Abstract: The confined impinging jet reactor (CIJR) has emerged as a critical device in the production of lipid nanoparticles and other advanced materials, owing to its superior ability to achieve rapid and energy-efficient mixing. Among the key design parameters, the incidence angle between opposing jets plays a decisive role in governing flow dynamics and mixing performance, yet its effects remain insufficiently explored. In this study, a combined approach of large eddy simulation (LES) and micro-particle image velocimetry (micro-PIV) experiments was employed to systematically investigate the influence of incidence angle (0°~30°) on the flow field characteristics and mixing efficiency of CIJRs across a wide Reynolds number (Re) range (90~800). The results revealed three distinct flow regimes—separated flow, transitional flow, and chaotic flow—across all configurations. For Re<400, smaller incidence angles promoted an earlier transition to chaotic flow, yielding more vigorous vortex formation and enhanced macroscopic mixing. However, at Re≥400, larger incidence angles improved flow stability, constrained stagnation point oscillations, and promoted more homogeneous mixing over time. Notably, at α=30°, the inlet jets exhibited a wavy profile induced by wall confinement and recirculating vortices, which further intensified macroscopic mixing, although excessive confinement tended to restrict vortex development at higher Reynolds numbers. On the microscale, increasing the incidence angle improved spatial uniformity of mixing but was accompanied by longer micromixing times, reflecting a trade-off between mixing intensity and efficiency. These findings highlight that the incidence angle acts as a tunable parameter for regulating mixing performance in CIJRs. Overall, this study provides fundamental insight into the interplay between inlet geometry, turbulence dynamics, and mixing characteristics, offering a theoretical basis for optimizing CIJR design and operational strategies in chemical, pharmaceutical, and materials engineering applications.

Key words: confined impinging jet reactor, incidence angle, numerical simulation, mixing performance

摘要： 受限撞击流反应器因其优异的混合能力成为生产脂质纳米颗粒的核心装置，入射角度是影响其混合性能的重要因素。本工作结合大涡模拟方法和micro-PIV实验，探究了入射角度(0°~30°)对受限撞击流反应器宏观和微观混合性能的影响。结果表明，Re<400时，较小的入射角度促使分离流更早转变为混沌流从而具有更好的宏观混合效果；Re≥400时，增大入射角度可以增强宏观混合的稳定性；入射角度增大至30°时，入口射流的波浪化增强了宏观混合；增大入射角度可以提高受限撞击流反应器微观混合的均匀性，但总体微观混合时间增加。研究结果揭示了入射角度对混合性能的调控机制，可为优化受限撞击流反应器设计提供理论支撑。

关键词: 受限撞击流反应器, 入射角度, 数值模拟, 混合性能