Hybrid Bearings Research Articles

Dynamic Response of a Rotor Supported on Hybrid Bearings in Air, Water, and Liquid Nitrogen: Measurements and Comparisons to Predictions

Abstract Modern liquid rocket engine turbopumps implement hybrid bearings, which combine hydrostatic and hydrodynamic fluid film principles, in compact and lightweight units known for their superior reusability, durability, and reliability. This study aims to provide extensive and reliable test data for the purpose of anchoring and benchmarking predictive tools for these bearings. This paper provides comprehensive dynamic response measurements of a rotor weighing 10.40 kg and approximately 60 mm in diameter at the bearing locations. The test rotor is supported on two hybrid journal bearings with a bearing length to bearing diameter ratio of approximately 0.42 and a bearing radial clearance to rotor radius ratio of around 0.0017. The bearings are tested with air, water, and liquid nitrogen, serving as surrogate test fluids for common propellants in liquid rocket engines. Rotor run-up and speed coast-down tests are conducted to measure shaft motion responses. The results clearly demonstrate that the rotordynamic characteristics of the test rotor supported on the hybrid journal bearings largely rely on properties of the test fluids and their feeding conditions. Notably, when air is pressurized into the test bearings, the shaft motion responses differ markedly from those observed with water and liquid nitrogen, primarily due to significantly lower stiffness and damping coefficients. Furthermore, rotor speed coast-down tests for each test fluid exhibit notable differences in coast-down speed over time characteristics, depending on the test fluid properties. The predicted rotor imbalance responses exhibit excellent correlation with the measurement data. The steady increase of demand and growth of the fluid film bearing technology for reusable rocket engines require accurate bearing design tools, the extensive component testing, and the implementation of the technology. The validated and developed bearing predictive models from previous research demonstrate well the characteristics of bearings under various operating fluids conditions. The findings and database presented in this work contribute not only to comprehending the performance of hybrid bearings but also to understanding and enhancing the dynamic characteristics of rotor systems supported on hybrid bearings.

Functionality of Bearings in the Shafts of a Vertical-Axis Wind Turbine

The article contains a description of the design solutions proposed by the authors for a hybrid wind turbine bearing, in which the sliding part takes over the load to the turbine shaft after reaching the shaft rotation speed, ensuring hydrodynamic lubrication of the plain bearing and relieving the rolling bearing. This allows for low starting resistance of the power plant and ensures quiet operation during use. Two conceptual solutions of a hybrid bearing were presented, differing in the shape of the plain bearing journal. A mechanism for automatic switching of the load between a rolling and a plain bearing was developed. A solid simulation model of this mechanism was built in the Autodesk Inventor—Dynamic Simulation software Inventor Professional 2023 environment, and its operation was simulated. The results confirmed the usefulness of using this design in shaft-bearing systems of wind turbines with a vertical axis of rotation. Based on the simulation, the speed at which the thrust roller bearing will be released was determined. Technical parameters of a plain bearing with a spherical journal shape were calculated. The height of the lubrication gap and the shaft rotational speed at which the bearing load capacity index reaches a critical value were determined.

Experimental investigation and numerical analysis of a hybrid bridge isolation system utilizing bonded and unbonded laminated rubber bearings

To enhance the seismic resilience of bridges equipped with nonseismic laminated rubber bearings, a novel seismic isolation system is proposed, leveraging hybrid bonded and unbonded laminated rubber bearings. An experimental program is conducted to investigate the seismic behavior of this innovative hybrid bearing system. Cyclic loadings are applied to bonded, unbonded, and hybrid bearings to assess their force-displacement hysteretic response, energy dissipation, and restoring performance. The experimental findings reveal that unbonded rubber bearings exhibit significant energy dissipation through sliding but show limitations in restorability. Conversely, bonded bearings demonstrate superior restoring capacity but offer limited energy dissipation. The proposed hybrid bearings, combining bonded and unbonded bearings, achieve a favorable equilibrium between energy dissipation and restoring performance. Compared to individual bonded and unbonded bearings, the hybrid bearings exhibit a remarkable increase in energy dissipation by 110 % and restoring performance by 185 %. Furthermore, a numerical simulation method is proposed to accurately capture the critical hysteretic behavior of the hybrid bearings.

