Operating Conditions Of Bearings Research Articles

Improved Estimation of Bearing Pads' Inlet Temperature: A Model for Lubricant Mixing at Oil Feed Ports and Validation against Test Data

Energy efficient operation of fluid film bearings demands savings in delivery flow while also managing to reduce the temperature in the fluid film and bearing pads. To achieve this goal, tilting pad journal bearings (TPJBs) implement a variety of oil feed arrangements, use pads with highly conductive material and engineered back surface, and also end seals to keep (churning) lubricant within the bearing housing. This paper introduces a novel model for the mixing of flow and thermal energy transport at a lubricant feed port and which sets the temperature of the lubricant entering a pad leading edge. Precise estimation of this temperature (and inlet oil viscosity) largely determine the temperature, and the current model aids to deliver improved temperature predictions in conditions that limit a conventional model, including the ability to impose an actual lubricant supplied flow, specifically when the bearing is operating in either an over-flooded or a reduced flow conditions. An empirical groove efficiency parameter regulates the temperature of the above-mentioned flows to represent conventional and direct lubricant feeding arrangements as well as end-sealed (flooded) or evacuated bearing configurations. Predicted temperatures are compared against published test data for two bearings while revealing the advantages of the novel model, in particular for operation under lubricant starvation. This paper delivers recommendations for the feed port efficiency parameter for various types of oil supply configurations. This parameter, not being a function of bearing operating conditions, allows for proper sizing of pumps, oil reservoirs, and heat exchangers in lube oil delivery systems for a packaged-unit machine.

Self-Lubricating and Friction Performance of a Three-Dimensional-Printed Journal Bearing

In recent years, through the development of three-dimensional (3D) printing technology, 3D‐printed parts have been used in various industries, such as medical equipment and robotics. Various 3D printing methods have been developed. Today, a 3D printer can be used even in precision parts, such as bolts and bearings. In this study, journal bearings are manufactured by a 3D printer to evaluate friction performance and self-lubricating performance. The journal bearings are fabricated using two types of 3D printing method: fused deposition modeling (FDM) and selective laser sintering (SLS). The specimens manufactured by FDM are produced by plastic materials with three-layer thicknesses. Nylon-based materials and aluminum-based materials are used to fabricate the SLS specimen. Micropores are created in the specimens during the printing process. Therefore, the self-lubricating performance can occur by micropores. The experimental setup is designed and constructed to evaluate the friction performance by varying rotational speed and the radial load. Through this study, the self-lubricating performance and friction performance of 3D-printed journal bearings are evaluated, and proper operating conditions for 3D-printed bearings are suggested.

CFD simulation of water lubricated conical hydrodynamic journal bearings

In concern with the environmental impact of lubricating fluids, water-lubricated bearings have been preferred and recommended instead of conventional oil-lubricated bearingsin food and pharmaceutical industries. Conical hydrodynamic journal bearing with having the ability to support the load in radial as well as in axial direction is beneficial to use in rotating machines, i.e. turbine, compressor etc. Performance of the conical hydrodynamic journal bearing depends on many operational parameters such as aspect ratio, semi cone angle, clearance ratio, eccentricity ratio and speed. At present Computational Fluid Dynamics (CFD) models are used as an alternative to experimental methods in research for overcoming the cost and operational difficulties. In this study conical hydrodynamic journal bearing have been investigated for aspect ratio (λ=0.5, 0.8, 1.0), semi cone angles (γ= 00, 50, 100, 200, 300), clearance ratio (e =0.001, 0.002) and speed (N = 2000, 5000, 10000 rpm) by using Ansys Fluent software. Fluid film pressure is one of the key operating parameters for describing the operating conditions of hydrodynamic journal bearings. Load carrying capacity, fluid film thickness and stability of bearing is evaluated based on pressure developed in clearance space of bearingwith rotation of journal. It was found that numerically simulated results of water lubricated conical journal bearing are influenced by the operational parameters of bearing. Present workis useful indesign ofcompact size conical hydrodynamic journal bearingfor combined radial and axial load application to replace two separate bearings i.e. journal and thrust.

