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

预混火焰容易发生扩散热不稳定和流体动力不稳定。这些不稳定性在实际中同时运行，并经常与燃烧室的声学模式相耦合，导致大范围的声学不稳定性，其特征是强烈的压力波动。在过去，声学不稳定性的各个方面都是孤立地建模的，而且往往是在经验的基础上进行的。申请人和他的合作者在激活能渐近性的基础上推导出第一原理模型来描述火焰区的火焰-声学耦合机制。我们现在建议开发一个有效的数值算法来求解渐近约化系统，并将其应用于与Searby(1992)实验有关的情况。我们还计划在一个统一的框架内研究流体力学和扩散-热不稳定性，特别是预测普林斯顿小组所做的一些值得注意的观测，即在球形火焰上流体动力单元和螺旋波的共存。流体动力不稳定性和扩散-热不稳定性与声学的耦合将在薄反应区进行研究。建立了一般的声学-流体力学-火焰耦合理论，并将其应用于研究声学模式之间的共振和起爆条件下的脉动不稳定性。

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.