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首页> 外文期刊>Journal of the American Helicopter Society >Three-Dimensional Sound Directivity around a Helicopter Tlirboshaft Engine
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Three-Dimensional Sound Directivity around a Helicopter Tlirboshaft Engine

机译：直升机三角轴发动机周围的三维声音指向性

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Turboshaft engines can be the main source of noise due to a helicopter at takeoff. Some new silencing designs of the inlets and of the ejector were tested on a Turbomeca Arrius 2B2 engine in an open-air static facility. Intake and exhaust are not axisymmetric, and conventional directivity patterns of sound field on a horizontal arc of circle are insufficient. A special microphone array on a vertical half-circle translating axially was built. Data processing has been implemented to plot maps of sound pressure levels in third-octave bands and to compute sound power levels. Intake and exhaust radiations are separated thanks to mufflers on the other side. The lined fins in the secondary lateral inlet well reduce the compressor tone, which is largely dominant in intake radiation. Its sound power level is decreased by 7 dB. The novel ejector is also successful to reduce exhaust broadband noise above 1 kHz with a gain of 5 dB on sound power level. Finally, the benefit on the acoustic emission of the helicopter in flight is appraised.
机译：由于直升机在起飞时，涡轮轴发动机可能是主要的噪声源。在Turbomeca Arrius 2B2发动机的露天静态设施中对进气口和喷射器的一些新消音设计进行了测试。进气和排气不是轴对称的，并且在水平圆弧上的常规声场方向性模式不足。在垂直平移的半圆上构建了一个特殊的传声器阵列，该传声器轴向平移。已执行数据处理以绘制三倍频程频段的声压级图并计算声功率级。另一侧的消声器将进气和排气辐射分开。次要侧进气孔中的衬里散热片降低了压缩机的音调，这在进气辐射中占主导地位。它的声功率级降低了7 dB。新型喷射器还成功地降低了1 kHz以上的排气宽带噪声，使声功率级增加了5 dB。最后，评估了飞行中直升机在声发射方面的优势。

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