Influence of balancing of internal combustion engines on the operating conditions of hydrodynamic bearings

We studied the influence of balancing internal combustion engines on the performance of hydrodynamic plain bearings. A non-linear approach makes it possible to calculate the forces of pressure generated by the lubricant film. This approach is coupled with a dynamic calculation, which determines the inertia forces of the rod. The counterweight to balance the engine is applied to the heads of rods and not to the crankshaft. We chose three models of connecting rod (rod of an engine in series, rod with partial and rod with complete counterweight). To determine the lubricant pressure field in the bearing, the modified Reynolds equation was solved using the finite difference method, taking into account the boundary conditions of Reynolds. Since the bearing is subjected to a variable load, the mobility method was used to facilitate the resolution of the Reynolds equation. The proposed numerical simulation allowed us to analyze the influence of counterweight applied to the connecting rod head on the variation of the lubricant pressure field, the minimum film thickness, the axial flow and the friction torque in the big end bearing during the operating cycle.

Pad attitude adjusting moment in large multi-pocket pivoted pad used in static oil journal bearing

PurposeLarge scale is a trend of the ball mill, so the loads on their bearings become very large, bearing operating conditions turn into more severe. The moment of inertia to their pivot of the pad increase significantly, so it leads to the difficult of the pad attitude adjustment and makes the pad tilting angles time response slow, the key factor to effects attitude adjustment is the oil film moment to the pad pivot at unbalance position. the oil film moment and its effect factors must be studied in the design of the bearing used in ball mill.Design/methodology/approachModels about the lubrication of multi-pocket pivoted pad hydrostatic bearing is established, the complicated relationship of the oil flow rate between the oil pockets are taken into account. Finite differential method is used to solv the model, and theroy of finite element method is use to calculate the oil flow rate out of the pocket edges. Newton’s methods are used to determine the pressure of pockets.The pad tilting moment to its pivot is numerically analyzed.FindingsThe tilting moment to its pivot is set as an indicator of the ability for a pad to adjust its attitude. The effects of the diameter of throttling capillary and the pocket area on the attitude adjusting capacity is studied. Relations between the attitude adjustment capacity for a pad and there effects factors are presented.Practical implicationsThe methods and results have the special reference to the design and operation of multiple pockets tilted pad hydrostatic journal bearing.Originality/valueMethods to studied the pad attitude adjustment are given in the article for the multi-pocket pivot pad hydrostatic beairng.The influence factors on pad attitude adjusting capacity are discussed for a this specail kind hydrostatic bearing, the how the factors influence the pad tilting angle adjustment are presented.

Weighted Kernel Entropy Component Analysis for Fault Diagnosis of Rolling Bearings.

This paper presents a supervised feature extraction method called weighted kernel entropy component analysis (WKECA) for fault diagnosis of rolling bearings. The method is developed based on kernel entropy component analysis (KECA) which attempts to preserve the Renyi entropy of the data set after dimension reduction. It makes full use of the labeled information and introduces a weight strategy in the feature extraction. The class-related weights are introduced to denote differences among the samples from different patterns, and genetic algorithm (GA) is implemented to seek out appropriate weights for optimizing the classification results. The features based on wavelet packet decomposition are derived from the original signals. Then the intrinsic geometric features extracted by WKECA are fed into the support vector machine (SVM) classifier to recognize different operating conditions of bearings, and we obtain the overall accuracy (97%) for the experimental samples. The experimental results demonstrated the feasibility and effectiveness of the proposed method.

A bearing fault diagnosis technique based on singular values of EEMD spatial condition matrix and Gath-Geva clustering

This paper employs a combined ensemble empirical mode decomposition (EEMD) and singular value decomposition (SVD) technique to extract useful fault features from the condition monitoring data of rolling element bearings. The fault features is then classified by a Fuzzy clustering method, Gath-Geva (GG) clustering, to obtain the cluster center and membership matrix of each bearing condition for pattern recognition. The bearing fault recognition is realized by calculating the hamming approach degree between the test samples and the known fault clustering centers from the GG clustering. The proposed algorithm is then evaluated first on several sets of simulated bearing defect data with different signal to noise ratios (SNRs) to represent bearing defects with various degrees of severities. Satisfying diagnosis outcome can be obtained from this set of simulation when the SNR is greater than 1. The algorithm is further evaluated using a set of experimental data from a bearing fault test rig. It is found that the proposed algorithm can diagnose all bearing operation conditions accurately based on the experimental data.

