权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Consequences of non-normality and nonlinearity in flow / premixed flame / acoustic interactions for combustion instability

流动/预混火焰/声学相互作用的非正态性和非线性对燃烧不稳定的影响

基本信息

批准号：
196670088
负责人：
Professor Wolfgang Polifke, Ph.D.
金额：
--
依托单位：
Lehrstuhl für Thermofluiddynamik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2011
资助国家：
德国
起止时间：
2010-12-31 至 2013-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/196670088?language=en
关键词：
Consequences non normality nonlinearity flow

项目摘要

In dynamical systems with non-normal eigenmodes, modal interactions can result in large transient growth even if all modes are linearly stable. Under such circumstances, subcritical transition to instability may occur in the presence of low-amplitude perturbations, and classical linear stability analysis becomes a poor indicator of system behaviour.The non-normal nature of thermo acoustic interactions has been identified only recently; possible consequences for combustion dynamics have until now been explored only in the context of very simple, idealized model problems. The current proposal aims to examine non-normality and nonlinearity in the context of flow / premixed flame / acoustic interactions, and to develop corresponding tools that have the potential to handle with quantitative accuracy also configurations of applied interest, e.g. turbulent premix swirl flames.It is proposed to proceed systematically: Starting from a “monolithic” approach based on a compressible flow formulation, a variety of coupled modelling strategies shall be developed and validated. The monolithic approach, which is in a sense model-free, shall be used primarily to generate reference data, as it is computationally very expensive. Coupled approaches, which make use of an incompressible model for the flow / combustion interaction and subsequent model reduction, are much more efficient. However, their accuracy in particular in regard to non-normal effects, must be validated.Results from these simulations will be used to develop methodologies for system identification that can capture non-normal and nonlinear effects. Of particular interest is the role of the internal dynamics (corresponding to internal degrees of freedom) of the flame in thermo acoustic evolution. This touches the question of the appropriate definition of fluctuation energy (mathematically speaking: the choice of “norm” of the system state vector) as well as the appropriate model structure for identification of reduced models. The following point is also important for the latter: according to asymptotic analysis, acoustic Reynolds stress terms appear in the hydrodynamic flow/combustion sub-model. It has to be investigated, if and how these terms should be considered in the identification of flame model parameters.The application of complementary numerical and experimental tools as well as analytical methods for thermo acoustic stability analysis ensures synergistic benefits.

在具有非正常本征模的动力学系统中，即使所有模式都是线性稳定的，模式相互作用也会导致大的瞬态增长。在这种情况下，亚临界过渡到不稳定可能会发生在低振幅的扰动，经典的线性稳定性分析成为一个穷人的指标系统behavior.The非正常性质的热声相互作用已被确定最近，可能的后果燃烧动力学到现在为止，只有在非常简单的，理想化的模型问题的背景下进行了探讨。目前的建议旨在研究流动/预混火焰/声学相互作用背景下的非正态性和非线性，并开发相应的工具，这些工具有可能以定量的准确性处理应用感兴趣的配置，例如湍流预混旋流火焰。从基于可压缩流公式的“整体”方法开始，应开发并验证各种耦合建模策略。整体方法在某种意义上是无模型的，主要用于生成参考数据，因为它在计算上非常昂贵。耦合的方法，利用不可压缩模型的流动/燃烧相互作用和随后的模型简化，是更有效的。然而，它们的准确性，特别是在非正常效应方面，必须加以验证。这些模拟的结果将被用来开发系统识别的方法，可以捕捉非正常和非线性效应。特别感兴趣的是热声演化的火焰的内部动力学（对应于内部自由度）的作用。这涉及波动能量的适当定义（数学上讲：系统状态向量的“范数”的选择）以及用于识别简化模型的适当模型结构的问题。对于后者，以下一点也是重要的：根据渐近分析，声学雷诺应力项出现在流体动力流动/燃烧子模型中。它必须调查，如果以及如何这些条款应考虑在火焰模型参数的识别。互补的数值和实验工具，以及热声稳定性分析的分析方法的应用，确保协同效益。