Definition of Brush Seals

Brush seals represent a highly efficient damping seal technology applied in turbomachinery. Originally developed for aircraft engines, their application subsequently expanded to fields such as industrial gas turbines and steam turbines. By utilizing a flexible contact structure to significantly reduce leakage rates, they have emerged as a pivotal technology in modern turbomachinery.

A brush seal consists of densely arranged metal bristles typically composed of a cobalt-based alloy. These bristles are angled to form a flexible contact surface capable of accommodating rotor eccentricities and thermal deformations; furthermore, the contact surface is coated with wear-resistant materials to minimize abrasion. As fluid leaks through the seal, it generates vortex flows within the bristle pack, converting kinetic energy into thermal energy to achieve a self-sealing effect; consequently, the leakage rate is merely one-fifth to one-tenth that of traditional labyrinth seals. Structurally, brush seals are categorized into welded and clamped types; the latter supports the incorporation of non-metallic materials to enhance adaptability, while multi-stage designs enable the seals to withstand pressure differentials of up to 1.8 MPa. Optimization strategies involve adjusting parameters such as the bristle angle (typically between 45° and 55°), the number of bristle rows, and the inter-stage flow area; additionally, the adoption of novel materials-such as carbon fiber-can effectively reduce the coefficient of friction. However, challenges persist, including the risk of circumferential bristle slip instability under high pressure differentials and uneven pressure drops on the downstream side; these issues necessitate mitigation through the implementation of pressure-balancing chambers or structural modifications tailored to specific operating conditions.