Using Simplified Models to Assist Fault Detection and Diagnosis in Large Hydrogenerators

Based on experimental evidence collected in a set of twenty 700 MW hydrogenerators, this article shows that the operating conditions of large hydrogenerators journal bearings may have unpredictable and significant changes, without apparent reasons. These changes prevent the accurate determination of bearing dynamic coefficients and make the prediction of these machines dynamic behavior unfeasible, even using refined models. This makes it difficult to differentiate the normal changes in hydrogenerators dynamics from the changes created by a fault event. To overcome such difficulty, this article proposes a back-to-basics step, the using of simplified mathematical models to assist hydrogenerators vibration monitoring and exemplifies this proposal by modeling a 700 MW hydrogenerator. A first model estimates the influence of changes in bearing operating conditions in the bearing stiffnesses, considering only the hydrodynamic effects of an isoviscous oil film with linear thickness distribution. A second model simulates hydrogenerators dynamics using only 10 degrees of freedom, giving the monitored vibrations as outputs, under normal operating conditions or in the presence of a fault. This article shows that simplified models may give satisfactory results when bearing operating conditions are properly determined, results comparable to those obtained by more refined models or by measurements in the modeled hydrogenerator.

A combined model of calculating the durability of aircraft engine high speed rolling bearings

Based on analyzing the operating conditions for high speed rolling bearings of aircraft engines in a medium of low viscosity fuel components, we substantiated a combined model of calculating the bearing life with respect to two criteria of efficiency, namely, the contact fatigue resistance and wear resistance of their working surfaces. An algorithmic procedure and special features of calculating the durability with respect to these criteria were shown.

Steady Characteristics of High-Speed Micro-Gas Journal Bearings With Different Gaseous Lubricants and Extreme Temperature Difference

High-speed micro-gas journal bearing is one of the essential components of micro-gas turbines. As for the operating conditions of bearings, the high-speed, high-temperature, ultra-high temperature difference along the axial direction and the species of gaseous lubricants are extremely essential to be taken into account, and the effects of these factors are examined in this paper. The first-order modified Reynolds equation including the thermal creep, which results from the extremely large temperature gradient along the axial direction, is first derived and coupled with the simplified energy equation to investigate the steady hydrodynamic characteristics of the micro-gas bearings. Under the isothermal condition, it is found that CO2 can not only improve the stability of bearings but also generate a relatively higher load capacity by some comparisons. Thus, CO2 is chosen as the lubricant to further explore the influence of thermal creep. As the rotation speed and eccentricity ratio change, the thermal creep hardly has any effect on the gas film pressure. However, the shorter bearing length can augment the thermal creep. Compared with the cases without the thermal creep, the thermal creep could remarkably destroy the stability of gas bearing, but it might slightly enhance the load capacity.

Fast EEMD Based AM-Correntropy Matrix and Its Application on Roller Bearing Fault Diagnosis

Roller bearing plays a significant role in industrial sectors. To improve the ability of roller bearing fault diagnosis under multi-rotating situation, this paper proposes a novel roller bearing fault characteristic: the Amplitude Modulation (AM) based correntropy extracted from the Intrinsic Mode Functions (IMFs), which are decomposed by Fast Ensemble Empirical mode decomposition (FEEMD) and employ Least Square Support Vector Machine (LSSVM) to implement intelligent fault identification. Firstly, the roller bearing vibration acceleration signal is decomposed by FEEMD to extract IMFs. Secondly, IMF correntropy matrix (IMFCM) as the fault feature matrix is calculated from the AM-correntropy model of the primary vibration signal and IMFs. Furthermore, depending on LSSVM, the fault identification results of the roller bearing are obtained. Through the bearing identification experiments in stationary rotating conditions, it was verified that IMFCM generates more stable and higher diagnosis accuracy than conventional fault features such as energy moment, fuzzy entropy, and spectral kurtosis. Additionally, it proves that IMFCM has more diagnosis robustness than conventional fault features under cross-mixed roller bearing operating conditions. The diagnosis accuracy was more than 84% for the cross-mixed operating condition, which is much higher than the traditional features. In conclusion, it was proven that FEEMD-IMFCM-LSSVM is a reliable technology for roller bearing fault diagnosis under the constant or multi-positioned operating conditions, and as such, it possesses potential prospects for a broad application of uses.

