Theoretical Comparison of Characteristics between Elliptical and Conventional Hydrodynamic Journal Bearing

Abstract

In this research, two subjects are presented. The first one was, studying the effect of the ellipticity ratio on the bearing performance characteristics (flow rate, load number, power absorbed, and stiffness coefficients), where three different values of the ellipticity ratio (0.5, 1, and 1.5) were studied and the conventional bearing was considered as a reference for comparison with the elliptical bearing of different values of ellipticity ratio to demonstrate the effect of ellipticity ratio on the bearing performance, while the other aspect was, studying the effect of aspect ratio on the elliptical bearing performance. Three different values of aspect ratio (0.5, 1, and 1.5) were studied. This was achieved within the range (0.1 - 0.8) for the eccentricity ratio. The finite difference method was used to solve Reynold’s equation numerically to obtain the pressure distribution on the bearing surface and then the bearing characteristics were computed. The computer program (Matlab R2015a) was used for solving the equations used in this study. From the results, it was observed that increasing the ellipticity ratio gives an increase in the flow rate values and a decrease in the (load number, power losses, Krr, Kss, |Krs| and Ksr) values, while, increasing the aspect ratio gives an increase in the (flow rate, power losses, Krr, Kss, |Krs| and Ksr) values and a decrease in the load number values. It was also observed that the elliptical bearing has a (higher flow rate, lower load capacity, and less power losses), than the conventional bearing. In addition, the elliptical bearing has higher principle stiffness coefficients (Krr and Kss) in the region (n<0.41) and (n<0.66), respectively, and lower cross-coupling stiffness coefficients (Krs and Ksr), than the conventional bearing.