2015 Volume 57 Issue 181 Pages 174-182
Thermo-acoustic instability is induced by interaction between fluctuations of pressure and heat release rate to satisfy Rayleigh's criteria. Some important mechanisms to couple pressure fluctuation and heat release rate are introduced. Then, two fundamental coupling mechanisms, pressure coupling and velocity coupling, are investigated experimentally by using novel technique developed by the authors, laser irradiation method. In the research the transition process through a laminar flat flame, local deformation of the flame, generation of corrugated structure and transition to the turbulent motion is observed in detail by high-speed camera. Simultaneously, time dependent pressure measurement have been done to compare with flame structure change. The results suggested that even with flat flame, pressure fluctuation would occur by pressure coupling, but strong pressure fluctuation occurs with corrugated structure induced by acoustic vibration. The critical condition to start such corrugated structure have been discussed and it was pointed out that the generation of concave structure at the flame tip can be a trigger of strong acoustic vibration initiation.
