14,086 research outputs found
Measurement of airfoil heat transfer coefficients on a turbine stage
A combined experimental and analytical program was conducted to examine the impact of a number of variables on the midspan heat transfer coefficients of the three airfoil rows in a one and one-half stage large scale turbine model. Variables included stator/rotor axial spacing, Reynolds number, turbine inlet turbulence, flow coefficient, relevant stator 1/stator 2 circumferential position, and rotation. Heat transfer data were acquired on the suction and pressure surfaces of the three airfoils. High density data were also acquired in the leading edge stagnation regions. Extensive documentation of the steady and unsteady aerodynamics was acquired. Finally, heat transfer data were compared with both a steady and an unsteady boundary layer analysis
The effects of inlet turbulence and rotor/stator interactions on the aerodynamics and heat transfer of a large-scale rotating turbine model. Volume 2: Heat transfer data tabulation. 15 percent axial spacing
A combined experimental and analytical program was conducted to examine the effects of inlet turbulence on airfoil heat transfer. The experimental portion of the study was conducted in a large-scale (approx 5X engine), ambient temperature, rotating turbine model configured in both single stage and stage-and-a-half arrangements. Heat transfer measurements were obtained using low-conductivity airfoils with miniature thermcouples welded to a thin, electrically heated surface skin. Heat transfer data were acquired for various combinations of low or high inlet turbulence intensity, flow coefficient, first-stator/rotor axial spacing, Reynolds number and relative circumferential position of the first and second stators. Aerodynamic measurements obtained as part of the program include distributions of the mean and fluctuating velocities at the turbine inlet and, for each airfoil row, midspan airfoil surface pressures and circumferential distributions of the downstream steady state pressures and fluctuating velocities. Analytical results include airfoil heat transfer predictions produced using existing 2-D boundary layer computation schemes and an examination of solutions of the unsteady boundary layer equations. The results are reported in four separate volumes, of which this is Volume 2: Heat Transfer Data Tabulation; 15 Percent Axial Spacing
Measurement of airfoil heat transfer coefficients on a turbine stage
A turbulence generating grid was designed and installed in the turbine inlet which produced the target nominal value of 10 percent free stream turbulence. Aerodynamic documentation of the rotor and stator midspan surface pressure distributions were obtained. Midspan heat transfer data were obtained on the rotor and stator for variations in inlet turbulence, rotor-stator axial spacing, and rotor incidence
The effects of inlet turbulence and rotor/stator interactions on the aerodynamics and heat transfer of a large-scale rotating turbine model. Volume 3: Heat transfer data tabulation 65 percent axial spacing
This is Volume 3 - Heat Transfer Data Tabulation (65 percent Axial Spacing) of a combined experimental and analytical program which was conducted to examine the effects of inlet turbulence on airfoil heat transfer. The experimental portion of the study was conducted in a large-scale (approximately 5X engine), ambient temperature, rotating turbine model configured in both single stage and stage-and-a-half arrangements. Heat transfer measurements were obtained using low-conductivity airfoils with miniature thermocouples welded to a thin, electrically heated surface skin. Heat transfer data were acquired for various combinations of low or high inlet turbulence intensity, flow coefficient, first-stator/rotor axial spacing, Reynolds number and relative circumferential position of the first and second stators
Measurement of airfoil heat transfer coefficients on a turbine stage
The Primary basis for heat transfer analysis of turbine airfoils is experimental data obtained in linear cascades. These data were very valuable in identifying the major heat transfer and fluid flow features of a turbine airfoil. The first program objective is to obtain a detailed set of heat transfer coefficients along the midspan of a stator and a rotor in a rotating turbine stage. The data are to be compared to some standard analysis of blade boundary layer heat transfer which is in use today. A second program objective is to obtain a detailed set of heat transfer coefficients along the midspan of a stator located in the wake of an upstream turbine stage
The effects of inlet turbulence and rotor/stator interactions on the aerodynamics and heat transfer of a large-scale rotating turbine model. Part 4: Aerodynamic data tabulation
A combined experimental and analytical program was conducted to examine the effects of inlet turbulence and airfoil heat transfer. The experimental portion of the study was conducted in a large-scale (approx. 5X engine), ambient temperature, rotating turbine model configured in both single-stage and stage-and-a-half arrangements. Heat transfer measurements were obtained using low-conductivity airfoils with miniature thermocouples welded to a thin, electrically heated surface skin. Heat transfer data were acquired for various combinations of low or high inlet turbulence intensity, flow coefficient, first stator-rotor axial spacing, Reynolds number and relative circumferential position of the first and second stators. Aerodynamic measurements obtained include distributions of the mean and fluctuating velocities at the turbine inlet and, for each airfoil row, midspan airfoil surface pressures and circumferential distributions of the downstream steady state pressures and fluctuating velocities. Results include airfoil heat transfer predictions produced using existing 2-D boundary layer computation schemes and an examination of solutions of the unsteady boundary layer equations
The Magellanic System: What have we learnt from FUSE?