Improved Embeddability for Polymeric Bearing Overlays

Recent engine developments toward higher loads (down-sizing) and thinner oil films have increased the severity of plain bearing operating conditions [1]. These factors, combined with lower viscosity oils, have resulted in a greater sensitivity of bearings to damage by foreign debris particles. Traditional highly embeddable materials, such as lead, are being progressively phased out. This lead-free trend observed in the passenger car market is likely to spread to the truck market in the future. As a result, it is becoming increasingly challenging to balance the conflicting hard and soft requirements of bearing materials. Although new generations of bearing materials, particularly polymeric overlays, have shown excellent fatigue and wear capabilities [2], they would benefit from enhanced embeddability properties. This demand has led MAHLE to take a new approach with the development of a polymeric overlay material that has both hard and soft characteristics. This newly developed soft-phase copolymer resin has been synthesized from monomers selected to give the desired properties. Conventional polyamide-imide (PAI) monomers have been combined with polydimethylsiloxane (PDMS) macromonomers. PDMS was selected to improve embeddability as it is softer and offers more flexibility than PAI. Via a polymerization reaction, chains of hard, fatigue resistant PAI are alternately combined with short chains of PDMS. This produces a polymer matrix which has a very fine distribution of soft phase due to the microphase segregation created as the soft and hard segments of neighboring polymer chains preferentially align with each other [3,4]. The relative lengths of the hard and soft sections can be “tuned” to produce domains of differing size and therefore adjust the balance of properties. Experiments have been carried out varying the overall percentage of PDMS and also with the molecular weight of the PDMS segments. Initial embeddability testing has shown an improvement in embedment over current polymer products and further work is ongoing to optimize this new resin system.

Method of calculating high-speed rolling bearings intended for an aircraft engine based on considering the wear process

The operating conditions of high-speed rolling bearings intended for aircraft engines are analyzed for operation in low-viscous fuel components. The extreme operating conditions are shown. The calculation procedure of bearing durability according to two operability criteria, i.e., contact fatigue resistance and the wear resistance of their working faces are grounded. The algorithm for calculating the high-speed bearings intended for the aircraft engines according to the aforementioned criteria is presented.

The Numerical Analysis of Influence of Crankshaft Main Spindles Regeneration in Marine Engine on Stiffness and Eigenfrequency of the Crankshaft

Engine operating conditions of the main propulsion, static in principle with steady-state rotation speed of the crankshaft and engine load, also work under dynamic load conditions. These conditions cause additional distortion of the crankshaft and changes in the operating conditions of the shaft bearings. However, the greatest impact on the long and trouble-free operation has proper engine maintenance. Variable operating conditions and engine operating errors, unfortunately, often cause damage to the main bearings of the crankshaft. Repair of the damaged main bearing spindles of the shaft involves performing the machining of the spindle surface then its re-hardening and selecting new bearing bushings with the appropriate bearing clearance. Trusting the engine manufacturer, there is no check of the influence of the machining of bearing spindles on the structural properties of the shaft. Therefore, the paper presents the model tests of the structure of medium-rev marine engine crankshaft aimed at determining the changes in the mechanical properties of the structure resulting from carrying out the regeneration of the main shaft spindles.

Study on wear behaviours for NBR/stainless steel under sand water-lubricated conditions

Nitrile Butadiene Rubber (NBR) is widely used to make ship water-lubricated rubber stern tube bearings for marine applications. The sand in water is an important factor that affects the tribological properties of the rubber stern tube bearings. This study aimed to investigate the wear behaviours of NBR pins and 1Cr18Ni9Ti stainless steel disc rubbing pairs under sand water-lubricated conditions. A CBZ-1 tribo-tester was used to conduct sliding wear tests under the sand and pure water-lubricated conditions. The friction coefficients, wear volumes and different mass concentrations of sand were measured and compared. In addition, their surface morphologies were examined using optical microscopy and laser-interference profilometry. The results showed that the sliding velocity, applied load and mass concentration of sand had significant effects on the tribological properties of the rubbing pairs. The wear volumes and surface roughness of the rubbing pairs increased as the sliding velocity, applied load and mass concentration of sand increased. The friction coefficient also increased with the increase of applied load and mass concentration of sand, while it became smaller firstly and then bigger as the velocity increased. The sand particles destroyed the water-film between the rubbing pairs to reduce their tribological properties, and the abrasive wear was the main wear mechanism under the sand water-lubricated conditions. The data gained herein provides a better insight in to the wear process of NBR/1Cr18Ni9Ti stainless steel discs, and will be useful for selecting proper operating conditions for water-lubricated rubber stern tube bearings and will ensure the completion of missions by ships, reliably and safely.

