Further Improvements in the SNUF Blade Design by Numerical Design Optimization Framework

Abstract

This paper focused on improving a small-scaled helicopter rotor blade prototype with a flap-driving mechanism termed the Seoul National University Flap (SNUF). The design of the SNUF included realizing vibratory load reduction. First, a multibody structural dynamics analysis was performed to determine the influence of the flap dimension and location within the rotor blade with respect to hub vibratory load reduction. This process was followed by selecting a specific blade configuration that maximized vibration reduction capability. Following this, a numerical optimization technique was applied to improve the cross sectional design of the SNUF blade. The design optimization procedure obtained improved blade sectional design with decreased first torsional frequency and reduced blade weight, and it satisfied sufficient structural integrity. Three-dimensional nonlinear static structural analysis also was performed for the optimized SNUF design. The von Mises stress distribution on the blade and components was predicted by considering external aerodynamic loads, centrifugal loads because of rotation, and contact among the internal components. Future studies will include fabricating the prototype blade on the basis of the optimized design and performing a whirl tower test.