Abstract High-temperature buoyant jets generally exist at the exhaust port during the casting process. Canopy hoods are employed to capture these jets in industrial plants. However, because of the lack of flow-field evolution and vortex structure characteristics of the buoyant jets, the optimal design of canopy hood is lack of guidance. In this study, the effects of different initial temperatures (T0) of buoyant jets on the evolution of the temperature, velocity, and vorticity magnitude fields and vortex structure characteristics were studied by large-eddy simulation. The results showed that for 100–1200 °C buoyant jets, the contracted section, which is useful in determining the preferred canopy hood installation position, is generated within 0.7–2 times the source diameter from the nozzle (Z/D). As T0 increases, the position of the contracted section tends to come closer to the nozzle, and the space height for temperature attenuation in the core region is reduced. The contracted section formation results from the rupture of the vortex ring. Because the vortex ring can restrict the diffusion of the buoyant jet, the initial temperature has little effect on the diffusion angle within 4 Z/D. In addition, the spiral vortex structure entrains a large quantity of ambient air, which causes the exhaust flow rate to increase sharply. These conclusions may guide for the design of the exhaust hood installation height for high-temperature buoyant jets to achieve energy savings.

中文翻译：

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高温浮力射流流场演化及涡结构特征

摘要 铸造过程中排气口处普遍存在高温浮力射流。在工业厂房中，使用遮篷来捕捉这些射流。然而，由于缺乏浮力射流的流场演化和涡结构特征，对雨篷罩的优化设计缺乏指导。本研究通过大涡模拟研究了不同的浮力射流初始温度（T0）对温度、速度和涡量场以及涡结构特征演化的影响。结果表明，对于 100–1200 °C 的浮力射流，在喷嘴源直径 (Z/D) 的 0.7–2 倍范围内产生收缩部分，这有助于确定首选的顶篷安装位置。随着 T0 的增加，收缩段的位置趋向于靠近喷嘴，降低了芯区温度衰减的空间高度。收缩段的形成是涡环破裂的结果。由于涡环可以限制浮力射流的扩散，初始温度在4 Z/D以内对扩散角影响不大。此外，螺旋涡流结构夹带了大量的环境空气，导致排气流量急剧增加。这些结论可为高温浮力射流排烟罩安装高度的设计提供指导，以实现节能。收缩段的形成是涡环破裂的结果。由于涡环可以限制浮力射流的扩散，初始温度在4 Z/D以内对扩散角影响不大。此外，螺旋涡流结构夹带了大量的环境空气，导致排气流量急剧增加。这些结论可为高温浮力射流排烟罩安装高度的设计提供指导，以实现节能。收缩段的形成是涡环破裂的结果。由于涡环可以限制浮力射流的扩散，初始温度在4 Z/D以内对扩散角影响不大。此外，螺旋涡流结构夹带了大量的环境空气，导致排气流量急剧增加。这些结论可为高温浮力射流排烟罩安装高度的设计提供指导，以实现节能。