Novel Combustion for Aerospace and Power Generation: Multi-Scale Combustion Dynamics

燃气轮机是航空推进的主要动力源，在电力生产中发挥着越来越大的作用。燃气轮机发动机的研发驱动力包括减少污染物排放(主要是NOx、CO和颗粒物)和增加可持续性/减少气候影响(通过使用生物燃料)，同时保持安全性、健壮性和成本。实现这些目标的两个主要抑制因素可概括如下：*1)对于在燃气轮机发动机中发生的相当极端的湍流条件下，湍流/燃烧相互作用使反应物转化为产物(即化学能转化途径)的潜在轨迹，缺乏根本的了解。虽然传统的模型给出了层流火焰中相同的轨迹，但最近的实验和计算证据对此提出了异议。这种非层流轨迹对燃烧室的设计有重大影响，并为新技术打开了可能性。*2)目前所有已知的实现上述目标的方法都增加了各种形式的非稳态燃烧动力学发生的可能性。特别值得关注的现象是热声不稳定、井喷、闪回和自燃，其中任何一种都可能导致系统无法操作或造成(潜在的灾难性)损害。由于机械理解上的差距和缺乏预测性框架，目前无法预测设计或业务变化如何影响这些现象发生的可能性。*拟议的研究通过两个同时进行的研究主题处理这些问题。首先，我们将进行独特的实验，在具有实际意义的条件下揭示湍流反应流的微观动力学。具体地说，我们将使用激光测量技术通过温度、成分和流体从反应物转化为产品时的反应速度来描述无数的轨迹。*第二个主题着眼于燃烧室动力学的更大范围，目的是提供一种基于实际大型系统的工程师可以获得的数据来预测非平稳现象的物理降阶方法。要做到这一点，我们首先将使用激光诊断学来发现和解释我们假设的驱动不同形式的非静止行为的各种反馈机制。然后，这些机制将在低维空间中表达，最好地捕捉燃烧室的关键扰动/响应行为，但可以在实际的发动机开发程序中访问。然后，我们将生成并测试各种指标，这些指标描述这种行为如何随着动态概率的增加而变化，从而产生一个预测性框架。

Gas turbine engines are the de facto power source for aeronautical propulsion, and also play an increasingly large role in electrical power generation. Research and development drivers for gas turbine engines include reducing pollutant emissions (primarily NOx,, CO, and particulates) and increasing sustainability/decreasing climate impact (through use of biofuels), while maintaining safety, robustness, and costs. Two of the major inhibitors to achieving these goals can be summarized as follows:***1) There is a fundamental lack of understanding regarding the potential trajectories for converting reactants to products (i.e. chemical energy conversion pathways) that are enabled by turbulence/combustion interactions at the rather extreme turbulence conditions occurring in gas turbine engines. While traditional models prescribe the same trajectories found in laminar flames, recent experimental and computational evidence disputes this. Such non-laminar trajectories have major implications for how combustors are designed, and open possibilities for novel technologies.***2) All currently known methods for achieving the aforementioned goals increase the probability of various forms of non-stationary combustion dynamics occurring. Phenomena of particular concern are thermoacoustic instabilities, blowout, flashback, and autoignition, any of which can render a system inoperable or cause (potentially catastrophic) damage. It currently is not possible to predict how design or operational changes influence the probability of these phenomena occurring due to gaps in mechanistic understanding and lack of a predictive framework. ***The proposed research addresses these issues through two concurrent research themes. Firstly, we will conduct unique experiments that unravel the micro-scale dynamics of turbulent reacting flows at conditions of practical relevance. Specifically, we will use laser measurement techniques to describe the myriad of trajectories through temperature, composition, and reaction rate that fluid can take as it converts from reactants to products. ***The second theme takes a larger scale view of combustor dynamics, with the objective of providing a physically-grounded reduced-order method for predicting non-stationary phenomena based on data that is obtainable by engineers working on realistic large-scale systems. To do so, we first will use laser diagnostics to discover and explain the various feedback mechanisms that we hypothesize to drive the different forms of non-stationary behavior. These mechanisms will then be expressed in low-dimensional spaces that best capture the critical perturbation/response behavior of the combustor, but could be accessed in real engine development programs. We then will generate and test various metrics that describe how this behavior changes as the probability of dynamics increases, leading to a predictive framework.