Vertical-axis wind turbines (VAWTs) are attractive tools for wind energy extraction particularly suitable for small consumers or off-grid areas. Although their geometry is simple (here, rectangular blade of constant airfoil is assumed), aerodynamic analysis may be quite complex. Computational fluid dynamics (CFD) approach is employed for the estimation of rotor aerodynamic performances. This paper provides a review of possible multiobjective optimization strategies for the design of small-scale VAWT laminate blades in terms of its main structural parameters: ply-order and ply-number. Numerous structural analyses of the composite turbine blades were performed by finite element method (FEM). Multi-criteria constrained optimizations, by an evolutionary method − particle swarm optimization (PSO), were performed with respect to blade total mass, maximum blade tip deflection under static loading, computed natural frequencies and failure index along the blade. By combining different input and output parameters (cost functions and constraints) a large variety of feasible solutions can be achieved.
Three-dimensional printed plastic products developed through fused deposition modelling (FDM) take long-term mechanical loading in most industrial prototypes. This article focuses on the impact of the 3D printing parameters, type of thermal treatment and variation of characteristic dimensions of standard specimens on the tensile properties of poly(lactic acid) (PLA) material. Two mediums were used for thermal treatment: NaCl powder and plaster. The specimens immersed in NaCl powder were heated to the melting temperature of the filament (200 °C), while the processing of the plastered specimens was performed at a temperature of 100 °C. After treatment, the specimens were cooled at room temperature (25 °C), and the dimensions of the annealed and untreated specimens were controlled. The tensile test of the specimens was performed on the universal test machine. The response surface methodology (RSM) is employed to predict the tensile stress by undertaking input parameters. The analysis of variance (ANOVA) results revealed that the untreated specimens, orientation –45/45 and layer thickness of 0.1 mm had the highest tensile stress value. Thermal treatment in plaster showed a significant increase in tensile strength, while the best specimens were obtained after treatment in NaCl, and all refer to the –45/45 (0.1 mm) orientation.
The main roles of unmanned air vehicles (UAVs) include: observation, surveillance, transportation, remote sensing and various security tasks. Improved, augmented type of UAVs are high-altitude long-endurance (HALE) aircraft capable and designed, as their name suggests, for lengthy flights at higher altitudes (which also usually implies subsonic cruising velocities). Different variants, in both size and applied technical solutions, have been tried. Common approach incorporates standard wing-fuselage-aft empennage configuration and propelled flight as the most efficient for the required speed range. The paper gives a brief overview of a preliminary aerodynamic analysis of the main lifting surfaces as well as a detailed description of the performed multi-objective optimization of the propeller capable of producing a sufficient amount of thrust at the cruising altitude and speed. Aerodynamic performances of the investigated propellers are estimated by a simple blade element momentum theory (BEMT). The chosen optimizing method, genetic algorithm (GA), is suitable for dealing with a large number of input variables.
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