5.5 m×4 m航空声学风洞是2015年投入使用的中国首座大型航空声学风洞，填补了中国在飞行器气动声学试验地面研究平台领域的空白。针对该风洞具有气动声学试验能力、开闭口试验状态快速切换以及模型支撑系统适应多工况的试验需求等特点进行了风洞总体和主要部段结构设计与研究。采用可更换的大型钢结构与砼结构相结合的风洞回路，实现了风洞气动与声学、开口与闭口兼顾的多功能布局需求；采用整体可移动、推杆驱动的多功能腹撑装置和沉入式大行程、高精度、可升降尾撑机构，实现了开/闭口试验等试验功能和状态的快速切换；采用球面轮毂、球面叶根桨叶角可调叶片、法兰对顶叶柄防松结构，最大限度地降低了叶根气动噪声，同时实现了风扇转子的可靠运行，结合壁面降噪措施，满足了风扇的低噪声要求。试验结果表明该风洞运行结构安全可靠，试验效率高，证明5.5 m×4 m航空声学风洞结构设计是成功的。

The 5.5 m × 4 m aeroacoustic wind tunnel， as the first large aeroacoustic wind tunnel in China， was put into use at 2015， which filled the gap in the field of ground test research platform on aircraft aeroacoustic in China. In this work. The overall structure design of wind tunnel and detailed structure design of main sections are carried out in consideration of the wind tunnel characteristics including test capability on aeroacoustic， fast switching between open test status and closed test status and adaptability of model support system to test requirements under multiple working condition. The wind tunnel loop is made up of the replaceable large steel structure and concrete structure， which satisfies the multifunctional layout requirements of aerodynamics-acoustics and opening-closing status. The integrally movable multifunctional abdominal support device driven by handspike and the deeply embedded long stroke liftable tail support mechanism with the advantage of high accuracy are employed to achieve the fast switching between open test status and closed test status. The spherical wheel hub， the spherical blade with the adjustable blade angle and the locking structure between the flange and apical petiole are adopted to reduce the aerodynamic noise of blade root as far as possible and to achieve the reliable operation of fan rotor， which can satisfy the requirement of low noise of fan in combination of noise reduction measures taken at the wall. The test results show the safe and reliable operation of wind tunnel structure and the high test efficiency， which proves the success of structure design of 5.5 m × 4 m aeroacoustic wind tunnel.