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The burning velocity, v0, has been a subject of controversy for curved flames. This curvature is the macroscopic result of stream tube area variation. The flow can not be one-dimensional, but for small curvatures it is quasi-one-dimensional. As usually defined, v0, varies with curvature due to ducting. However, if the primary reaction zone is narrow, the velocity there, vr, is approximately independent of curvature. vr is a function of the reaction rate and is related to v0 by the density ratio ρr/ρ0 and the stream tube area ratio A0, a geometric factor. Thus, the burning velocity in the absence of curvature, v0*, can be defined by v0* = vrρr/ρ0 = v0A0. It can be derived from measurements on flame tips or expanding flame kernels, and appears to be reproducible and independent of external variables such as geometry, inlet flow and flame curvature. The concept was substantiated by measurements on the microstructure of matched flames of differing curvature and by quantitatively correlating the variation of v0 with flame curvature in flame tips, expanding flame kernels and turbulent flamelets.

The microwave spectrum of sulfuryl fluoride, SO2F2, has been reinvestigated. The spectra of the S32 and S34 species in natural abundance have been analyzed, and the structure has been determined with the aid of the S34 isotope shift. The correction for zero-point vibration was shown to be small. The structural parameters are: rSO=1.405±0.003 A, rSF=1.530±0.003 A, <OSO=123°58′±12′, and <FSF=96°7′±10′. The molecular dipole moment is 1.110±0.015 Debye units. A number of satellite lines were observed and assigned to excited vibrational states. Some anomalies in the measured rotational constants for the excited states have been interpreted in terms of a Coriolis-type interaction between the fundamentals ν4(A1) and ν5(A2). From an analysis of this interaction the frequency of the hitherto unobserved ν4(A1) fundamental was found to be 388±15 cm—1.

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