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- Farré-Lladós, Josep, et al.
(författare)
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New method for lubricating wind turbine pitch gears using embedded micro-nozzles
- 2017
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Ingår i: Journal of Mechanical Science and Technology. - : Springer. - 1738-494X .- 1976-3824. ; 31:2, s. 797-806
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Tidskriftsartikel (refereegranskat)abstract
- The increase of power generated by wind turbines has increased the stresses applied in all of its components, thereby causing premature failures. Particularly, pitch and yaw gears suffer from excessive wear mainly caused by inappropriate lubrication. This paper presents a novel method to automatically lubricate the wind turbine pitch gear during operation. A micro-nozzle to inject fresh grease continuously between the teeth in contact was designed, manufactured, and installed in a test bench of a 2 MW wind turbine pitch system. The test bench was used to characterize the fatigue behavior of the gear surface using conventional wind turbine greases under real cyclic loads. Measurements of wear evolution in a pitch gear with and without micro-nozzle show a decrease of 70 % of the wear coefficient after 2×104 cycles.
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| 4. |
- Farré-Lladós, Josep, et al.
(författare)
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New solution to preent excessive wear in wind turbine gears
- 2014
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Ingår i: Society of Tribologists and Lubrication Engineers Annual Meeting and Exhibition 2014. - : Society of Tribologists and Lubrication Engineers. - 9781634391351 ; , s. 548-550
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Konferensbidrag (refereegranskat)
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| 5. |
- Farré-Lladós, Josep, et al.
(författare)
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On the Flow Dynamics of Polymer Greases
- 2022
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Ingår i: Lubricants. - : MDPI. - 2075-4442. ; 10:4
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the flow dynamics of polymer greases was investigated using micro-particle image velocimetry. Polymer greases have a different thickener structure, compared to widely used lithium-based greases, and they have the well-known ability to release oil. How these properties affect grease deformation and its ability to flow is investigated and compared to the corresponding behavior of a lithium complex grease with the same consistency. Two main tests were carried out, where velocity profiles in a straight channel were measured and analyzed, and velocity evolution during the transition period from a no-flow to a fully-established flow was measured, respectively. It was found that the polymer grease flow dynamics is different from that of the lithium grease. This indicates that the internal structure of the grease and the grease ability to bleed oil have a strong influence on the deformation on a global scale, which in turn entails other lubricating abilities for the two grease types.
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| 6. |
- Farré-Lladós, Josep, et al.
(författare)
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The use of Rapid Prototyping techniques (RPT) to manufacture micro channels suitable for high operation pressures and µPIV
- 2016
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Ingår i: Rapid prototyping journal. - 1355-2546 .- 1758-7670. ; 22:1, s. 67-76
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Tidskriftsartikel (refereegranskat)abstract
- Purpose– This paper aims to present a new methodology to manufacture micro-channels suitable for high operating pressures and micro particle image velocimetry (μPIV) measurements using a rapid-prototyping high-resolution 3D printer. This methodology can fabricate channels down to 250 μm and withstand pressures of up to 5 ± 0.2 MPa. The manufacturing times are much shorter than in soft lithography processes. Design/methodology/approach– The novel manufacturing method developed takes advantage of the recently improved resolution in 3D printers to manufacture an rapid prototyping technique part that contains the hose connections and a micro-channel useful for microfluidics. A method to assemble one wall of the micro-channel using UV curable glue with a glass slide is presented – an operation required to prepare the channel for μPIV measurements. Once built, the micro-channel has been evaluated when working under pressure and the grease flow behavior in it has been measured using μPIV. Furthermore, the minimum achievable channels have been defined using a confocal microscopy study. Findings– This technique is much faster than previous micro-manufacturing techniques where different steps were needed to obtain the micro-machined parts. However, due to current 3D printers ' resolutions (around 50 μm) and according to the experimental results, channels smaller than 250-μm2 cross-section should not be used to characterize fluid flow behaviors, as inaccuracies in the channel boundaries can deeply affect the fluid flow behavior. Practical implications– The present methodology is developed due to the need to validate micro-channels using μPIV to lubricate critical components (bearings and gears) in wind turbines. Originality/value– This novel micro-manufacturing technique overcomes current techniques, as it requires less manufacturing steps and therefore it is faster and with less associated costs to manufacture micro-channels down to 250-μm2 cross-section that can withstand pressures higher than 5 MPa that can be used to characterize microfluidic flow behavior using μPIV.
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| 7. |
- Westerberg, Lars-Göran, et al.
(författare)
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Contaminant particle motion in lubricating grease flow : a Computational Fluid Dynamics approach
- 2018
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Ingår i: Lubricants. - : MDPI. - 2075-4442. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- In this paper numerical simulations of particle migration in lubricating grease flow is presented. The rheology of three lithium greases with NLGI grade 00, 1, and 2 respectively are considered. The grease is modeled as a single-phase Herschel-Bulkley fluid, and the particle migration has been considered in two different grease pockets formed between two concentric cylinders where the inner cylinder is rotating and driving the flow. In the wide grease pocket the width of the gap is much smaller compared to the axial length scale, enabling a one-dimensional flow. In the narrow pocket the axial- and radial length is of the same order, yielding a three-dimensional flow. It was found that the change in flow characteristics due to the influence of the pocket lateral boundaries when going from the wide- to the narrow pocket, leads to a significantly shorter migration time. Comparing the results with an existing migration model treating the radial component contribution it was concluded that a solution to the flow in the whole domain is needed together with a higher order numerical scheme to obtain a full solution to the particle migration. This is more pronounced in the narrow pocket due to gradients in the flow induced by the lateral boundaries.
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| 8. |
- Westerberg, Lars-Göran, et al.
(författare)
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Grease flow in an elbow channel
- 2015
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Ingår i: Tribology letters. - : Springer Science and Business Media LLC. - 1023-8883 .- 1573-2711. ; 57:3
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Tidskriftsartikel (refereegranskat)abstract
- The flow of lubricating greases in an elbow channel has been modeled and validated with velocity profiles from flow visualizations using micro-particle image velocimetry. The elbow geometry induces a nonsymmetric distribution of shear stress throughout its cross section, as well as varying shear rates through the transition from the elbow inlet to the outlet. The flow has been modeled both for higher flow rates and for creep flow. The influence of the grease rheology and flow conditions to wall slip, shear banding and an observed stick–slip type of motion observed for low flow rates are presented. The effect on the flow of the applied pressure is also modeled showing that the flow is sensitive to the pressure in the angular ( ϕ ) direction of the elbow. For high pressures, it is shown that the flow is reversed adjacent to the elbow walls.
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| 9. |
- Westerberg, Lars-Göran, et al.
(författare)
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Grease flow in elbow channel
- 2014
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Ingår i: Society of Tribologists and Lubrication Engineers Annual Meeting and Exhibition 2014. - : Society of Tribologists and Lubrication Engineers. - 9781634391351 ; , s. 398-400
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Konferensbidrag (refereegranskat)
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