Numerical investigation of gas journal foil bearing performance with thick top foil

A type of gas journal foil bearing with thick top foil (TTF-GJFB) was presented, and its modeling and analysis were carried out. The Newton-Raphson iterative method was used to solve the Reynolds equation and the force equilibrium equation to predict this novel bearing static performance. The dynamic stiffness and damping coefficients of this bearing were derived and solved by using reduced coefficient method and small perturbation method. Based on those methods, the comparative study of TTF-GJFB and traditional foil bearing was carried out, and the effects of bearing initial clearance, bump foil width and top foil mass on the bearing performance of novel foil bearing were studied. Results showed that TTF-GJFB had higher bearing load capacity and deflection angle than traditional foil bearing. The capacity increase was at least 23%. The dynamic characteristics of TTF-GJFB differed from those of traditional foil bearing. The initial clearance of TTF-GJFB affected the attitude angle and bearing load capacity. The width of the bump foil had great effect on the dynamic characteristics. Within the range of medium and low excitation ratio, the dynamic coefficients decreased with the declining width of the bump foil. The mass of top foil of TTF-GJFB affected the dynamic characteristics of bearing at high excitation ratio, dynamic stiffness coefficient increased and dynamic damping coefficient decreased.