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

预混火焰容易出现扩散热和流体动力不稳定性。这些不稳定性在实际中是同时发生的，并且经常与燃烧室的声学模式相耦合，导致大规模的声学不稳定性，其特征是强烈的压力波动。过去，声学不稳定性的各个方面都是孤立地建模的，而且往往是基于经验的。申请人和他的合作者在活化能渐近的基础上推导了一个第一性原理模型来描述小火焰状态下火焰-声波耦合机制。我们现在建议开发一种有效的数值算法来求解渐近约简系统，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中研究流体动力和扩散热不稳定性，其特别目的是预测普林斯顿小组所做的一些显著观察，即流体动力细胞和螺旋波在球形火焰上的共存。水动力和扩散热不稳定性与声学的耦合将在薄反应区进行研究。将建立一个通用的声-水动力-火焰耦合理论，并将应用于研究声模式之间的共振和脉动不稳定性的开始条件。

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.