Influence of Straight Radial Groove Texture On the Performance of Gas Foil Thrust Bearings with and Without Slip Flow

Abstract

Gas foil thrust bearings (GFTBs) have a wide range of applications in oil-free turbo machinery due to their advantages such as low maintenance, high speed ability, environmental friendliness, and wide range of temperature adaptability. However, the use of GFTBs is limited due to the low load-carrying capacity (LCC). This study develops a novel GFTB, engraving the straight radial grooves on the top foil surface to enhance the LCC. For numerical simulations, the 2D compressible, isothermal and isoviscous Reynolds equation is solved by the finite difference method (FDM) to obtain gas film thickness and pressure distribution. A marked increase of LCC and a nominal decrement of frictional torque is seen with a speed of 50 krpm compared to its conventional non groove GFTBs. Additionally, As GFTBs operate at very low clearance and at high-speed slip flow is considered at the solid gas interface. For accurate prediction of LCC and frictional torque Reynolds equation is modified by inserting the Knudsen number. The LCC and frictional torque with slip flow is assessed and the result is compared to no-slip conditions. The result declares that the conventional Reynolds equation overestimates the LCC and frictional torque by 6% at 50 krpm.