On the Static and Dynamic Performance of Short Spiral Hydrodynamic Journal Bearing

Hydrodynamic journal bearings with circular cross section, when used in high speed rotating machinery such as Turbines, Compressors, Pumps, Engine Cranks and Large Milling Systems, etc., often face the problem of instability. In such high speed machinery non-circular bearings are widely used to support the oil whirl. The present paper focuses on one of the non-circular bearings called Spiral Bearing. Out of the two forms of spiral bearings i.e., convergent and divergent types, the study is done on static performance characteristics of short convergent spiral hydrodynamic journal bearing. After evaluating the fluid film thickness for the convergent spiral bearing, Reynolds equation is used to find the fluid film pressure and then in turn load carrying capacity, attitude angle and friction parameter are calculated. To obtain a closed form solution, the short bearing approximation is considered. Theoretical investigations on stability characteristics of hydrodynamic spiral journal bearing are also presented and then comparing with circular bearing. The results show that the effect of preload factor on bearing performance is significant. Compared to the narrow circular bearing, short spiral bearing has more load carrying capacity and stability towards oil whirls.