Search results

The purpose of this paper is to enhance sealing and rotordynamic performance of hole-pattern damping seal (HPDS) and labyrinth seal (LS) by structural innovation and geometrical optimization of special-shaped hole or annular-groove cavity.

The unsteady flow was transformed into steady one using moving reference frame method. The full period numerical models of LS and HPDS were established. The influence of special-shaped hole or annular-groove cavity at axial inclined angle on leakage rate and rotordynamic coefficient of these two seals at different whirl angular speed were investigated.

The results show that dynamic characteristics of straight-tooth LS are better than that of slanted-tooth LS. Compared to typical straight-hole damping seal, HPDS with windward oblique-hole when axial inclined angle ranges from 50 to 60° has superiority in both leakage and rotordynamic characteristics by considering smaller cross-coupled stiffness coefficient and whirl frequency ratio, larger direct damping coefficient and effective damping coefficient.

A novel HPDS with special-shaped three-dimensional hole cavity was proposed to enhance leakage and rotordynamic performance. The optimized geometrical structures of HPDS for excellent sealing and rotordynamic characteristics were obtained.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2020-0262/

This paper aims to combine the grooves with an annular air thrust bearing with multi-hole restrictors and discusses the influence of the groove parameters on the bearing performance.

Four models of aerostatic bearings with grooves of different geometries are established. The pressure distribution, load-carrying capacity (LCC), stiffness and flow characteristics of the flow field in the bearing clearances are obtained by computational fluid dynamics simulation.

The numerical and simulation results show that air bearing with grooved restrictors can slow down the pressure drop at the air inlet and increase the LCC and stiffness of the bearing. The gas flow in the aerostatic bearing is also studied, and the air vortex in the recess is analyzed.

This research optimizes the structure of the annular air thrust bearing, analyzes the gas vortex in the recess, improves the LCC and stiffness of the bearing and provides a reference for the bearing in the selection of groove parameters.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2023-0006/

This study aims to develop a new method to treat the numerical singularity at the critical nodes of two skew coordinates, and optimize the leakage of micro herringbone grooved journal bearings (MHGJBs) with this method.

A side leakage numerical algorithm is proposed by using the skew meshes with a virtual node (SMVN) method to evaluate the effects of groove angle, bank/groove ratio, groove depth and groove number on load capacity, friction and side leakage of MHGJB.

The SMVN method is effective in treating the numerical singularity at the critical nodes of two skew coordinates. Besides, a group of optimized parameters of micro herringbone groove is obtained which can not only minimize the side leakage but also improve the load capacity and friction force.

A virtual node method was proposed, which can significantly improve the calculation accuracy in the side leakage model.

SELECTING the correct bearing for any particular application involves more than the determination of the correct type and size. It is true that the calculation of the nominal working life will give an indication of the operational life before failure, but this calculation only takes into account the fatigue life of the material. If this theoretical life is to be obtained—and perhaps exceeded—then additional factors must be taken into account when initially designing the bearing arrangement. Lubrication and protection from the operating environment are two very important considerations.

This paper aims to give the guidance for the design of the bearing.

The finite element method, the multi-body dynamics method, the finite difference method and the tribology are combined to analyze the lubrication.

The performance parameters of crankshaft-bearing system such as the misalignment, the oil filling ratio and the oil groove are also investigated. Misalignment causes the pressure to incline on one side and the pressure increases obviously. Filling ratio has great relationship with pressure distribution; the factors influencing the filling ratio are also analyzed. Different oil groove models are investigated, as it can provide the theory for oil groove design, and three factors above are always combined to influence the lubrication characteristics.

The optimization of bearing system is conducted by orthogonal test and neural network, unlike the linear optimization theory. Neural network uses the nonlinear theory to optimize crankshaft-bearing system.

The comparative performance of plain journal bearings having various arrangements of oil holes and grooves, operating in a four‐bearing friction machine with forced‐feed lubrication, was determined1 by S. A. McKee and H. S. White of the National Bureau of Standards (U.S.A.). This investigation, part of a research programme on plain‐journal lubrication sponsored by the National Advisory Committee for Aeronautics, has provided much useful knowledge on different methods of bearing lubrication.

The purpose of this paper is to propose a quasi-three-dimensional (3D) thermohydrodynamic (THD) model for oil film bearings with non-Newtonian and temperature-viscosity effects. Its performance factors, including precision and time consumption, are investigated.

