Search Results (61)

Periodic abnormal vibration in large pressurized water reactor (PWR) nuclear steam turbine generator units is difficult to diagnose because the parameter-level link among three-pad tilting-pad journal bearings, oil-film thermal asymmetry, and possible Morton-effect susceptibility remains insufficiently quantified. This study investigates an ARABELLE-type unit and establishes a finite-difference bearing rotor model by solving the oil-film thickness equation, Reynolds pressure equation, two-dimensional energy equation, pad moment balance, and linearized stiffness and damping coefficients. The bearing load, radial clearance, rotational speed, and inlet oil temperature are examined as controllable variables, while only the calculated pad temperature rises are directly validated against field measurements from eight support bearings. The calculated temperature rise deviations range from −7% to 8%, with a root-mean-square deviation of approximately 0.32 °C and a mean absolute percentage error of approximately 4.2%. The model results suggest that the load and speed mainly intensify the total oil-film heating, whereas the radial clearance and inlet oil temperature more directly govern the circumferential temperature difference, used here as an indirect indicator of the Morton effect risk. For the investigated Bearing 3, a radial clearance near 0.52 mm and an inlet oil temperature of 48–52 °C are suggested as bearing-specific operating windows for reducing thermal imbalance while maintaining engineering stability. The main contribution is a traceable engineering chain from field abnormal vibration to three-pad bearing thermal asymmetry, cautious Morton-effect risk interpretation, and operational adjustment for large nuclear rotating machinery. Full article

This paper presents a performance analysis of a hybrid tilting pad journal bearing (TPJB) for reusable liquid methane (LCH₄) turbopumps. The numerical model incorporates temperature- and pressure-dependent density and viscosity of LCH₄ using fourth-order polynomial correlations based on the National Institute of Standards and Technology (NIST) data. A bulk-flow thermohydrodynamic analysis solves the Reynolds and energy equations considering turbulence, compressibility, recess inertia effects, and thermal mixing. The model calculates the pressure and temperature fields using the finite element and finite difference methods, respectively. The results of the static load and length-to-diameter ratio identify the available load range for the present bearing geometry. The cryogenic LCH₄ supplied through the recess locally suppresses temperature rise and produces spatial variations in its density and viscosity. The preload and radial clearance design can compensate for the limited load-carrying capacity of low-viscosity LCH₄, while they also can increase friction coefficient and temperature rise. The supply pressure ratio is the dominant parameter because it strengthens hydrostatic support and compensates for the weak hydrodynamic effect of LCH₄. In contrast, larger recess area weakens hydrostatic support and reduces dynamic coefficients. These results provide bearing-level design guidance for reusable LCH₄ turbopumps. Full article

Tribotronic machine elements achieve active control by incorporating sensing, control and actuation into engineering components that are otherwise conventionally passive. There has been a trend towards the development and use of active tribological (tribotronic) components over recent years. This paper briefly recounts the historical development of tribotronics, then presents two examples of research on components as case studies based on research by the authors to demonstrate how tribotronics can drive forward the technical capabilities of two common machine elements. In this context, this paper deals with the tribotronics of tilting-pad thrust bearings as well as active lubrication for internal combustion engine cylinder systems. The aim of the paper is to demonstrate how tribotronic technology can be applied to realise transformative reductions in energy loss by controlling friction well beyond those that could be gained by more conventional improvements in design or the use of enhanced materials, In addition to the technical discussion, this paper incorporates a short reflection the very significant financial and environmental gains that can potentially be obtained by using tribotronic components in the field. Finally, closing remarks are made regarding the more general advantages of tribotronic approaches and the potential future of this technology. Full article

