The rotor motion of supercritical carbon dioxide turbine has the nonlinear characteristics and induces the changes of the sealing flow field. In order to explore the leakage flow characteristics of supercritical carbon dioxide seals under rotor nonlinear whirling conditions

this paper constructs a nonlinear whirling model of the rotor-seal to achieve dynamic simulation of the seal flow field. The flow characteristics and the evolution law of the vortex in seal are analyzed under the rotor nonlinear whirling. The results under the nonlinear whirling show that the precession displacement generated by the rotor whirling makes the vortex squeezed in the upper part of the chamber. The vortex in the lower part of the chamber is stretched. The stretching and compression of the vortex are related to the direction of rotor precession. As the rotor whirling downwards

the axial velocity in the lower part of the seal decreases. The velocity difference between the upper and lower part near the rotor wall surface increases. The end wall vortex and the backflow vortex undergo expansion and contraction deformations. As the rotor rotational speed increases

the axial velocity of the fluid inside the seal decreases. The pressure of the flow direction in chamber increases. While the pressure gradient increases

there are simultaneously vortex expansions

contractions

convergences

divergences and movements. Under the rotor nonlinear whirling

the leakage amount is reduced by 0.9%. For every 10 000 r/min increase in the rotor's rotational speed

the leakage amount decreases by 11.6% Nonlinear whirl motion in the rotor can induce displacement related changes in the sealing flow field and reduce leakage.