Water Pump Porous Bearing Design Analysis

Applying hydrodynamic lubrication theory for porous bearings and boundary lubrication theory, this paper presents a method of analyzing the performance of a water-lubricated sleeve type porous bushing in an automotive water pump design. Relations of bearing load capacity versus shaft speed have been obtained and compared for sintered iron-graphite bushings (a cermet material developed by the Ford Motor Co.), sintered iron or sintered bronze bushings, and steel bushings. The load capacity was computed, based on a minimum allowable film thickness during hydrodynamic operation, and on a maximum allowable temperature during boundary lubrication operation. The results show that sintered iron-graphite bushings are superior to sintered iron or sintered bronze bushings, as well as steel bushings, in this application, due to the lower coefficient of friction. The computations are in agreement with bench test and vehicle test results on an experimental water pump having a sintered iron-graphite bushing, both analytical and experimental results indicating acceptable performance of the coolant lubricated sintered iron-graphite bushing. The present analysis, therefore, offers a bearing design method for this or similar applications.