Characteristics of ventilating flow generated by a rotating swirler in a vortex vent

A vortex ventilation system with a rotating annular disk installed coaxially with the exhaust inlet is a very effective local ventilator. A swirling flow generated by a rotating swirler makes the ventilation flow concentrated around the axis of rotation, which can increase the ventilation depth by a factor of five compared to a conventional exhaust hood. Despite the well-documented excellent ventilation performance of such a system, detailed flow characteristics are not well understood. In this study, the swirling flow field in the vortex vent was tested, and a number of peculiar flow characteristics were observed. When the rotational speed was varied, a series of different flow patterns appeared, and the changes in the flow pattern showed rapid transition, hysteresis, and flow instability similar to the vortex. The transition of the flow pattern could be explained based on the ratio of the centrifugal force to exhaust pressure. Hysteresis of the flow transition occurred in an unstable equilibrium mode between the two forces, and an unstable flow pattern occurred when the secondary recirculating flow was located beneath the swirler. A formula for the critical rotational speed was derived, which showed satisfactory agreement with experimental observation.     

化学激光器燃烧室两步反应法的实验研究

 在环柱型增益发生器实验系统燃烧室的设计中,将主稀释剂He从两个不同的区域注入燃烧室,其中一部分与D2预混以后通过D2喷注孔注入,另一部分通过主喷管叶片后端的后向喷注孔注入。讨论了不同区域的主稀释剂流量的变化对激光器特性的影响。实验结果表明：后He流量改变时,激光器的功率变化及点火稳定性等明显优于前He流量改变的情况。若要增加主稀释剂比例,应优先考虑调整后He。