Modelling dislocation assisted tempering during rolling contact fatigue in bearing steels

Rolling contact fatigue in bearing steels is manifested by dark-etching regions, which are attributed to deformation induced tempering. In order to quantitatively explain this phenomenon, a model is suggested for martensite tempering assisted by dislocation glide during rolling contact fatigue. In the model, dislocations transport carbon from the matrix to carbide particles, provided that the carbon is located at a certain distance range from the dislocation contributing to the tempering process. By calculating the amount of carbon in the matrix, the kinetics of carbide thickening and hardness reduction are computed. It is found that the dark-etching region kinetics can be controlled by both bearing operation conditions (temperature and deformation rate) and microstructure (type, size, and volume fraction of carbides). The model is validated against tested bearings, and its limitations are discussed.

Surface texturing effect comparative analysis in the hydrodynamic journal bearings

The journal bearing is a complex system with high film convergence and with cavitation hydrodynamic phenomena. The surface texturation influence study on journal bearing performances requires unavoidably experimental investigations followed by a numerical modelling of the problem. This work consists in modellization and understanding of the journal bearing characteristics in both cases of presence or absence of textures onto the bearing surface. The finite difference method is used as numerical approach in the analysis. The textured bearing performance enhancement passes essentially by an improvement of a minimum film thickness, a maximum pressure and a friction torque through an appropriate surface texture geometry and appropriate texture distribution on the contact surface. It is found that the simulations results are in good concordance with litteratures. The texture area position on the bearing surface is the primary endpoint for journal bearing performance enhancement. The best design of textured area depends strongly on the geometrical parameters and the journal bearing operating conditions.

Refrigerant foil bearing behavior—A Thermo-HydroDynamic study: (Application to rigid bearings)

Internal experiments at Liebherr-Aerospace FRANCE (LTS) on new refrigerant-lubricated compressor designs have shown that under specific operating conditions, a mixture of vapor and liquid appears in the compressor, instead of a single-phase vapor flow. Therefore, refrigerant-lubricated foil bearings behavior is studied, including the likelihood of two-phase flow in the lubricant. In this paper, we focus on the lubricant behavior only, in the operating conditions of foil bearings. The coupling with structural behavior is a complex process and will be the topic of another paper. The Thermo-HydroDynamic approach describes lubricant characteristics such as pressure, density, viscosity, and temperature. It involves the use of a Generalized Reynolds Equation for turbulent flow, a nonlinear cubic Equation of State for two-phase flow and a 3D turbulent thin-film energy equation. Journal bearing global parameters are calculated for steady-state conditions.

Sustainable wind power generation by online sensor oil condition monitoring against premature gearbox bearing failures

An online web-based oil sensor diagnosis system for continuous lubricant quality monitoring in wind turbine gearboxes is presented. The fundamental innovation is that bearing operating conditions, critical for premature failures, are detectable in an early stage before any raceway damage. The electrical oil properties are identified as a sensitive loading indicator. Common condition monitoring systems, such as vibration analysis, visual or endoscopic inspection, filters and particle counters, do not respond until initial spalling. With the novel sensor unit, the specific electrical conductivity and the relative permittivity of the oil are measured in real time. A thermocouple is integrated for accompanying online temperature measurement. Under the impact of vibration loading of the rolling contact, which represents the root cause of premature bearing failures, chemical aging of the lubricant by polycondensation reactions and degradation of its additives occur. The resulting conductivity increase due to, e.g., cracked oil molecules or forming acids thus provides a crucial indication of critical operating conditions of the monitored wind turbine gearbox before component damage. The gradual consumption of additives is reflected in a reduction of the electrical permittivity of the lubricant. As the conductivity of the oil rises with temperature, a self-learning adaptive compensation program is implemented. The measuring signals can be transmitted to a web-based condition monitoring system via LAN, WLAN or serial interfaces of the sensor.

Fault diagnosis of rolling bearing based on wavelet transform and envelope spectrum correlation

Monitoring of incipient faults is vital for the safe and reliable operation of rolling element bearings. In this paper, the combination of discrete wavelet transform and envelope analysis is proposed to extract the characteristic spectrum of rolling bearing vibration data. Then spectrum cross-correlation coefficient is applied to identify different operating conditions of rolling bearings. The proposed method is applied to fault diagnosis of rolling bearings with several different faults. The results show that the proposed method has high classification accuracy, and performs better than alternative approaches based on conventional characteristic defect frequency extraction.