Efficiency prediction on a 2.5 MW wind turbine gearbox

This paper is a case study of the efficiency of a 2.5 MW wind turbine gearbox including the influence of each gearbox element: gear tooth geometry, rolling bearings and oil formulation. The power loss model used to predict the gearbox efficiency was previously validated with experimental results. The calculations showed that the efficiency of a wind turbine gearbox can be improved by selecting different wind turbine gear oil formulations, modifying gear tooth geometry. The energy savings can be even more significant if both gear tooth geometry and oil formulation are adequately selected.The authors gratefully acknowledge the funding supported by: National Funds through Fundação para a Ciência e a Tecnologia (FCT), under the project EXCL/SEM-PRO/0103/2012; COMPETE and National Funds through Fundação para a Ciência e a Tecnologia (FCT), under the project Incentivo/EME/LA0022/2014; Quadro de Referência Estratégico Nacional (QREN), through Fundo Europeu de Desenvolvimento Regional (FEDER), under the project NORTE-07-0124- FEDER-000009 - Applied Mechanics and Product Development; without whom this work would not be possible

Power loss of FZG gears lubricated with wind turbine gear oil using ionic liquid additive

This work presents a study of the tribological behaviour of a mineral fully-formulated wind turbine gear oil additised with [BMP][NTf2] ionic liquid. The target application are the wind turbine gearboxes, thus the fully formulated oil with and without ionic liquid additive was tested in a rolling bearings test rig to measure the thrust rolling bearing torque loss and was also tested in a FZG gear test rig to measure the gears torque loss at operating conditions similar to the observed in a wind turbine gearbox. The results show that a wind turbine gear oil additised with ionic liquid can reduce the torque loss and improve the gearbox efficiency while producing less wear particles as observed in the oil analysis.The authors thank to the Ministry of Science and Innovation (Spain) and to the Foundation for the Promotion in Asturias of the Applied Scientific Research and Technology (FICYT) for supporting this research within the framework of the Research Projects WINDTRIB (DPI2010-18166) and GRUPIN14-023, respectively. The authors thank to Repsol S.A. that provided the wind turbine gear oil. The authors gratefully acknowledge the funding supported by: National Funds through Fundação para a Ciência e a Tecnologia (FCT), under the project EXCL/SEMPRO/ 0103/2012; COMPETE and National Funds through Fundação para a Ciência e a Tecnologia (FCT), under the project Incentivo/EME/LA0022/2014; Quadro de Referência Estratégico Nacional (QREN), through Fundo Europeu de Desenvolvimento Regional (FEDER), under the project NORTE-07-0124-FEDER- 000009 - Applied Mechanics and Product Development; without whom this work would not be possible

Identification of gear wear damage using topography analysis

Gear failure modes and their underlying mechanisms are usually identified by visual inspection, which relies on the skills and experience of the human observer and hence is prone to subjectivity and bias. Therefore, it is essential to design and implement objective methods to improve the identification of gear failure modes. In the present study, the 3D topography of gear surfaces affected by different types of wear modes, i.e., micropitting, pitting, and scuffing, was measured by means of white light interferometry. The surfaces were evaluated in terms of height, spatial, and function roughness parameters, according to ISO 25178-2. Besides, a new roughness parameter, named surface motion orientation (Smo), was proposed. Three features were found relevant to identify the differences between the gear surfaces affected by different failure modes: the shape of asperities distribution, the severity of damage, and the surface texture orientation with respect to the motion direction. The combination of the roughness parameters selected to quantify each of these features (Ssk, Sq, Smo) resulted in an objective classification of the assessed gear failure modes

Safety of hospital discharge before return of bowel function after elective colorectal surgery

Background: Ileus is common after colorectal surgery and is associated with an increased risk of postoperative complications. Identifying features of normal bowel recovery and the appropriateness for hospital discharge is challenging. This study explored the safety of hospital discharge before the return of bowel function. Methods: A prospective, multicentre cohort study was undertaken across an international collaborative network. Adult patients undergoing elective colorectal resection between January and April 2018 were included. The main outcome of interest was readmission to hospital within 30 days of surgery. The impact of discharge timing according to the return of bowel function was explored using multivariable regression analysis. Other outcomes were postoperative complications within 30 days of surgery, measured using the Clavien\u2013Dindo classification system. Results: A total of 3288 patients were included in the analysis, of whom 301 (9\ub72 per cent) were discharged before the return of bowel function. The median duration of hospital stay for patients discharged before and after return of bowel function was 5 (i.q.r. 4\u20137) and 7 (6\u20138) days respectively (P < 0\ub7001). There were no significant differences in rates of readmission between these groups (6\ub76 versus 8\ub70 per cent; P = 0\ub7499), and this remained the case after multivariable adjustment for baseline differences (odds ratio 0\ub790, 95 per cent c.i. 0\ub755 to 1\ub746; P = 0\ub7659). Rates of postoperative complications were also similar in those discharged before versus after return of bowel function (minor: 34\ub77 versus 39\ub75 per cent; major 3\ub73 versus 3\ub74 per cent; P = 0\ub7110). Conclusion: Discharge before return of bowel function after elective colorectal surgery appears to be safe in appropriately selected patients