Wind Turbine Gear Oils Research Articles

Demonstration of Sensor Monitoring of Lubricants

Due to the spread of carbon neutral, the effective use of lubricant has been drawing attention. Since the main component of lubricant is petroleum-derived hydrocarbon oil, reducing the amount used by 1 kg will reduce CO2 by approximately 3 kg. The value of CO2 reduction is very important. In order to reduce the amount of lubricant used, there is a movement to reduce the frequency of lubricant exchange or continue to use lubricant without exchanging it. However, it is known that lubricant-induced mechanical failures occur. For this reason, equipment condition monitoring using oil sensors has been spread. The color of the lubricant, also called machine blood, indicates the condition of the machine. The oil sensor measures contamination, which has a fatal effect on machine failure, and oxidation degradation, which is related to the performance of lubricant and the machine failure. Contamination includes water and wear debris, and oxidative degradation includes consumption of additives and oxidation of base oil. By digitizing the hue of wind turbine gear oil through color diagnosis using an oil sensor, the oil contamination and degradation is identified. Additives in the gear oil were quantified by liquid chromatography-mass spectrometry, and it was found that the color change of gear oil was highly correlated with the depletion of the extreme pressure additive. It is known that the depletion of the extreme pressure additive is correlated with the useful life of the gear oil. Using the technique, the remaining life diagnosis of the gear oil was shown. Demonstration in the gearbox with the oil sensor was succeeded by avoidance of the effects of air bubbles in the gear oil.

Spectroscopic Methods for Lubricant Quality Control in Engines and Gear Boxes

Lubricants play a vital role in reducing the wear and tear of engine/gear box metal parts. Number of analytical and spectroscopic methods have been used to analyze the quality of the lubricant oil. Moreover some parameters such as Total Acid Number (TAN), viscosity index also have been used to analyze the quality of the oil. Several used wind turbine gear oil samples were analyzed by various spectroscopic methods such as UV-Visible, Fourier-transform infrared (FTIR) and Fluorescence Spectroscopy. Fluorescence method gave promising results among those three spectroscopic methods. In order to study thermal degradation, motor oil samples were subjected to artificial aging in the laboratory conditions by heating them up to different temperatures for different time periods and then subsequently analyzed with fluorescence spectroscopic method. Subsequently two used engine oil samples from a same diesel engine vehicle were analyzed using fluorescence spectroscopic method. Notable variation in fluorescence emission intensities was observed with oil aging. Intensity of the fluorescence emission signal decrease with oil degradation. Therefore fluorescence spectroscopic method can be used to predict the reusability of gear oils as well as to identify the oil degradation. This method can be further extended to develop a novel potential sensor to detect the quality of oil in various types of engines. KEYWORDS : Lubricant oil, Oil degradation, Fluorescence spectroscopy, Analytical methods.

Performance of lubricating oils for wind turbine gear boxes and bearings

In this study, the friction and wear properties of six different new and used wind turbine gear oils (ISO VG 320), with different base oil formulations and additives packages, were investigated. For that purpose, a four-ball tribometer and an Optimol SRV were used. Moreover, the lubricants extreme pressure properties were also evaluated, using the same four-ball tribometer. The study also includes a characterization of the lubricants. The main objective was to compare the new and used gear oils in order to identify performance differences and predict oil change intervals. The results indicate that a use of 3 to 4 years is within the lifetime of the lubricant.

Influence of water contamination in gear lubricants on wear and micro-pitting performance of case carburized gears

PurposeWater can alter the performance of modern gear lubricants by influencing the flank load carrying capacity of gears significantly. The purpose of this paper is to investigate the influence of water contaminations in different kinds of base oils on the micro-pitting and wear performance of case carburized gears.Design/methodology/approachConcerning micro-pitting and wear, tests, based mostly on the following standardized tests, are performed on a Forschungsstelle fuer zahnraeder und getriebebau (FZG)-back-to-back gear test rig: micro-pitting short test Graufleckenkurztest (GFKT) according to DGMK 575 (screening test), micro-pitting test Graufleckentest (GT) according to FVA 54/7 (load stage test and endurance test) and Slow-speed wear test according to DGMK 377. To investigate the effect of water on the gear load carrying capacity dependent on different types of base oils, two polyglycol oils (PG1 and PG2), a polyalphaolefin oil, a mineral oil and an ester oil E are used. Each of these oils are common wind turbine gear oils with a viscosity ISO VG-220. Additionally, a manual transmission fluid with a viscosity of society of automotive engineers (SAE) 75W-85 is tested.FindingsConsidering the micro-pitting and wear performance, a significant decrease caused by water contaminations could not be detected. Regarding pitting damages, a generally negative influence was observed. This influence was differently distinctive for different base oil types. Especially non-polar lubricants seem to be affected negatively. The documented damages of the tooth flanks confirm this observation. While typical pitting damages appeared in test runs with polar lubricants, the disruption in test runs with non-polar lubricants was more extensive. Based on the experimental investigations, a general model of the damaging mechanisms of water contaminations in lubricants was derived. It is split into three partitions: interaction lubricant–water (effect of water on the molecular structure of base oils and additives), chemical-material-technological (especially corrosive reactions) and tribological influence (effect of water droplets in the contact zone). It has to be considered that the additive package of lubricants affects the influence of water contaminations on the flank load carrying capacity distinctively. An influence of water on the micro-pitting and wear performance in other than the given lubricants cannot be excluded.Originality/valueWhile former research work was focused more on the effects of water in mineral oils, investigations concerning different types of base oils as well as different types of damages were carried out within this research project.

