Abstract
We experimentally investigated the influence on reducing noise of blade loading on both single and two-stage jet-fans. To obtain high blade loading, We applied NACA 65 series airfoil to rotor blades. For the single-stage fan, the blade loading for fan with eight rotor blades was higher than for fan with four blades. The blade loadings were the same for two-stage fans with either four or eight blades. We found that the broadband noise depended on the blade loading, but the noise at the blade passing frequency (BPF) was independent of the loading. The noise level of the BPF in the two-stage fan was higher than that in the single-stage fan, and this decreased as the number of blades was increased from four to eight. The specific noise level of the two-stage fan was lower than that of the conventional jet-fan. We concluded that applying NACA 65 airfoil to the blades was useful for reducing jet-fan noise.