I review some of the findings on the Magellanic System produced by the Far
Ultraviolet Spectroscopic Explorer (FUSE) during and after its eight years of
service. The Magellanic System with its high-velocity complexes provides a
nearby laboratory that can be used to characterize phenomena that involve
interaction between galaxies, infall and outflow of gas and metals in galaxies.
These processes are crucial for understanding the evolution of galaxies and the
intergalactic medium. Among the FUSE successes I highlight are the coronal gas
about the LMC and SMC, and beyond in the Stream, the outflows from these
galaxies, the discovery of molecules in the diffuse gas of the Stream and the
Bridge, an extremely sub-solar and sub-SMC metallicity of the Bridge, and a
high-velocity complex between the Milky Way and the Clouds.Comment: A contributed paper to the FUSE Annapolis Conference "Future
Directions in Ultraviolet Spectroscopy.", 5 pages. To appear as an AIP
Conference Proceedin
Tracking The Post-BBN Evolution Of Deuterium
The primordial abundance of deuterium produced during Big Bang
Nucleosynthesis (BBN) depends sensitively on the universal ratio of baryons to
photons, an important cosmological parameter probed independently by the Cosmic
Microwave Background (CMB) radiation. Observations of deuterium in
high-redshift, low-metallicity QSO Absorption Line Systems (QSOALS) provide a
key baryometer, determining the baryon abundance at the time of BBN to a
precision of 5%. Alternatively, if the CMB-determined baryon to photon ratio is
used in the BBN calculation of the primordial abundances, the BBN-predicted
deuterium abundance may be compared with the primordial value inferred from the
QSOALS, testing the standard cosmological model. In the post-BBN universe, as
gas is cycled through stars, deuterium is only destroyed so that its abundance
measured anytime, anywhere in the Universe, bounds the primordial abundance
from below. Constraints on models of post-BBN Galactic chemical evolution
follow from a comparison of the relic deuterium abundance with the
FUSE-inferred deuterium abundances in the chemically enriched, stellar
processed material of the local ISM.Comment: 8 pages, 5 figures, to appear in the Proceedings of the Future
Directions in Ultraviolet Spectroscopy Conferenc
A Comparison of Ultraviolet, Optical, and X-Ray Imagery of Selected Fields in the Cygnus Loop
During the Astro-1 and Astro-2 Space Shuttle missions in 1990 and 1995, far
ultraviolet (FUV) images of five 40' diameter fields around the rim of the
Cygnus Loop supernova remnant were observed with the Ultraviolet Imaging
Telescope (UIT). These fields sampled a broad range of conditions including
both radiative and nonradiative shocks in various geometries and physical
scales. In these shocks, the UIT B5 band samples predominantly CIV 1550 and the
hydrogen two-photon recombination continuum. Smaller contri- butions are made
by emission lines of HeII 1640 and OIII] 1665. We present these new FUV images
and compare them with optical Halpha and [OIII], and ROSAT HRI X-ray images.
Comparing the UIT images with those from the other bands provides new insights
into the spatial variations and locations of these different types of emission.
By comparing against shock model calculations and published FUV spectroscopy at
select locations, we surmise that resonance scattering in the strong FUV
permitted lines is widespread in the Cygnus Loop, especially in the bright
optical filaments typically selected for observation in most previous studies.Comment: 21 pages with 10 figures. See http://www.pha.jhu.edu/~danforth/uit/
for full-resolution figure
Intergalactic Baryons in the Local Universe
Simulations predict that shocks from large-scale structure formation and
galactic winds have reduced the fraction of baryons in the warm, photoionized
phase (the Lya forest) from nearly 100% in the early universe to less than 50%
today. Some of the remaining baryons are predicted to lie in the warm-hot
ionized medium (WHIM) phase at T=10^5-10^7 K, but the quantity remains a highly
tunable parameter of the models. Modern UV spectrographs have provided
unprecedented access to both the Lya forest and potential WHIM tracers at z~0,
and several independent groups have constructed large catalogs of far-UV IGM
absorbers along ~30 AGN sight lines. There is general agreement between the
surveys that the warm, photoionized phase makes up ~30% of the baryon budget at
z~0. Another ~10% can be accounted for in collapsed structures (stars,
galaxies, etc.). However, interpretation of the ~100 high-ion (OVI, etc)
absorbers at z<0.5 is more controversial. These species are readily created in
the shocks expected to exist in the IGM, but they can also be created by
photoionization and thus not represent WHIM material. Given several pieces of
observational evidence and theoretical expectations, I argue that most of the
observed OVI absorbers represent shocked gas at T~300,000 K rather than
photoionized gas at T<30,000 K, and they are consequently valid tracers of the
WHIM phase. Under this assumption, enriched gas at T=10^5-10^6 K can account
for ~10% of the baryon budget at z<0.5, but this value may increase when bias
and incompleteness are taken into account and help close the gap on the 50% of
the baryons still "missing".Comment: Invited review to appear in "Future Directions in Ultraviolet
Spectroscopy", Oct 20-22, 2008, Annapolis, MD, M. E. Van Steenberg, ed.
(April 2009). 8 pages, five figure
- …