Doty Michael J, Brooks Thomas F, Burley Casey L, Bahr Christopher J, Pope Dennis S
NASA Langley Research Center, MS 461, Aeroacoustics Branch Hampton, VA, 23681.
Int J Aeroacoust. 2018 Mar 1;17(1-2):135-158. doi: 10.1177/1475472X17743659. Epub 2018 Feb 24.
One approach toward achieving NASA's aggressive N+2 noise goal of 42 EPNdB cumulative margin below Stage 4 is through the use of novel vehicle configurations like the Hybrid Wing Body (HWB). Jet noise measurements from an HWB acoustic test in the NASA Langley 14- by 22-Foot Subsonic Tunnel are described. Two dual-stream, heated Compact Jet Engine Simulator (CJES) units are mounted underneath the inverted HWB model on a traversable support to permit measurement of varying levels of shielding provided by the fuselage. Both an axisymmetric and low noise chevron nozzle set are investigated in the context of shielding. The unshielded chevron nozzle set shows 1 to 2 dB of source noise reduction (relative to the unshielded axisymmetric nozzle set) with some penalties at higher frequencies. Shielding of the axisymmetric nozzles shows up to 6.5 dB of reduction at high frequency. The combination of shielding and low noise chevrons shows benefits beyond the expected additive benefits of the two, up to 10 dB, due to the effective migration of the jet source peak noise location upstream for increased shielding effectiveness. Jet noise source maps from phased array results processed with the Deconvolution Approach for the Mapping of Acoustic Sources (DAMAS) algorithm reinforce these observations.
实现美国国家航空航天局（NASA）激进的N+2噪声目标（即比第4阶段累计低42等效连续感觉噪声级（EPNdB）裕度）的一种方法是使用新型飞行器构型，如混合翼身（HWB）。本文描述了在NASA兰利14×22英尺亚音速风洞中进行的HWB声学试验的喷气噪声测量结果。两台双流、加热的紧凑型喷气发动机模拟器（CJES）单元安装在倒置的HWB模型下方的可移动支架上，以测量机身提供的不同程度的屏蔽效果。在屏蔽的背景下，研究了轴对称和低噪声锯齿形喷嘴组。未屏蔽的锯齿形喷嘴组显示源噪声降低了1至2分贝（相对于未屏蔽的轴对称喷嘴组），但在较高频率下有一些代价。轴对称喷嘴的屏蔽在高频时显示出高达6.5分贝的降噪效果。屏蔽和低噪声锯齿形的组合显示出的益处超过了两者预期的叠加益处，高达10分贝，这是由于喷气源峰值噪声位置有效地向上游迁移，从而提高了屏蔽效果。用用于声源映射的反卷积方法（DAMAS）算法处理相控阵结果得到的喷气噪声源图强化了这些观察结果。
