Abstract
This work presents a novel design of a hybrid thrust foil bearing (HTFB) with an outer diameter of 154mm, along with simulation and test results. The HTFB incorporates a high-pressure air/gas injection to the taper portion of the thrust foil bearing, boosting the hydrodynamic effect on the main bearing surface and hydrostatic load capacity at zero speed. As a result, this bearing has high load capacity, low power loss, and no friction/wear during startup and shutdown. Firstly, push-pull tests were conducted on a double-acting HTFB configuration to evaluate the nonlinear structural stiffness of the bump foil structure. The measured nonlinear stiffness model was adopted to predict the overall bearing performance under various speeds and external loads. The bearing performance was predicted at 40krpm, 3000N axial load, and 6 bar absolute hydrostatic pressure in both hydrodynamic and hybrid modes. The simulation uses an advanced model which predicts the 2D plate top foil deflection with physical bump locations mapped from the actual hardware. The simulation confirms that the hybrid operation significantly increases the minimum film thickness compared to hydrodynamic bearing due to the boost effect of hydrodynamic pressure in the main film. The preliminary experimental measurements on load capacity at zero speed agree with the prediction. Rotational tests were conducted at 10krpm, 15krpm and 20krpm. Ultimately, the novel HTFB shows excellent static performance with potential for use in Organic Rankine Cycle (ORC) generators and other large oil-free turbomachines.
