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Prediction of fan acoustic blockage on fan/outlet guide vane broadband interaction noise using frequency domain linearised Navier–Stokes solvers
Journal of Sound and Vibration ( IF 4.7 ) Pub Date : 2021-02-18 , DOI: 10.1016/j.jsv.2021.116033
Ricardo Blázquez-Navarro , Roque Corral

Fan/Outlet-Guide-Vane (OGV) interaction is a major broadband noise source in high bypass ratio turbofan engines. This paper assesses the acoustic shielding created by the fan rotor on the broadband noise generated by the interaction between the fan and the OGV. With this objective in mind, an efficient methodology to account for broadband noise transmission through a fan rotor using two-dimensional linearised frequency domain Navier–Stokes solvers is presented. The radial variations of the flow are retained using a strip-wise approach, which is key to estimate the fan blockage accurately. The methodology has been applied to the AneCom Aerotest (ACAT1) fan rig that is representative of a modern fan, at the three noise certification points and compared with acoustic measurements, namely, frequency spectra and azimuthal mode decompositions. Overall, good agreement on the impact of the rotor shielding on the upstream noise spectra has been achieved. Rotor shielding produces a decrease in the upstream emitted noise of about 2.5, 7 and 9 dB at Approach, Cutback and Sideline conditions, respectively. Thus, its modelling is of paramount importance for an accurate prediction of the engine’s noise footprint. The predicted sound pressure azimuthal decompositions show an excellent qualitative agreement with the experimental data, demonstrating the suitability of the methodology to predict this phenomenon. It is concluded that fan blockage cannot be predicted with conventional semi-analytical techniques based on flat plate approximations. The supersonic pockets and shock-waves present in the fan play a principal role in the upstream acoustic emission at high-speed operating points, which cannot be retained in flat plate-like methodologies. The simulations show that at Sideline, the broadband noise emitted by the engine core can become dominant, which was not anticipated. This conclusion is indirectly supported by measurements.



中文翻译:

使用频域线性化的Navier–Stokes解算器预测风扇/出口导向叶片宽带相互作用噪声上的风扇声阻塞

风扇/出口-导向-叶片(OGV)相互作用是高旁路比涡轮风扇发动机中的主要宽带噪声源。本文评估了风扇转子对OGV与风扇之间的相互作用所产生的宽带噪声产生的声屏蔽。考虑到这一目标,提出了一种使用二维线性化频域Navier-Stokes求解器解决宽带噪声通过风扇转子传播的有效方法。使用条状方法可以保持气流的径向变化,这是准确估算风扇阻塞的关键。该方法已应用于AneCom Aerotest(ACAT1)代表现代风扇的风扇装置,位于三个噪声认证点,并与声学测量(即频谱和方位角模式分解)进行比较。总的来说,已经在转子屏蔽对上游噪声频谱的影响方面达成了良好的共识。在进近,切入和边线条件下,转子屏蔽罩分别使上游发射噪声降低了约2.5、7和9 dB。因此,其模型对于准确预测发动机的噪声足迹至关重要。预测的声压方位角分解显示出与实验数据极好的定性一致性,表明该方法可预测这种现象。可以得出结论,使用基于平板近似值的常规半分析技术无法预测风扇堵塞。风扇中存在的超音速腔和冲击波在高速运行点的上游声发射中起主要作用,而在平板状方法中则无法保留这些超声波和冲击波。仿真显示,在Sideline,引擎核心发出的宽带噪声可能占主导地位,这是无法预料的。这一结论得到测量的间接支持。引擎核心发出的宽带噪声可能占主导地位,这是无法预料的。这一结论得到测量的间接支持。引擎核心发出的宽带噪声可能占主导地位,这是无法预料的。这一结论得到测量的间接支持。

更新日期:2021-02-28
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