1,022 research outputs found
Aircraft Engine Technology for Green Aviation to Reduce Fuel Burn
The NASA Fundamental Aeronautics Program Subsonic Fixed Wing Project and Integrated Systems Research Program Environmentally Responsible Aviation Project in the Aeronautics Research Mission Directorate are conducting research on advanced aircraft technology to address the environmental goals of reducing fuel burn, noise and NOx emissions for aircraft in 2020 and beyond. Both Projects, in collaborative partnerships with U.S. Industry, Academia, and other Government Agencies, have made significant progress toward reaching the N+2 (2020) and N+3 (beyond 2025) installed fuel burn goals by fundamental aircraft engine technology development, subscale component experimental investigations, full scale integrated systems validation testing, and development validation of state of the art computation design and analysis codes. Specific areas of propulsion technology research are discussed and progress to date
Heat Transfer Measurements for a Film Cooled Turbine Vane Cascade
Experimental heat transfer and pressure measurements were obtained on a large scale film cooled turbine vane cascade. The objective was to investigate heat transfer on a commercial high pressure first stage turbine vane at near engine Mach and Reynolds number conditions. Additionally blowing ratios and coolant density were also matched. Numerical computations were made with the Glenn-HT code of the same geometry and compared with the experimental results. A transient thermochromic liquid crystal technique was used to obtain steady state heat transfer data on the mid-span geometry of an instrumented vane with 12 rows of circular and shaped film cooling holes. A mixture of SF6 and Argon gases was used for film coolant to match the coolant-to-gas density ratio of a real engine. The exit Mach number and Reynolds number were 0.725 and 2.7 million respectively. Trends from the experimental heat transfer data matched well with the computational prediction, particularly for the film cooled case
Acoustic Liners for Turbine Engines
An improved acoustic liner for turbine engines is disclosed. The acoustic liner may include a straight cell section including a plurality of cells with straight chambers. The acoustic liner may also include a bent cell section including one or more cells that are bent to extend chamber length without increasing the overall height of the acoustic liner by the entire chamber length. In some cases, holes are placed between cell chambers in addition to bending the cells, or instead of bending the cells
Number-phase-squeezed few-photon state generated from squeezed atoms
This paper develops a method of manipulating the squeezed atom state to
generate a few-photon state whose phase or photon-number fluctuations are
prescribed at our disposal. The squeezed atom state is a collective atomic
state whose quantum fluctuations in population difference or collective dipole
are smaller than those of the coherent atom state. It is shown that the
squeezed atom state can be generated by the interaction of atoms with a
coherent state of the electromagnetic field, and that it can be used as a
tunable source of squeezed radiation. A variety of squeezed states, including
the photon-number squeezed state and the phase squeezed state, can be produced
by manipulating the atomic state. This is owing to the fact that
quantum-statistical information of the atomic state is faithfully transferred
to that of the photon state. Possible experimental situations to implement our
theory are discussed.Comment: 17 pages, RevTex, 14 figures, using epsf.sty, title is changed,
discussion about dissipation is added, accepted for publication in Physical
Review
Contractive Schroedinger cat states for a free mass
Contractive states for a free quantum particle were introduced by Yuen [Yuen
H P 1983 Phys. Rev. Lett. 51, 719] in an attempt to evade the standard quantum
limit for repeated position measurements. We show how appropriate families of
two- and three component ``Schroedinger cat states'' are able to support
non-trivial correlations between the position and momentum observables leading
to contractive behavior. The existence of contractive Schroedinger cat states
is suggestive of potential novel roles of non-classical states for precision
measurement schemes.Comment: 24 pages, 7 encapsulated eps color figures, REVTeX4 style. Published
online in New Journal of Physics 5 (2003) 5.1-5.21. Higher-resolution figures
available in published version. (accessible at http://www.njp.org/
Quantum correlated twin atomic beams via photo-dissociation of a molecular Bose-Einstein condensate
We study the process of photo-dissociation of a molecular Bose-Einstein
condensate as a potential source of strongly correlated twin atomic beams. We
show that the two beams can possess nearly perfect quantum squeezing in their
relative numbers.Comment: Corrected LaTeX file layou
Stable nondegenerate optical parametric oscillation at degenerate frequencies in Na:KTP
We report the realization of a light source specifically designed for the
generation of bright continuous-variable entangled beams and for
Heisenberg-limited inteferometry. The source is a nondegenerate, single-mode,
continuous-wave optical parametric oscillator in Na:KTP, operated at frequency
degeneracy and just above threshold, which is also of interest for the study of
critical fluctuations at the transition point. The residual
frequency-difference jitter is 150 kHz for a 3 MHz cold cavity half-width
at half maximum. We observe 4 dB of photon-number-difference squeezing at 200
kHz. The Na:KTP crystal is noncritically phase-matched for a 532 nm pump and
polarization crosstalk is therefore practically nonexistent
Macroscopic test of quantum mechanics versus stochastic electrodynamics
We identify a test of quantum mechanics versus macroscopic local realism in the form of stochastic electrodynamics. The test uses the steady-state triple quadrature correlations of a parametric oscillator below threshold
Two Mode Quantum Systems: Invariant Classification of Squeezing Transformations and Squeezed States
A general analysis of squeezing transformations for two mode systems is given
based on the four dimensional real symplectic group Sp(4,\Re)\/. Within the
framework of the unitary metaplectic representation of this group, a
distinction between compact photon number conserving and noncompact photon
number nonconserving squeezing transformations is made. We exploit the
Sp(4,\Re)-SO(3,2)\/ local isomorphism and the U(2)\/ invariant squeezing
criterion to divide the set of all squeezing transformations into a two
parameter family of distinct equivalence classes with representative elements
chosen for each class. Familiar two mode squeezing transformations in the
literature are recognized in our framework and seen to form a set of measure
zero. Examples of squeezed coherent and thermal states are worked out. The need
to extend the heterodyne detection scheme to encompass all of U(2)\/ is
emphasized, and known experimental situations where all U(2)\/ elements can
be reproduced are briefly described.Comment: Revtex 37 pages, Latex figures include
Micro Concentrator Concept for Cost Reduction and Efficiency Enhancement of Thin Film Chalcopyrite Photovoltaics Results from EU Joint Research Program CHEETAH
Results for research on chalcopyrite micro concentrator solar cells obtained within the framework of CHEETAH joint program are shown. A top down proof of concept study reveals close to 30 relative efficiency increase under light concentration using inkjet printed CIGSSe. A novel bottom up approach for local chalcopyrite absorbers grown from indium islands demonstrates working CISe micro cells. Millimeter sized lenses are fabricated from PMMA by a casting process to be applied as concentrator optics. For a combined exploitation of direct and diffuse light components an angular splitting concentrator based on chalcopyrite and kesterite absorber material is proposed. The scientific innovation brought will enrich further development of CIGSe solar cells and contribute to their relevance in photovoltaic energy productio
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