A rotating detonation engine (RDE) is a realization of pressure-gain combustion, wherein a traveling detonation wave confined in a chamber provides shock-based compression along with chemical heat release. Due to the high wave speeds, such devices can process high mass flow rates in small volumes, leading to compact and unconventional designs. RDEs involve unsteady and multiscale physics, and their operational characteristics are determined by an equilibrium between large- and small-scale processes. While RDEs can provide a significant theoretical gain in efficiency, achieving this improvement requires an understanding of the multiscale coupling. Specifically, unavoidable nonidealities, such as unsteady mixing, secondary combustion, and multiple competing waves associated with practical designs, need to be understood and managed. The secondary combustion processes arise from fuel/air injection and unsteady and incomplete mixing, and can create spurious losses. In addition, a combination of multiple detonation and secondary waves compete and define the dynamical behavior of mixing, heat release distribution, and the overall mode of operation of the device. This review discusses the current understanding of such nonidealities and describes the tools and techniques used to gain insight into the extreme unsteady environment in such combustors.

中文翻译：

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旋转爆震发动机中的非理想性

旋转爆震发动机（RDE）是压力增益燃烧的实现，其中限制在室内的行进爆震波提供基于冲击的压缩以及化学热释放。由于波速高，此类设备可以在小体积内处理高质量流量，从而实现紧凑且非常规的设计。 RDE 涉及非定常和多尺度物理，其运行特性由大尺度和小尺度过程之间的平衡决定。虽然 RDE 可以在理论上显着提高效率，但实现这种改进需要了解多尺度耦合。具体来说，需要理解和管理不可避免的非理想情况，例如不稳定混合、二次燃烧以及与实际设计相关的多个竞争波。二次燃烧过程是由燃料/空气喷射以及不稳定和不完全混合引起的，并且可能产生虚假损失。此外，多重爆炸和二次波的组合竞争并定义了混合的动力学行为、热释放分布以及装置的整体操作模式。本综述讨论了目前对此类非理想情况的理解，并描述了用于深入了解此类燃烧器中极端不稳定环境的工具和技术。