A study of orifice compensated multilobe hole-entry hybrid journal bearing

The hydrostatic and hybrid journal bearings are finding increasing applications due to their excellent characteristics. The non-recessed hydrostatic/hybrid journal bearings have been developed so to provide an improved performance over the recessed/pocketed hydrostatic/hybrid journal bearings. The stability and unsteady behavior of the journal bearings is greatly influenced by bearing geometry, and accordingly various designs have been used by designers to achieve the desired objective. The non-circular journal bearings i.e. the multilobe journal bearing exhibits better stability as well as a superior capability to suppress whirl. In the present paper a theoretical study pertaining to a novel journal bearing configuration i.e. two-lobe hole-entry hybrid journal bearing is being presented. The work presented in this paper aims to study the performance of a two-lobe hole-entry hybrid journal bearing system compensated by a orifice restrictors. The Reynolds equation governing the flow of lubricant in the clearance space between the journal and bearing together with the equation of flow through an orifice restrictor has been solved using FEM and Galerkin's method. The bearing performance characteristics results have been simulated for an orifice compensated non-recessed two-lobe hole-entry hybrid journal bearing symmetric configuration for the various values of offset factor(delta), restrictor design parameter ((c) over bar (s2)) and the value external load((w) over bar (o)). Further, a comparative study of the performance of a two-lobe non-recessed hole-entry hybrid journal bearing system vis a vis circular hole-entry symmetric hybrid journal bearing system have also been carried out so that a designer has a better flexibility in choosing a suitable bearing configuration. The simulated numerical results for the non-recessed two-lobe symmetric hole-entry hybrid journal bearing system with an offset factor(delta) greater than one indicates a significant improvement of the order of 30 to 50 percent in the values of direct stiffness and direct damping coefficients as compared to a circular symmetric hole entry hybrid journal bearing system. The results presented in the paper are expected to be quite useful to the bearing designers as well as for the academic community.