Bearing Power Loss Research Articles

Friction power loss in ball bearings: Correlation with bearing skidding and cage motion stability

Friction power loss in ball bearings: Correlation with bearing skidding and cage motion stability

Effect of Planetary Gear Set Designs on Thrust Bearing Power Loss in Automatic Transmission

Effect of Planetary Gear Set Designs on Thrust Bearing Power Loss in Automatic Transmission

Optimization of high-speed angular contact ball bearing for aircraft gearbox utilizing an evolutionary multi-objective algorithm, NSGA-III

We develop a program for predicting bearing performance, including the maximum contact stress, bearing power loss, minimum lubricating film thickness, static safety factor, and dynamic life, and an optimal design for high-speed angular contact ball bearings in aircraft gearboxes using optimization algorithms. A program is developed to predict bearing performance by calculating the loads and displacements of individual balls based on the bearing’s kinematic and static equilibrium equations. Next, an optimization program is developed with non-dominated sorting genetic algorithm III (NSGA-III), wherein calculated bearing performance indicators serve as constraints or objective functions. The performance of individuals within the final Pareto front is evaluated using the inter-criteria correlation (CRITIC) and weighted product methods. The optimization performances of NSGA-III and NSGA-II are compared based on their hypervolume indicators. A solution of the kinematic and static equilibrium equations under the load cases and duty cycles of real aircraft gearboxes is obtained, enhancing the prediction accuracy. Furthermore, optimization, including bearing performance metrics rarely considered in previous studies, is performed. Optimal specifications superior to reference bearings employed in aircraft gearboxes are obtained, enhancing all three objective functions or specific objective functions. The optimization performance of NSGA-III is confirmed to surpass that of conventional NSGA-II.

Frictional power loss in journal bearing considering parabolic shape for the bearing edges under misalignment

In recent years, there has been a rising demand for minimizing any power loss in industrial applications due to the direct relation to economic as well as climate considerations. This work investigates the parameters that affect the frictional power loss in journal bearings as they are widely used in such applications. The frictional power loss is calculated considering misalignment conditions in the vertical and horizontal planes with the use of a modified bearing shape. Wide ranges of misalignment and bearing shape parameters are considered in the numerical investigation to study the combined effects of misalignment and bearing shape. It has been found that the misalignment significantly increases the frictional power loss at high operating speed levels. The use of a modified bush shape can play an important role in reducing the frictional power loss as well as, it added further advantages in elevating the lubricant film thickness and reducing the pressure levels. Results show that using a modified bearing shape despite the presence of severe misalignment levels reduces the maximum pressure from 20.30 to 17.94 MPa, increasing the minimum film thickness from 2.66 to 8.21 [Formula: see text] and reducing the fictional power loss from 1179.74 to 1094.41 W.

Numerical modeling and experimental validation of power loss and efficiency in an electric-drive axle system

Power loss and efficiency are pivotal performance metrics significantly impacting the quality of electric-drive axles. This study outlines a numerical method for determining the electric-drive axle system power loss, which includes gear meshing, gear churning, and bearing power losses. Power loss from gear meshing was calculated by analyzing load distribution and friction coefficient. The frictional loaded tooth contact analysis method was employed to ascertain the load distribution during gear meshing. A formula based on a weighting function was utilized to compute the friction coefficient. The finite element method was used to verify the gear load distribution and meshing power loss. Subsequently, empirical formulas were used to calculate the gear churning and bearing power losses. To substantiate the proposed numerical method, an experimental apparatus was employed to measure the power loss and efficiency of an electric-drive axle under various operating conditions. The experimental study demonstrated a strong correlation between the numerical and calculated results. These findings suggest that the proposed method can be an effective tool in predicting the power loss and efficiency of electric-drive axles.

