Abstract
As the power output of direct drive generators increases, they become prohibitively large with much of this material structural support. In this work, implicit modeling was coupled to finite element analysis through a genetic algorithm variant to automate lattice optimization for the rotor of a 5 MW permanent magnet direct drive generator for mass reduction. Three triply periodic minimal surfaces (TPMS) were chosen: Diamond, Schwartz Primitive, and Gyroid. Parameter and functionally graded lattice optimization were employed to reduce mass within deflection criteria. Inactive mass for the 5 MW Diamond, Schwartz Primitive, and Gyroid optimized designs was 10,043, 10,858, and 10,990 kg, respectively. The Schwartz Primitive rotor resulted in a 34% reduction in inactive mass compared to a 5 MW baseline design. Radial and axial deflections were below the critical limit of 0.65 and 32.17 mm, respectively. The lowest torsional deflection was seen in the Schwartz Primitive TPMS lattice at 3.89 mm. Based on these designs, hybrid additive manufacturing with investment casting was used to validate manufacturability in metal. A fused deposition modeling (FDM) TPMS topology was printed for validation of the FEA results. Comparison between digital image correlation of the FDM printed design and FEA design resulted in a 6.7% deformation difference for equivalent loading conditions.
Highlights
As of 2019, wind energy provided 7.2% of the US electricity supply and is projected to grow to 12.5% by 2050 [1]
A fused deposition modeling (FDM) triply periodic minimal surfaces (TPMS) topology was printed for validation of the finite element analysis (FEA) results
A structural optimization tool using parameter optimization with an evolutionary algorithm was developed for wind turbine permanent magnet direct drive (PMDD) generator rotor optimization
Summary
As of 2019, wind energy provided 7.2% of the US electricity supply and is projected to grow to 12.5% by 2050 [1]. In a direct drive generator, the gearbox is removed with direct coupling of the blade shaft to the generator This is of particular interest as it can lead to improved reliability and lower levelized cost of energy by removing expensive gearbox replacements and transmission losses [2]. For a 5 MW direct drive generator, the structural mass can be up to 80% of its entire weight [4]. This large mass poses a particular concern for offshore installation where direct drive generators hold potential for greater reliability. Research into reducing structural mass through shape optimization has lacked a link to manufacturing these large complex designs on a large scale. Mueller et al [6] developed a C-core electromagnetic topology with
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