Hybrid Bearings Static Load Capacity and Its Application

Hybrid Bearings Static Load Capacity and Its Application

Detection of Contamination and Failure in the Outer Race on Ceramic, Metallic, and Hybrid Bearings through AI Using Magnetic Flux and Current

Bearings are one of the most essential elements in an induction motor, and they are built with different materials and constructions according to their application. These components are usually one of the most failure-prone parts of an electric motor, so correct and accurate measurements, instrumentation, and processing methods are required to prevent and detect the presence of different failures. This work develops a methodology based on the fusion of current and magnetic stray flux signals, calculation of statistical and non-statistical indicators, genetic algorithms (GAs), linear discriminant analysis (LDA), and neural networks. The proposed approach achieves a diagnostic effectiveness of 99.8% for detecting various damages in the outer race at 50 Hz frequency and 96.6% at 60 Hz. It also demonstrates 99.8% effectiveness for detecting damages in the presence of contaminants in lubrication at 50 Hz and 97% at 60 Hz. These results apply across metallic, ceramic, and hybrid bearings.

Seismic performance upgrade of highway bridges using a novel hybrid placement of bonded and unbonded laminated rubber bearings

To enhance the seismic performance of highway bridges supported by laminated rubber bearings, this study proposes a novel hybrid placement of bonded and unbonded bearings. The typical analytical models of the hybrid bearing system are obtained and its critical design parameters are identified through theoretical analysis. A design procedure is then established to rapidly determine the design parameters for the hybrid bearing system according to specified design objectives. Nonlinear time history analyses are conducted to demonstrate the impact of the hybrid bearing system on the seismic responses of bridges. The analytical results indicate that the hybrid bearing system, when designed using the proposed procedure, can achieve the desired hysteretic behavior. The hybrid system combines the benefits of both bonded and unbonded bearings, effectively controlling maximum and residual bearing displacements without significantly increasing the seismic demand on bridge piers. The design parameters for the hybrid bearing system should be determined by carefully balancing the responses between the bearings and the piers.

ВПЛИВ УМОВ РОБОТИ НА ТЕМПЕРАТУРНИЙ РЕЖИМ ПІДШИПНИКІВ З МЕТАЛЕВИМИ ТА КЕРАМІЧНИМИ КУЛЬКАМИ

The results of an experimental study of the temperature mode of operation of rolling bearings under different lubrication conditions are presented. Comparative tests of all-metal bearings and similar bearings with rolling elements made of silicon nitride (hybrid bearings) when lubricated with an oil jet and an oil-air mixture in the range of rotor rotation frequencies from 0 to 35000 rpm were carried out. For the experiments, a specially created set was used, which allows you to study the temperature of the bearings and the temperature of the lubricant at the entrance and exit from the bearings. The axial load on the bearings was created with the help of a compression spring, which rested on the outer rings of the bearings. This made it possible to close the load inside the system. During the tests, the load was 0 N, 1000 N, and 2000 N. Tests were carried out for two modes of bearing lubrication: oil jet and oil-air mixture. The method of measuring the temperature of the outer ring of bearings is described. The temperature measurement error was considered as a complex of instrumental error and method error. It was assumed that the temperature error is subject to a normal distribution. The conducted analysis showed that the error of measuring the temperature of the bearing ring was ± 2.8 °C with a confidence probability of 95 %. It has been established that bearings with ceramic balls in the entire studied range behave qualitatively and quantitatively in approximately the same way as with steel ones. The temperature level of hybrid bearings is slightly higher when lubricated with both an oil jet and an oil-air mixture. There is a clear connection between the values of the bearing temperature and the moment of resistance in the bearing: the increase in temperature is observed under the same conditions under which the moment of resistance increases.

Composite thermal oil film lubrication model for hybrid journal bearings

Hybrid journal bearings are crucial components in many equipment, such as nuclear reactor cooling pumps and hydraulic motors. However, there exists a significant challenge to understand the lubrication behaviors of hybrid bearings with multiple thermal effects at low-speed, heavy-load conditions. Therefore, a composite thermal lubrication model is proposed, which includes four thermal effects: edge suction heat, hydrostatic pressure loss heat, oil viscous friction heat, and asperity friction heat. The lubrication and contact model are modified by actual rough surfaces to evaluate friction heat accurately. The experiments from a homemade testing rig verify the model well. Friction and temperature characteristics of the hybrid bearing are obtained, and the influence of hydraulic pressure and speed on four types of heat are analyzed.

