Aeroacoustic Design of a 6-Bladed Propeller

Abstract

By reducing the diameter of a transonic propeller at constant rotational speed a significant noise reduction can be achieved. The number of blades is increased to retain the thrust. For a given design quality a loss in efficiency due to the increase propeller loading can be expected. This has to be compensated by a good design for minimum induced loss and use of optimised airfoils such as the DLR propeller airfoil family. After comparison of a blade element method, a panel and an Euler method, the blade element method was chosen for the aerodynamic design and the panel method was chosen for the aeroacoustic numbers and different numbers of blades. Tip shape studies based on the inviscid panel method exhibit little effects on noise but do effect efficiency.