The severe operating conditions encountered in today's gas turbine engines and increased environmental concerns have created a need for an alternative to labyrinth seals. Brush seals can offer as much as 17% reduction in specific fuel consumption over labyrinth seals. Actually, labyrinth seals in many aircraft gas turbine engines are being replaced by brush seals because brush seals are compliant, reliable, and cost competitive and have been shown to leak less and to enhance rotor stability. Hence, brush seal may be a good candidate in cryogenic turbopumps, where long-life, low-leakage, reliable seals are essential.
WHAT IS BRUSH SEAL? Brush seals are circumferential seals comprised of densely packed, fine nickel chromium ally wires arrayed on a 45 degree angle against the tangent of the shaft surface they are configured to run against. These are very high tip speed, high temperature seals usually applied in the secondary and territory flow paths in gas turbine engines. They are capable of surface speeds of upwards of 1,000 feet per second and 1,000 degrees F. BRUSH SEALS In order to accommodate radial movements between the static brush seal and the dynamic rotor shaft, the bristles are designed to flex. The free length and angle of the bristles, as well as the wire diameter, are adapted to each application in order to optimize seal stiffness. The result is low wear and low leakage. For higher pressure drop applications, two or three brush seal elements can be mounted in a single housing to form a multi-staged seal This reduces the pressure drop across any single seal location, thus ensuring low pressure stiffening and bristle recovery. STRAIGHT BRUSH SEALS Advanced concept technology of brush seal design has accelerated pace of technology development, have challenged our ability to adequately respond to rapidly evolving another needs. Straight brush seals are derivative products originated in circumferential brush seal. It shows promise in meeting the demands of straight clearance static seals. These demands are particularly identical in the application of larger size of turbine engines where large size of the composition yields larger clearance and it's associated increased leakage.