Analysis and Experimental Research on the Fluid–Solid Coupled Heat Transfer of High-Speed Motorized Spindle Bearing Under Oil–Air Lubrication

Abstract For high-speed motorized spindle bearing, temperature rise is the primary factor that restricts the maximum speed of spindle and affects the stability of system. This paper addresses the lubrication and cooling of spindle bearing by exploiting the precise oil control and high cooling efficiency of oil–air lubrication. Enlightened by the bearing tribology and two-phase flow theory, a numerical model of oil–air two-phase flow heat transfer inside bearing cavity is created, with which the effects of operating condition and nozzle structure parameters on the temperature rise are studied. As the results show, with the elevation in speed, the heat generation increases rapidly, and despite the somewhat enhanced heat transfer effect, the temperature still tends to rise. Given the higher volume fraction of air than oil in the two-phase flow, the temperature rise of bearing is suppressed greatly as the air inlet velocity increases, revealing a remarkable cooling effect. When a single nozzle is used, the bearing temperature increases from the inlet to both sides, which peaks on the opposite side of the inlet. In case multiple evenly distributed nozzles are used, the high-temperature range narrows gradually, and the temperature distributions in the inner and outer rings tend to be consistent. With the increase in the nozzle aspect ratio, the airflow velocity drops evidently, which affects the heat dissipation, thereby resulting in an aggravated temperature rise. Finally, the simulation analysis is verified through experimentation, which provides a theoretical basis for selecting optimal parameters for the oil–air lubrication of high-speed bearing.