Parametric Study of Leakage Flow in Braided Fiber Seals

Abstract

In applications of braided fiber engine seals, the preload and engine pressures are the two main parameters determining seal leakage, and experiments evaluating seal leakage flow are designed using these pressures. To simplify seal performance evalu ation, an empirical expression for the relationship of seal leakage resistance against preload and engine pressures is proposed. The basis for this approach is that seal leakage resistance depends on both preload and engine pressures. The physics of these pressure effects is studied both theoretically and experimentally. The main effect of preload pressure is to change seal porosity and thus leakage flow resistance. At the low porosity range of seal fiber architecture, seal porosity change due to imposed engine pressure is negligible; the effect of engine pressure is related to the flowing fluids, which also contribute to overall seal leakage resistance. Experimental data show that the proposed empirical model can be used to predict seal leakage within a range of engine and preload pressures of practical interest. Its simple form is advantageous in estimating seal performance under various pressures.