METHANE-AIR MARKSTEIN NUMBERS FROM MEASUREMENTS OF THERMOACOUSTIC INSTABILITY

ABSTRACT

Markstein numbers characterizing the influence of stretch on the speed of thin laminar flames are determined computationally for lean and rich methane-air mixtures using results from a recent experimental study of thermoacoustic instability in a Taylor-Couette burner. A model describing the response of a thin laminar flame to acoustic flow-field excitation, which is found to exhibit dependence of thermoacoustic-instability characteristics on Markstein number, is used to determine Markstein numbers from measurements of the critical acoustic-velocity amplitudes associated with the onset of the secondary thermoacoustic instability. The model accounts for the Saffman-Taylor influence of viscosity on thermoacoustic instability for adiabatic flame propagation between closely separated walls.

Keywords:

• Markstein number
• thermoacoustic instability
• Saffman-Taylor instability