Review of Rate Data for Reactions of Interest in HF and DF Lasers.

Cohen, N.; Bott, J. F.

doi:10.21236/ada122175

Cited by 16 publications

(25 citation statements)

References 3 publications

(6 reference statements)

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“…The cold reaction, which carries 25% of the total heat release, is faster than the hot reaction by about an order of magnitude at 300 K (k 1 ~ 1.6 x 10 13 , k 2 ~ 9.5 x 10 11 ). These values are quoted from Cohen & Bott (1982). Examination of the explosion limits of fluorine-hydrogen mixtures (see Chen, Daugherty & Fyfe 1975;Gmelin 1980) shows that, for the conditions of this experiment, the H 2 -F 2 mixture is in a stable region.…”

Section: Chemical Reactionsmentioning

confidence: 74%

Mixing and combustion with low heat release in a turbulent shear layer

1984

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Turbulent mixing and combustion are investigated in a gaseous shear layer formed between two streams: one containing a low concentration of hydrogen in nitrogen and the other containing a low concentration of fluorine in nitrogen. The resulting temperature field is measured simultaneously at eight points across the width of the layer using fast-response cold-wire thermometry. The results show the presence of large, hot structures separated by tongues of cool fluid that enter the layer from either side. The usual bell-shaped mean-temperature profiles therefore result from a duty cycle whereby a fixed probe sees alternating hot and cool fluid, which results in the local mean. The adiabatic flame temperature is not achieved in the mean, at any location across the layer. For fixed velocities, it is found that, in general, two different mean-temperature profiles result from a given pair of reactant compositions if the sides of the layer on which they are carried are exchanged ('flipped'). This finding is a direct consequence of the asymmetric entrainment of fluid into the layer. Results are compared with the predictions of Konrad and discussed in the context of the Broadwell-Breidenthal model. By comparison with the liquid result of Breidenthal, the amount of product formed in the layer at high Reynolds number is found to be dependent upon the Schmidt number. Results for a helium-nitrogen layer are discussed briefly.

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Section: Chemical Reactionsmentioning

confidence: 74%

Mixing and combustion with low heat release in a turbulent shear layer

1984

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“…Presented as Paper 85-0142 at the AIAA 23rd Aerospace Sciences Meeting, Reno, NV, Jan. [14][15][16][17]1985; received Sept. 18,1985; revision received Sept. 15,1986 …”

Section: Introductionmentioning

confidence: 99%

Heat release effects on shear-layer growth and entrainment

1987

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The effects of heat release were studied in a planar, gaseous reacting mixing layer formed between two subsonic freestreams; one Containing hydrogen in an inert diluent, the other containing fluorine in an inert diluent. Sufficiently high concentrations of hydrogen and fluorine reactants were employed to produce adiabatic flame temperature rises of up to 940 K (adiabatic flame temperature of 1240 K absolute). Although the displacement thickness of the layer for a zero streamwise pressure gradient showed an increase with increasing heat release. the actual thickness of the mixing layer at a given downstream location was not observed to increase and, in fact. was characterized by a slight Ihinning. The overall entrainment into the layer was seen to be substantially reduced by heat release. The large-wale vortical nature of the flow appeared to persist over all levels of heat release in this investigation. Imposition of a favorable pressure gradient, though resulting in additional thinning of the layer. was observed to have no resolvable effecl on the amount of chemical product formation and hence on the mixing.

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“…One is attributed to Cohen and Bott (1982) and the other to Baulch (1981). At room temperature these expressions differ by -40% and in lieu of more information Manke and …”

Section: Hot Pumping Reactionmentioning

confidence: 99%

Spatially resolved sub-Doppler overtone gain measurements on a small-scale supersonic HF laser

et al. 2004

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Public reporting burden for this collection of information te Bstimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information. The overtone gain of a small-scale HF laser was measured using a sub-Doppler tunable diode laser system. Two-dimensional spatially resolved small signal gain and temperature maps were generated, which show a highly inhomogeneous gain medium indicating the dominant role that mixing of the fuel and oxidizer streams has in HF laser performance. The measured gain and temperature data were analyzed with the aid of a two-dimensional computational fluid dynamics code. To reduce uncertainty of important modeling input parameters, novel measurements of reactant concentration, flow velocity and gain length were made. Results show that reactant mixing mechanisms such as turbulence and large-scale vortex structures have a large effect on the gain averaged over a vertical profile while kinetic rate mechanisms such as reaction rate constants and reactant concentration have a greater effect on the maximum system gain. Overtone gain data measured while operating the laser saturated on the fundamental transitions are compared with fundamental lasing output spectra. In all cases, the data are consistent with an equilibrium rotational distribution.

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Review of Rate Data for Reactions of Interest in HF and DF Lasers.

Cited by 16 publications

References 3 publications

Mixing and combustion with low heat release in a turbulent shear layer

Mixing and combustion with low heat release in a turbulent shear layer

Heat release effects on shear-layer growth and entrainment

Spatially resolved sub-Doppler overtone gain measurements on a small-scale supersonic HF laser

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