2,355 research outputs found
NASA Quiet Clean General Aviation Turbofan (QCGAT) program status
The suitability of large engine technology to reduce noise, emissions, and fuel consumption of small turbine engines and develop new technology where required is determined. The design, fabrication, assembly, test, and delivery of the experimental engines to NASA are discussed
Preliminary QCGAT program test results
NASA Lewis Research Center is conducting a program to demonstrate that large commercial engine technology can be applied to general aviation engines to reduce noise, emissions and fuel consumption and to develop new technology where required. The overall engine program, design, and technology incorporated into the QCGAT engines are described. In addition, preliminary engine test results are presented and compared to the technical requirements the engines were designed to meet
Summary of NASA QCGAT program
The application of large turbofan engine technology to small general aviation turbofan engines to achieve low noise, low emissions, and acceptable fuel consumption is described
Fuel savings potential of the NASA Advanced Turboprop Program
The NASA Advanced Turboprop (ATP) Program is directed at developing new technology for highly loaded, multibladed propellers for use at Mach 0.65 to 0.85 and at altitudes compatible with the air transport system requirements. Advanced turboprop engines offer the potential of 15 to 30 percent savings in aircraft block fuel relative to advanced turbofan engines (50 to 60 percent savings over today's turbofan fleet). The concept, propulsive efficiency gains, block fuel savings and other benefits, and the program objectives through a systems approach are described. Current program status and major accomplishments in both single rotation and counter rotation propeller technology are addressed. The overall program from scale model wind tunnel tests to large scale flight tests on testbed aircraft is discussed
Preliminary Analysis of Over-all Performance of an Eight-stage Axial-flow Research Compressor with Two Long-chord Transonic Inlet Stages
Investigation of Reynolds Number Effect on Performance of an Eight-stage Axial-flow Research Compressor with Long- and Medium-chord Lengths in the Two Transonic Inlet Stages
Discrete breathers in polyethylene chain
The existence of discrete breathers (DBs), or intrinsic localized modes
(localized periodic oscillations of transzigzag) is shown. In the localization
region periodic contraction-extension of valence C-C bonds occurs which is
accompanied by decrease-increase of valence angles. It is shown that the
breathers present in thermalized chain and their contribution dependent on
temperature has been revealed.Comment: 5 pages, 6 figure
Acoustic breathers in two-dimensional lattices
The existence of breathers (time-periodic and spatially localized lattice
vibrations) is well established for i) systems without acoustic phonon branches
and ii) systems with acoustic phonons, but also with additional symmetries
preventing the occurence of strains (dc terms) in the breather solution. The
case of coexistence of strains and acoustic phonon branches is solved (for
simple models) only for one-dimensional lattices.
We calculate breather solutions for a two-dimensional lattice with one
acoustic phonon branch. We start from the easy-to-handle case of a system with
homogeneous (anharmonic) interaction potentials. We then easily continue the
zero-strain breather solution into the model sector with additional quadratic
and cubic potential terms with the help of a generalized Newton method. The
lattice size is . The breather continues to exist, but is dressed
with a strain field. In contrast to the ac breather components, which decay
exponentially in space, the strain field (which has dipole symmetry) should
decay like . On our rather small lattice we find an exponent
90GHz and 150GHz observations of the Orion M42 region. A sub-millimeter to radio analysis
We have used the new 90GHz MUSTANG camera on the Robert C. Byrd Green Bank
Telescope (GBT) to map the bright Huygens region of the star-forming region M42
with a resolution of 9" and a sensitivity of 2.8mJy/beam. 90GHz is an
interesting transition frequency, as MUSTANG detects both the free-free
emission characteristic of the HII region created by the Trapezium stars,
normally seen at lower frequencies, and thermal dust emission from the
background OMC1 molecular cloud, normally mapped at higher frequencies. We also
present similar data from the 150GHz GISMO camera taken on the IRAM telescope.
This map has 15" resolution. By combining the MUSTANG data with 1.4, 8, and
21GHz radio data from the VLA and GBT, we derive a new estimate of the emission
measure (EM) averaged electron temperature of Te = 11376K by an original method
relating free-free emission intensities at optically thin and optically thick
frequencies. Combining ISO-LWS data with our data, we derive a new estimate of
the dust temperature and spectral emissivity index within the 80" ISO-LWS beam
toward OrionKL/BN, Td = 42K and Beta=1.3. We show that both Td and Beta
decrease when going from the HII region and excited OMC1 interface to the
denser UV shielded part of OMC1 (OrionKL/BN, Orion S). With a model consisting
of only free-free and thermal dust emission we are able to fit data taken at
frequencies from 1.5GHz to 854GHz.Comment: 18 pages, 8 figures, submitted to the Astrophysical Journa
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