Effects of oil inlet pressure and inlet position of axially grooved infinitely long journal bearings. Part I: Analytical solutions and static performance

This paper presents analytical expressions for the dynamic pressure and dynamic fluid force in axially grooved long journal bearings with consideration of oil inlet pressure and inlet position. The effects of oil inlet pressure (in the range of , where the dimensionless oil inlet pressure ) and oil inlet position (in the range of 0Θ_i90°) on the static oil film configuration, pressure distribution, and steady state journal position in axially grooved journal bearings are discussed. In this paper, Reynolds–Floberg–Jakobsson boundary conditions are assumed to account for the appropriate starting position of the cavitation, the reformation of oil film at the end of caviation, and the effect of oil inlet pressure and inlet position.     

Thermo-hydrodynamic analysis of herringbone grooved journal bearings

Steady-state and stability characteristics of herringbone grooved journal bearings (HGJBs) are found considering thermal effect. The temperature of the fluid film rises significantly due to the frictional heat, thereby the viscosity of the fluid and the load carrying capacity decrease. A thermodynamic analysis requires the simultaneous solution of Reynolds equation along with energy equation of the fluid and heat conduction equations in the bush and the shaft. The linearized first-order perturbation technique is employed for the prediction of stiffness and damping coefficients of the oil film. Thereafter mass parameter and whirl ratio are found from the stability analysis. It is difficult to obtain the solution due to the numerical instability when the bearing is operated at high eccentricity ratios.     

内燃机进气压力的小波分析

探讨了进气压力信号与气阀机构状态之间的关系，对进气压力信号进行二进小波分解，利用分解后尺度1信号的频域特征对气阀机构进行状态分类与识别。结果与实例分析表明方法是有效和可行的。     

Stability analysis of externally-pressurized gas-lubricated porous bearings with journal rotation Part 1. Cylindrical whirl

Whirl stability (cylindrical) of externally-pressurized gas-lubricated porous journal bearings, considering one-dimensional flow through the porous matrix, is analysed by a first-order perturbation method. The effect of supply pressure, feeding parameter, porosity parameter and length-to-diameter ratio on the stability is also investigated.     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

Stability analysis of externally-pressurized gas-lubricated porous bearings with journal rotation Part 2. Conical whirl

The stability analysis of externally pressurized gas journal bearings under conical mode of vibration has been obtained using a first-order perturbation method. The effect of journal speed, feeding parameter, supply pressure, porosity parameter and length-to-diameter ratio on the conical whirl and whirl ratio has been investigated.     

Maximum oil film pressure and temperature of two‐iobe journal bearings with different bush profiles

This paper presents data on the maximum oil film pressure and temperature of two‐lobe journal bearings with different bore profiles. A bearing with a cylindrical non‐continuous bore profile, and another with a pericycloid continuous profile have been evaluated. For an assumed relative length of the bearings, and parallel orientation of the journal and bearing axes, the minimum values of oil film thickness, maximum pressure values, and temperatures of the oil film have been determined. The calculations were carried out on the assumption of an adiabatic oil film and a static equilibrium position of the journal.     

On the Dynamics of Lubricated Cylindrical Roller Bearings,Part II: Linear and Nonlinear Vibration Analysis

This article is the second part of two companion papers. In the first article, curve-fitted relations of stiffness and damping coefficients of a single roller-to-race contact of lubricated roller bearings were developed. In the present work, these relations are applied to a rotor–bearing system. Two cases are studied to investigate the influence of lubricated cylindrical roller bearings on the vibration characteristics of the rotor system. In the first case, lubricated contacts are simulated as a linear spring–damper model. The overall stiffness and damping matrices are calculated by using the dynamic coefficients of individual load sharing rollers. These matrices are used in the finite element analysis of flexible rotor. In the second case, the nonlinear structural vibration of a lubricated cylindrical roller bearing is studied. Equations of motion of bearing elements are derived using the Lagrange equation. A nonlinear load–deflection contact model developed through the derived curve-fitted relations of dynamic coefficients is used in the equations of motion. Equations of motion are solved by a fourth-order Runge-Kutta integration method. The response of bearing elements under free vibration and due to rotating unbalance is studied for damped and undamped cases. Furthermore, results obtained using elastohydrodynamic finite and infinite contact theories are compared.     

Limit analysis of strain-hardening viscoplastic cylinders under internal pressure by using the velocity control: Analytical and numerical investigation

The paper aims to assess plastic limit loads of thick-walled hollow cylinders of strain-hardening viscoplastic materials under internal pressure. Particularly, the problem concerned features in the interaction between strengthening and weakening behavior during the deformation process. Therefore, the relating onset of instability and the stability condition also deserve to be further investigated. Analytical and finite-element limit analysis efforts are both made for complete and comparative investigation. By the concept of sequential limit analysis, the plastic limit loads were acquired by solving a sequence of limit analysis problems via computational optimization techniques. Applying the velocity control as a computational strategy to simulate the action of pressure, the paper investigates analytically and numerically the plastic limit load, the onset of instability and the stability condition of plane-strain circular cylinders. Especially, analytical solutions of the onset of instability were solved explicitly by the fixed point iteration. Validation of the present analytical and finite-element efforts was made completely with good agreement between the analytical solutions and the numerical results.     

Influence of an applied electric field on the torque of rotary lip seals on metal shafts. Part II: Effects of oil type

The experimental results are presented of research on the tribocharging of selected engine oils and on the effect of an auxiliary external DC electric field on the work of rotary machinery. There exists an effect of the type of oil, its temperature, and the electric field on the braking torque of rotating parts such as shafts, crankshafts, etc. sealed with lip seals. The research was especially aimed at the possibility of reduction in the torque under external electric fields for different engine oils. To obtain the auxiliary electric field the DC voltage was applied between the stiffening ring of a fluorocarbon lip seal and the rotating, earthed shaft in the metal shaft–oil film–lip seal system. The measurements of the torque were performed under steady state conditions for given different oil temperatures, angular shaft velocities, and voltages; also three different oils were used. It was found that for the lip seal under test the negative voltage applied produced a beneficial effect on the torque depending on the type of oils.