Abstract
Efficiency and durability are critical issues that affect widely-adopted aerofoil-power generator as a sustainable source of electrical power. Even though high wind power density can be achieved; installing wind turbines in desert condition has difficulties including thermal variation, high turbulence and sand storms. Sand blasting on turbine blade surface at high velocities causes erosion resulting turbine efficiency drop. Damage-induced erosion phenomena and aeroelastic performance of the blades needed to be investigated. Suitable coating may prevent erosion to a great extent. A numerical investigation of erosion on NACA 4412 wind turbine blade has been performed using commercial computational fluid dynamics software ANSYS FLUENT 14.5 release. Discrete phase model (DPM) has been used for modelling multi-phase flow of air and sand particles over the turbine blade. Governing equations have been solved by finite volume method (FVM). Conventional 30-70% glass fibre resin and non-conventional jute fibre composite have been used as turbine blade material. Sand particles of diameter have been injected from 20, 30, 45, 60 and 90 degree angles at 500C temperature. Erosion rate, wall shear stress and strain rate have been calculated for different wind velocities and impingement angles. Simulation results for higher velocities deviate from the results observed at lower wind velocities. In simulation, erosion rate is highest for impingement angle at low wind velocities, which has been validated by experiment with a mean absolute error (MAE) of 5.56%. Erosion rate and wall shear stress are higher on jute composite fibre than glass fibre resin. Developed shear stress on wind turbine blade surface is highest for impingement angle at all velocities. On the other hand, exerted pressure on turbine blade surface is found highest for 9 angle of attack. Experimental results, with or without Titanium nitride(TiN) nano-coating, also revealed that surface roughness augments with increasing impingement angles. Nano-coating (TiN) by RF sputtering technique reduced the surface roughness significantly as oppose to uncoated samples. Highest roughness has been observed on uncoated blade surface collided with 0.3-0.69 mm diameter brown aluminium oxide particles.
Highlights
5.1 Simulation results 5.1.1 Erosion rate Figure 4 shows the contour plot of erosion on wind turbine blade surface of glass fibre resin for 60 ms−1 wind velocity and 90° impingement angle
Erosion rate is highest for 30° impingement angle, which is followed by 90°, 60°, 45° and 20° angles respectively
It shows clearly that erosion rate on jute fibre composite blade is higher than glass fibre resin. 5.1.2 Wall shear stress In Figure 7, development of shear stress on wind turbine blade surface is shown by contour plot
Summary
Patnaik et al [12] numerically and experimentally investigated erosion rate on zinc-aluminum alloy metal (ZA27) filled with titania (TiO2) for different particle impact velocity, size, temperature and impingement angle. They observed that highest erosion rate occurs at 600 impingement angle. Simulation was carried out by Fiore et al [14] to investigate erosion on wind turbine blade for insects and sand particles impact. Hamed et al [16] explored surface damage of turbine blade both numerically and experimentally Their results show that erosion and surface roughness enhance with increasing impact angle and particle size. Hasan and Ahmed (2017): International Journal of Engineering Materials and Manufacture, 2(3), 37-48
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