DEVELOPMENT OF BRAIDED ROPE SEALS FOR HYPERSONIC ENGINE APPLICATIONS - FLOW MODELING

A new type of engine seal is being developed to meet the needs of adva nced hypersonic engines. A seal braided of emerging high-temperature c eramic fibers comprised of a sheath-core construction has been selecte d for study based on its low leakage rates. Flexible, low-leakage, hig h-temperature seals are required to seal the movable engine panels of advanced ramjet-scramjet engines, either preventing potentially danger ous leakage into backside engine cavities or limiting the purge coolan t flow rates through the seals. To predict the leakage through these f lexible, porous seal structures, new analytical flow models are requir ed. Two such models based on Kozeny-Carman equations are developed her ein and are compared to experimental leakage measurements for simulate d pressure and seal preload conditions, showing good agreement. The mo dels developed allow prediction of the gas leakage rate as a function of fiber diameter, fiber packing density, gas properties, and pressure drop across the seal. The first model treats the seal as a homogeneou s fiber bed. The second model divides the seal into two homogeneous fi ber beds identified as the core and the sheath of the seal.