Evaluation of friction calculation methods for rolling bearings

In gearboxes, rolling bearing power losses often make up a large amount of the total gearbox power losses. Therefore, an exact calculation of rolling bearing power losses is very important for resource and energy efficient gearbox design. The state of the art offers numerous friction calculation methods with different levels of detail to calculate power losses of rolling bearings. Bearing manufacturers like SKF and Schaeffler offer popular bearing-based/global calculation methods for standard rolling bearings. Contact-based/local calculation methods can consider a wider application field by generalization of tribological relations, which enables its application to e.g. hybrid bearings or non-standard bearings. The different methods may yield widely differing results. For its validation, measurement results are required. In this study, a broad comparison of calculation results with substantial measurement results is shown. Based on the validation a classification of the calculation methods is derived, which provides guidance for the design engineer to choose the appropriate method for the respective application. Contact-based/local calculation methods have the potential to predict friction in rolling bearings precisely.

Power Losses of Oil-Jet Lubricated Ball Bearings With Limited Applied Load: Part 1—Theoretical Analysis

This study presents a theoretical analysis to quantify power losses generated by an oil-jet lubricated deep groove ball bearing. Loaded rolling elements (RE) have been thoroughly studied in the past for the elastohydrodynamic lubricated (EHL) regime, while a well-known problem concerning rolling element bearing (REB) power losses is the estimation of dissipation sources in the case of limited or no applied load. The model presented in this article aims to solve this problem by describing the physics involved on the unloaded zone. Unloaded RE are considered in an isoviscous rigid (IVR) regime. The model is compared with global power loss models such as the Harris–Palmgren or SKF models. This work shows that unloaded RE can generate around 40% of the losses when the applied radial load is about 5% of the static capacity.

Research on the Power Loss of High-Speed and High-Load Ball Bearing for Cryogenic Turbopump

This paper studies the lubrication characteristics of ball bearings for cryogenic turbopumps. First, the frictional coefficients between 440C and a Ag coating, 440C and solid PTFE (polytetrafluoroethylene), and 440C and a PTFE coating in LN2 (liquid nitrogen) are obtained using a ball-on-disk testing machine under a high sliding speed in the range of 0 to 8 m/s and a high contact stress in the range of 2.5 to 3.5 GPa. Dynamic and power loss models of high-speed and high-load ball bearings are established to study the key factors affecting the heat generation characteristics. In order to verify the correctness of these two theoretical models, a coupled fluid-thermal finite element model is built to evaluate the temperatures of the outer ring under different bearing speeds, which are then proved by experiments with ball bearings for cryogenic turbopumps. The results show that the power loss due to the spinning-sliding of the ball and the churning and drag of LN2 account for more than 80% of the total power loss; the spin-roll ratio of the ball on the inner raceway is a key indicator for this type of ball bearing, and the relatively small radial clearance and contact angle are suggested. Both of the proposed theoretical models have sufficient accuracy and can be used in the performance evaluation and optimization design of bearings.

Studi Efisiensi Sistem Reduction Gear pada Pembangkit Listrik Tenaga Gas

Gas p ower p lants produce electrical energy by a generator driven by a gas turbine through a rotational transmission device called a Reduction Gear. Reduction gear consists of two rotating gears tangent to each other with different diameter sizes. This difference in diameter size makes the output side shaft of the reduction gear, which has a larger diameter, rotate slower than the input side shaft of the reduction gear which has a smaller diameter of the gear. Analysis of the performance of the reduction gear device is done by calculating its efficiency. In this study, the total power loss is 459.18 kW where the gear power loss (Pvz) is 112.53 kW, the bearing power loss (Pvz0) is 342.24 kW, and the power loss due to seals (Pvs) of 4.41 kW. With an input power of 33,000 kW, the efficiency of this reduction gear is 98.61%.

Design and experimental investigation of a herringbone grooved gas bearing supported turbocharger

The design of an oil free turbocharger supported on herringbone grooved gas bearing was formulated as a multi-objective problem, which was solved by coupling a reduced order parametric model for gas bearing supported rotors with an evolutionary algorithm. The resulting Pareto curve offers the best possible tradeoff between the two competing objectives of maximizing the rotordynamic stability and minimizing the power losses. After manufacturing, the turbocharger was successfully operated up to 170 krpm, beyond a hybrid mode composed of a rigid body cylindrical and a flexural mode. Supercritical operation above a flexural bending mode on rigid gas lubricated bearings was possible due to the smart selection of the location of two balancing planes, to avoid the excitation of the flexural mode. A coast down test suggests minimum friction torque and therefore lift-off at 3 krpm. Bearing power loss tests performed at 40 ℃ and 100 ℃ showed that the herringbone grooved gas bearing supported oil-free turbocharger yields only 50% to 70% of the traditional semi-floating oil bearing supported turbochargers, which is a distinct advantage in terms of efficiency and cut in emissions. The theoretical and experimental results presented in this paper clearly demonstrate the rotordynamic feasibility of oil-free turbochargers supported on herringbone grooved gas bearings.

