Dynamics of Swirl and Jet Flames (SWJET)

热声燃烧不稳定性的预测和控制对开发高效的贫油预混燃烧系统提出了严峻的挑战。当前TCI模型的一个关键输入是火焰传递函数（FTF），它代表火焰对声学强迫的响应。目前，它是从广泛的测量，高保真度的数值模拟，或强烈简化的分析模型推导出来的。在SWJET项目中，我们建议开发一种整体的方法来确定FTF和相关的流动和火焰动力学从有关的控制方程线性化的基础状态，即未扰动湍流火焰的流量变量的时间平均分布。这种线性反应流（LRF）方法最近由Avdonin等人探索，Proc. Comb. Inst. 2019.得到了有希望的结果，但研究仅限于基于一步化学的层流火焰。SWJET项目的中心目标是将LRF求解器的应用范围扩展到更复杂的反应机制和湍流火焰。SWJET项目分为三个工作区（WA）。WA 1将重点关注层流火焰。更先进的化学模型将被集成到线性化求解器中。在线性框架中获得的火焰动力学将对强迫和自激火焰的非线性数值模拟进行验证。WA 2是该项目的核心，将探索线性化方法对湍流反应流的适用性，并验证湍流射流火焰LES的结果。 线性方法将被应用于预测的流动和火焰响应声谐波强迫，并提高相关的物理机制的理解。在WA 3中，针对湍流旋流火焰重复WA 2的工作流程。特别关注的是旋流波的产生和运输，以及它们对火焰动力学的影响。这两个研究小组都对火焰动力学的分析和建模做出了重大贡献。特别是，TUB的专业知识是描述高度湍流反应流中的流动动力学。相比之下，TUM的小组在线性化框架中处理反应层流方面获得了重要的补充经验。两个研究所的线性化求解器将在项目的早期阶段合并。由于他们的互补专业，这将推动本提案中列出的研究。在SWJET中开发的方法构成了燃烧科学的飞跃，因为它们开辟了分析和控制火焰动力学的新方法，特别是TCI。SWJET项目将由FVV共同资助，比例为24%，包括第三个WA的个人费用。该项目进一步受益于TUB的另一个实验FVV项目，为湍流射流和旋流火焰的模型验证提供了经验数据。

The prediction and control of thermoacoustic combustion instabilities (TCIs) poses severe challenges to the development of efficient lean premixed combustion systems. A crucial input for current TCI models is the flame transfer function (FTF), which represents the response of the flame to acoustic forcing. It is currently deduced from extensive measurements, high-fidelity numerical simulations, or strongly simplified analytic models. In the SWJET project we propose to develop a holistic method to determine the FTF and the related flow and flame dynamics from the pertinent governing equations linearized around a base state, i.e. time-averaged distributions of flow variables of the unperturbed turbulent flame. This Linearized Reactive Flow (LRF) approach was recently explored by Avdonin et al., Proc. Comb. Inst. 2019. Promising result were obtained, but the study was limited to a laminar flame based on one-step chemistry. The central goal of the SWJET project is to extend the application range of LRF solvers to more complex reaction mechanisms and turbulent flames. The SWJET project is structured in three Work Areas (WA). WA 1 will focus on laminar flames. More advanced chemistry models will be integrated in the linearized solver. Flame dynamics obtained in the linear framework will be validated against nonlinear numerical simulations of forced and self-excited flames. WA 2, which constitutes the core of this project, will explore the applicability of the linearized methods to turbulent reacting flows and validate results against LES of a turbulent jet flame. The linear methods will be applied to predict the flow and flame response to acoustic harmonic forcing and to improve the understanding of the relevant physical mechanisms. In WA 3, the workflow of WA 2 is repeated for a turbulent swirl flame. Special focus will be on the generation and transportation of swirl waves, as well as their impact on flame dynamics. Both research groups contributed significantly to the state-of-the-art of analysis and modeling of flame dynamics. In particular, the expertise at TUB is on describing flow dynamics in highly turbulent reacting flows. The group at TUM, in contrast, has acquired significant complementary experience in treating reacting laminar flows in a linearized framework. The linearized solvers from both institutes will be merged in an early stage of the project. Due to their complementary specialties this will propel the research lined out in this proposal. The methods that are to be developed in SWJET constitute a leap forward in combustion science, as they open up new ways to analyze and control flame dynamics in general and TCIs in particular. The SWJET project will be co-funded by the FVV at a rate of 24%, which covers the personal costs of the third WA. The projects further benefits from another, experimental FVV project at TUB, providing empirical data for model validation of the turbulent jet and swirl flames.