Analysis of virtual profiles of rotor sections and loss of angle of attack in hovering state

Abstract

Generally, the performance advantages of rotor airfoils with high aerodynamic efficiency might be reduced when applied on rotors, however, the quantitative research on the three-dimensional effects of rotor that lead to this problem is still very lacking. In order to quantitatively investigate the influences of three-dimensional effects on the aerodynamic characteristics of rotor airfoils, a novel numerical strategy for analyzing equivalent angle of attack and aerodynamic shape of blade profiles is proposed based on high-precision CFD method and the inverse design method, and the simulations on equivalent profiles and their equivalent angles of attack are conducted at various tip Mach numbers and aspect ratios of rotor blades. The numerical results indicate that the equivalent profiles in hover are mainly affected by radial flow on rotor, and the difference of aerodynamic shapes between equivalent airfoils and blade profiles are larger with the section closer to blade tip. The major influence on equivalent angle of attack is the vertical induced velocity, and the loss of angle of attack at root is larger than at tip. Additionally, lower tip Mach number and larger aspect ratio of rotor blades help to reduce the variation of the equivalent airfoil and loss of angle of attack. The quantitative results could provide theoretical references for the design of high-performance rotor airfoils and their applications on rotors.