Energy efficiency tests in a full scale wind turbine gearbox

A 850kW wind turbine gearbox, widely used in wind farms, was used to perform efficiency tests of different wind turbine gear oil formulations.One mineral and three polyalpholephin commercially available lubricants were chosen, all them are ISO VG 320 wind turbine gear oils.Study the influence of different gear oil technologies in the overall gearbox transmission efficiency is the main objective of this work.The results show that different energetic efficiency and different oil particle counting were obtained even when the same base oil is used.

Power loss prediction: Application to a 2.5 MW wind turbine gearbox

A 2.5 MW wind turbine gearbox design was considered to perform a power loss prediction using different wind turbine gear oil formulations. A gearbox power loss model, previously validated with experimental results, was used to predict the efficiency of a full wind turbine planetary gearbox. The power loss model account the gears and rolling bearing losses using well established models calibrated with a method proposed by the author. The calculations clearly showed that significant energy savings can be achieved by selecting different base oils, modifying gear tooth geometry, or combining both.

Evaluation of bearing, gears and gearboxes performance with different wind turbine gear oils

AbstractThe oil viscosity specification for wind turbine gear oils is ISO VG 320, although there are quite different viscosity indexes oils for that viscosity specification. This work evaluates the behaviour of different base oil formulations, since polyalphaolefin (PAO), mineral, ester and polyalkeleneglycol (PAG) that withstand quite different viscosity indexes. The oils evaluation was done in rolling bearing tests and gear tests. Their behaviour was compared for operating conditions in the range observable in a wind turbine gearbox.The experimental results showed considerable differences between the different oils and it was observed that depending on the contact type the relative behaviour of the lubricants would change, i.e., the best lubricant for the rolling bearing would not imply the best result on the gear tests.The gear geometry is also very important toward the transmission efficiency, once using a low loss gear concept a decrease of up to 25% in torque loss could be achieved.Numerical models were implemented with the purpose of performing a better simulation of the mechanical system and also to obtain the friction coefficient promoted by the tested oils.

Efficiency of a planetary multiplier gearbox: Influence of operating conditions and gear oil formulation

In this study a single stage planetary multiplying gearbox with helical gears was tested on a back-to-back gearbox test rig with recirculating power under the operating conditions that matched the tangential velocities and operating contact pressures found in a planetary stage of a 2.5MW wind turbine. The study was done with four different wind turbine gear oils. The gearbox oil sump temperature was set free.The load and no-load losses were measured and compared with the results yielded by an existing numerical model which takes into account the influence of the lubricant formulation in the load losses.The results have indicated that each gear oil formulation promoted different power loss results resulting in distinct stabilized operating temperatures.

Torque loss and wear of FZG gears lubricated with wind turbine gear oils using an ionic liquid as additive

This work presents a study of the tribological behavior of a mineral fully-formulated wind turbine gear oil additised with [BMP][NTf2] ionic liquid. The target application is 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.

Gearbox power loss. Part III: Application to a parallel axis and a planetary gearbox

In the third part of this work, the rolling bearing torque loss model, the lubricant factor extracted from the FZG tests with wind turbine gear oils and the loss factor for helical gears, developed in Part I and Part II of this work, will be applied to predict the power loss in a parallel axis and a planetary gearbox. The numerical results obtained are compared with those from experimental tests.

Film thickness and traction curves of wind turbine gear oils

The film thickness and the traction curves of four fully formulated wind turbine gear oils were measured on a ball-on-disc device. All oils have the same viscosity grade (ISO VG 320) and different formulations: ester, mineral, PAO and mineral+PAMA.Film thickness and traction coefficient results will be presented. The film thickness measurements were compared with predictions using film thickness equations from the literature.

Gearbox power loss. Part II: Friction losses in gears

The second part of the study presents an extensive campaign of experimental tests in an FZG test rig. An average coefficient of friction between meshing gears was devised from the experimental results. Several aspects regarding the meshing gears power loss are discussed such as gear loss factor, coefficient of friction and the influence of gear oil formulation (wind turbine gear oils).

