Mechanical Efficiency and Noise Reduction of Segmented Stator Vanes

Abstract

Model experiments indicating the possibility of several decibels of noise reduction with small change of mechanical efficiency in axial flow compressors using segmented stator vanes have been reported [J. Acoust. Soc. Amer. 47, 111 (A) (1970)]. Compared with straight-edged vanes, the serrated vanes provide 2–5 dB of noise reduction and no change in efficiency at the design conditions. Changing relative numbers of rotor blades and stator vanes gives either improved efficiency and no noise reduction or reduced efficiency and greater noise reduction. Off-design flow angles present a complicated pattern of results, but, in general, the serrated vanes compared with straight-edged vanes are equally efficient and have increased broad-band noise, but less blade-passage-frequency noise. As a noise reduction mechanism for turbine engines, it may be used with most other techniques, and the effects are likely to be additive; however, its maximum benefit is likely to be about 5 dB.