Oil Journal Bearings Research Articles

Fault location of tribo-mechanical systems—a graph theory and matrix approach

Abstract A procedure for the fault location of tribo-mechanical systems based on graph theory and matrix approach is presented. A component digraph which represents the failure propagation network of the tribo-mechanical system is developed for identification of fault location sources and failure paths. Starting from the nodes that indicate abnormal states, some nodes from the component digraph are selected as the probable candidates of failure origin by back-tracing. These candidates are further screened by using failure propagation probabilities and failure propagation time between adjacent nodes, and back-tracing. Finally, the failure propagation probabilities and failure rates of the devices are used to evaluate the ranking order among the screened candidates for fault location. The faults are located through pre-processing and alarm processing of the digraph. The methodology is applied to a journal bearing oil supply system for a thermal power plant.

Stability of Flexibly Supported Oil Journal Bearings Using Non-Newtonian Lubricants: Linear Perturbation Analysis

The purpose of this paper is to study the effect of non-Newtonian lubricant on the stability of oil film journal bearings mounted on flexible support using linear perturbation technique. The model of non-Newtonian lubricant developed by Dien and Elrod is taken into consideration. The dynamic co-coefficients are calculated for different values of power law index and length to diameter ratio. These are then used to find stability margin for different support parameters to study the effect of the non-Newtonian lubricant.

Effect of fluid inertia on stability of flexibly supported oil journal bearings: linear perturbation analysis

A theoretical analysis to study the effect of fluid inertia on the stability of oil film journal bearings mounted on flexible support using linear perturbation technique is presented. The Navier–Stokes equations have been solved using the parabolic velocity profile. The dynamic coefficients are calculated without neglecting the mass of the oil in the bearing for different length to diameter ratios and modified Reynolds numbers. These are then used to find stability margin for different support parameters to study the effect of fluid inertia.

Effect of Fluid Inertia on Stability of Oil Journal Bearings

In the analysis of hydrodynamic journal bearings the effect of fluid inertia is generally neglected in view of its negligible contribution compared to viscous forces. However, the fluid inertia effect is to be taken in the analysis when modified Reynolds number is around one. Though there are a few attempts to analyze steady-state and dynamic characteristics of finite journal bearings, stability of the journal under the effect of fluid inertia is yet to be investigated. An attempt has been made to evaluate the mass parameter (a measure of stability) besides finding out the steady-state characteristics of finite journal bearings considering the effects of fluid inertia. The analysis is carried out for modified Reynolds number ∼O(1.), which is assumed to be laminar. A nonlinear time transient analysis is carried out for the stability analysis. [S0742-4787(00)00204-6]

Thermohydrodynamic Analysis of Submerged Oil Journal Bearings Considering Surface Roughness Effects

A theoretical study of a submerged oil journal bearing is made considering surface roughness and thermal effects. The total load-supporting ability under such condition is due to the thermohydrodynamic as well as the asperity contact pressure. The effect of surface roughness and viscosity-temperature dependency on hydrodynamic pressure has been found by solving the average Reynolds equation, energy equation and heat conduction equations simultaneously. The cavitation model of Jacobsson-Floberg has been modified to take the surface roughness effects into consideration. A parametric study of steady-state behavior has been carried out. Finally, the isothermal, thermohydrodynamic, and contact loads for a model bearing have been calculated, assuming the surface height distribution as Gaussian.

Stability Analysis of Flexibly Supported Rough Submerged Oil Journal Bearings

A theoretical analysis is presented to study the effect of support stiffness and damping on the transient response of flexibly supported rotor-bearing systems, considering surface roughness. The transient response of rotor is plotted in the form of trajectories. The average Reynolds equation, which uses the Patir and Cheng flow simulation model of rough surfaces, is solved by the finite difference method with a successive over-relaxation scheme (Gauss-Seidel), while the equations of motion of both the rotor and bearing are solved by the fourth-order Runge-Kutta method. It has been found that the surface roughness considerably affects the stability of a rotor-bearing system and the stability may be improved greatly by a proper design of bearing supports.

