Excitation of spectra of OH in hydrogen flames and its relation to excess concentrations of free atoms

1958 ◽  
Vol 245 (1240) ◽  
pp. 84-92 ◽  
Keyword(s):  
Reaction Zone ◽  
Intensity Distribution ◽  
Selective Excitation ◽  
Strong Excitation ◽  
Free Atoms

Measurements have been made of the rotational and vibrational intensity distribution of OH bands in oxygen + hydrogen + nitrogen flames. Simultaneous observations have been made of the strength of Na and Li lines and their variation with height in the flame. The anomalously strong excitation of OH bands with v ' = 2 and 3 is accompanied by selective excitation of the f 1 spin levels of the 2 ∑ + state. This confirms that the anomaly results from an inverse predissociation, associated with an excess of free atoms in the flame gases. This excess is most important for the cooler flames and near the base of these flames. There is also strong excitation of the (0, 0) band of OH near the reaction zone and the mechanism for this is briefly discussed.

Predissociation in the spectrum of OH; the vibrational and rotational intensity distribution in flames

1951 ◽  
Vol 208 (1092) ◽  
pp. 63-75 ◽  
Keyword(s):  
Reaction Zone ◽  
Intensity Distribution ◽  
Atmospheric Pressure ◽  
Low Pressure ◽  
The Other ◽  
Spin Component ◽  
Reverse Process ◽  
Free Atoms

In the main 3064 Å system of OH higher rotational levels of bands with v' = 1 and all levels with v' ≥ 2 are affected by a weak predissociation. One spin component of the 2Ʃ + levels is more strongly affected than the other. Of the three molecular states, 4II, 4Ʃ ¯ and 2Ʃ ¯ which could conceivably cause the predissociation, only the 2Ʃ ¯ could produce this effect. The predissociation is observed in the OH bands from a discharge and from the reaction zone of an oxy-acetylene flame at low pressure, and also to some extent in a flame at atmospheric pressure. The predissociation, and its reverse process, a ‘pre-association’, may also affect the vibrational intensity distribution if there is departure from equilibrium. Striking anomalies of this type in hydrogen flames are interpreted in this way. For flames at 1 atm. pressure there appears to be an excess of free atoms in the flame, and at low-pressure emission of radiation from the flame disturbs the equilibrium.

Role of Fuel Injection Scheme in a High Intensity Combustor

2016 ◽  
Author(s):  
Ahmed O. Said ◽  
Ashwani K. Gupta
Keyword(s):  
Reaction Zone ◽  
Intensity Distribution ◽  
Fuel Injection ◽  
Mixing Time ◽  
Fuel Mixture ◽  
Fuel Distribution ◽  
Mixture Preparation ◽  
Injection Scheme ◽  
Pollutants Emission

Fuel injection at two locations in a combustor using premixed, partially pre-mixed and non-premixed schemes has been explored for improved distributed combustion. The effect of dual location fuel injection to the combustor is examined and the results compared from single fuel injection. Focus of dual and single injection scheme was on enhancing reaction zone uniformity in the combustor. A cylindrical combustor at a combustion intensity of 36MW/m3.atm and heat load of 6.25 kW was used. Three different schemes of dual location fuel injection with different proportions of fuel injected from each injector were investigated using methane as the fuel. The role of fuel distribution between the two injection ports using constant air flow rate to the combustor at room temperature was examined on reaction zone distribution and pollutants emission. Three different equivalence ratios of 0.6, 0.7 and 0.8 were examined with different fuel distributions between the two injectors to the combustor at a constant overall thermal load. The results showed lower emission with dual location fuel injection as compared to single location. Dual location fuel injection showed 48% NO reduction with 90% of the total fuel from injector 1 while only 13% reduction was achieved with 80% of the fuel injection from this location. . OH* Chemiluminescene intensity distribution within the combustor showed that under favorable fuel injection condition, the reaction zone shifted downstream to allow longer fuel mixture preparation time prior to ignition. The longer mixing time resulted in improved mixture preparation and lower emissions. The OH* Chemiluminescene intensity distribution with fuel introduced through two injectors showed improved OH* distribution in the combustor. Improved mixture preparation enhanced reaction distribution in the combustor and lower emission.

Structure images of Si, Ge and Mos2 crystals and some application to radiation damage studies

1978 ◽  
Vol 36 (1) ◽  
pp. 292-293 ◽  
Author(s):  
K. Izui ◽  
T. Nishida ◽  
S. Furuno ◽  
H. Otsu ◽  
S. Kuwabara
Keyword(s):  
Radiation Damage ◽  
Exposure Time ◽  
Gaussian Distribution ◽  
Intensity Distribution ◽  
Chromatic Aberration ◽  
Magnetic Lens

Recently we have observed the structure images of silicon in the (110), (111) and (100) projection respectively, and then examined the optimum defocus and thickness ranges for the formation of such images on the basis of calculations of image contrasts using the n-slice theory. The present paper reports the effects of a chromatic aberration and a slight misorientation on the images, and also presents some applications of structure images of Si, Ge and MoS2 to the radiation damage studies.(1) Effect of a chromatic aberration and slight misorientation: There is an inevitable fluctuation in the amount of defocus due to a chromatic aberration originating from the fluctuations both in the energies of electrons and in the magnetic lens current. The actual image is a results of superposition of those fluctuated images during the exposure time. Assuming the Gaussian distribution for defocus, Δf around the optimum defocus value Δf0, the intensity distribution, I(x,y) in the image formed by this fluctuation is given by

TEM characterization of reaction zone in a SiC fiber-reinforced titanium alloy

1988 ◽  
Vol 46 ◽  
pp. 738-739
Author(s):  
G. Das ◽  
R. E. Omlor
Keyword(s):  
Titanium Alloys ◽  
Reaction Zone ◽  
Carbon Layer ◽  
Fiber Reinforced ◽  
Reaction Products ◽  
Sic Fibers ◽  
Sic Fiber ◽  
The Matrix ◽  
Immense Potential

Fiber reinforced titanium alloys hold immense potential for applications in the aerospace industry. However, chemical reaction between the fibers and the titanium alloys at fabrication temperatures leads to the formation of brittle reaction products which limits their development. In the present study, coated SiC fibers have been used to evaluate the effects of surface coating on the reaction zone in the SiC/IMI829 system.IMI829 (Ti-5.5A1-3.5Sn-3.0Zr-0.3Mo-1Nb-0.3Si), a near alpha alloy, in the form of PREP powder (-35 mesh), was used a茸 the matrix. CVD grown AVCO SCS-6 SiC fibers were used as discontinuous reinforcements. These fibers of 142μm diameter contained an overlayer with high Si/C ratio on top of an amorphous carbon layer, the thickness of the coating being ∽ 1μm. SCS-6 fibers, broken into ∽ 2mm lengths, were mixed with IMI829 powder (representing < 0.1vol%) and the mixture was consolidated by HIP'ing at 871°C/0. 28GPa/4h.

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