Experimental study of spray entrainment characteristics in recirculation zone of integrated strut flameholders

In order to investigate the liquid spray entrainment distribution characteristics of the recirculation zone in different trailing edge configurations of the afterburner integrated strut flameholders， eight configurations with expansion structures （labeled A~I） were designed. Experiments were conducted under various operating conditions， including ambient temperature and pressure， as well as medium temperature and pressure （500 K & 0.3 MPa）， with fuel injection angles of 90° and 130°， and trailing edge heights of 30， 35， and 40 mm. The results show significant differences in liquid spray entrainment patterns within the recirculation zones among different trailing edge configurations. Compared with the purely straight strut structure， increasing the trailing edge height helps improve recirculation entrainment， and reverse injection results in a larger longitudinal distribution range behind the trailing edge. Under medium temperature and pressure conditions， the small droplets generated during the breakup and atomization of the jet in the straight strut evaporate quickly. The time-averaged contour images reveal fuel break-up， which could lead to discontinuous combustion. In the lobe-shaped G configuration， the narrow gap causes gas to entrain the liquid spray， and this phenomenon should be considered when designing the location of the igniter. Additionally， the comparison of the recirculation zone’s time-averaged vortex flow field and liquid spray distribution at the same freestream Mach number for the nozzle-to-trailing edge distance used in the study shows large differences， which may be due to the poor followability of the larger-sized droplets from the lateral jet atomization.

为研究加力燃烧室一体化支板火焰稳定器（afterburner integrated strut flameholders）不同尾缘构型下回流区（recirculation zone）的液滴夹带分布特性，本研究设计了8种带有扩张结构（expansion structures）的构型（标注为A~I）。实验在多种工况下开展，涵盖环境温压条件（ambient temperature and pressure）与中温中压条件（500 K、0.3 MPa），设置的燃料喷射角（fuel injection angles）为90°与130°，尾缘高度分别为30 mm、35 mm及40 mm。研究结果表明，不同尾缘构型的回流区内液滴夹带流型存在显著差异。相较于纯直支板结构（purely straight strut structure），增大尾缘高度有助于提升回流夹带效果，而反向喷射（reverse injection）可使尾缘后方的纵向分布范围更大。在中温中压条件下，直支板结构中射流破碎雾化产生的细小液滴会快速蒸发。时均等值线图像（time-averaged contour images）显示存在燃油破碎现象，这可能会引发燃烧不连续问题。在瓣状G构型（lobe-shaped G configuration）中，窄间隙会导致气体夹带液滴，该现象在设计点火器（igniter）安装位置时需予以考虑。此外，针对本研究采用的喷嘴至尾缘的距离（nozzle-to-trailing edge distance），在相同来流马赫数（freestream Mach number）下对回流区时均涡旋流场与液滴分布进行对比后发现，二者差异显著，这可能是侧向射流雾化（lateral jet atomization）产生的大尺寸液滴跟随性较差所致。