Low-Noise Propeller Optimization Via Blade Sweep and Uneven Spacing

The present study investigates the impact of propeller planform on noise emission. Both balanced and unbalanced configurations are considered, acting on blade spacing and sweep. A global optimization, where the objective function is the sound pressure in the plane of rotation, confirms that uneven blade spacing can reduce noise. However, this does not necessarily lead to a reduction in emitted power. It is indeed the case that a stronger radiation in other directions results in an increase in the total noise from the source. Conversely, sweep optimization yields greater benefits, ensuring both local and overall noise reduction. An analysis of unbalanced rotors provides slightly improved results, but not enough to justify such a design.