Tilting pad journal bearings are critical components in high-speed turbomachinery. The use of sensors within the bearing is crucial to ensure operational safety and to validate computational models. The objective of this study is to improve the experimental investigation of the performance of a tilting pad journal bearing by enhancing the selection and placement of conventional and non-conventional sensors based on the results of a thermohydrodynamic model. The multi-sensor system measures film pressure and pad temperature at multiple locations, as well as pad tilt and film thickness. Redundant measurements are also performed to evaluate the performance of new induction coils capable of detecting magnetic flux variations due to vibrations. This work contributes to the discussion of bearing instrumentation by proposing a synergic sensor system comprising a suitable number of appropriately located conventional sensors together with non-conventional, non-invasive sensors. The experimental results obtained with the refined conventional sensor system agree with the predicted results, with differences that can be attributed to manufacturing and assembly tolerances of the bearing and simplified assumptions in the model. The results of the non-conventional sensor device, although promising, need further investigation. Full article

Hydrostatic bearings are extensively utilized in precision and ultra-precision machinery. Owing to the small oil film clearance of such bearings, they are prone to tilting under eccentric loads, which may ultimately lead to bearing failure. To investigate the eccentric load characteristics of hydrostatic bearings, a typical rectangular hydrostatic oil pad unit was selected as the research object. First, an analytical model for the eccentric load-carrying capacity of the rectangular oil pad was established. This model was then validated through computational fluid dynamics (CFD) simulations. On this basis, the static and dynamic characteristics of the rectangular hydrostatic oil pad were systematically studied. The results indicate that oil supply pressure, orifice diameter, and oil pad dimensions exert significant influences on the angular stiffness and angular damping of hydrostatic bearings. Specifically, increasing the oil supply pressure to above 3 MPa can facilitate the enhancement of anti-eccentric load capacity. Under the premise of ensuring static load-carrying capacity, a moderate increase in orifice diameter is conducive to improving anti-eccentric load capacity. When the oil pad area is fixed, adjusting the width-to-height ratio of the oil pad can modify the angular damping coefficient in the corresponding direction. However, the adjustment tends to reduce the angular damping coefficient in other directions, necessitating a comprehensive evaluation in practical applications. Full article

The purpose of this study is to explore the influence of different spring support structures and hydrostatic recess areas on the characteristics of hybrid tilting pad bearings lubricated by high-pressure CO₂ to promote the development of high-pressure CO₂-lubricated bearings. A high-pressure CO₂ hybrid tilting pad bearing experiment system was designed and built, and performance comparison experiments were carried out under various speed and load conditions. The performance differences of bearings with different spring support structures and hydrostatic recess areas under high-pressure CO₂ lubrication were obtained. The results show that compared with the bearing structure, the bearing stiffness has a more significant effect on the bearing performance. The design of the bearing should consider the matching of stiffness and rotor dynamics. Full article

Active vibration control designs for journal bearings have improved rotordynamic stability and led to advancements in adjustable bearing types that enable precise control of bearing geometry. In this study, optimized machine learning (ML) algorithms were modeled and implemented to accurately predict the static performance envelope of a four-pad active journal bearing with features of controlling the radial and tilt positions of pads in real time. ML models developed for the adjustable bearing system help predict its behavior as a function of three key input parameters such as the eccentricity ratio and radial and tilt positions of pads. Four supervised regression models, such as Random Forest Regression (RFR), Extreme Gradient Boosting (XGBoost), Light Gradient Boosting Machine (LightGBM), and a feedforward Artificial Neural Network (ANN), were chosen for their demonstrated ability to capture complex nonlinear patterns and their robustness against overfitting in such tribological applications. Hyperparameter tuning for each model was performed using the Optuna framework, which applies Bayesian optimization to efficiently determine the best parameter settings. The Optuna-optimized ensemble and neural network models were used to identify the optimal combinations of input variables that maximize the static performance envelope of the active bearing system with geometric adjustments. Full article