Vibration behavior of a 3D-printed hybrid polymer bearing with outer race defect

PurposeIn industry applications, polymer hybrid bearings have become widespread in recent years owing to the lack of lubricant requirements, particularly in areas requiring hygiene. The additive manufacturing method gives significant advantages to have complex machinery parts, and it has become popular in the industry in recent years. However, it has some inherent disadvantages caused by layered deposition/addition of the materials, and the probability of the localized defect is much higher than in the conventional manufacturing methods. This study aims to investigate the effect of the outer race defect on the characteristics of vibration and service lifetime of hybrid polymer ball bearings produced with the stereolithography (SLA) additive manufacturing method.Design/methodology/approachIn this study, polymer bearings’ races were produced with the additive manufacturing SLA method, and the outer race defect was analyzed with measured vibrations.FindingsThe results show that the additive manufacturing method suggests a practical solution for producing a polymer hybrid ball bearing. On the other hand, the hybrid three-dimensional-printed bearing, which has an outer race defect, worked for approximately 8 h without any problems under a 1 kg load and a shaft speed of around 1,000 rpm. In addition, when there is a defect in the outer and/or inner race of the ball bearing, the crest factor and kurtosis of the vibration are higher than faultless ball bearing, as expected.Originality/valueThis paper provides valuable information on the lifetime and vibration characteristics of polymer hybrid ball bearing produced by means of additive manufacturing.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-06-2023-0183/

A study of the vibrations of a rotor bearing suspended by a hybrid spring system of shape memory alloys

Abstract The study of rotor-bearing vibration is crucial across various fields, encompassing applications such as rotating machinery, wind turbines, washing machines, and elevators. However, operational challenges can arise from these machines’ propensity to vibrate under specific conditions. To address this issue, the current research investigates the utilization of shape memory alloy (SMA) springs as intelligent materials in the rotor suspension system. SMA’s unique property of changing stiffness with temperature-induced phase shifts is harnessed, leading to the construction of a test rig for validating vibration characteristics. A novel hybrid bearing is devised to effectively manage vibrations, particularly in resonance zones. To the authors’ knowledge, this new model is never reported in the literature. Then, an accelerometer is employed to measure the rotor shaft response corresponding to disc position vibration signals. Furthermore, a numerical model is developed to validate experimental results, taking into account the phase change of SMA springs and the disc’s influence on the rotor bearing’s natural frequency. Temperature variations from 20 to 80°C resulted in a 13% change in natural frequency for the hybrid spring configuration. The experimental findings align closely with ANSYS simulations, displaying an acceptable error ratio, with the highest error remaining within 20% thresholds.

Flow field analysis and structure optimization of liquid sodium hybrid bearing

AbstractLiquid sodium hybrid bearing is mechanical pump shaft bottom key support components, that play a balanced radial force of the impeller by fluid effect, in order to improve the bearing performance, based on the calculation model, simulation analysis, structure improvement and other aspects of analysis, this paper based on the theory of fluid mechanics of bearing finite element model for numerical calculation and analysis of flow field. Under different eccentricities and vibration velocities, the influence of structure improvement on bearing capacity is analysed. The results show that the bearing capacity of the liquid sodium hybrid bearing is mainly the hydrostatic bearing capacity, and the hydrodynamic pressure only plays an auxiliary role. After the improvement of the load‐bearing structure, the load‐bearing capacity is increased by 4%–7.3%. And the leakage is reduced by 27%–38% when the depth of the annular groove is 0.6 mm.

A Hybrid Bearing Prognostic Method With Fault Diagnosis and Model Fusion

Accurate bearing fault diagnosis and prognosis (FDP) is critical for optimal maintenance schedules, safety and reliability. The existing methods face some problems and challenges in detecting the starting time for prognosis and using a single model to describe fault dynamics. With these motivations, this paper presents a hybrid bearing FDP framework with fault detection and automatic fault model selection. In the proposed approach, convolutional neural network is used to detect fault and select the appropriate fault dynamic model. To improve the performance, power spectrum of vibration signals are fused with operating conditions to built information maps for fault detection and model selection. After a fault is detected, a Bayesian method is triggered to estimate the fault state and predict the remaining useful life. In the prognosis, Dempster-Shafer theory is employed to fuse prediction results from different models if necessary. The proposed approach is verified with bearings under different operating conditions. Experimental results and comparison studies verify the high accuracy and efficiency of the proposed method.

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.