Steady-state behaviour of flexible rotordynamic systems with oil journal bearings

This paper deals with the long term behaviour of flexible rotor systems, which are supported by nonlinear bearings. A system consisting of a rotor and a shaft which is supported by one oil journal bearing is investigated numerically. The shaft is modelled using finite elements and reduced using a component mode synthesis method. The bearings are modelled using the finite-length bearing theory. Branches of periodic solutions are calculated for three models of the system with an unbalance at the rotor. Also self-excited oscillations are calculated for the three models if no mass unbalance is present. The results show that a mass unbalance can stabilize rotor oscillations.

Non-linear Transient Analysis of Submerged Oil Journal Bearings Considering Surface Roughness and Thermal Effects

A time-transient non-linear analysis has been carried out to study the influence of surface roughness and viscosity-temperature dependency on stability of a submerged oil journal bearing. The average Reynolds equation has been solved simultaneously along with the energy equation and heat-transfer equation in bush and shaft. The cavitation model, proposed by Kicinski along the lines of Jacobsson-Floberg theory, has been modified to account for the surface roughness effects. The effect of various surface roughness parameters, such as the composite surface roughness, roughness orientation pattern and variance ratio, on the stability has been studied. The non-linear transient analysis of submerged oil journal bearings under (a) a unidirectional constant load, (b) a unidirectional periodic load and (c) a variable rotating load is performed.

Robust Control of Rotor-Bearing Systems Using H-infinity Design

This paper describes a procedure for designing an H-infinity (H∞) controller for a rotor-bearing system. The system consists of a rotor, supported by journal bearings, together with a magnetic actuator which is used to apply the control forces. The frequency characteristics of the actuator and modelling uncertainty at higher frequencies are accounted for. A computer simulation shows that rotor vibration can be significantly reduced by using the H∞ control strategy. The system robustness is also demonstrated in a comparison with pole placement strategies. In particular, the H∞ strategy does not suffer from modelling uncertainty spillover and is effective in stabilising the system at high running speeds. the destabilising influence being caused by journal bearing oil whirl.

Stability of submerged oil journal bearings, considering thermal effects

The stability of submerged oil journal bearings was investigated considering thermal effects. The generalized Reynolds equation was integrated using the cavitation model proposed by Kicinski along the lines of Jakobsson-Floberg-Olsson theory. Heat transfer between the film and both the bush and the shaft is taken into account. The viscosity is assumed to vary with temperature according to an exponential law. The results are compared with those obtained when temperature effects were neglected.

Stability of submerged four-lobe oil journal bearings under dynamic load

A non-linear transient method was used to predict the journal centre trajectory for a submerged four-lobe oil journal bearing under (1) unidirectional constant load, (2) unidirectional periodic load, and (3) variable rotating load. The Reynolds equation was integrated using the Jakobsson-Floberg-Olsson cavitation zone model, and oil film prehistory effects were taken into account. The journal centre trajectories obtained were compared with those obtained for submerged plain cylindrical bearings under similar loading conditions. It was observed that the excursions of the journal centre were subdued, unlike for the plain cylindrical bearings, where the journal centre had a large excursion before it became stable or ended in a limit cycle. Interesting trajectories were observed for the periodic load. A three-dimensional plot of the pressure distribution in the bearing clearance was obtained using computer graphics.

Theoretical analysis on conical whirl instability of unloaded submerged oil journal bearings

A nonlinear transient method is used to analyse the stability characteristics of an unloaded rigid rotor supported in submerged oil journal bearings undergoing conical whirl. The rotor has two degrees of freedom of motion in a self-excited conical whirl. The analysis considers cavitation effects, takes account of the oil film history and assumes that antisymmetry is maintained in the conical mode of vibration. The time-dependent form of the Reynolds equation (with the journal in the misaligned position) is solved by a finite-difference method with a successive over-relaxation scheme to obtain the moment components. Using these moment components, the equations of motion are solved by a fourth-order Runge-Kutta method, to predict the transient behaviour of the rotor. Journal centre trajectories in orthogonal coordinates are obtained for different operating conditions, using a high-speed digital computer and graphics.

Ultrasonic monitoring of bearing wear in situ.

Of concern are wear measurements of surfaces of bearing seals and valves. It will be seen that these may be implemented in terms of ultrasonic transducer arrays, constructed so as to be an integral part of the wear surface, monitoring insitu the amount and rate of the material removed. The associated data are assembled and manipulated in real time allowing for computer control and prediction. Technical aspects of the device will be discussed including journal bearing oil film measurements and the displacement and orbit of the rotating shaft. [Work supported by TecSonics, Inc. of Twinsburg, Ohio, Ohio Edison, and EPRI.]

