Determining Division Location for Sectional Wind Turbine Blades

Abstract

Sectional wind turbine blades, by dividing an intact blade into multiple segments, have the advantage of being easy to handle and transport. To determine a suitable blade division location, this study was performed to clarify some crucial aspects and challenges for sectional blades. This paper proposes a method to estimate the effects of the location of the blade division on structural, manufacturing, and assembling performance of sectional blades. The advantage of this method is the ease of the assessment process, since it can be performed at an early stage of blade design, where only the aerodynamic profile, mass density and stiffness distribution, and service fatigue loads of original blades are essential. A case study with the proposed method was carried out based on a 38-meter commercial blade. Results show that the best position for the division of sectional blades is located 20% from the blade root by balancing the three aspects listed above. The key approaches to reduce additional increases in stiffness and weight of sectional blades are related to improving the fatigue strength and the choice of low-modulus materials for connecting bolts. The effects of the division location on assembling accessibility and natural frequencies of scaled sectional blades are consistent with the basic sectional blade. Unfavorable effects occur when up-scaling the diameter of the bolts; and, harsh external loads on the connections have negative effects on the application of sectional blades with larger wind turbines. In this regard, lightweight design is indispensable to reduce bolt stress.

Development of an open-source segmented blade design tool

“…Qin et al [6] developed a method to determine spanwise joint location based on structure, vibration, manufacturing, and assembly performance, and made several key observations: Choosing a relatively uniform blade thickness/chord location for the joint eased manufacturing and assembly. Modal excitation was promoted for midpoint and blade-tip joints, regardless of blade size, and could be somewhat mitigated by controls.…”