Performance of hybrid thrust bearing textured surface operating with electro-rheological lubricant

This article concerns with the numerical simulations of textured surface hybrid thrust bearings operating with Electro-rheological (ER) lubricant. An ER fluid comprises dielectric particles suspended in an insulating viscous medium. Electrorheological (ER) lubricants are considered smart lubricants. Reynold's equation is used to model the flow of an ER lubricant in textured surface thrust bearings. The texture is provided as hemispherical, cylindrical, elliptical, and square shape micro-depression oriented along the circumferential and radial direction. The Patir and Cheng model is used to describe micro-roughness on a thrust pad. The continuous Bingham model is used to define the viscosity of the ER lubricant in terms of yielding stress, electric field, and shear-strain rate. The Reynolds equation is solved by applying the finite element method to obtain film pressure, load-supporting capacity, frictional power loss, film stiffness, and damping parameters. The texture shapes are optimized for dimple size, depth, and length for getting maximum load-supporting capacity and stiffness coefficient, and minimum frictional power loss. The numerical results predicted an enhancement in the load-supporting capacity (+257.3%) and film stiffness parameters (+323.2%) owing to the synergistic use of ER lubricant and optimized geometric parameters of square/elliptical dimples. The frictional power loss was reported to reduce significantly (−48.8%) by the use of micro-dimples. The application of ER lubricant was also found to slightly enhance (+4.3%) the frictional power loss in textured bearings. The transverse surface roughness vis-à-vis smooth surface is observed to improve the load-supporting capacity, stiffness, and damping parameters of textured surface bearings.

Gear and bearing power losses: from dip to minimum quantity lubrication

PurposeThis paper aims to address the influence of lubrication methods on operational characteristics, power losses and temperature behavior of gears and bearings. It contributes to the improvement of resource and energy efficiency of geared transmissions.Design/methodology/approachExperimental investigations were performed at a gear and bearing power loss test rig. Thereby, dip lubrication, injection lubrication with injection volumes from 0.05 to 2.00 l/min and minimum quantity (MQ) lubrication with an injection volume as little as 28 ml/h were considered. Measurements were evaluated in terms of no-load and load-dependent power loss, bulk temperatures and mean gear coefficients of friction.FindingsResults show strongly reduced no-load gear and bearing losses for lubrication methods with low lubricant quantities. Load-dependent losses are similar to conventional lubrication methods and tend to be lower at high speed. This is related to higher bulk temperatures, as the heat dissipation of lubrication methods with low oil quantities is limited. Limited thermal load limits were shown to be extended by LowLoss gears.Originality/valueSystematic investigations were conducted to evaluate the influence of dip, injection and MQ lubrication on power loss and temperature behavior of gears and bearings. The results of this study support further research on needs-based lubrication methods for gearboxes.

Dynamic characteristics modelling and analysis for dry screw vacuum pumps

This paper modeled the dynamic characteristics of dry screw vacuum pumps considering the forces induced by gas, gear, bearings, and rotor gravity, and discussed the load on bearings and gear comprehensively employing the proposed model. First, the balance equations on force and torque were proposed based on a simplified force analysis model for a test dry screw vacuum pump. Next, the detailed calculation methods of gas force, gear load, bearing load, and motor power were presented, respectively. Furthermore, the calculated motor power was verified by comparing the measured results from a test experiment. Finally, the gas force, gear load, bearing load, and bearing power loss under different inlet pressures was discussed comprehensively. Results showed that the proposed model could effectively analyze the load and power distribution for dry screw vacuum pumps. The torque of synchronous gear could be reduced by reasonably selecting the driving shaft. The axial gas force acting on the end face of rotors showed the main contribution for the power loss of bearings, which accounted for up to 3.2% of total input power. The obtained conclusions could guide the reasonable design and selection of the supporting and driving components for dry screw vacuum pumps.

