Hybrid Bearing Design Research Articles

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.

Effect of Recess Shape on the Performance of a High-Speed Hybrid Journal Bearing

Hybrid bearings are getting more and more attention because of their ability to provide both hydrodynamic support for high-speed rotors and hydrostatic lift in low-speed conditions such as during startup. Hybrid bearings are typically designed with recess grooves to modify the pressure profile and as a result to enable the lift capacity of the bearing under various operating conditions. The literature has shown that the size and shape of the recesses have not been systematically and quantitatively studied in detail. The goal of this study is to build a 3D analytical model for a hybrid-recessed bearing with five pockets and provide a comprehensive analysis for the effect of recess geometry on the overall performance of the bearing. In this study, a baseline model selected from the literature is constructed and validated using the ANSYS cfx computational fluid dynamics software package. A sensitivity analysis of the design variables on the performance of the bearing has been performed using design expert software. The length, width, and depth of the recess as well as the diameter and location of the five inlet ports have been selected as design variables. A multivariable and multi-objective genetic algorithm has also been solved using isight software with the goal of optimizing the geometry of the recess to maximize load capacity while minimizing bearing power loss from friction torque. The results of the baseline model show reasonable agreement with the experimental data published in the literature. The regression models for lift force and friction torque were both found to be statistically significant and accurate. It has been shown that friction torque decreases as the length of recess in the circumferential direction increases. The results showed that the load capacity is highly correlated to the diameter of the orifice, d. These results provide a deeper understanding of the relationship between the shape of the recess and bearing performance and are expected to be useful in practical hybrid-bearing design.

Modelling and analysis of elastic and thermal deformations of a hybrid journal bearing

Abstract The continuous demand for higher power density leads to a very challenging operational environment for sliding bearings regarding pressures and deformations. Understanding of the deformation behavior of heavily loaded bearings becomes even more pronounced when modern hybrid multilayer designs are considered. The aim of this study is to develop a numerical, multi-physical model for the evaluation of journal bearing performance. Hydrodynamics were based on the Reynolds equation and deformations were calculated using the integrated finite element method. Elastic and thermal deformations have a significant effect on bearing performance and those deformations can be adjusted with properties of polymer layer. The design of hybrid bearings is delicate and their properties must be tailored according to the operating conditions.

Study on the Static Performance and Stability of a Water-Lubricated Hybrid Bearing with Circumferential Grooves and Stepped Recesses Considering the Influence of Recess Sizes

Bearings are key components in high-speed and high-precision machine tools. Temperature rise and stability are significant for a rotor–bearing system in a high-speed spindle. This study proposes a water-lubricated hybrid bearing with circumferential grooves and stepped recesses to lower the temperature rise and improve bearing stability. A bulk-flow thermohydrodynamic model is developed to predict the static performance and stability of the bearing. A comparison of the results confirms the validity of the model and the improved characteristics of the hybrid bearing. A sensitivity analysis is conducted to quantify the influence of recess sizes on bearing performance. The discussion defines the key parameters of bearing performance and provides a useful guide for the optimal design of hybrid bearings.

A comparison of desing methodologies for journal bearings under pulsatile loads

The paper expands the work by Kinnear and Weston[1] on squeeze film bearing design to the general case and compares the revised methodology with classical bearing design[2,3,4] and hybrid bearing design[5]. The analysis, which employs a partial differentiation of the Poisseuille and Hagen-Poiseuille bearing flow equations, enables a mathematical model for the bearing squeeze film to be developed. This yields a transfer function between bearing displacement and load. Subsequent parameter maps are developed from the transfer function for stiffness and damping coefficients.The method enables hybrid journal bearings under pulsatile load to be considered. Current design methodologies employed do not cater for this situation adequately which limits effective design of these bearings in applications such as in internal combustion engine crankshaft bearings.

The influences of capillary restriction and journal eccentricity on the stability of the rigid rotor‐hybrid bearing system

PurposeThe present paper proposes a theoretical analysis of the stability characteristics of a rigid rotor‐hybrid bearing system. It is intended that on the basis of the numerical results drawn from this study, the optimal restriction parameter for stable operation can be determined for use in the bearing design process.Design/methodology/approachA rigid rotor supported by hybrid oil film bearings with six recesses and capillary‐compensated restrictors is studied. In order to facilitate the calculation of film dynamics, using the perturbation method, the Reynolds equation was linearized and subsequently solved using finite difference techniques, whilst the stability maps were determined by the Routh‐Hurwitz method.FindingsThe data reported here suggest that the stability characteristics of the rigid rotor‐bearing system could be improved by the use of shallow, dual‐recessed hybrid bearings with capillary compensation. For the same restriction parameter and the same land‐width ratio used in large eccentricity case the stability characteristics of a shallow‐recessed bearing is superior to that of a deep‐recessed bearing, however, a deep‐recessed bearing with a small land‐width ratio and a small restriction parameter can provide better stability than a shallow‐recessed bearing with a large land‐width ratio or with a large restriction parameter.Originality/valueThis study proposes an extensive database as a critical requirement in the design of hybrid bearings, in order to ensure that a rotor bearing system is operating stably.

Influences of recess depth on the stability of the Jeffcott rotor supported by hybrid bearings with orifice restrictors

PurposeThe present paper proposes a theoretical analysis of the stability characteristics of a Jeffcott rotor‐hybrid bearing system. It is intended that on the basis of the numerical results drawn from this study, appropriate recess depth, land size, orifice location and speed parameter for stable operation can be determined for use in the bearing design process.Design/methodology/approachA Jeffcott rotor supported by hybrid oil film bearings with dual‐row recesses and orifice‐ compensated restrictors is studied. In order to facilitate the calculation of film dynamics, using the perturbation method, the Reynolds equation was linearized and subsequently solved using finite difference techniques, whilst the stability maps were determined by the Routh‐Hurwitz method.FindingsThe data reported here suggest that the stability characteristics of the Jeffcott rotor‐bearing system could be improved by the use of shallow, dual‐recessed hybrid bearings with orifice compensation. In addition to greater eccentricity ratios, smaller land‐width ratios and greater shaft stiffness may also provide shallow‐recessed bearings with better stability. In all cases, the stability provided by upstream orifice‐sited bearings is better than that provided by center orifice‐sited bearings, whilst high‐speed parameters may also provide a greater stability threshold.Originality/valueThis study proposes an extensive database as a critical requirement in the design of hybrid bearings, in order to ensure that a rotor bearing system is operating stably.

A new basis for the optimization of hybrid journal bearings

A design strategy is presented for hybrid hydrodynamic/hydrostatic journal bearings which maximizes the hybrid load for minimum total power dissipation. It is shown that the detailed design of hybrid bearings is quite different from the design of recessed hydrostatic bearings. It is found that design for hybrid operation may lead to substantial increases in load support with significantly less total power dissipation than would be required if the designs were developed from hydrostatic bearing procedures. A new technique for optimizing hybrid journal bearings is presented. The method involves the comparison of the bearings to be optimized with a reference bearing on the basis of load/total power, load/pumping power and load/flow.