Limits of Dynamic Coefficients of Self-Acting Tilting-Pad Gas Bearings

Many previously published articles have studied the effects of perturbation frequency on the dynamic coefficients of gas bearing, but they all do not give the rounded definition of dynamic coefficients in the whole frequency range. In this article, the dynamic stiffness and damping coefficients of tilting-pad bearings are calculated by the partial derivative method and the limits of dynamic coefficients are obtained by using the limit theory. Furthermore, the equivalent dynamic coefficients of tilting-pad bearings are also calculated, which makes it possible to denote the dynamic characteristics of the tilting-pad bearing with eight dynamic coefficients. In the article, the dynamic coefficients of the bearing are investigated in the whole frequency range. The numerical results indicate that the changing trends of dynamic coefficients with perturbation frequency are well in agreement with their limits. With the increase of perturbation frequency, the dynamic stiffness coefficients are all close to their corresponding limits, and the limits of all dynamic damping coefficients are equal to zero. Moreover, the cross-coupling terms of dynamic coefficients of the tilting-pad gas bearing are close to zero, which further reveals the main reason that the performance of the tilting-pad bearings is better than the generic fixed-pad bearings.