Controlling Transcritical Thermoacoustic Interactions for Space Propulsion and Novel Energy Systems

火箭科学可以为我们提供一些现代能源问题的新解决方案。液体火箭发动机的燃烧不稳定性是空间推进中最重要和最具挑战性的问题之一。这些不稳定性是由于燃烧的非稳定热释放与燃烧室中的声学模式耦合而发生的；这种相互作用的复杂性因低温推进剂的高度非线性、跨临界热力学基态而变得更加复杂。需要确定自激热声耦合，因为声学模式中的能量积累是发动机灾难性故障的最重要原因。然而，火箭推进界的这一非常严重的挑战实际上可能被证明是我们一些能源问题的新解决方案，特别是在工业环境中。通过仔细地控制熵-声耦合，通过这种非线性相互作用产生的能量可以在热声热机中被收集以产生有用的机械动力，从而允许工业废热的有效再利用。*该研究计划将建立在申请者对液体火箭发动机的研究基础上，以扩展与高压、跨临界系统中热声耦合的基本机制相关的知识和专业知识。这一理解是从声学、热力学和流体力学之间相互作用的正则流设置的基于第一原理的高质量数值模拟中收集的。这些专业知识将应用于科学和工程这两个看似截然不同但却令人惊讶的切线领域。1)我们将试图确定跨临界扩散火焰中的固有不稳定模式，以此来解释火箭发动机中高频自激不稳定模式的开始。2)然后，我们将把我们在火箭推进系统中热声耦合方面的专业知识转移到开发用于将工业废热转化为机械能的跨临界热声热机上。在工业环境中消耗的总能源中，高达50%是通过热废气和液体损失的。利用热声热机回收工业废热，提高了整体效率，节省了资金，减少了排放。此外，在高压系统中获得的燃烧不稳定性知识将与燃气轮机、预混汽车喷射系统和吸气式推进技术直接相关。

Rocket science can provide us with novel solutions to some of our modernday energy concerns. Combustion instabilities in liquid rocket engines are one of the most important and challenging problems in space propulsion. These instabilities occur as the unsteady heat release of combustion couples with the acoustic modes in the combustion chamber; the complexity of this interaction is compounded by the highly non-linear, transcritical thermodynamic base state of the cryogenic propellants. The self-excited thermoacoustic coupling needs to be identified, as energetic build-up in the acoustic mode is the most important cause of catastrophic engine failure. However, this very serious challenge in the rocket propulsion community may actually prove to be a novel solution to some of our energy concerns, particularly in industrial settings. By carefully controlling the entropic-acoustic coupling, the energy created through this non-linear interaction may be harvested in a thermoacoustic heat engine to produce useful mechanical power, thus, permitting the efficient re-use of industrial waste heat. ******The research program will build upon the research of the applicant on liquid rocket engine to extend the knowledge and expertise related to the fundamental mechanisms of thermoacoustic coupling in high-pressure, transcritical systems. This understanding is gleaned from first-principal-based, high-quality numerical simulations of canonical flow setups of the interaction between acoustics, thermodynamics and fluid mechanics. This expertise will be applied to two seemingly distinct, yet surprisingly tangential fields of science and engineering. 1) We will seek to identify intrinsic instability modes in transcritical diffusion flames as a means to explain the onset of high-frequency, self-excited instability modes in rocket engines. 2) We will then transpose our expertise in thermoacoustic coupling in rocket propulsion systems towards the development of a transcritical thermoacoustic heat engine for the conversion of industrial waste heat to mechanical energy. Up to 50% of the total energy consumed in industrial settings is lost through hot exhaust gases and liquids. The recuperation of industrial waste heat by means of a thermoacoustic heat engine increases overall efficiency, saves money and reduces emissions. Additionally, the acquired knowledge of combustion instabilities in high-pressure systems will have direct relevance to gas turbine, premixed automotive injection systems and air-breathing propulsive technology.********