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布置有多层孔板(丝网)的大开角扩散段通过参数的优化设计,可有效缩短暂冲式风洞启动时间,均匀进入稳定段的气流速度,并降低阀后噪声和气流脉动。针对某大型暂冲式风洞大开角扩散段设计关键技术开展专题研究,设计并进行了不同扩散段扩开角角度和中心体分流锥型式的组合实验,从压力损失、出口截面速度分布和降噪特性三个方面进行了对比分析。试验结果表明:试验件45°扩开角+65°平底锥的压力损失相对最小,而增加导流尾锥的中心分流锥由于底部难以形成稳态的分离涡使得其压力损失明显偏大,其它试验件组合的压力损失值则相接近;各试验件出口截面的速压分布均呈现以中轴线对称分布的双驼峰趋势,且孔板的开孔率偏高时出口剖面速度分布相对更平滑;试验马赫数下的大开角段对气流噪声的消声量约为12~14dB,对频率在2kHz以上的气流噪声具有相对较强的消声能力,同时气流经过设置有多层孔板的大开角扩散段后,气流波动幅值明显降低,气流脉动得到有效地抑制。
The wide open-angle diffusing section with multi-layer perforated plate (screen) can effectively shorten the start-up time of the temporary impingement wind tunnel, the airflow velocity into the stable section evenly, and reduce the valve noise and air flow pulsation by the parameter optimization design. Aiming at the key technology of the design of large open angle divergent section in a large temporary buffer wind tunnel, a special research was carried out on the key technologies. The combination experiment of divergence angle and divergence cone of divergent section was designed and carried out. From the pressure loss, Noise reduction characteristics of the three aspects of a comparative analysis. The experimental results show that the pressure loss of the flat bottom cone with the 45 ° flare angle of +45 ° is relatively minimum, whereas the increase of the central diverting cone of the tail cone causes the pressure loss to be obviously larger due to the difficulty in forming the steady-state separation vortex at the bottom. The pressure loss values of the combination of test pieces are close to each other; the distribution of velocity and pressure in the exit cross section of each test piece shows a double hump trend symmetrically distributed along the central axis; and the exit section velocity distribution is relatively smoother when the perforated opening ratio is higher; The large angular section under test Mach number can reduce the noise of the airflow noise by about 12 ~ 14dB. It has a relatively strong ability to silence the airflow noise with the frequency above 2kHz. At the same time, the airflow passes through the opening of the multilayer aperture plate After the angular diffusion zone, the amplitude of the airflow fluctuation is obviously reduced, and the pulsation of the airflow is effectively suppressed.