Gearbox power loss. Part I: Losses in rolling bearings

This work is devoted to the analysis, modeling and validation of gearbox power loss, considering the influence of the gears, rolling bearings and seals, the influence of the operating conditions, lubricant formulation and the lubrication method.The first part of this work a rolling bearing torque loss model is calibrated for several wind turbine gear oils and for ball and roller contacts. The results achieved clarify the importance of a rolling bearing in a gearbox power loss.In the second part of this work will be presented the same approach for gears. The final part will converge in the application of findings in two full gearboxes, a planetary and a parallel axis gearbox, both in multiplying configuration.

Efficiency of a gearbox lubricated with wind turbine gear oils

In this study a two stage multiplying gearbox with helical gears and four fully formulated wind turbine gear oils were tested, on a back-to-back gearbox test rig with recirculating power, at low input speeds (100–500rpm) and high input torques (500–1000Nm). The gearbox oil sump temperature was set free.A numeric power loss model simulating all the relevant power loss mechanisms was implemented, aiming to evaluate the relative influence of each power loss component.The experimental results have shown that each wind turbine gear oil formulation generated different power loss resulting in distinct stabilized operating temperatures.

Torque loss of type C40 FZG gears lubricated with wind turbine gear oils

Five fully formulated wind turbine gear oils were characterised. The gear oils have 320 ISO VG grade and different formulations: ester, mineral, PAO, PAG and mineral+PAMA.A back-to-back FZG test machine, with re-circulating power, was used and a torque-cell was included on the test rig in order to measure the torque loss. Eight thermocouples were included to monitor the temperatures in different locations of the test rig.Tests at 1.13, 2.26 and 6.79m/s were performed for different FZG load stages: K1, K5, K7 and K9. Both gearboxes were jet-lubricated with an oil flow of 3l/min. The input flow temperature was kept almost constant (80 ±1°C).Friction generated between the meshing teeth, shaft seals and rolling bearing losses was predicted.

Torque loss in cylindrical roller thrust bearings lubricated with wind turbine gear oils at constant temperature

Six fully formulated wind turbine gear oils with the same viscosity grade and different formulations were selected and their physical properties were determined.Cylindrical roller thrust bearing friction torque tests were performed on a modified Four-Ball Machine at a constant temperature of 80°C under the following operating conditions: speed between 75 and 1200rpm and two loads (700N and 7000N).The experimental results showed that wind turbine gear oil formulation has a significant influence on rolling bearing friction torque.

Torque loss in thrust ball bearings lubricated with wind turbine gear oils at constant temperature

Six fully formulated wind turbine gear oils with the same viscosity grade and different formulations were selected and their physical properties were determined.Thrust ball bearing friction torque tests were performed on a modified Four-Ball Machine at a constant temperature of 80°C under the following operating conditions: speed between 75 and 1200rpm and two loads (700N and 7000N).The experimental results showed that wind turbine gear oil formulation has a significant influence on rolling bearing friction torque.

Power losses at low speed in a gearbox lubricated with wind turbine gear oils with special focus on churning losses

In this study gear oils were tested for power loss behaviour in a two stage multiplying gearbox, on a back-to-back test rig with recirculating power. The tests were performed at low input speeds and high input torques with oil sump temperature set free.A power loss model simulating the power loss mechanisms was implemented to evaluate gear power losses, but failed to correctly describe the gear churning.Two lubricant flow regimes were identified, which are related to the nature of the fluid circulation, as well as with the gearbox case. A calibration method for the gear churning loss is proposed based on these results and a method to identify the transition between the fluid flow regimes inside the gearbox.

Torque loss in a gearbox lubricated with wind turbine gear oils

ABSTRACTIn this study, four different fully formulated ISO VG 320 wind turbine gear oils were select: a mineral oil‐based, a polyalphaolefin‐based, an ester‐based and a polyalkyleneglycol‐based fluids. Their physical properties (viscosity, thermoviscosity, piezoviscosity etc.) were characterised for a wide range of operating temperatures.A two‐stage multiplying gearbox, with helical gears, was selected to evaluate the influence of the wind turbine gear oil formulation on torque loss with the gearbox operating at low speed (130–230 rpm) and high torque (500–1000 Nm).The results obtained showed that each wind turbine gear oil formulation generated very different torque losses, evacuated heat flows and operating temperatures, with differences above 20 °C under the most severe operating conditions. A numerical model was developed, simulating all power loss mechanisms inside the gearbox, in particular the churning and friction losses. The coefficients of friction, between gear teeth and between rolling elements and bearing raceways, were calculated for all the tested oils. Copyright © 2013 John Wiley & Sons, Ltd.

Friction torque of thrust ball bearings lubricated with wind turbine gear oils

Planetary gearboxes used in wind turbines very often have premature bearing and gear failures, some of them related to the lubricants used. Five fully formulated wind turbine gear oils with the same viscosity grade and different formulations were selected and their physical characterization was performed. The lubricant tribological behaviour in a thrust ball bearing was analyzed. A modified Four-Ball Machine was used to assemble the bearings. They were submitted to an axial load and the tests were performed at velocities ranging between 150 and 1500rpm. Experimental results for the operating temperatures and for the internal friction torque are presented.