Static Performance of a Hydrostatic Thrust Foil Bearing for Large Scale Oil-Free Turbomachines

Abstract

This work presents a novel design of a hydrostatic thrust foil bearing (HSTFB), with an outer diameter of 154 mm, along with simulation and test results up to a specific load capacity of 223 kPa (32.3 psi). This bearing has high load capacity, low power loss, and no friction/wear during startup and shutdown. In addition, the HSTFB allows for bidirectional operation. The paper also presents an advanced simulation model that adopts the exact locations of tangentially arranged bumps to a cylindrical two-dimensional plate model of the top foil. This method predicts top foil deflection with better accuracy than the traditional independent elastic foundation model, which distributes the bump locations over the nodal points in the cylindrical coordinates, and with less computational resources than the finite element method applied to the entire bumps/top foils. The presented HSTFB was designed for organic Rankine cycle (ORC) generators, but its performance was predicted and measured using air in this paper. The bearing static performance is compared analytically against the rigid counterpart and presented at different supply pressures, speeds, and minimum film thicknesses. Experimental verification is conducted at 10, 15, and 20 krpm. The measured load capacity and frictional loss agree well with the prediction. The measured film thickness also agrees with the prediction after the structural deflection of the thrust runner disk is compensated. Overall, the novel HSTFB demonstrates excellent static performance and good potential for the intended ORC generators and other large oil-free turbomachines.