Numerical Analysis of Oil Lubricated Journal Bearing with Herringbone Grooves

Herringbone grooved journal bearings (HGJBs) have been used for several high-speed turbomachinery such as turbo expanders, turbo generators, etc. The shallow herringbone grooves cut in one of the bearing surfaces act as a viscous pump, and it provides uniform pressure distribution and higher stability compared to the plain bearing. In practice, the herringbone grooves are made on the journal due to ease of fabrication compared to that of the inner side of the bearing surface. In case of any damage to the grooves, a complete replacement of the rotor is needed instead of the bearing. Mostly, this replacement is costly as the turbine or compressor wheels are an integral part of the rotor. The present manufacturing technology is quite advanced and cost-effective for the fabrication of herringbone grooves on the inner surface with precise dimensions and tolerances. Therefore, an attempt has been made by the authors to design an oil-lubricated journal bearing with herringbone grooves on the inner side of the bearing. This chapter describes the static characteristics analysis of HGJBs for high-speed applications. In this study, the numerical model has been developed using Reynold’s equation and is solved by the finite difference method. The film thickness profile, hydrodynamic pressure distribution, and load carrying capacity (LCC) are calculated. Further, the influences of structural parameters such as groove width ratio, groove depth ratio, number of grooves, groove angle, and eccentricity ratio for the performance of HGJBs are analyzed. Results are then compared with plain journal bearings (PJBs).