A New Singularity Treatment Approach for Journal-Bearing Mixed Lubrication Modeled by the Finite Difference Method With a Herringbone Mesh

Purpose




The prediction model to estimate the stability of a rotor-bearing system is established, which can predict the stability of gas bearings by applying Routh–Hurwitz stability criterion. This paper aims to provide the theoretical foundation for controlling actively the bearing running stiffness and damping and stemming the instability of a gas film.




Design/methodology/approach




The nonlinear dynamic lubrication analysis mathematical model of spherical hybrid gas bearings is established. Perturbation control equation is derived by the partial derivative method. The finite difference method is used to discrete the perturbation control equation in generalized coordinate system, and the difference expression of perturbation pressure is derived. The relational expression which involves the relationship between the dynamic characteristic coefficients of HSGHGB systems and perturbation pressure is deduced. So, the transient perturbation pressure distribution of a three-dimensional micro gas film, nonlinear gas film force, dynamic stiffness and dynamic damping coefficients of bearings are numerically computed using VC++6.0 programs.




Findings




The results show that the influence of supply pressure, speed and eccentricity on the dynamic characteristics of bearings is significant.




Originality/value




The influence law of supply pressure, speed and eccentricity ratio on the dynamic stiffness and damping coefficients of HSGHGB systems is researched. The prediction model to estimate the stability of rotor-bearing system is established, which can predict the stability of gas bearings by applying the Routh–Hurwitz stability criterion.

Analysis of dynamic characteristics and stability prediction of gas bearings

Taking the hemisphere spiral groove hybrid gas bearings (HSGHGB)as the research object, the nonlinear dynamic lubrication analysis mathematical model of spherical hybrid gas bearings is established with the axis instantaneous position and instantaneous displacement speed as the parameters. The perturbation pressure control equation is solved by means of the finite difference method in generalized coordinate system. The calculation program is prepared based on VC++6.0, and the transient perturbation pressure distribution of three-dimensional gas film, nonlinear gas film force, and dynamic stiffness and damping coefficients are numerically calculated. The influences of different speeds, eccentricity ratios and gas supply pressures on the dynamic characteristic coefficients of gas film are studied. The results show that the influence of bearing's supply pressure, speed and eccentricity on the dynamic characteristics of gas film is significant. The dynamic equations of rotor-bearing system containing the gas film dynamic stiffness and the damping coefficients are established, and the stability of the gas film is predicted based on the Routh-Hurwitz stability criterion. The research provides the theoretical foundation for controlling actively the bearing running stiffness and damping and stemming the instability of gas film.

Dynamic Stability Prediction of Spherical Spiral Groove Hybrid Gas Bearings Rotor System

As a self-acting fluid-lubricated herringbone grooves journal bearing, a trapezoidal cross-sectional shape of grooves is considered. Trapezoidal groove shape effects on its bearing characteristics such as variations of load capacity, attitude, and friction torque for various trapezoidal angle of groove are determined.

/pdf/the-effects-of-trapezoidal-groove-on-a-self-acting-fluid-17q8qtkdwa.pdf

The Effects of Trapezoidal Groove on a Self-Acting Fluid-Lubricated Herringbone Grooves Journal Bearing

This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/). Bearing Capacity Analysis of Spherical Hybrid Gas Bearings with Tangential Gas Supply Chenhui Jia , Jing Gao , Ming Qiu c and Wensuo Ma d School of Mechatronics Engineering, Henan University of Science and Technology, Luoyang 471003, China. xjiachenhui@163.com, 15838842452@163.com, qiuming69@126.com, mawensuo@126.com

/pdf/bearing-capacity-analysis-of-spherical-hybrid-gas-bearings-2w0oplqzgo.pdf

Bearing Capacity Analysis of Spherical Hybrid Gas Bearings with Tangential Gas Supply

A modified Reynolds equation for an oil-lubricated journal bearing is derived, including curvature effect under a lubrication theory, and the curvature effect on characteristics of the journal bearing is discussed. In addition, in case of a herringbone-grooved journal bearing with trapezoidal cross-sections, the modified Reynolds equation is solved, using a spectral finite difference method to get characteristics such as variation of load capacity and attitude angle for trapezoidal angles of from 1.8 through 7.2 degrees.

Jun Liu

Papers

Analysis of oil-lubricated herringbone grooved journal bearing with trapezoidal cross-section, using a spectral finite difference method