In this paper, an innovative method for the determination of the dynamic coefficients of tilting pad journal bearings (TPJBs) is described, and some of its characteristics are analyzed. The calculation is based on a parabolic modeling of the dependence of the dynamic coefficients on the excitation frequency, on the estimation of the forces acting on the bearing as a function of the estimated displacements using a linear model and, finally, on the search for the best estimate of the parabola coefficients by minimizing the sum of the squares of the normalized residuals of displacements and forces on the bearings. The normalization is performed by dividing the deviations (between the measured values and those calculated by the model) by an estimate of the standard deviation of the force and displacement measurements. The results for a flooded tilting pad journal bearing, TPJB, are presented and compared with those obtained using traditional methods. The synchronous coefficients are also calculated and compared with those determined by linear interpolation. A preliminary statistical analysis of the sensitivity of the results to the variation in the standard deviation of the forces and displacements is presented. An extension of the model is proposed so that the coefficients of the optimal parabolas can be estimated as a function of the shaft rotation frequency. Full article

The elastic-supported tilting pad journal bearing brings new momentum and opportunities for improving the lubrication performance and dynamic stability of high-speed bearing–rotor systems. The objective of this study is to investigate the dynamic and lubrication characteristics of a dual parallel spring-supported tilting pad journal bearing (DPSTPJB) system under unbalanced journal excitation. Considering the tilting angle and radial displacement of the pads, a 10-DOF dynamic model of the four-pad DPSTPJB system is established, accounting for the effects of unbalanced load, nonlinear fluid film force, and parallel spring force/moment. Numerical solutions are obtained for the dynamic responses of the journal and pads as well as the minimum film thickness and maximum film pressure. The effects of spring stiffness, stiffness ratio, and included angle on journal vibration, minimum film thickness, and maximum film pressure are revealed. The results show that the parallel spring parameters have a positive effect on the optimization of bearing performance with an optimal stiffness ratio that minimizes journal vibration and optimizes fluid film thickness and pressure. This research provides a theoretical basis for the optimization design and application of the DPSTPJB. Full article

Tilting pad thrust bearings are widely utilized in large rotating machinery such as steam turbines and hydraulic turbines. Defects in their shaft tiles directly impact lubrication characteristics, thereby influencing the overall safety performance of the entire unit. To address this issue, this paper presents a fault diagnosis method for tilting pad thrust bearings using a modified multi-feature fused convolutional neural network (MMFCNN). Initially, an experimental bench for diagnosing faults in tilting pad thrust bearings was developed to collect multi-channel acoustic emission (AE) signals from both normal and faulty pads. Subsequently, the squeeze-and-excitation (SE) module was employed to reallocate the weights of each channel and fuse the features of multi-channel signals. Learning was then conducted on the signal fused with multiple features using the inverse-add module and spanning convolution. Next, a comparative analysis was carried out among the CNN1D, ResNet, and DFCNN models, and the MMFCNN model proposed in this study. The results show that under consistent operating conditions, the MMFCNN model achieves an average fault diagnosis accuracy of 99.58% when utilizing AE signal data from tilting pad thrust bearings in four states as inputs. Furthermore, when different operational conditions are introduced, the MMFCNN model also outperforms other models in terms of accuracy. Full article

Tilting pad bearings are core components of rotating machinery. Due to factors such as manufacturing, installation and operation, there may be a mismatch between the bearing pad surface and the shaft diameter, leading to issues like high bearing temperature and rotor system vibration. In engineering practice, surface grinding is often used to resolve these problems. This paper analyzed the mechanism of surface grinding, systematically studies the impact of individual or combined surface grinding on the static and dynamic characteristics of tilting pad bearings and summarizes reasonable pre-load adjustment schemes. The results show that the principle of pad surface grinding is to change the pre-load coefficient of the bearings. The grinding of the oil inlet and outlet sides of the pad surface changes the clearance of the pad, increases the pre-load coefficient, reduces the working temperature of the bearing, increases the thickness of the oil film, and increases power consumption; the grinding of the middle parting surface of the pad changes the clearance of the bearing, increases the pre-load coefficient, and increases the main stiffness and damping coefficient of the bearing. Using these results, a fault diagnosis was performed on a turbine unit with excessive vibration during an on-site operation, leading to effective control. The research provides technical references for the condition monitoring of turbine tilting pad bearing vibrations and the safe operation of units, offering significant engineering implications. Full article

