Abstract: In order to reduce the operation cost of large supersonic wind tunnel, a new design of secondary-throat diffuser characterized by ejection of low total pressure cold air is proposed and verified numerically. The main structural characteristic of the new-designed diffuser is that: a groove is added to the front of diffuser contraction section and the low total pressure cold air is ejected into diffuser to form the air film adjacent to the diffuser wall, which adjusts the actual flow area of secondary-throat diffuser so that the ability of static pressure recovery is enhanced. Meanwhile, the wall thermal load of the new-designed diffuser is reduced by cold air film as well. Such advantages of the new-designed secondary-throat diffuser are evaluated by numerical simulations. The results reveal that the new-designed diffuser case can self-adapt wide operating conditions, protect the diffuser wall from high temperature gas contacting directly and improve the ability of static pressure recovery effectively by adjusting the ejection air rate. The evaluation of required primary flow rate of relay ejector shows an almost 30% saving, indicating a great promotion of the operation economy of supersonic wind tunnel by application of the new-designed diffuser.

Key words: Supersonic wind tunnel;Diffuser;Throat;Convergent section;Ejection;Numerical simulation

摘要： 为提高大型超声速风洞的运行经济性，设计了一种通过引射低总压冷介质提高扩压性能的新型二次喉道扩压器，其结构特征是在扩压器收敛段前方增加侧壁凹槽，在凹槽前沿位置引入低总压常温空气作为冷介质，通过引射扩散作用在扩压器壁面形成气膜，调节二次喉道实际流通直径，较大程度上增强二次喉道的静压恢复能力，同时又降低二次喉道壁面热负荷，冷却壁面。数值验证结果表明，所设计新型二次喉道方案可通过调节引射气量自适应较宽范围的运行条件，有效隔离扩压器壁面直接接触高温燃气，同时提高了扩压能力，节省后段接力引射器的主动流流量近30%，对风洞运行经济性提升十分明显。

关键词: 超声速风洞;扩压器;喉道;收敛段;引射;数值模拟