Does the automotive industry need a standard engine test to measure journal bearing oil film thickness?

AbstractAutomotive manufacturers are dissatisfied with the high‐temperature portion of the SAE Viscosity Classification, J300. This dissatisfaction occurs because the low‐shear, 100°C conditions at which viscosities are specified are not representative of the conditions to which oils are subjected at operating temperatures in an engine. Recent efforts to modify the high‐temperature viscosity specifications have dealt primarily with developing correlations between oil film thickness measured in the journal bearings of operating engines and viscosity values measured at different high‐temperature, high‐shear rate conditions in laboratory viscometers. However, it has also been suggested that the industry develop a standard engine test for measuring journal bearing oil film thickness, and that oils be ‘classified’ on the basis of film thickness rather than viscosity. This paper reviews the methods which have been developed to measure bearing film thickness, the correlations which have been calculated between film thickness and viscosity, and the conclusions drawn from such efforts. Reasons for relying on high‐temperature, high‐shear viscosity specifications rather than a standard industry bearing film thickness test are offered. In addition, the merits and drawbacks of developing an industry bearing distress test are also discussed.

Stability of submerged oil journal bearings under dynamic load

This paper analyses the stability characteristics of submerged oil journal bearings taking into account the oil film history. A linearized perturbation theory about the equilibrium point can predict the threshold of stability but does not reveal post-whirl orbit detail. For this reason a non-linear analysis of a rigid rotor supported on oil journal bearings under unidirectional constant load, unidirectional periodic load and variable rotating load is carried out. The time-dependent form of the Reynolds equation is solved by a finite difference method with a successive overrelaxation scheme to obtain the hydrodynamic forces. Using these forces, the equations of motion are solved by the fourth-order Runge-Kutta method to predict the transient behaviour of the rotor. Journal centre trajectories are obtained for different operating conditions using a high speed digital computer and graphics.

Stability of a Rigid Rotor Supported on Rough Oil Journal Bearings

This investigation deals with the stability of rigid rotors supported on finite rough oil journal bearings using perturbation method. The effect of various surface roughness parameters, viz., composite surface roughness, roughness orientation pattern and variance ratio on the stability has been studied. In general, surface roughness effect when incorporated into the analysis does not show a significant change in the stability for surfaces having same roughness structure. However, the effect of variance ratio (i.e., surfaces having different roughness structure) on stability is quite marked.

Closure to “Discussion of ‘Stability of a Rigid Rotor Supported on Flexible Oil Journal Bearings’” (1988, ASME J. Tribol., 110, p. 579)

Closure to “Discussion of ‘Stability of a Rigid Rotor Supported on Flexible Oil Journal Bearings’” (1988, ASME J. Tribol., 110, p. 579)

Stability of a Rigid Rotor Supported on Flexible Oil Journal Bearings

This investigation deals with the stability characteristics of oil journal bearings, including the effect of elastic distortions in the bearing liner. Graphical results are presented for (1) steady-state load, (2) stiffness and damping coefficients, and (3) the stability. These results are given for various slenderness ratios, eccentricity ratios, and elasticity parameters. The lubricant is first assumed to be isoviscous. The analysis is then extended to the case of a pressure-dependent viscosity. It has been found that stability decreases with increase of the elasticity parameter of the bearing liner for heavily loaded bearings.

Stability of a Rigid Rotor in Finite Externally Pressurized Oil Journal Bearings With Slip

A theoretical analysis has been carried out to determine the stability characteristics of externally pressurized porous oil journal bearings of finite length considering the tangential velocity slip at the bearing-film interface. The stability curves have been drawn for different slip parameters, eccentricity ratios, slenderness ratios, bearing speed parameters etc.

Study of conical whirl instability of hydrodynamic porous oil journal bearings with tangential velocity slip

A theoretical analysis is presented for the stability characteristics of the conical whirling of an unloaded rigid rotor supported in hydrodynamic porous oil journal bearings with tangential velocity slip on the bearing film interface. The rotor has a two degree of freedom motion in self-excited conical whirling. In the stability analysis, the effect of various parameters on stability has also been investigated.