Hybrid hydrodynamic–hydrostatic lubrication of journal–thrust coupled bearings in high-speed pumps

High-speed pumps hold substantial potential in high-performance and highly integrated applications. Bearings are critical for ensuring stable operation of high-speed pumps. Fluid-lubricated bearings offer low friction and nearly negligible wear, thereby providing superior reliability and service life. However, existing journal–thrust coupled fluid bearings rely predominantly on hydrodynamic lubrication, which requires surface grooves on thrust bearings or tilting thrust pads and thus imposes stringent demands on manufacturing and assembly accuracy. To overcome these limitations, this study proposes a novel journal–thrust coupled bearing (JTCB) that integrates hydrodynamic and hydrostatic lubrication mechanisms. A full-pump numerical model that simultaneously accounts for the hydraulic flow domain and the lubrication film domain was developed, and its correctness was validated through experimental tests. Using this model, the pressure distribution, velocity field, and force characteristics of the JTCB were comprehensively analyzed, demonstrating that the journal bearing operates under hydrodynamic lubrication, whereas the thrust bearing provides support through hydrostatic lubrication, thereby confirming the unique hybrid-lubrication mechanism of the JTCB. Furthermore, the coupling effects between the journal and thrust bearings were explored, revealing significant impacts on the surface pressure distribution, load capacity, and friction behavior. Finally, the variation of the lubrication characteristic parameters of the JTCB under different rotational speeds was investigated.