Investigation of the Influences of Thrust Loads Resulted by Helix Angle Directions of Planetary Gear Sets on Bearing Power Losses in Automotive Planetary Gear Trains

In the recent automotive industries, automotive technologies for improving fuel efficiency have focused on the developments of reducing power losses in a transmission. As a well-developed and conventional power transmitting system, an automatic transmission is still widely used in many automotive vehicles. The automatic transmission is co-axially designed with several planetary gear sets and other mechanical parts. The co-axial arrangements and gear helix angles make the transmission necessarily include bearings for supporting loads and allowing relative rotations. In this study, the influences of thrust loads yielded by helix angle directions of planetary gear sets on bearing power losses are presented by performing the structural and power loss analysis. Bearing power losses consist of mechanical and spin power losses. For calculating thrust loads and bearing rotations, a complete transmission model is constructed by using an example structure, and structural analysis is performed for the combinations of helix angle directions of the gear sets. Finally, bearing power losses are computed by using the bearing power loss model, and the results of the entire combinations of helix angle directions are discussed.

Real-time rolling bearing power loss in wind turbine gearbox modeling and prediction based on calculations and artificial neural network

This paper investigates the bearing power loss in gearbox for wind turbines under actual operating wind speed. Actual power loss values are calculated using calibrated SKF model for three different wind turbine gearbox oils. The gearbox applied load at each operating step is determined by using the wind turbine power curve. Wind data from experiments in Cameroon are used for validation. The back-propagation neural network is designed for actual power loss modeling and predicting desired values. The achieved results revealed that the bearing power loss is highly influenced by the wind turbine operating parameters, capacity, and oil. The difference between actual and neural network predicted bearing power loss values under real-time operating parameters showed the effectiveness of the proposed approach.

Additively Manufactured Compliant Hybrid Gas Thrust Bearing for Supercritical Carbon Dioxide Turbomachinery: Experimental Evaluation and Fluid–Structure Model Predictions

Abstract This paper presents rotating test results and advances an analytical predictive fluid–structure model for a new type of gas-lubricated thrust bearing fabricated using direct metal laser melting. The bearing concept in this study is a compliant hybrid gas thrust bearing that uses external pressurization to increase load carrying capacity, where the testing campaign in this study was only focused on steady-state static performance. The need for the bearing concept comes from enabling highly efficient supercritical carbon dioxide (sCO2) turbomachinery by replacing oil-lubricated bearings with process gas lubrication. Leveraging the process gas of the turbomachine for bearing lubrication results in lowered bearing power loss, simplified mechanical design, and allows for novel oil-free hermetic drivetrains resulting in an efficient emission-free system. The new concept utilizes hydrostatic pressurization on individual tilting pads flexibly mounted with hermetic squeeze film dampers (HSFDs). This paper focuses on rotating tests of a 173 mm outer diameter gas thrust bearing in air up to 10 krpm and hydrostatic inlet pressures to 365 psi (2.52 MPa). The influence of thrust runner speed and bearing inlet pressure on force deflection characteristics and load carrying capability of the gas film were experimentally evaluated. This work also advances a predictive fluid–structure thrust bearing model using an isothermal ideal-gas-based compressible Reynolds flow equation directly coupled to a lumped stiffness element possessing axial and rotational degrees-of-freedom. The rotating testing demonstrated load capability of 1816 lbs (8.1 kN), which equates to a thrust bearing unit load of 67 psi (0.46 MPa). Gas film force–deflection curves reveal a nonlinear relationship between thrust load and film clearance. Comparison of film thickness values with the predictive model show good agreement under high load and inlet pressure, however deviate as load and pressure decrease. Load capability was shown to increase with increasing hydrostatic inlet pressure, while the increase in thrust runner speed revealed a small decrease in load capacity.

