管内を下方に伝播する火炎の音響パラメトリック不安定性に対する管の長さの影響

抄録

The influence of tube length on the self-excited thermoacoustic parametric instability of laminar premixed flames is investigated experimentally and analytically. Lean propane-air flames were propagated in a quarter-wavelength resonator where the tube length is systematically modulated to allow the observation of planar flames and parametrically unstable flames. Theory and experiments show that longer (shorter) tubes, resonating lower (higher) frequencies, lead to larger (smaller) length scales of sinusoidal flame wrinkling at the onset of parametric instability. The difference between the experimental and theoretical critical wavenumbers are attributed to the value of the Markstein number.