Performance prediction of externally pressurized gas bearings for high-speed turbo-expander involving hydrogen, helium and air working fluids

Abstract

High-speed hydrogen turbo-expander is widely employed in hydrogen liquefaction systems due to its high efficiency. The hydrogen bearings in high-speed turbo-expander are usually applied for low viscosity and pollution-free advantages. Nevertheless, the load capacity of hydrogen bearing is low and the research on maximizing the load capacity is limited by the complicated solution process and danger hydrogen experiment. The purpose of the paper is to easily and quickly acquire the load capacity of high-speed orifice externally pressurized hydrogen journal bearing for optimization of bearing performance. A new simple load capacity predicted model, that is universal for various working fluids involving hydrogen, helium and air, was proposed through the hydrostatic and hydrodynamic analysis. In the model, the evaluation indicators of hydrodynamic and hydrostatic effects were proposed. Based on the model, no numerical analysis and computer programming are needed to calculate the load capacity of journal bearing and numerous key design variables are considered. The results from the predicted model agree very well with those obtained from the finite difference method (FDM) technique. In view of the danger of hydrogen bearing experiment, the load capacity predicted model can be used to design the equivalent experiment of load capacity through substituting air for hydrogen working fluid.