Some views on the mapping of erosion of coated composites in tidal turbine simulated conditions

This article presents a study of the erosion resistance of coated and uncoated polymer matrix composites for tidal turbine conditions. It focuses on the development of comparative erosive wear mode and mechanism maps for such materials. In our earlier work, testing of glass-fiber-reinforced polymer composites for tribological applications in marine simulated conditions, several erosion-related issues were highlighted. The combined effects of the NaCl solution and sand dramatically enhanced the erosive wear of the uncoated specimens. In order to address those issues, an erosion-resistant polymeric coating was applied to the composite and tested in marine simulated conditions with an extended range of sand particle size. The test results of the uncoated and coated composite have been compared in this research by erosive wear mode and mechanism maps techniques. These maps reveal that the coating has enhanced the erosion resistance. These findings provide significant progress toward materials selection approaches to manufacture of tidal turbine blades

Tribology of tidal turbine blades : impact angle effects on erosion of polymeric coatings in sea water conditions

Tidal energy, of all marine renewables energies, possesses higher persistency and predictability over long time scales. Due to the aggressive marine environment, there are barriers in the development of tidal power generation technology. In particular, with regard to increased rotor diameter, the selection of material presents significant challenges to be addressed including the tribological environment, such as solid particle erosion, cavitation erosion, the effect of high thrust loading on the turbine blade tips, and the synergy between sea water conditions and such tribological phenomena. This research focuses on producing and testing a variety of advanced materials and surface coatings to investigate two main tribological issues in tidal environments: matrix cutting and reinforcement fracture. In our previous work, a G10 epoxy glass laminate was tested in this environment and the results revealed tribological issues. In this present work, G10 epoxy glass laminate base erosion resistant polymeric coatings have been tested for the range of sand particles size in our our previous work and in NaCl solution. The test results reveal that the coating has enhanced the quality of performance of the composite with respect to tribological behaviour, and has diminished the synergy between sea water and tribological phenomena. This indicates progress toward the selection of advanced materials to manufacture tidal turbine blades

Tribological challenges of scaling up tidal turbine blades

Generating electricity from renewable resources (wind, wave and tidal) is of increasing interest. Of all marine renewables, tidal energy, by comparison, possesses the higher persistency and predictability over long time scales and the higher density of water than air results in greater power output from a tidal turbine than a wind turbine with similar dimensions. However, due to the nature of the tides, developing a reliable device for such environments, especially with an increased rotor diameter, raises more challenges to be addressed including the tribological challenges such as sediment erosion, cavitation erosion and their possible synergistic effects on the tidal turbine blades. This research focuses on testing and developing materials for improved tribological performance in tidal environments. This includes producing a variety of composite materials with different fibres and layouts reinforcement to evaluate two main tribological issues of composite materials in tidal environments: matrix cutting and reinforcement fracture using a loped test rig, which measures the effects of impact angle, particle size and concentrations at different tip speeds. The test samples are analysed using scanning electron microscopy (SEM) to conduct a surface topography and characterisation

On the effect of pre-formed scales in mitigating corrosion of steels in CO2 environments

Chromium (Cr) containing steels were tested to analyse corrosion behaviour in carbon dioxide saturated water of varying salinities with extended exposure time. Both potentiodynamic and mass loss data were collected to gain a better understanding of the corrosion mechanisms. It was found that both the high Cr steels displayed degradation in the form of pitting with increasing salinities. However, the carbon steel reference material showed uniform iron carbonate (FeCO₃) precipitation. The use of high salinity precipitated layers to aid corrosion protection in lower salinity seawater environments was then established as an interesting area for greater examination. Subsequently, samples of the carbon steel previously corroded in solutions of 7, 14 and 28% sodium chloride (NaCl) concentration were then tested in seawater salinities of 3.5% NaCl. It was found that both the 7 and 14% NaCl pre-corroded samples resulted in a significant reduction in the corrosion rate when compared with non-pre-corroded samples. The 7% NaCl pre-corroded sample showed the greatest reduction in corrosion rate, and through SEM analysis of the layer both on the surface and cross-section it was found to display an iron carbonate layer more densely packed and defect free. This indicated the potential benefits of high salinity pre-corrosion techniques to aid protection in seawater salinity environments

