Mathematical Models for Wide-Band Nongray Gas Radiation in Spherical and Cylindrical Geometries

1980 ◽  
pp. 149-170
Keyword(s):  
Mathematical Models ◽  
Wide Band ◽  
Gas Radiation ◽  
Cylindrical Geometries

Calculation of Radiation Signal of Rocket Plume after Atmospheric Attenuation Using Wide Band K-Distribution Model

2013 ◽  
Vol 295-298 ◽  
pp. 2437-2441
Author(s):  
Xue Mei Yin ◽  
Qiu Yang Ma ◽  
Xue Hong Wu ◽  
Yi Gong ◽  
Yan Li Lu
Keyword(s):  
Remote Sensing ◽  
Rocket Engine ◽  
Wide Band ◽  
Distribution Model ◽  
Climatic Effects ◽  
Radiation Process ◽  
Gas Radiation ◽  
Atmospheric Remote Sensing ◽  
Rocket Plume ◽  
Liquid Rocket

The calculation of the gas radiation process plays an important role in the study of atmospheric remote sensing and climatic effects of greenhouse gas. The remote sensing of rocket plume has important significance for early warning, interception, detection, identification and tracking of flight vehicle. A model was established to calculate the remote sensing signal of rocket plume by wide band k-distribution, the liquid rocket plume remote sensing signals in atmospheric window region and the detectors’ working spectrum are calculated, and the results were compared with the results calculated by line-by-line approach. The results showed that in some of the detectors’ working spectral regions, the wide band k-distribution model can be used for the calculation of the remote sensing of liquid rocket engine exhaust plume.

Radiation Modeling in Oxy-Fuel Combustion Scenarios

2009 ◽  
Author(s):  
Gautham Krishnamoorthy ◽  
Muhammad Sami ◽  
Stefano Orsino ◽  
Anura Perera ◽  
Mehrdad Shahnam ◽  
...  
Keyword(s):  
Fluid Dynamic ◽  
Wide Band ◽  
Full Scale ◽  
Radiative Properties ◽  
Band Model ◽  
Particle Radiation ◽  
Gas Radiation ◽  
Gaseous Media ◽  
Wide Band Model ◽  
Radiation Modeling

Three gray models for the radiative properties of gases were examined for their usage in oxy-combustion simulations of a full scale boiler with flue gas recycle. Fully coupled computational fluid dynamic (CFD) simulations of a full scale boiler were carried out employing the weighted-sum-of-gray-gases model (WSGGM) at air burn, dry-recycle and wet-recycle conditions. The resulting thermal and composition fields were then frozen and the radiative properties of the gaseous media recomputed employing the Exponential Wide Band Model (EWBM) and correlations for total emissivities of gas mixtures. It is shown that when high CO2/H2O ratios were encountered within the boiler such as in dry-recycle scenarios, employing emissivity correlations developed for purely CO2 media within the models can result in incorrect gas properties. The errors associated with this can be significant when there are large pockets within the furnace where the gas radiation dominates the particle radiation.

Radiation-Natural Convection Interactions in Two-Dimensional Complex Enclosures

1983 ◽  
Vol 105 (1) ◽  
pp. 89-95 ◽  
Author(s):  
L. C. Chang ◽  
K. T. Yang ◽  
J. R. Lloyd
Keyword(s):  
Natural Convection ◽  
Finite Thickness ◽  
Wide Band ◽  
Temperature Fields ◽  
Two Dimensional ◽  
Transfer Rates ◽  
Gas Radiation ◽  
Radiation Exchange ◽  
Radial Flux ◽  
Physical Phenomena

A numerical finite-difference study has been carried out for the two-dimensional radiation-natural convection interaction phenomena in square enclosures with equal vertical finite-thickness partitions located at the centers of the ceiling and floor. Both participating gases (CO2 and NH3) and nonparticipating gas (air) are considered. In the radiation calculations, the nongray exponential wide-band models for CO2 and NH3 are used, together with a radial flux method utilizing a more realistic polar description for the radiation exchange in the enclosure. Results on the effects of both surface and gas radiation on the velocity and temperature fields and the overall heat transfer rates as functions of the partition heights at two levels of the Grashof number are presented and discussed in terms of the physical phenomena.

