ACOUSTIC AND AERODYNAMIC PERFORMANCE OF A 6-FOOT-DIAMETER FAN FOR TURBOFAN ENGINES Ⅱ - PERFORMANCE OF QF-1 FAN IN NACELLE WITHOUT ACOUSTIC SUPPRESSION

摘要

This fan, designed for low-noise output, produced significantly less perceived noise at take-off and approach conditions than fans in current use. Measured broad-band noise varied with speed but not with aerodynamic blade loading. Multiple pure-tone noise was present at 80 percent of design speed and above and at 90 percent of design speed was strongly dependent on loading. Blade-passing tone noise contributed substantially to noise radiation in front of the fan, but very little rearwards. At 90 percent of design speed this noise component varied strongly with loading in a manner opposite to the loading variation of the multiple pure tones.