An enhanced estimation on heat generation of angular contact ball bearings with vibration effect

Power loss impacting the thermal performances, operating precision and even service life of angular contact ball bearings has not been thoroughly addressed so far. Evidently, ignoring the effect of vibration on heat generation may be partly responsible for the difference. This paper devotes to the thermal estimation on angular contact ball bearings with vibration effect. The experiments about vibration effect on bearing temperature were first implemented. To explore the causes, the energy exchange in vibration was discussed and then the shaft-bearing system was simplified to a forced vibration model to analyze the bearing loads in vibration. Considering the contact stiffness and damping between balls and rings, the instantaneous force balance equations were built. Next, the vibratory-induced additional load and additional spin power loss of balls was proposed successively. The vibration-induced heat was integrated into a novel forecasting model of bearing power loss. For validation, the muti-node model for angular contact ball bearings was referred to create the thermal network of spindle front bearing, and then the contrast and discussion were done. The excitation force and vibration response, meanwhile, were also measured to validate the developed model further. With the help of improved heat generation model, the bearing temperature rise can be better forecasted.

The effect of outer ring elastodynamics on vibration and power loss of radial ball bearings

Ball bearings are an integral part of many machines and mechanisms and often determine their performance limits. Vibration, friction and power loss are some of the key measures of bearing performance. Therefore, there have been many predictive analyses of bearing performance with emphasis on various aspects. The current study presents a mathematical model, incorporating bearing dynamics, mechanics of rolling element-to-races contacts as well as the elastodynamics of the bearing outer ring as a focus of the study. It is shown that the bearing power loss in cage cycles increases by as much as 4% when the flexibility of the outer ring is taken into account as a thick elastic ring, based on Timoshenko beam theory as opposed to the usual assumption of a rigid ring in other studies. Geometric optimisation has shown that the lifetime power consumption can be reduced by 1.25%, which is a significant source of energy saving when considering the abundance of machines using rolling element bearings. The elastodynamics of bearing rings significantly affects the radial bearing clearance through increased roller loads and generated contact pressures. The flexible ring dynamics is shown to generate surface waviness through global elastic wave propagation, not hitherto taken into account in contact dynamics of rollers-to-raceways which are generally considered to be subjected to only localised Hertzian deflection. The elastodynamic behaviour reduces the elastohydrodynamic film thickness, affecting contact friction, wear, fatigue, vibration, noise and inefficiency.

The Effect of Waviness Error on the Power Loss of the Planet Bearing

The power loss of planet bearings can affect the energy efficiency of planetary gear transmission systems. Although many works studied the power loss of various planet bearings, the effect of the waviness error on the power loss of the planet bearings was missed. To overcome this problem, an analytical model of the power loss of a planet bearing with the waviness error is proposed. The power loss of the planet bearing caused by the elastic material hysteresis, differential slipping, and lubricating oil viscosity is considered in this model. The results from the proposed model and experiment in the reference are compared to show the model validation. The effects of the pinion bore diameter, input speed, external moment, waviness amplitude, and waviness order on the power loss of the planet bearing are analyzed. It shows that this study can give a useful method to predict the power loss of the planet bearing with and without the waviness error. Moreover, the results can also give some guidance to reduce the power loss and improve the fatigue life of the planet roller bearings.

Experimental and numerical investigations on rolling element bearing thermal behaviour

In the present study, some measurements have been conducted on a dedicated test rig to investigate rolling element bearing thermal behaviour. This test rig makes possible the determination of the tested rolling element bearing power losses through the resistive torque measurement. Some thermocouples are located on fixed parts of the system (housing, rolling element bearing outer ring) and others on rotating parts (rolling element bearing inner ring and shaft) via a telemetry system. A deep groove ball bearing, whose pitch diameter is equal to 85 mm, has been tested under oil jet lubrication for different operating conditions. Measurements of the penetration ratio, defined as the proportion of oil actually entering the rolling element bearing versus the oil injected, have also been conducted. An extended thermal network of the test rig has been established to enable a closer understanding of the rolling element bearing inner thermal behaviour. Based upon the first principle of thermodynamics for transient conditions, the studied system is divided into lumped elements at uniform temperature connected by thermal resistances which account for conduction, radiation and convection. Convection within the rolling element bearing depends on the amount of oil in the oil–air mixture known as the volume fraction. At specific test conditions, the developed model found good agreements with experiences for a given oil volume fraction of 15%. This value of volume fraction leads to an adapted formula for volume fraction in the case of jet lubrication which includes the measured penetration ratio.