Abstract:
In a highly twisted blade combined with a variable chord, the effective thrust-weighted twist angle often differs from that of a rectangular blade under the same thrust conditions. Very few articles directly analyze the thrust-weighted effective twist angle as a function of blade planform changes. This paper introduces a design process to systematically predict rotor blade effective solidity and twist angle due to planform changes. Several planforms have been investigated, including blades with servo-flap, taper, dihedral, sweep and peddle tip. Interesting results are presented in the paper: i) With a servo-flap located at the outboard of 80%R, the blade flap-weighted effective twist angle (θFW) is increased in the design and the θFW is decreased if a servo-flap is placed at the inboard of 70%R; ii) For a 20% increase of the mid-span blade chord size design and a 3:1 tip taper ratio with the blade taper starting from 85%R to the tip, the maximum change of the effective blade twist angle is around 7.07%; iii)The blade dihedral-weighted effective solidity (θDW) has an 11.6% reduction when a rotor blade has a 30° dihedral starting from 70%R to the tip. In addition, the dihedral-weighted blade effective twist angle (σDW) has a 3.99% reduction; iv) The blade thrust-weighted effective solidity is reduced by 13.6% when a blade has an outboard 30% blade swept aft with a 30° angle. The blade effective twist angle has been reduced by 9.79% under the same outboard blade sweep condition.