A dynamic model to predict the occurrence of skidding in wind-turbine bearings

Abstract

Abstract. Despite use of the best in current design practices, high-speed shaft (HSS) bearings, in a wind-turbine gearbox, continue to exhibit a high rate of premature failure. As HSS bearings operate under low loads and high speeds, these bearings are prone to skidding. However, most of the existing methods for analyzing skidding are quasi-static in nature and cannot be used to study dynamic operating conditions. This paper proposes a dynamic model, which includes gyroscopic and centrifugal effects, to study the skidding characteristics of angularcontact ball-bearings. Traction forces between rolling-elements and raceways are obtained using elastohydrodynamic (EHD) lubrication theory. Underlying gross-sliding mechanisms for pure axial loads, and combined radial and axial loads are also studied. The proposed model will enable engineers to improve bearing reliability at the design stage, by estimating the amount of skidding. IntroductionWind energy is the fastest growing renewable energy sector with an average annual growth rate of around 30% during last 10 years. In order to harvest energy most efficiently and reliably, various wind-turbine design concepts have been developed over the years. Most of the modern wind-turbine designs utilize a gearbox which connects the rotor-shaft to high-speed shaft, and increases rotational speed from 15-30 rpm (at blades) to 1000-1800 rpm -the speed required by most generators to produce electricity. As wind-turbines have grown larger, gearbox failure rates have gone up as well. Since gearbox is one of the most expensive components of a wind turbine, higher-than-expected failure rates increase the cost of energy production. For a typical turbine, 20% of the downtime is due to gearbox failures and an average gearbox failure takes about 250 hours to repair [1].Most of the problems in wind turbine gearboxes appear to emanate from bearings [2]. Bearings supporting the high speed shaft exhibit a high rate of premature failure and are identified as one of the most critical components [1,2]. These bearings operate under low loads and high speeds, and therefore, are prone to skidding, i.e., gross-sliding of rolling-elements on raceways. Sliding can lead to rolling surface distress and eventually to premature failure. Hence, skidding is an important design criterion for wind-turbine bearings. Both ball-bearings and roller-bearings are commonly used to support HSS. The focus of this work is on angular-contact ball-bearings.Researchers have developed numerous analytical and numerical models of varying complexity to understand the skidding behaviour of bearings. Jones [3,4] developed the first mathematical theory to analyze the motion of rolling-elements in ball bearings. He evaluated the frictional

Nonlinear dynamic model for skidding behavior of angular contact ball bearings

“…[17]. However, current research has shown that greater error would be found using Barus' equation for the case of large contact pressures.…”

“…A study of sliding between the rollers and the races was carried out as an application of the dynamic contact model. Jain and Hunt [17] ignored the effect of centrifugal force and gyroscopic force on the contact angle of the ball, and presented a dynamic model of a high speed output shaft bearing in wind turbine transmission system. Selvaraj and Marappan [18] developed a cylindrical roller bearing test rig to measure the running speed of bearing elements at various operating condition.…”

Dynamic Skidding Behavior of Skew Cylindrical Roller Bearings under Time-variable Loads

“…LANIADO-JACOME 等 [10] 建立滚子轴承有限元接 触仿真模型，研究滚子与内外滚道之间的滑动。 JAIN 等 [11] 忽略离心力和陀螺力对接触角的影响， 建 立了风电装备高速输出轴轴承的动力学模型，研究 了滚动体的打滑特性。邵毅敏等 [12] 针对某车用深沟 球轴承，建立滚动体自转和公转两自由度动力学模 型，研究了滚动体进入载荷区所出现的咬入滑动现 象，并考虑转子加速等瞬态工况的影响规律。最近， 作者 [13] 基于 EULER 方程建立了角接触轴承时变动 力学模型，初步分析了滚动体三维空间运动行为。 尽管国内外相关学者均对轴承打滑的动力学 问题进行了一些研究工作，但研究对象局限于止推 滚动轴承(承受轴向载荷)和深沟球轴承(承受径向载 荷)。近期，刘红彬等 [14] 、贾永川和邓四二 [15] …”

Multi-body modelling of rolling element bearings and performance evaluation with localised damage

“…Cui and Zheng [5] also considered this 3D motion but used a five DOF model to model a rotor-bearing system. Jain and Hunt [15] introduced a different approach; they calculated the friction forces between the balls and the races in each contact using the EHL theory. Although they did not consider the dynamics of the cage, they inserted springs of very high stiffness between the balls.…”

“…The majority of the literature on dynamic models of REBs focuses on ball bearings, with single-row deep-groove ball bearings receiving the most attention. Other dynamic models are related to other configurations of single-row ball bearings, such as angular-contact ball bearings [5,15,26,42]. There are a few models for double-row ball bearings in the research literature [20,46].…”