本文系统研究了自激扫掠喷嘴的出口扩张段几何角A对其扫掠张角α、扫掠形态以及雾化效果等射流特性的影响规律。首先在放大尺度(进口喉道宽度WT=2.5 mm)下对出口几何角在较宽范围内(A=50°~110°、0°)的影响规律进行初步研究，进而选取典型出口几何角结构，在真实亚毫米尺度(WT=0.5 mm)下对其特性开展详细测试。采用高速阴影成像法和马尔文激光粒度仪测量外部射流特性和雾化粒径分布。研究结果表明：自激扫掠喷嘴的出口几何角A显著影响其扫掠张角α与扫掠形态。当自激扫掠喷嘴无出口扩张段时，喷嘴内流道在自然射流状态下形成的扫掠张角为α0；当出口几何角A略大于α0时，射流在康达效应的作用下，贴附于出口扩张段壁面，射流处于附壁状态，扫掠张角α接近出口几何角A，并形成“类梯型”扫掠形态，伴随拉伸液膜与残留液丝结构；特定构型喷嘴在相应工况下能达到的最大扫掠张角为αmax，当出口几何角A超过αmax时，射流的康达效应失效，射流脱离出口扩张段壁面影响，扫掠张角将回落至α0，呈现“类S型”扫掠形态，并在较高压降下出现主副张角结构。雾化粒径分布受扫掠形态影响，“类梯型”扫掠形态下，其两侧边界位置雾化粒径较大，中间位置雾化粒径较小；“类S型”扫掠形态下，射流破碎更为均匀，展向粒径变化幅度更小。本研究揭示了出口几何角对自激扫掠喷嘴喷雾特性的影响规律及内在机制，为自激扫掠喷嘴的优化设计提供了理论依据。

This study systematically investigated the influence of the outlet expansion section geometry angle A of a self-excited sweeping nozzle on jet characteristics, such as sweeping angle α, sweeping morphology, and atomization performance. Preliminary studies were first conducted on the influence of outlet geometry angles across a wider range of outlet geometry angles (A=50°~110°、0°) under an enlarged scale (inlet throat width WT = 2.5 mm). Subsequently, detailed experiments were carried out at a realistic submillimeter scale (WT = 0.5 mm) using selected typical angles. The external jet characteristics and droplet size distribution were measured using high-speed shadowgraphy and a Malvern laser particle size analyzer, respectively. Results indicate that the outlet geometry angle A of the self-excited sweeping nozzle significantly affects both the sweeping angle α and sweeping morphology. When the self-excited sweeping nozzle has no outlet expansion section, the sweeping angle formed by the nozzle flow channel in the natural jet state is α0. When A is slightly bigger than α0, under the Coanda effect, the jet attaches to the wall of the outlet expansion section, putting the jet in an attached state, resulting in a sweeping angle α close to A and forming a quasi-trapezoidal sweeping morphology, accompanied by stretched liquid films and residual liquid ligaments. A given nozzle configuration under specific operating conditions exhibits a maximum attainable sweeping angle αmax. When A exceeds αmax, the Coanda effect ceases to function, causing the jet to detach from the influence of the expansion section wall. The sweeping angle then reverts to α0, forming a quasi-S-shaped sweeping morphology, with a main-secondary angle structure emerging at higher pressure drops. The atomization droplet size distribution is also influenced by the sweeping morphology. Under the quasi-trapezoidal sweeping morphology, droplet sizes are larger near the two lateral boundaries and smaller in the central region. Conversely, the quasi-S-shaped sweeping morphology promotes more uniform jet breakup, and the variation range of the droplet size in the spanwise direction is smaller. This study reveals the influence patterns and underlying mechanisms of the outlet geometry angle on the spray characteristics of self-excited sweeping nozzles, providing a theoretical basis for their optimized design.