The effect of casing boundary-layer removal on noise produced by a turbofan rotor was measured. The outlet guide vanes were removed for these tests. A comparison was made between the noise measurements when the boundary layer was bled off and under zero bleed conditions. When the boundary layer was removed, overall sound pressure level was reduced 2 dB with moderate blade loading and 3 dB with heavier blade loading. An analysis of the changes in the spectral density with bleed is presented.

Sound measurements on a 4000-pound-thrust high-bypass-ratio turbofan engine

Citations

Effects of casing boundary-layer removal on noise of a turbofan rotor

On noise of a turbofan rotor boundary-layer removal

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