Noise and Wake Structure Measurements in a Subsonic Tip Speed Fan |
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1/3-octave band 95 percent span acoustic acoustic data aerodynamic air angle Airfoils Anemometer angle and tip blade passing frequency blade wake broadband noise CALCULATION EXCLUDING ENDWALL CENTER FREQUENCY COMPARISON OF MEASUREMENTS COMPARISONS FOR TEST constant pressure ratio constant thrust DEG BLADE ANGLE degree blade DIAMETER FAN NOISE DIMENSIONLESS EXCLUDING ENDWALL LOSS FAN NOISE VARIATION FAN PRESSURE RATIO flow angle Flow Condition FRACTIONAL VELOCITY DEFECT FRACTIONAL WAKE WIDTH FT/S ft/sec Hamilton Standard harmonic noise harmonics of blade HERTZ hot wire INVISCID FLOW KILOHERTZ m/sec MAXIMUM PERCEIVED NOISE measured wakes MEASUREMENTS AND PREDICTIONS microphone minimum noise modulation NACA NASA noise measurements PERCEIVED NOISE LEVEL plotted PN dB PNdB POWER LEVEL dB probe RESULTANT VELOCITY PROFILES rotor coordinate system rotor wakes shown in figure shows SOUND POWER LEVEL SOUND PRESSURE LEVEL SPEED AT CONSTANT stator noise subsonic tip speed TEST CONDITION test data tip speed fan VARIATION WITH TIP wake data