Experiment and simulation analysis of tribological and dynamic characteristics in aeroengine hybrid ceramic bearing

Purpose This paper aims to research the tribological and dynamic characteristics of aeroengine hybrid ceramic bearings through wear experiments and simulation analysis. Design/methodology/approach First, the authors carried out wear experiments on Si3N4–GCr15 and GCr15–GCr15 friction pairs through the ball-disc wear test rig to explore the tribological properties of their materials. Second, using ANSYS/LS-DYNA simulation software, the dynamic simulation analysis of hybrid bearings was carried out under certain working conditions, and the dynamic contact stress of all-steel bearings of the same size was simulated and compared. Finally, the change of the maximum contact stress of the main bearing under the change of load and rotation speed was studied. Findings The results show that the Si3N4–GCr15 pair has better tribological performance. At the same time, under the conditions of high speed and heavy load, the simulation analysis shows that the contact stress between the ceramic ball and the raceway of the ring is smaller than the steel ball. That is, hybrid bearings have better transient mechanical properties than all-steel bearings. With the speed increasing to 12,000 r/min, the maximum stress point will shift in the inner and outer rings. Originality/value In this study, the tribological and transient mechanical properties of Si3N4 material were comprehensively analyzed through wear experiments and dynamic simulation analysis, which provided a reference for the design of hybrid bearings for next-generation aeroengines.

Numerical Process Design for the Production of a Load-Adapted Hybrid Bearing Bushing

Due to increasing product requirements regarding lightweight, functional integration and resource efficiency, research into and use of hybrid parts are steadily increasing. Tailored Forming provides an innovative process chain for manufacturing hybrid parts by using pre-joined semi-finished products. In addition to the potentials, however, challenges also result in the production of hybrid components. In particular, the material combination of steel and aluminium is demanding due to strongly differing physical properties. An inhomogeneous temperature distribution within the pre-joined semi-finished part can be used to equalize flow properties during the forming process. However, processes are sensitive to temperature deviations resulting in critical stresses and failure of the final part. This study focuses on a process design of a hybrid bearing bushing consisting of the aluminium alloy EN-AW-6082 and the steel 100Cr6 using numerical simulation. First, a closed-die forging process is analysed regarding sensitivity to process fluctuations resulting in deviations in temperature distribution. To increase process stability, a new hollow forward-impact extrusion process is numerically designed and investigated regarding its potential to reduce critical stresses and thus the risk of part failure. Furthermore, a numerical model of inductive heating is used for the consideration of inhomogeneous temperature fields. Finally, hybrid bearing bushings are produced using closed-die forging and hollow-forward extrusion to evaluate numerical results.

Lubrication analysis of hydrodynamic-static hybrid bearing with deep-shallow chambers considering thermal conduction

The oil film separates the shaft-bearing system to reduce the frictional force of contact surfaces with large temperature variations owing to thermal conduction. Multiple impact factors seriously affected the lubrication behavior of the bearing during actual working process. An applicable model regarding the lubrication analysis of a hydrodynamic-static hybrid bearing with deep-shallow chambers is proposed and validated with published literature. The lubrication behavior includes film pressure, load capacity, bearing stiffness and flow rate is numerically calculated with centered finite difference method by solving the Reynolds equation. The influence of film thickness and working temperature are considered, over a range of eccentricity ratio. Moreover, the temperature variation caused by thermal conduction is analyzed in details. To investigate the influence of thermal conduction on the lubrication behavior, the results show that the load capacity, bearing stiffness, friction power, and flow power significantly decline with the consideration of thermal conduction. This study proposes an accurate model that is helpful for the design of hydrodynamic-static hybrid bearings with deep-shallow chambers under low rotational speed, heavy load, and high temperature conditions.

The Friction of Radially Loaded Hybrid Spindle Bearings under High Speeds

Friction losses are an important parameter for evaluating the operational behaviour of high-speed rolling bearings. Specifically, in machine tool applications, the bearings are subjected to high radial loads and high speeds, which lead to increased forces in the rolling contact and, as a result, increased bearing friction. In this high-speed application, hybrid spindle bearings, typically made of ceramic balls and steel raceways, show better frictional behaviour compared to full steel-made bearings. Therefore, precise knowledge of the friction characteristics of high-speed hybrid bearings can improve friction models and generalise them to spindle bearings with different types, geometries, and operating conditions. In this article, a new straightforward and cost-efficient method for measuring the frictional torque in spindle bearings is presented. A rigidly arranged 7008 hybrid spindle bearing pair was tested up to rotational speeds of 24,000 rpm and high radial loads of 3 kN. The effects of oil–air and grease lubrication are discussed in characteristic diagrams of the tested bearings. Then, based on the test results, a friction calculation model is presented and validated for the outer race control and minimised power dissipation regarding the influence of radial forces.

