primary particle sizes varied and nanostructure mixed. Comparisons are made to more familiar laboratory flame-generated soot as a well-studied point of reference. Results are interpreted in terms of turbulence interacting with the different stages of particle formation and growth.

soot↗
NASA NTRS2014

Chemistry Characterization of Jet Aircraft Engine Particulate by XPS: Results from APEX III

This paper reports XPS analysis of jet exhaust particulate from a B737, Lear, ERJ, and A300 aircraft during the APEX III NASA led field campaign. Carbon hybridization and bonding chemistry are identified by high-resolution scans about the C1s core-shell region. Significant organic content as gauged by the sp3/sp2 ratio is found across engines and platforms. Polar oxygen functional groups include carboxylic, carbonyl and phenol with combined content of 20 percent or more. By lower resolution survey scans various elements including transition metals are identified along with lighter elements such as S, N, and O in the form of oxides. Burning additives within lubricants are probable sources of Na, Ba, Ca, Zn, P and possibly Sn. Elements present and their percentages varied significantly across all engines, not revealing any trend or identifiable cause for the differences, though the origin is likely the same for the same element when observed. This finding suggests that their presence can be used as a tracer for identifying soots from aircraft engines as well as diagnostic for monitoring engine performance and wear.

soot↗
NASA NTRSDate not supplied

Aerosol Wind Profiler (AWP) Doppler Wind Lidar Airborne Observations During the NOAA Joint Venture 3-D Wind Measurement Demonstration and NASA Active-Passive Profiling Experiment (APEX)

The NASA Langley Research Center (LaRC) has recently completed development of the Aerosol Wind Profiler (AWP) airborne Doppler wind lidar (DWL) instrument. AWP was supported by the NASA Earth Science Technology Office and the Earth Science Division, a project that adapted the Wind-Space Pathfinder (Wind-SP) DWL transceiver onto a structure for flight aboard a variety of NASA research aircraft. AWP demonstrates many technologies required for a space DWL mission, including a coherent-detection, optical heterodyne laser transmitter with high pulse energy (up to ~55 mJ) and repetition rate (200 Hz), electronic control of the beam path allowing for multiple viewing angles (allowing vector wind measurements) with no moving parts, compact highly-stable and tunable reference lasers allowing for high-precision measurement of velocity at long ranges while mitigating the impact of satellite platform velocity, and many others. AWP represents NASA’s only currently operational airborne 3-D wind profiling sensor. NASA LaRC was selected by the NOAA Joint Venture (JV) program to conduct a suborbital 3-D Wind measurement campaign demonstrate how data from a coherent-detection DWL like AWP could serve NOAA’s weather analysis and forecasting needs. The NOAA JV program is designed to work with the private sector, academia and other federal agencies to explore the feasibility and capability of emerging technologies spacecraft and other mission-specific tools to meet NOAA’s mission requirements. AWP was initially demonstrated on the NASA DC-8 within this JV program in October 2023, piggybacking on the NASA EcoDemonstrator mission focused on in-situ sampling of jet aircraft emissions and contrail formation from Everett, Washington. The in-situ sampling resulted in very frequent and rapid aircraft attitude changes which unfortunately degraded AWP data quality. But, during times with level flight and AVAPS dropsonde operations, AWP demonstrated excellent precision (< 2 m/s RMS) with high vertical (< 100 meter) resolution and 2 km spacing between profiles. AWP will be flown again on the NASA LaRC Gulfstream-3 from mid-September to mid-October 2024 out of Hampton, VA to complete the NOAA JV 3-D wind demonstration. Additional AWP flights will occur in early November from southern California during the NASA Active-Passive Profiling Experiment (APEX), focused on underflights of the NASA ER-2 equipped with many atmospheric profiling sensors. This presentation will summarize AWP measurements collected during these two fall 2024 flight campaigns, and how the AWP data compares with AVAPS dropsonde, NOAA weather prediction model, and GOES atmospheric motion vector data.

Kristopher Bedka↗
NASA NTRS1977

Aerodynamic loads near cranks, apexes, and tips of thin, lifting wings in incompressible flow

The calculation of the incompressible and irrotational flow in the vicinity of tips and corners of thin, lifting wings is considered. It is shown that the important characteristics of the flow are governed by an eigenvalue problem, which is nonlinear at the trailing edge because of the shed wake (assumed to be in the wing plane). A new solution method was devised because either the existing methods were not valid for the trailing edge case or they would have required excessive amounts of computer time. The new method, which is fundamentally different than the previous ones, was used to calculate solutions for a number of cases, including some for which correct answers had not previously been obtained. Two of these solutions were used to determine the validity of drag and leading-edge-suction distributions near the tips of a delta wing and a swept wing as calculated by using both the vortex lattice method and a kernel function method. The calculations for the swept wing resolved the question of whether or not the induced drag should be zero at the wing tip.

Medan, R. T.↗