Two-dimensional (2D), 3D and quasi-3D numerical models are built. The thermal and mechanical behaviors of two types of oil film bearings are simulated. All the results are compared with solutions of commercial ANSYS CFX.

The 2D THD model fails to predict the temperature and pressure field. The results of the quasi-3D THD model coincide well with those of the 3D THD model and CFX at any condition. Compared with the 3D THD model, the quasi-3D THD model can greatly reduce the CPU time consumption, especially at a high rotational speed.

This quasi-3D THD model is proposed in this paper for the first time. Transient mechanical and thermal analyses of high-speed rotor-bearing system are widely conducted using the traditional 3D THD model; however, the process is very time-consuming. The quasi-3D THD model can be an excellent alternative with high precision and fast simulation speed.

The purpose of this paper is to provide a nondestructive monitoring method based on wireless sensor technology to measure the continuous circumferential film pressure on radial cross-section of water-lubricated bearing, in addition, to study the influence factors to wireless communication.

The unique shaft and wireless equipments are designed, the pressure sensors are installed in right shoulder of shaft, the wireless transmitter is installed at the end of shaft and the sensors are connected with wireless transmitter by data cable. By this way, the film pressure can be obtained via wireless communication. The film pressure of eight grooved water-lubricated rubber bearings with concave staves is measured, the performance evaluation of wireless equipments is conducted and the influence factors to wireless communication is analyzed by Doppler frequency shift theory.

The rupturing and nonuniform water film is observed, the grooves decrease the film pressure of rubber bearing which is in mixed lubricating state. The main influence factor to wireless communication is shaft speed which has greater effect on packet loss rate than that on bit error rate.

By studying the actual continuous water film pressure, the bearing properties can be studied in-depth, and this has significant meaning to the design and application of bearing. Moreover, the study on influence factors to wireless communication can be used for references to other wireless monitoring on rotating machinery.

The continuous water film pressure can be monitored by this method, the lubricating state of bearing working surface cannot be damaged and the signal attenuation can be avoided. Therefore, the measuring accuracy is promoted and the measuring process also becomes convenient and high efficiency.

The purpose of this study is to numerically investigate the time-varying mixed lubrication performance of microgroove journal-thrust coupled bearing (MJTCB) under nonlinear excitation.

A three degree of freedom (3-DOF) dynamic model of the rotor coupling with the transient mixed lubrication behavior is established. Based on numerical predictions, the role of the microgroove on the time-varying mixed lubrication performance of MJTCB is identified. The effects of the microgroove depth, microgroove shape and external load on the time-varying mixed lubrication performance of MJTCB are also studied.

Numerical results show that the effect of the coupling hydrodynamic on the time-varying mixed lubrication performance of the coupled bearing is strengthen with the increasing of microgroove depth. Furthermore, it is found that the optimal microgroove shape for the thrust bearing, arc or rectangle, highly depends on the microgroove depth. Finally, the contact performance of the thrust bearing is slightly affected by the radial external load.

This study is expected to achieve a better understanding of the time-varying mixed lubrication performance of MJTCB under nonlinear excitations.

For moderate pressure and high pressure gear pumps, the temperature failure problem of bearings is now of considerable concern because of their heavy loads. However, the compact structure and the efficiency consideration make it extremely difficult to improve the bearing cooling. A self-circulating oil bearing system is developed for gear pumps with self-lubricating bearings to solve this problem. The oil is aspirated in from the low pressure chamber of the gear pump and discharged to the same chamber by using the pressure difference in the journal bearing, thus achieving the self-circulation.

An experiment test rig has been built for the feasibility study. The oil flow rate under different speeds has been recorded. Furthermore, the temperatures of the bearings with or without the oil circulation have been compared. Additionally, the oil flow in the test rig has been simulated using computational fluid dynamics codes.

The experimental and numerical results agree well. The experimental results indicate that the oil flow rate increases approximately linearly with the speed and the bearing temperature can be lowered successfully. The calculation results indicate that the bearing load capacity is nearly the same. Both the experimental and numerical studies establish that the self-circulating oil bearing system works successfully.

As far as the authors know, it is the first time to find that the self-circulation can be built using the pressure difference in the bearing oil film, and this principle can be applied in the cooling and lubrication of the gear pumps to solve the temperature failure problem.