Copy of Coupling the Intrinsic Instabilities of Premixed Combustion - Overseas Travel Grant

Premixed flames are prone to diffusional-thermal and hydrodynamic instabilities. These instabilities in practice operate simultaneously, and are often coupled with the acoustic modes of a combustion chamber, leading to large-scale acoustic instability, which is characterized by intense pressure fluctuations. In the past, various aspects of acoustic instability were modelled in isolation, and often on an empirical basis. The applicant and his collaborators derived a first-principlesmodel on the basis of the activation-energy asymptotics to describe flame-acoustic coupling mechanisms in the flamelet regime. We now propose to develop an efficient numerical algorithm to solve the asymptotically reduced system, and apply it to situations pertaining to Searby's (1992) experiments. We also plan to investigate hydrodynamic and diffusional-thermal instabilities in a unified framework, with the particular aim of predicting some remarkable observations made in the Princeton group, namely the coexistence of the hydrodynamic cells and spiral waves on spherical flames. The coupling of both hydrodynamic anddiffusional-thermal instabilities with acoustics will be investigated in the thin-reaction-zone regime. A general acoustic-hydrodynamic-flame coupling theory will be formulated, and will applied to investigate the resonance between acoustic modes and the pulsating instability at the onset condition.