Combustion Noise and Dynamics of partially premixed flames

燃烧噪声，特别是燃烧不稳定性是发展可靠、低排放喷气发动机的两个重要问题。与其他类型的航空噪声相比，在过去的几十年里，燃烧噪声的相对重要性有所增加。热声燃烧不稳定性是航空发动机为满足氮氧化物排放要求而向精益工况发展的过程中必须面对的设计挑战。因此，开发建模概念和仿真工具来调查和控制这两种现象-这两种现象在基本层面上彼此密切相关-对于设计清洁，安静，稳定和能够在广泛的操作条件下工作的发动机来说是必不可少的。巴黎Centrale Supelec和德国慕尼黑工业大学（TU m<e:1> nchen）联合开展的ANR/DFG项目“NoiseDYN”开发并验证了用于模拟和识别受限湍流预混火焰动力学以及相应的直接燃烧噪声源的工具。为了继续这些努力，拟议的项目“NoiSI”将有助于开发一个通用的、统一的框架来模拟航空燃气轮机的燃烧噪声和热声不稳定性。该框架依赖于基于数据的火焰动力学和燃烧噪声的降阶模型。它包括三个步骤：1)对受限的、湍流的、部分预混的火焰进行高保真的数值模拟；2)通过先进的系统识别方法评估火焰动力学以及直接和间接燃烧噪声的来源；3)将单个元素（源和火焰响应）整合到一个低阶声学网络模型中，以评估燃烧噪声水平和不稳定边界。NoiSI项目的主要目标如下：首先，建立并验证一个框架，以评估火焰对声音和燃料浓度扰动的响应以及相应的燃烧噪声和熵波的来源。设想的方法依赖于高保真数值模拟（LES），先进的系统识别（SI）和不确定性量化，并且被认为在计算上也可以负担得起应用感兴趣的配置。其次，通过结合先前用LES/SI评估的源和火焰响应，建立一个考虑了与燃烧噪声和湍流火焰不稳定性相关的所有物理机制的热声网络模型。将对高压液体燃料燃烧试验台（DLR Köln的SCARLET试验台）和ETH zrich的实验室规模的气体燃料燃烧器进行研究。数值模拟和建模策略将与实验结果进行对比验证。

Combustion Noise and in particular combustion instability are two significant problems for the development of reliable, low emission jet engines. Compared to other types of aeronautical noise, the relative importance of combustion noise has increased in the last decades. Thermoacoustic combustion instability is a design challenge that must be confronted as aero engine combustion moves towards lean operating conditions in order to satisfy emission regulations on oxides of nitrogen. Consequently, the development of modeling concepts and simulation tools to investigate and control these two phenomena - which are closely related to each other on a fundamental level - becomes mandatory for the design of engines that are clean, quiet, stable and capable of working over a wide range of operating conditions.A joint ANR/DFG project "NoiseDYN'" between Centrale Supelec in Paris and TU München developed and validated tools for the simulation and identification of the dynamics of confined turbulent premixed flames as well as the corresponding sources of direct combustion noise. In continuation of these efforts, the proposed project “NoiSI” will contribute to the development of a general, unified framework to model combustion noise and thermoacoustic instability in aeronautical gas turbines.This framework relies on data-based, reduced order models of flame dynamics and combustion noise. It comprises three steps: i) perform high-fidelity numerical simulation of confined, turbulent, partially premixed flames, ii) evaluate the flame dynamics and the sources of direct as well as indirect combustion noise by means of advanced system identification, and iii) integrate individual elements (sources and flame responses) in a low-order acoustic network model for the assessment of combustion noise levels and instability margins. The main objectives of the NoiSI project are the following: First, to establish and validate a framework to evaluate the response of flames to acoustic and fuel concentration perturbations and the corresponding sources of combustion noise and entropy waves. The approach envisaged relies on high-fidelity numerical simulation (LES), advanced system identification (SI) and uncertainty quantification and is conceived to remain computationally affordable also for configurations of applied interest. Second, establish a thermoacoustic network model that takes into account all physical mechanisms relevant for combustion noise and instability of turbulent flames by incorporating the sources and flame responses evaluated previously with LES/SI. A high-pressure, liquid fuel combustion test rig (SCARLET rig at DLR Köln) and a lab-scale, gaseous fuel combustor at ETH Zürich will be investigated. The numerical simulations and modeling strategies proposed will be validated against experimental results.