Noise characteristics of tip clearance in a fan and engineering aerodynamic-aeroacoustic performance are obtained from skewed-swept rotating blades.Two methods of tip clearance modification have been carried out:(1)Experimental results are applied to decreasing the radial tip clearances of the rotating blades

thereby the aerodynamic efficiency increases about 3-4 percent

the average noise is reduced by 2-3 dB(A)

and the steady working margin is widened over 20 percent;(2)Aerodynamic-aeroacoustic characteristics are calculated with a revised formula.