Lubrication performance analysis of Lead-Bismuth Internal-Feedback bearings in the nuclear main pump system

The significant equipment of the rotor system and circulating pump are lubricated bearings. Lead-bismuth pumps use high-temperature liquid lead–bismuth as the lubricant in its internal feedback dynamic and hydrostatic bearings. Through the numerical simulations, the lubrication capabilities of a lead–bismuth bearing are examined in this work. The pressure distribution, load-carrying capacity, minimum film thickness and power loss of a lead–bismuth bearing with various radial gaps are evaluated in relation to three parameters: rotational speed, eccentricity, and differential pressure. The findings demonstrate that the lead–bismuth internal-feedback hybrid bearing's bearing capacity is mostly dependent on static pressure, with some support from dynamic pressure. The dynamic pressure effect is related to the eccentricity, rotating speed and radius gap of lead–bismuth bearings. Throttling is accomplished via the feedback groove. Lead-bismuth bearings with various radius gaps exhibit a similar pattern in their static properties. These bearings need a particular construction to support radial forces because of their unique physical characteristics, which include low dynamic viscosity and high density. Their spiral and feedback grooves are crucial components for heat dissipation and hydrostatic throttling. This article can serve as a reference for the lead–bismuth bearing's lubrication theory.

Theoretical and Numerical Investigation of Reduction of Viscous Friction in Circular and Non-Circular Journal Bearings Using Active Lubrication

Reducing friction losses is one of the most common ways to improve fluid film bearings, whose adjustable design provides additional opportunities to improve their dynamic and tribological properties. Previous studies have shown the possibility of reducing viscous friction in actively lubricated bearings by adjusting the rotor position. This work provides a theoretical justification for the mechanism of this effect for the cases of purely laminar lubricant flows in journal bearings. The operating modes connected with the transition to turbulent phenomena and the occurrence of Taylor vortices are beyond the scope of this paper. Conditions that ensure the minimization of friction losses in hydrodynamic and hybrid bearings with hydrostatic parts are determined based on the equations describing viscous friction in a fluid film. In non-adjustable plain hydrodynamic bearings, the minimum of friction is achieved with the centered shaft position that is actually unstable due to the resulting forces configuration. In actively lubricated hybrid bearings, a further reduction in viscous friction is possible by combining film thickness and pressure distributions. Recombining them, along with adjustment of the shaft position, allows the optimization of the distribution of shear stresses in the fluid film. As a result, the shear stresses caused by the rotation of the shaft can be partially compensated by the stresses caused by the pressure gradient, reducing the torque-resisting rotation. In addition, additional benefits can be obtained in the minimum friction state by the reduced lubricant flow and power losses to its pumping. A series of numerical calculations for elliptical, 3-, and 4-lobe bearings show that non-circular bores provide additional variability in film thickness distribution and a premise for optimizing the bearing tribological parameters. Four-lobe bearing demonstrated the best ability for reducing viscous friction among the considered designs. The results obtained can be used as a basis for further optimization of the geometry of fluid film bearings of both active and passive designs by reducing power losses due to viscous friction.

Analysis and Multi-target Optimisation of the Characteristics with Stepped Cavity of the Hybrid Bearing

In this paper, the peak pressure, stiffness, flow rate, and temperature rise of the oil film in the stepped cavity of the hybrid bearing are investigated. The pressure and flow equations for the central section of the stepped cavity and the axial section of the deep and shallow cavity are derived using the simplified Navier-Stokes equations and the boundary conditions of a liquid bearing. Using the control variable method, the influence of the geometrical parameters of the stepped cavity and the process parameters on the oil film characteristics was simulated, and the correctness of the pressure and flow equations was verified. The results show that: the spindle speed is positively correlated with the peak oil film pressure and flow rate; the oil film thickness is negatively correlated with the peak oil film pressure and positively correlated with the flow rate; the depth and width of the shallow cavity are correlated with the peak oil film pressure, but the correlation with the flow rate is low; the maximum error between the theoretical calculation and the simulation analysis is less than 7.3%. The pressure equation and the flow equation are used to establish the objective function with the maximum oil film stiffness, load-bearing capacity, and minimum temperature rise, and the ideal point evaluation function method is used to do a multi-target optimization design to optimize the ladder cavity and obtain the optimal oil cavity geometric parameters. And an 8.75% increase in peak pressure and a 4.1% reduction in temperature rise for the same process parameters.