Various processes take place in rotor systems with tilting pad bearings. It is important not only to control but also to manage these processes. Due to the instability of the oil film layer in a bearing with inclined pads, oil whirl/whip can occur. Such whirl/whip destabilize the operation of the rotor system. Additional elastic elements between the tilt pads suppress oil whirl/whip and thus reduce rotor vibration excitation. By identifying the working zones of such bearings where oil whirl and whip occur, the problems of rotor rotation instability can be solved. In order to determine the effectiveness of the elastic elements between the tilting pads, research was conducted. A special stand with diagnostic equipment was used for the tests. The clearance between the rotor and the bearing was 50 μm. During the research, the rotor rotation speed was varied from 0 to 5000 rpm. After conducting the research, stable and unstable rotor working zones were determined (Zone I: 0 to 1938 rpm; Zone II: 1938–3923 rpm; Zone III: 3923–5000 rpm). Based on the obtained research results, it is possible to control the working process of the rotor system. Full article

To improve the vibration performance of oil-lubricated tilting pad bearing systems, this paper investigates the impact of different structural parameters on the vibration reduction effect of piezoelectric actuators on flexible tilting pad bearings. Four sets of flexible tilting pad bearings were designed and manufactured, including a flexible hinge tilting pad bearing and three sets of double-layer spring-supported flexible tilting pad bearings with different parameters. The radial displacement of the bearing load pad was controlled to varying degrees using a piezoelectric actuator, and semi-active control experiments were conducted on the flexible tilting pad bearings. The experimental results show that appropriately reducing the radial clearance and the stiffness of the bearing’s flexible structure can effectively suppress vibrations, enhance the vibration reduction effect of the piezoelectric actuation, and increase the stability of the bearing-rotor system. This study is of significant importance for the design of flexible tilting pad bearings and the vibration suppression of rotor systems. Full article

Lubrication modeling has long been dominated by the well-established Patir and Cheng flow factors method. The flow factors approach allows for accurate estimates of macroscale parameters (such as friction) in a reasonable amount of time. These methods are stochastic representations of microscale interactions and are not able to predict local scale (pressure, film thickness) phenomena with a suitable degree of accuracy. This contrasts with a deterministic approach, where a numerical grid must be applied that fully defines the microscale surface topography across the contact. The mesh resolution required leads to prohibitively long execution times and lacks scalability to engineering systems, but provides accurate predictions of local scale phenomena. In this paper, heterogeneous multiscale methods (HMM) are expanded to model varying and are, therefore, more representative of surface topography within lubricated contacts. This representative topography is derived from measured data, thereby allowing the accuracy of deterministic methods to be achieved with the speed of a flow factor method. This framework is then applied to compare key performance characteristics (pressure, film thickness, etc.) when idealized, Gaussian, and measured surface topography are modeled. The variations in microscale geometry are defined by measurements from across two tilted-pad bearings, demonstrating the ability of the expanded HMM framework to model representative surface topography. A comparison with a deterministic method is included as validation, and outputs of the HMM are discussed in the context of the lubrication across multiple length scales. Full article

In high-speed and heavy-load conditions, ordinary rigid tilting pad journal bearings experience significant contact stress at the pad pivot points, leading to severe pad deformation and increased wear. A flexible structure tilting pad bearing (FSTPB) is presented in this paper, using spring supports to replace the traditional pivot supports and flexible hinge supports. A theoretical calculation model for tilting pad radial journal bearings considering flexible structure deformation is established, and the impact of elastic deformation on the performance of the flexible structure tilting pad bearings is discussed. Based on theoretical research, vibration experiments on flexible tilting pad bearings under different loading conditions were conducted. The influence of various structural parameters on the vibration characteristics of the flexible tilting pad radial bearings was studied. The results indicate that, compared to ordinary tilting pad bearings, flexible structure tilting pad bearings exhibit excellent vibration reduction characteristics at high speeds. Reducing the bearing clearance, lowering the stiffness of the flexible structure, and increasing the offset angle of the flexible structure contribute to enhancing the operational stability of the bearing–rotor system. Full article