A Theoretical and Experimental Study of Radiation–Convection Interaction in a Diffusion Flame

1977 ◽  
Vol 99 (2) ◽  
pp. 212-220 ◽  
Author(s):  
D. E. Negrelli ◽  
J. R. Lloyd ◽  
J. L. Novotny
Keyword(s):  
Diffusion Flame ◽  
Wide Band ◽  
Convection Boundary Layer ◽  
Band Model ◽  
Porous Cylinder ◽  
Stagnation Region ◽  
Stagnation Line ◽  
Gas Radiation ◽  
Composition Problem ◽  
Wide Band Model

An experimental and theoretical investigation of the interaction of gaseous thermal radiation with natural convection was made for a laminar methane-air diffusion flame in the lower stagnation region of a horizontal porous cylinder. The exponential wide-hand gas radiation model was employed in this nonhomogeneous (nonuniform in temperature and composition) problem through the use of scaling techniques. Using a numerical scheme, the compressible energy, flow, and species-diffusion equations were solved simultaneously with and without the radiative component. In the experiment, methane was blown uniformly from the surface of the porous cylinder, setting up (upon ignition) a diffusion flame within the free-convection boundary layer. Using a Mach-Zehnder interferometer and a gas chromatograph, temperature and composition measurements were obtained along the stagnation line. Excellent agreement was found between the results based on the nongray wide-band model and the experimental data. Furthermore, it was found that the wide-band model yielded results that were superior to those results that excluded radiation-interaction effects. Thus, this study demonstrates that the exponential wide-band model can be accurately applied to nonhomogeneous combustion situations in order to account for the radiation-convection interactions.

Seven-colour photometry at the Geneva Observatory

1966 ◽  
Vol 24 ◽  
pp. 262-266 ◽  
Author(s):  
M. Golay
Keyword(s):  
Wide Band ◽  
Electric System ◽  
Band Type

During the last 5 years, we have developed a seven-colour photometry at the Geneva Observatory. Our multicolour photo-electric system is of a wide-band type; the bandwidth being about 500Å for four filters. The three others are similar to theUBVsystem. In Table 1 we give the filter combinations used in our photometry (1).

TEM and cathodoluminescence of precipitates in II-VI semiconductors

1988 ◽  
Vol 46 ◽  
pp. 488-489
Author(s):  
Joanna L. Batstone
Keyword(s):  
Crystal Growth ◽  
Band Gap ◽  
Local Strain ◽  
Wide Band ◽  
Optoelectronic Device ◽  
Wide Band Gap ◽  
Bulk Crystal Growth ◽  
Transmission Electron ◽  
Device Applications ◽  
Stoichiometry Control

Interest in II-VI semiconductors centres around optoelectronic device applications. The wide band gap II-VI semiconductors such as ZnS, ZnSe and ZnTe have been used in lasers and electroluminescent displays yielding room temperature blue luminescence. The narrow gap II-VI semiconductors such as CdTe and HgxCd1-x Te are currently used for infrared detectors, where the band gap can be varied continuously by changing the alloy composition x.Two major sources of precipitation can be identified in II-VI materials; (i) dopant introduction leading to local variations in concentration and subsequent precipitation and (ii) Te precipitation in ZnTe, CdTe and HgCdTe due to native point defects which arise from problems associated with stoichiometry control during crystal growth. Precipitation is observed in both bulk crystal growth and epitaxial growth and is frequently associated with segregation and precipitation at dislocations and grain boundaries. Precipitation has been observed using transmission electron microscopy (TEM) which is sensitive to local strain fields around inclusions.

Electron microscopic characterization of diamond thin films and substrates for diamond heteroepitaxial growth

1989 ◽  
Vol 47 ◽  
pp. 592-593
Author(s):  
J.B. Posthill ◽  
R.P. Burns ◽  
R.A. Rudder ◽  
Y.H. Lee ◽  
R.J. Markunas ◽  
...  
Keyword(s):  
Thin Films ◽  
Wide Band ◽  
Deposition Process ◽  
Heteroepitaxial Growth ◽  
Electron Microscopic ◽  
Wide Band Gap ◽  
Lattice Matching ◽  
Different Types ◽  
Diamond Thin Films

Because of diamond’s wide band gap, high thermal conductivity, high breakdown voltage and high radiation resistance, there is a growing interest in developing diamond-based devices for several new and demanding electronic applications. In developing this technology, there are several new challenges to be overcome. Much of our effort has been directed at developing a diamond deposition process that will permit controlled, epitaxial growth. Also, because of cost and size considerations, it is mandatory that a non-native substrate be developed for heteroepitaxial nucleation and growth of diamond thin films. To this end, we are currently investigating the use of Ni single crystals on which different types of epitaxial metals are grown by molecular beam epitaxy (MBE) for lattice matching to diamond as well as surface chemistry modification. This contribution reports briefly on our microscopic observations that are integral to these endeavors.

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