CAREER: Control of Acoustic Instabilities in Large Combustors

摘要：由于尚未完全了解的原因，有利于高效率和低排放的燃烧室往往表现出燃烧不稳定性。这些不稳定性是由腔室声学和热波动之间的再生耦合引起的。一些不稳定性表现为基本推进系统和发电系统流动变量的极限环振荡。例子包括火箭发动机、冲压发动机、燃气轮机、加力燃烧室和大型工业燃烧室。该项目的研究阶段旨在开发一种综合的稳定性算法，该算法可作为大型燃烧器开发阶段的诊断工具。新开发的算法将以最新的技术进步为基础，这些技术进步建议将声波、热波和涡旋波的影响结合起来。室内声学的新表示将允许估计系统能量的增长或衰减与大多数旋转流动效应的考虑。在此过程中，将采用模拟实际腔室条件的广义平均流量描述。这种表示有望提高文献中使用的线性和非线性稳定性方程的准确性。预期的声学能量增益的改进也有望解释目前稳定性评估方法所无法解释的实验结果。作为意外收获，预计将阐明在固体、液体和混合火箭发动机中观察到的几种喷射驱动不稳定性的起源。这一职业发展计划的教育阶段说明了在筹资期间将进行的一系列活动。这些措施包括对本科课程发展的激励措施、为研究生和本科生提供研究机会的举措、鼓励跨学科互动的举措、课程改进方法以及招募代表性不足的群体。

Abstract: For reasons not entirely understood, combustion chambers that favor high efficiencies and low emissions often exhibit combustion instabilities. These instabilities arise due to a regenerative coupling between chamber acoustics and thermal fluctuations. Some instabilities appear as limit cycle oscillations in the flow variables of basic propulsion and power generation systems. Examples include rocket motors, ramjet engines, gas turbines, afterburners, and large industrial combustors. The research phase of this project aims at developing a comprehensive stability algorithm that can be used as a diagnostic tool in the developmental stages of large combustors. The newly developed algorithm will be based on the latest technological advances that suggest incorporating the effects of acoustical, thermal and vortical waves from the ground up. The new representation of chamber acoustics will permit estimating the growth or decay of the system energy with most rotational flow effects accounted for. In the process, a generalized mean-flow description that mimics realistic chamber conditions will be employed. This representation is expected to enhance the accuracy of both linear and nonlinear stability equations used in the literature. The anticipated improvements in acoustic energy gains are also hoped to explain experimental findings that elude the present stability assessment methodology. As a windfall, it is projected that the origins of several injection-driven instabilities observed in solid, liquid and hybrid rocket motors will be illuminated. The educational phase of this career development plan describes a sequence of activities to be undertaken during the funding period. These include incentives for undergraduate curriculum development, initiatives for promoting research opportunities for both graduates and undergraduates, initiatives for encouraging interdisciplinary interactions, course enhancement methodologies, and recruitment of underrepresented groups.