Rohit S. Paranjpe

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. Th 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 Crankshaft Bearings Using a Mass Conserving Algorithm

A mass conserving algorithm (Elrod algorithm) which uses the Jakobsson, Floberg, and Olsson cavitation boundary conditions has been implemented to analyze crankshaft bearings. The main and connecting rod bearings of a typical automotive engine are considered. Some sample steady-state results are presented. The inverse problem (given the load, find the journal orbit) is solved for real engine loads. Comparisons are made with a non-conservative algorithm based on the Reynolds boundary condition. Significant differences in the cavitation zones and oil flows are observed between the two algorithms. In all cases, the oil flow into the bearing is found to match the oil flow out of the bearing for the Elrod algorithm. Presented at the 44th Annual Meeting in Atlanta, Georgia May 1–4, 1989

A Study of the Thermohydrodynamic Performance of Steadily Loaded Journal Bearings

A comprehensive thermohydrodynamic (THD) analysis of steadily loaded journal bearings has been developed that includes mass conserving cavitation, full solution of the 3-D energy equation in the oil film, heat conduction in the bushing and journal, mixing of hot circulating oil with fresh supply oil and solution of the inverse problem (given the load, find the film thickness). The temperature distribution in the oil film and bushing is found using a coupled approach where the same 3-D energy equation is solved in both the oil film and bushing. With this approach the steady-state problem can be solved without iterations between the thermal solutions in the oil film and the bushing, thereby allowing ready analysis of multilayer bushings. Predictions of the analysis compared very well with measurements reported by Dowson et al. (1). A thermohydro-dynamic study of bearing performance as a function of clearance for a typical automotive bearing revealed that there is an optimum clearance that gives the largest ...

A Study of Dynamically Loaded Engine Bearings Using a Transient Thermohydrodynamic Analysis

A comprehensive, transient thermohydrodynamic (THD) analysis for dynamically loaded journal hearings presented earlier (1) is used to study the performance of dynamically loaded engine crankshaft hearings, i.e., main hearings and connecting rod. bearings. Oil film temperatures are found, to vary considerably over time and space. This variation can he explained, from the journal orbit diagram. A simplified thermal analysis which uses a single effective oil film temperature calculated from overall, energy conservation is also developed. Comparisons are made between the predictions of the full THD analysis, an adiabatic THD analysis and the simplified thermal analysis. The adiabatic THD analysis compares well with the full THD analysis. The simplified thermal analysis compares reasonably well with the full THD analysis and is a significant improvement over an isothermal analysis. Presented as a Society of Tribologists and Lubrication Engineers paper at the STLE/ASME Tribology Conference in Kissimmee, Florida...

Comparison between Theoretical Calculations and Oil Film Thickness Measurements Using the Total Capacitance Method for Crankshaft Bearings in a Firing Engine

Comparisons were made between theoretical calculations and experimental measurements for minimum bearing oil film thickness (MBOFT) in main and connecting rod bearings of a typical automotive V6 engine running at 1500 rpm under three load conditions (64, 128, and 192 Nm.). Data for five oils (SAE grades 5W–20, 20W–20, 5W–30, 10W–30, and 20W–50) were obtained for the main bearing and for two oils (SAE 5W–30 and 10W–30) for the connecting-rod bearing. The theoretical calculations were done using the FLARE computer code while the measurements were made using the total capacitance method (TCM). Considering the complexities involved in a firing engine, overall, reasonably good agreement between theory and experiment was observed, especially for the absolute minimum of the MBOFT (MBOFTmin). The experimental data showed higher dependence on the Sommerfeld number than that of the theoretical calculations for the main bearing. The shapes of the MBOFT vs. crank angle curves were also similar between theoretical predictions and experimental measurements, although there were differences as well. Several causes of discrepancy affecting both the calculations and the measurements were investigated. Bearing non-circularity, cavitation, and crankshaft flexibility and dynamics were identified to be the main causes of the discrepancy. A novel approach based on analysis was developed for estimating the error in the based on analysis was developed for estimating the error in the oil film thickness measurements using TCM due to cavitation and bearing non-circularity, including the presence of holes and grooves. Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999