Modular Wind Turbine Blade Spar Cap Joint With Non-Uniform Tapers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge of manufacturing and assembling modular wind turbine blades is exacerbated by the difficulty in creating accurate and strong scarf joints for spar caps that are split at the joint between blade modules, which are prone to stress concentrations and require long, challenging joints to transfer high bending loads.
Innovation Solution
A modular wind turbine blade design featuring spar caps with non-uniform tapers in their thickness bands, where the inner and outer bands have a lower taper rate than the intermediate band, allowing for a shorter joint span and improved load distribution, facilitated by a connecting element with matching taper profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the spar caps are configured with a very shallow taper (e.g., 1:100) to gradually transfer loads and provide a large bonding surface area, then the load transfer is improved and stress concentrations are reduced, but the joint length becomes very long (over 10 m) making it difficult to manufacture accurately and challenging to assemble on-site
Solution Approach 1:
The spar cap thickness is divided into multiple thickness bands (first, second, third bands) along the spanwise direction, each with different taper rates. This segmentation allows the joint to have varying local properties - steeper taper in some regions and shallower taper in others - thereby reducing the overall joint length while maintaining load transfer capability through the gradient structure
Solution Approach 2:
Different regions of the spar cap joint are assigned different taper rates according to the local load distribution. The thickness bands are configured with progressively varying taper rates, providing locally optimized stress distribution - steeper taper where loads are lower and shallower taper where loads are higher - thus reducing overall joint length while maintaining strength
2Strength
If the spar caps are configured with a very shallow taper to provide a large bonding surface area, then the bonding surface area is increased for better load transfer, but the manufacturing accuracy becomes difficult to achieve and assembly becomes challenging
Solution Approach 1:
The bonding surface is segmented into multiple thickness bands with different taper rates. This segmentation allows the total bonding area to be maintained through the cumulative effect of multiple bands, while each individual band has a manageable taper rate that is easier to manufacture with higher precision
Solution Approach 2:
The taper rate parameter is varied across different thickness bands rather than maintaining a uniform shallow taper. This parameter change allows optimization of each band's taper rate within manufacturable limits while the cumulative bonding area across all bands provides sufficient load transfer capability
Data Source
Figure 1
Figure 2
Figure 3
AI summary
According to the present invention there is provided a modular wind turbine blade comprising first and second blade modules connectable together to form at least part of the wind turbine blade, each blade module comprising an outer shell defining a pressure side and a suction side of the wind turbine blade. The first blade module comprises a first spar cap, and the second blade module comprising a second spar cap. The first spar cap has a tapered end portion in which the thickness of the first spar cap decreases towards the end of the first spar cap. The modular wind turbine blade further comprises an elongate connecting element for connecting the first and second blade modules together. The connecting element has a first tapered end portion in which the thickness of the connecting element decreases towards a first end of the connecting element. The first tapered end portion is configured for bonding to the tapered end portion of the first spar cap. The first spar cap has an inner surface and an outer surface, the thickness being defined between the inner surface and the outer surface. The first spar cap comprises (i) an intermediate thickness band; (ii) an inner thickness band between the intermediate thickness band and the inner surface; and (iii) an outer thickness band between the intermediate thickness band and the outer surface. Each of the thickness bands have a tapered end within the tapered end portion of the first spar cap. The connecting element has an inner surface and an outer surface, the thickness of the connecting element being defined between the inner surface and the outer surface. The connecting element comprises (i) an intermediate thickness band; (ii) an inner thickness band between the intermediate thickness band and the inner surface; and (iii) an outer thickness band between the intermediate thickness band and the outer surface. Each of the thickness bands has a tapered end within the first tapered end portion of the connecting element. The tapered end of the inner thickness band and/or the tapered end of the outer thickness band of the first spar cap has a lower rate of taper than the tapered end of the intermediate thickness band of the first spar cap. Additionally or alternatively, the tapered end of the inner thickness band and/or the tapered end of the outer thickness band of the connecting element has a lower rate of taper than the tapered end of the intermediate thickness band of the connecting element.