Brush Seal Structure And Working Principle

The basic structure of a brush seal consists of a front plate, a back plate, and a brush pack composed of high-density, high-temperature alloy bristles sandwiched between them. The bristles are oriented at a specific inclination angle-typically ranging from 35° to 60°-relative to the direction of the rotor's rotation.

Its core operating principle relies on a "self-sealing effect": leaking fluid flowing through the non-uniform interstitial spaces within the bristle pack generates deflected flows, jets, secondary currents, and vortices. This phenomenon causes the flow to shift from a predominantly forward direction to a lateral one, thereby increasing flow resistance and achieving a sealing effect. As the pressure ratio increases, the effective leakage area decreases due to the increased density of the bristles, resulting in a reduction in the leakage gradient.

Acting as cantilever beams, the bristles undergo bending deformation in response to pressure differentials and displacements of the sealing surface; the angle of the bristles determines the proportional distribution of the applied load between bending stress and column compression.

In terms of technological advancement, a patented design for a novel brush seal-incorporating a movable inner casing baffle-has been developed. This innovation serves to reduce the relative velocity between the bristle pack and the rotor's sealing track, thereby extending the seal's applicable range of pressure differentials.