Elrod Cavitation Algorithm Research Articles

Thermal Effects in Thrust Washer Lubrication

A numerical model was developed to study the thermal effects on the lubrication mechanism of radially-grooved thrust washers. A mass-conserving transient thermohydrodynamic (THD) analysis was performed by solving the modified Reynolds and energy equations for the lubricant pressure and temperature distributions. The heat transfer equations were also solved simultaneously to obtain the temperature fields of the solids (thrust washers). Due to different thermal time responses of the lubricant film and the solids, heat transfer equations of the runner and the thrust washer pad were treated as in quasi-steady state at each time step in the transient solution. Elrod cavitation algorithm was implemented to include lubricant cavitation. The results show that thermal effects do not only reduce load carrying capacity and the frictional torque but also increase side flow rate. Moreover, the numerical model also demonstrates that the thermal effects have greater influence on the load support when the groove depth and groove numbers increase. Furthermore, the analytical results also show that there exists certain operating conditions before thermal effects become the dominating factors in influencing the thrust washer performance.

Hydrodynamic lubrication of journal bearings including micropolar lubricants and three-dimensional irregularities

The effects of lubricant rheology and three-dimensional irregularities in hydrodynamic journal bearings are presented in this paper. This equation is incorporated into the Elrod cavitation algorithm. This numerical procedure, which conserves mass throughout the bearing, implicitly incorporates the JFO boundary conditions at rupture and reformation boundaries. Numerical simulation results show that the pressure distribution depends not only on micropolar fluid but also on asperity size.

A Transient Thermohydrodynamic Analysis Including Mass Conserving Cavitation for Dynamically Loaded Journal Bearings

A comprehensive transient thermohydrodynamic analysis for dynamically loaded journal bearings such as engine crankshaft bearings has been developed. A key element in this analysis is consideration of different time scales for the oil film, journal and bushing. Another important element of this analysis is consideration of moving grids in the oil film. Mass conserving cavitation is included via the Elrod cavitation algorithm. The 3-D energy equation is solved without any simplification in the oil film or the bushing. The journal is treated as a lumped thermal element. We found that the time scales for thermal transients in the oil film are of the same order as the period of the dynamic loading (one engine cycle for a crankshaft bearing); consequently, thermal transients in the oil film were considered. However, the time scales for thermal transients in the journal and bushing are several orders of magnitude greater than those for the oil film. Consequently, these elements were treated as if they were in quasi-steady state over one loading cycle. Results from this analysis are presented for an engine crankshaft main bearing under sinusoidal loading. Oil film temperatures are found to vary considerably over time and space.

Analysis of Hydrodynamic Journal Bearings Considering Lubricant Supply Conditions

A method of analysis of steadily loaded hydrodynamic journal bearings with a single axial groove (either on the load line or at 90° to the load line) or two diametrically opposed axial grooves is described. The method is based on Elrod's cavitation algorithm (which ensures conservation of mass flow in both the full film and the cavitated regions) and is able to accommodate specified lubricant supply conditions, namely groove size and location and supply pressure. Special attention has been given to the determination of flowrate. The equation governing the distribution of pressure around the bearing has been solved numerically using a finite differences approximation and multi-grid techniques to accelerate the convergence of the solution. Performance predictions of the analysis are compared with published experimental data and with experimental measurements obtained in laboratory tests carried out by the authors. The data used cover all grooving arrangements studied.

Performance Characteristics of Cavitated Noncircular Journal Bearings in the Turbulent Flow Regime

In this paper, the characteristics of noncircular bearings, considering the effects of turbulence and cavitation, are numerically analyzed. Four bearing profiles are considered: circular, worn-circular, two-lobe and elliptical. To model the turbulence, the linearized lubrication theory of Ng and Pan is used. Reynolds' equation is suitably modified to account for both turbulence and cavitation. The equation is incorporated into the Elrod cavitation algorithm. This numerical procedure, which conserves mass throughout the bearing, implicitly incorporates the JFO boundary conditions at rupture and reformation boundaries. JFO theory is considered to accurately model cavitation in moderately to heavily loaded bearings. Performance predictions are compared to results presented in a variety of earlier papers.

An Efficient, Robust, and Time Accurate Numerical Scheme Applied to a Cavitation Algorithm

In this paper, an implicit numerical scheme, based on an approximate factorization technique, is applied to a cavitation algorithm. The algorithm is a modified version of the Elrod cavitation algorithm, which automatically predicts film rupture and reformation in bearings. At each time step, Newton iterations are performed to achieve time accurate solutions for unsteady problems. This numerical scheme is applied in both orthogonal and nonorthogonal grid arrangements. An aligned finite grooved bearing and a flared, misaligned line grooved bearing are analyzed using this new approach. The predictions are compared with the results obtained with procedures currently being used. The new scheme is robust, quickly convergent, and provides time accurate solutions with a minimum expenditure of CPU time.

Effect of cavitation on the performance of a grooved misaligned journal bearing

A modified version of the Elrod cavitation algorithm, which automatically predicts film rupture and reformation in bearings, is used to analyze a misaligned grooved journal bearing. Two types of misalignment, axial (vertical displacement) and twisting (horizontal displacement), are considered. The predicted performance of the misaligned bearing is compared with available experimental and theoretical results. The analysis is performed on a line-grooved misaligned bearing for both flooded and starved inlet conditions. Effects of various degrees of starvation or higher lubricant supply pressure and bearing length-to-diameter ratio are also investigated for a particular misalignment condition.