Numerical research on contact friction force with different structural brush seal hysteresis characteristics under differential pressure

Abstract

The problems of leakage, frictional wear, and flow heat transfer caused by the hysteresis characteristics of brush seals are prominent, and existing models for solving the hysteresis characteristics of brush seals have convergence difficulties owing to the extreme degree of nonlinearity caused by additional contacts. In this study, numerical models based on the finite element software ABAQUS were proposed to address the hysteresis characteristics of brush seals with three different structures: basic, low-lag hysteresis, and low-wear high-pressure bearing. The models accounted for the contacts between: the brush, brush and the baffle, and brush and the rotor, while damping was introduced to improve the convergence of the models. The hysteresis of the three structures under differential pressure was investigated and compared with theoretical calculations and experimental test results. The hysteresis of the bristles was normalised by the contact force, the shift of the contact area, and the contact friction force when the hysteresis effect occurred in the brush seal. The results show that the basic model has the most obvious hysteresis characteristics in the presence of differential pressure. Although the low-lag hysteresis model and the low-wear high-pressure bearing model have the weakest hysteresis effect, the deformation variables of the last row of bristles of these two structures are larger than those of the basic model; therefore, the contact position is prone to fatigue fracture. Simultaneously, the hysteresis effect was verified by varying the contact area and contact friction force, and it was found that the larger the contact area and contact friction force, the larger the hysteresis.