风扇出口导向叶片低噪声设计Ⅱ:数值验证

作为风扇出口导向叶片（Outlet Guide Vanes，OGV）低噪声设计系列文章的第2篇，本文对气动/声学一体化设计获得的2个OGV低噪声方案的降噪效果进行了数值验证。为了对低噪声优化方案的降噪效果进行详细评估，首先，采用非线性谐波法对优化前后的风扇/增压级开展了数值仿真，对OGV不同截面和叶片表面脉动压力进行了对比分析，发现低噪声优化设计方案有效降低了转/静干涉引起的脉动压力；然后，通过掠形和倾斜的合理组合，改变了叶片表面的相位分布，沿径向的相位变化增加了OGV对尾迹响应相互抵消的机会，从而有利于噪声的降低；最后，采用Wilson的波分解方法开展了对各方案的模态分析，对降噪效果进行了量化评估。结果显示，优化后的低噪声方案除起飞状态1BPF外，降噪量均超过了5 dB。

Low noise design of fan outlet guide vane,part Ⅱ: Numerical verifications

As the second part of the ‘Low noise design of fan outlet guide vane’ serial articles, this paper numerically evaluates the rotor/stator interaction noise of the two swept and leaned Outlet Guide Vanes (OGVs) obtained in the first paper and explored the noise reduction mechanism. First, a non-linear harmonic method is adopted to simulate the fan stage with different OGVs. The perturbation pressure on several sections and blade surface of OGV is investigated and analyzed. It is found that the perturbation pressure amplitudes of the low-noise design OGVs and the interaction noise are significantly reduced. Then, the optimized combination of sweep and lean resulted in a different distribution of phase on the blade surface. The radical variation of phase enhances the cancelation of the response of OGV to the rotor wake, being conducive of noise reduction. Finally, Wilson's wave splitting method is employed to quantitatively evaluate the sound power levels. The results show that, the rotor/stator interaction noise is reduced dramatically due to the low noise design, and a minimum of 5 dB of noise reduction can be obtained at different power sets except at take off for the 1st BPF.