Repeated impact of simulated hail ice on glass fibre composite materials

Wind turbine blade damage, particularly leading edge erosion, is a significant problem faced by the renewable energy industry. Wind turbines are subject to a wide range of environmental factors during a 20 + year lifespan, with hailstones often touted as a key contributor to the deterioration of the blade profile. An experimental campaign was carried out to investigate the effects of repeated impact of smaller diameter simulated hail ice (SHI) on composite materials, to correspond to those most prevalent at wind farm locations. Hailstones of four different diameters (5 mm, 10 mm, 15 mm and 20 mm) were fired at velocities in the range of 50 ms −1 to 95 ms −1. Samples used for experimentation were manufactured from triaxial stitched glass fibre [0°/−45°/+45°] and epoxy resin. Damage was evaluated in terms of sample mass loss and microscopy of the composite surface. For all examples, mass loss was negligible and optical microscopy showed little evidence of surface damage. Surface degradation was discernible under scanning electron microscopy for the larger diameter SHI (≥15mm), with projectile velocity a notable factor in the extent of the damage. Even for large numbers of impacts, there was little noteworthy damage caused by smaller, more prevalent SHI (≤10mm). This suggests that hail is not a direct cause of wind turbine blade erosion

The erosion of functionally graded coatings under fluidized bed conditions

Details the erosion of functionally graded coatings under fluidized bed conditions

Impact angle effects on erosion maps of GFRP : applications to tidal turbines

Tribology in marine renewable technologies has become of increasing interest due to the implications for developing improved materials for tidal and wave energy conversion devices. This on-going research mainly focuses on tidal devices; the materials of interest are primarily polymer based composite materials that are used to provide structural integrity while reducing weight. These are specifically applied to turbine blades to withstand the high impact loadings in sea water conditions. At present, current materials in test trials have demonstrated some limitations in service. In this paper, some advanced experimental research has been carried out to investigate the tribological mechanisms of potential candidate composite materials to be used in tidal turbines by firstly considering the effects of various erosion parameters on the degradation modes, with and without particles in still and sea water conditions. The erosion mechanisms of composite materials used in tidal turbine blades have been evaluated using Scanning Electron Microscopy techniques to analyse the surface morphologies following testing in water representative of the constituents of coastal sea water. Generic erosion maps and the mechanistic maps have been constructed as a key to identify regions of minimum erosion for the operating conditions and to identify the significant effect of the sea water environment on the degradation of the composite. This research outcome will further help us to deeply understand and identify the erosion rates at different impact velocities and angles

Mapping synergy of erosion mechanisms of tidal turbine composite materials in sea water conditions

Tidal energy, of all marine renewables energy, possesses higher persistency and predictability over long time scales. Moreover, the higher density of water than air also results in greater power output from a tidal turbine than a wind turbine with similar dimensions. Due to the aggressive marine environment, there are barriers in the development of tidal power generation technology. In particular, with regard to increased rotor diameter, the selection of material presents significant challenges to be addressed including the tribological environment, such as solid particle erosion, cavitation erosion, the effect of high thrust loading on the turbine blade tips, and the synergy between sea water conditions and such tribological phenomena. This research focuses on producing and testing a variety of composite materials with different fibres and reinforcement layouts to evaluate two main tribological issues in tidal environments: matrix cutting and reinforcement fracture. A slurry pot test rig was used to measures the effects of different impact angles and particles sizes at constant tip speeds

Mapping the micro-abrasion mechanisms of CoCrMo : some thoughts on varying ceramic counterface diameter on transition boundaries invitro

The micro-abrasion wear mechanisms for CoCrMo against variable size alumina balls, representing typical artificial femoral head sizes, were investigated over a range of applied loads in foetal calf serum solution. SEM analysis of resulting wear scars displayed two-body and mixed-mode abrasion modes of wear. The wear factor, κ was found to range between 0.86 and 22.87 (10-6 mm3/ Nm). Micro-abrasion mechanism and wastage maps were constructed for parameter range tested. A dominant 3-2 body abrasion regime was observed with increasing load and ball diameter. A 28 mm ball diameter displayed the lowest wastage with increasing load. Proteins may act to reduce the severity of contact between abrasive particles and bearing surfaces. Wear volumes did not necessarily increase linearly with applied load and ball diameter, therefore, there is a need to develop further accurate models for wear prediction during micro-abrasion conditions. Wear mapping for hip replacement could provide a useful aid in pre-clinical hip wear evaluations and long-term performance

Some thoughts on mapping tribological issues of wind turbine blades due to effects of onshore and offshore raindrop erosion

This paper represents the investigation of liquid impacts on wind turbine blade materials in the simulation of onshore and offshore environmental conditions. G 10 epoxy glass laminate used as a specimen material. The experimental work carried out on a raindrop erosion test rig at the varying angles of attack for a range tip speed. Two solutions, i.e. pure and salt water were used to highlight the effects of offshore environment on this material when it is being used as wind turbine blades. Test results show that the erosive wear increased with an increase in droplet impact velocity. Erosion mapping techniques were used to compare the erosive wear behaviour of this material for application to onshore and offshore applications as candidate wind turbine materials