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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1987

Full CI studies of the collinear transition state for the reaction F + H2 yields HF + H

Full CI calculations on the collinear transition state for the reaction F + H2 yields HF + H are reported. The full CI results are compared with those obtained from single-reference and multireference CI calculations and from single-reference CPF calculations. In general, only those methods which attempt to account for the effects of higher excitations, such as CPF or CI plus the Davidson correction, yield a transition-state location and barrier height in good agreement with the full CI. In an extended basis, the effect of higher excitations is estimated to lower the barrier by as much as 1.5 kcal/mol; such an effect would essentially eliminate the present discrepancy between theory and experiment.

Bauschlicher, Charles W., Jr.↗

NASA NTRS1972

Energy distribution among reaction products. V.

Discussion of three reactions, one point of theoretical interest being the predicted correlation between barrier height and barrier location. The H + Br 2 reaction having a lower activation barrier than H + Cl 2, should have an earlier barrier, and hence a greater percentage attractive energy release and higher efficiency of vibrational excitation. Information is developed concerning the effect of isotopic substitution in the pair of reactions H + Cl 2 and D + Cl 2. The 'arrested relaxation' method was used. Essentially, the method involves reacting two diffuse reagent beams in a reaction vessel with background pressure less than 0.001 torr, and with walls cooled by liquid nitrogen or liquid helium.

Anlauf, K. G.↗

NASA NTRS1997

Acoustic Barrier Facilitates Inlet Noise Measurements for Aft-Dominated Fans

Noise levels for modern high-bypass-ratio subsonic turbofans tend to be aft dominated. That is, the highest flyover noise levels radiate from the fan exit. Measuring fan inlet sound radiation without aft radiation contamination requires selective suppression of the aft noise. In NASA Lewis Research Center's 9- by 15-Foot Low-Speed Wind Tunnel, an acoustic barrier was used to effectively isolate the inlet noise field for a model of an advanced turbofan. This proof-of-concept test was performed on a model turbofan manufactured for NASA Lewis by the Allison Engine Company as part of the Advanced Subsonic Technology program. The 8-cm-thick acoustic barrier was constructed in sections that were joined upon installation. These sections, which were composed of a wood frame with typically 0.64-cm tempered fiberboard skins, extended from the tunnel's floor to its ceiling and had an axial length of 61 cm. On the fan side of the barrier just downstream of the leading edge, the upstream section had an acoustic treatment--a bulk absorber with a perforated metal skin. It had a nominal full height and an axial length of 46 cm. In addition, an elliptical leading edge was faired into the upstream barrier section. The barrier was mounted on tracks on the tunnel floor and ceiling at a sideline distance of 15 cm from the fan nacelle. Tests were made with the barrier leading edge at the fan inlet highlight plane and 15 cm further aft. The barrier extended downstream essentially to the end of the treated tunnel test section.

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