Fan Noise Reduction with Increased Bypass Nozzle Area
Fan Noise Reduction with Increased Bypass Nozzle Area
复制标题
通过增加旁路喷嘴面积降低风扇噪音
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
G. Podboy
中科院分区：
文献类型：
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作者：
R. P. Woodward;C. Hughes;G. Podboy
在NASA格伦9 × 15英尺低速风洞中对一个涡轮风扇发动机模型进行了试验，以研究使用三个固定喷管流的可变面积旁路喷管的远场声学效应。基准喷管的尺寸设计应能在巡航状态下产生最大的级性能。然而，风洞试验是在接近海平面的条件下进行的。因此，为了模拟和获得其它运行条件下的性能，对另外两个喷管进行了试验--一个喷管的重量流量增加了+5%（面积增加了+5.4%），其尺寸可模拟级设计点（起飞）条件下的性能，另一个喷管的重量流量增加了+7.5%（面积增加了+10.9%），其尺寸可模拟海平面条件下的最大重量流量。测得的增加喷管面积的声学效益表明，有效的感知噪声水平降低了2分贝或更多（对于1500英尺风扇天桥，比例因子为3.35），而级推力实际上增加了2%至3%。噪音减少，主要是在宽带噪音的水平，观察到到处都在远场。转子下游的激光多普勒测速仪测量结果表明，总湍流速度随着喷嘴流量的增加而降低，这可以解释转子宽带噪声水平的降低。
A model turbofan was tested in the NASA Glenn 9- by 15-ft low speed wind tunnel to explore far-field acoustic effects of a variable area bypass nozzle using three fixed nozzle flows. The baseline nozzle was sized to produce maximum stage performance at cruise condition. However, wind tunnel testing is conducted near sea level condition. Therefore, to simulate and obtain performance at other operating conditions, two additional nozzles were tested-one with +5% increase in weight flow (+5.4% area increase), sized to simulate the performance at the stage design point (takeoff) condition, and the other with a +7.5% increase in weight flow (+10.9% area increase) sized for maximum weight flow at sea level condition. Measured acoustic benefits with increased nozzle area showed effective perceived noise level reductions of 2 or more dB (for a 1500 ft fan flyover with a 3.35 scale factor) while the stage thrust actually increased by 2 to 3%. Noise reductions, principally in the level of broadband noise, were observed everywhere in the far field. Laser Doppler velocimetry measurements downstream of the rotor showed that the total turbulent velocity decreased with increasing nozzle flow, which may explain the reduced rotor broadband noise levels.